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Journal of Animal Ecology now only accepts submissions online. When your manuscript has been prepared in accordance with the following instructions, please access the online submission site at You must select the Journal of Animal Ecology when you log on. [ABSTRACT FROM AUTHOR]

1. There is a current debate about the appropriateness of prey-dependent vs. ratio-dependent functional responses in predator–prey models. This is an important issue as systems governed by these models exhibit quite different dynamical behaviour. However, the issue is not yet resolved on a theoretical basis, and there is a lack of experimental evidence in natural systems. We used a paper wasp–shield beetle system in a natural setting to assess the validity of either approach.2. We manipulated the abundance of herbivorous insect prey on thistle plants and of predatory paper wasps in the immediate environment of the prey by opening or closing cages containing wasp nests.3. The number of wasps foraging at the site increased when cages were opened, but rapidly reached an asymptote, indicating predator interference. The predation rate per predator decreased with the number of wasps in the environment. Thus, the functional response depended on both prey and predator density.4. Neither a pure prey- nor a pure ratio-dependent model fitted perfectly our observations. However, the functional response of the paper wasps towards shield beetle larvae was closer to ratio-dependence. To our knowledge, this is the first experimental evidence discriminating between ratio- and prey-dependence in a natural setting with unconfined predators and prey.5. Predator interference was most probably responsible for the specific form of the functional response found. We found indications that both direct (e.g. aggression) and indirect interference mechanisms (e.g. depletion of easy-to-find prey) were at work in our system. We conclude that predator density cannot be ignored in models of predator–prey interactions.Journal of Animal Ecology(2005) doi: 10.1111/j.1365-2656.2004.00900.x [ABSTRACT FROM AUTHOR]

The article presents the winner of the Elton Prize of the "Journal of Animal Ecology." This award was presented to Diane L. Haughland whose winning research paper is entitled "Exploration Correlates With Settlement: Red Squirrel Dispersal in Contrasting Habitats." The journal editors selected this paper because it tackled a relevant but poorly studied ecological topic.

The article presents a brief introduction of the paper "Ecosystem alteration modifies the relative strengths of bottom-up and top-down forces in a herbivore population," by G. Moreau and colleagues. It presents the situation in the field of ecology. It offers an overview of the content of the paper of Moreau and colleagues. It shows that by reducing the mortality of larval sawfly, forest thinning practices add to increased outbreak densities of the sawfly. It tells that the authors combined empirical surveys with experimental manipulations.

1. Recent studies on butterflies have documented apparent evolutionary changes in dispersal rate in response to climate change and habitat change. These studies often assume a trade-off between dispersal rate (or flight capacity) and reproduction, which is the rule in wing-dimorphic species but might not occur equally in wing-monomorphic species such as butterflies. 2. To investigate the relationship between dispersal rate and fecundity in the Glanville fritillary butterfly Melitaea cinxia we recorded lifetime individual movements, matings, ovipositions, and maximal life span in a large (32 × 26 m) population cage in the field. Experimental material was obtained from 20 newly established and 20 old local populations within a large metapopulation in the Åland Islands in Finland. 3. Females of the Glanville fritillary from newly established populations are known to be more dispersive in the field, and in the cage they showed significantly greater mobility, mated earlier, and laid more egg clutches than females from old populations. The dispersive females from new populations exhibited no reduced lifetime fecundity in the cage, but they had a shorter maximal life span than old-population females. 4. These results challenge the dispersal–fecundity trade-off for nonmigratory butterflies but instead suggest a physiological trade-off between high metabolic performance and reduced maximal life span. High metabolic performance may explain high rates of dispersal and oviposition in early life. 5. In fragmented landscapes, an ecological trade-off exists between being more dispersive and hence spending more time in the landscape matrix vs. having more time for reproduction in the habitat. We estimate with a dispersal model parameterized for the Glanville fritillary that the lifetime egg production is 4% smaller on average in the more dispersive butterflies in a representative landscape, with much variation depending on landscape structure in the neighbourhood of the natal patch, from −26 to 45% in the landscape analysed in this paper. [ABSTRACT FROM AUTHOR]

1. Harmonia axyridis is a generalist predator with a high range of accepted prey. Prey differ in nutritive contents, energetic values and cost associated with their capture and ingestion. As a result of selection pressures, animals will tend to hunt for their prey efficiently. In this paper we evaluated the suitability of Myzus persicae and Aphis fabae to the adults of the aulica phenotype of H. axyridis, their feeding preferences and the impact of mixed diets on their fitness. Feeding preference of predators was evaluated through their response to different relative abundance of prey. 2. Under a single diet regime, the adults of the aulica phenotype fed on more individuals M. persicae than A. fabae but consumed less biomass from the former. None of those prey affect relative growth rate and reproductive capacity of the ladybeetles. 3. Males and females present different types of response to three levels of different relative abundance of prey. While males show a constant feeding preference for M. persicae, females did not show a feeding preference (i.e. null switching response). Under a mixed diet regime, adults' voracity gradually increased as the proportion of M. persicae increased, but biomass consumed and relative growth rate was not affected. On the other hand, fecundity and fertility increased. 4. Our results suggest that H. axyridis present self-selection behaviour because they agree with the basic criteria of Waldbauer and Friedman's self-selection, i.e. (i) the animal's choice of food or nutrients is non-random, and (ii) the coccinellid benefits from self-selecting. [ABSTRACT FROM AUTHOR]

Summary 1. Residuals from linear regressions are used frequently in statistical analysis, often for the purpose of controlling for unwanted effects in multivariable datasets. This paper criticizes the practice, building upon recent critiques. 2. Regression of residuals is often used as an alternative to multiple regression, often with the aim of controlling for confounding variables. When correlations exist between independent variables, as is generally the case with ecological datasets, this procedure leads to biased parameter estimates. Standard multiple regression, by contrast, yields unbiased parameter estimates. 3. In multiple regression parameters are estimated controlling for the effects of the other variables in the model, and thus multiple regression achieves what residual regression claims to do. 4. Several measures of correlation exist that differ in the way that variance is partitioned among independent variables. These can be estimated multiply, or sequentially if reasons exist for estimating effects of variables in a hierarchical manner. [ABSTRACT FROM AUTHOR]

Summary: 1. Many studies have provided evidence that first-time breeders have a lower survival, a lower probability of success, or of breeding, in the following year. Hypotheses based on reproductive costs have often been proposed to explain this. However, because of the intrinsic relationship between age and experience, the apparent inferiority of first-time breeders at the population level may result from selection, and experience may not influence performance within each individual. In this paper we address the question of phenotypic correlations between fitness components. This addresses differences in individual quality, a prerequisite for a selection process to occur. We also test the hypothesis of an influence of experience on these components while taking age and reproductive success into account: two factors likely to play a key role in a selection process. 2. Using data from a long-term study on the kittiwake, we found that first-time breeders have a lower probability of success, a lower survival and a lower probability of breeding in the next year than experienced breeders. However, neither experienced nor inexperienced breeders have a lower survival or a lower probability of breeding in the following year than birds that skipped a breeding opportunity. This suggests heterogeneity in quality among individuals. 3. Failed birds have a lower survival and a lower probability of breeding in the following year regardless of experience. This can be interpreted in the light of the selection hypothesis. The inferiority of inexperienced breeders may be linked to a higher proportion of lower-quality individuals in younger age classes. When age and breeding success are controlled for, there is no evidence of an influence of experience on survival or future breeding probability. 4. Using data from individuals whose reproductive life lasted the same number of years, we investigated the influence of experience on reproductive performance within individuals. Th... [ABSTRACT FROM AUTHOR]

Competition and predation are at the heart of community ecology. The theoretical concept of intraguild predation (IGP) combines these key interactions in a single community module. Because IGP is believed to be ubiquitous in nature, it has been subject to extensive research, and there exists a well-developed theoretical framework. We show that a general class of IGP models can be transformed to simpler, but equivalent community structures. This rather unexpected simplification depends critically on the property of 'indiscriminate predation', which we define broadly as the top-predator not distinguishing between its two different prey species. In a broader context, the great importance of IGP and of the simplifying transformation we report here is enhanced by the recent insight that the basic IGP structure extends naturally to host-parasitoid and host-pathogen communities. We show that parasites infecting prey (predators) tend to render IGP effectively into exploitative competition (tritrophic food chain, respectively). The equivalence between the original and simplified community module makes it possible to take advantage from already existing insights. We illustrate this by means of an eco-epidemiological IGP model that is strikingly similar to a classical exploitative competition model. The change of perspective on certain community modules may contribute to a better understanding of food web dynamics. In particular, it may help explain the interactions in food webs that include parasites. Given the ubiquity of parasitism, food webs may appear in a different light when they are transformed to their simplified analogue. [ABSTRACT FROM AUTHOR]

Summary 1. The aggregation model of coexistence has been used widely to explain the coexistence of competing species that utilize patchy and ephemeral resources. Over the years, it has been reformulated in many different ways, using different assumptions, indices and analyses, leading sometimes to contradictory conclusions. We present a general framework, from which many of the alternative approaches are derived as special cases. 2. A generalized distribution, composed of the distribution of visits across patches and the distribution of eggs per visit, is used to model changes in the mean individual-level experience of density that occur at different population-level densities. 3. New and more general criteria for coexistence are derived, based upon standard invasability analysis of Lotka–Volterra competition equations applied to a patchy system. 4. An important parameter in the new coexistence criteria is the mean per capita density of individuals in a single clutch (&formmu0;). Until now this measure has been relatively ignored, experimentally and theoretically. 5. We confirm earlier findings that the random distribution of clutches may be a sufficient cause of aggregated egg distributions to allow coexistence between species of unequal competitive ability, but only if the product of competition coefficients is less than one. [ABSTRACT FROM AUTHOR]

Summary 1. Individuals of the same species often exhibit consistent differences in metabolic rate, but the effects of such differences on ecologically important behaviours remain largely unknown. In particular, it is unclear whether there is a cause-and-effect relationship between metabolic rate and the tendency to take risks while foraging. Individuals with higher metabolic rates may need to take greater risks while foraging to obtain the additional food required to satisfy their energy requirements. Such a relationship could be exacerbated by food deprivation if a higher metabolic demand also causes greater mass loss and hunger. 2. We investigated relationships among metabolic rate, risk-taking and tolerance of food deprivation in juvenile European sea bass. Individual fish were tested for risk-taking behaviours following a simulated predator attack, both before and after a 7-day period of food deprivation. The results were then related to their routine metabolic rate (RMR), which was measured throughout the period of food deprivation. 3. The amount of risk displayed by individual fish before food deprivation showed no relationship with RMR. After food deprivation, however, the amount of risk among individuals was positively correlated with RMR. In general, most fish showed an increase in risk-taking after food deprivation, and the magnitude of the increase in risk-taking was correlated with the rate of individual mass loss during food deprivation, which was itself strongly correlated with RMR. 4. The observation that RMR was related to risk-taking behaviour after food deprivation, but not before, suggests that although RMR can influence risk-taking, the strength of the relationship is flexible and context dependent. The effects of RMR on risk-taking may be subtle or non-existent in regularly feeding animals, but may lead to variability in risk-taking among individuals when food is scarce or supply is unpredictable. This synergistic relationship between RMR and food deprivation could lead to an increased likelihood of being predated for individuals with a relatively high intrinsic energy demand during times when food is scarce. [ABSTRACT FROM AUTHOR]

Polyphagous predatory invertebrates play a key role in the top-down control of insect herbivores. However, predicting predation risk for herbivores is not a simple function of predator species richness. Predation risk may be reduced or enhanced depending on the functional characteristics predator species. We predict that where predator species spatially overlap this will reduce predation risk for herbivores by allowing negative inter-specific interaction between predators to occur. Where increased predation risk occurs, we also predict that this will have a cascading effect through the food chain reducing plant growth. We used a substitutive replicated block design to identify the effect of similarity and dissimilarity in predator hunting mode (e.g. 'sit and wait', 'sit and pursue', and 'active') and habitat domain (e.g. canopy or ground) on the top-down control of planthoppers in grasslands. Predators included within the mesocosms were randomly selected from a pool of 17 local species. Predation risk was reduced where predators shared the same habitat domain, independent of whether they shared hunting modes. Where predators shared the same habitat domains, there was some evidence that this had a cascading negative effect on the re-growth of grass biomass. Where predator habitat domains did not overlap, there were substitutable effects on predation risk to planthoppers. Predation risk for planthoppers was affected by taxonomic identity of predator species, i.e. whether they were beetles, spiders or true bugs. Our results indicated that in multi-predator systems, the risk of predation is typically reduced. Consideration of functional characteristics of individual species, in particular aspects of habitat domain and hunting mode, are crucial in predicting the effects of multi-predator systems on the top-down control of herbivores. [ABSTRACT FROM AUTHOR]

1. Understanding the structure of ecological networks is a crucial task for interpreting community and ecosystem responses to global change. 2. Despite the recent interest in this subject, almost all studies have focused exclusively on one specific network property. The question remains as to what extent different network properties are related and how understanding this relationship can advance our comprehension of the mechanisms behind these patterns. 3. Here, we analysed the relationship between nestedness and modularity, two frequently studied network properties, for a large data set of 95 ecological communities including both plant–animal mutualistic and host–parasite networks. 4. We found that the correlation between nestedness and modularity for a population of random matrices generated from the real communities decreases significantly in magnitude and sign with increasing connectance independent of the network type. At low connectivities, networks that are highly nested also tend to be highly modular; the reverse happens at high connectivities. 5. The above result is qualitatively robust when different null models are used to infer network structure, but, at a finer scale, quantitative differences exist. We observed an important interaction between the network structure pattern and the null model used to detect it. 6. A better understanding of the relationship between nestedness and modularity is important given their potential implications on the dynamics and stability of ecological communities. [ABSTRACT FROM AUTHOR]

1. Helpers that invest energy in provisioning the offspring of related individuals stand to gain indirect fitness benefits from doing so. First, if the helper’s effort is additional to that of the parents (additive) the productivity of the current breeding attempt can be increased. Secondly, if the parents reduce their workload (compensation) this can result in future indirect fitness gains to the helper via increased breeder survival; termed ‘load-lightening’. 2. Long-tailed tits ( Aegithalos caudatus) have a cooperative breeding system in which helpers assist kin and parents exhibit both additive and compensatory reactions in the presence of helpers. Offspring from helped nests are heavier and more likely to recruit into the breeding population, thus helpers gain indirect fitness benefits from increasing the productivity of the current breeding attempt. Despite breeders’ reduction of feeding effort in the presence of helpers, previous investigations found no subsequent increase in breeder survival. 3. The aim of this study was to test the hypothesis that load-lightening resulted in indirect fitness benefits for helpers. We used data from a 14-year study to investigate the provisioning rate, survival and future fecundity of male and female long-tailed tits that did and did not receive help at the nest. 4. We found an asymmetrical response to the presence of helpers at large brood sizes. Males reduced their feeding rate more than females, and this differential response was reflected in a significant increase in male survival when provisioning large broods assisted by helpers. We found no evidence of any increase in future fecundity for helped breeders. 5. The finding that males reduce their provisioning rate in the presence of helpers (at large brood sizes) to a greater degree than females, and that this is reflected in an increase in survival rate for males only, implies that the survival increase is caused by the reduction in work-rate rather than a non-specific benefit of a larger group size. 6. The marginal benefits of help for breeder survival are likely to be more difficult to identify than the increased productivity at helped nests, but should not be overlooked when investigating the potential indirect fitness gains that supernumeraries can accrue by helping. [ABSTRACT FROM AUTHOR]

1. Allee effects may result in negative growth rates at low population density, with important implications for conservation and management of exploited populations. Theory predicts prey populations will exhibit Allee effects when their predator exhibits a Type II functional response, but empirical evidence linking this positively density-dependent variation in predator-induced individual mortality to population growth rate and probability of extinction is lacking. 2. Here, we report a demonstration of extinction due to predator-driven Allee effects in an experimental Daphnia-Chaoborus system. A component Allee effect caused by higher predation rates at low Daphnia density led to positive density dependence in per capita growth rate and accelerated extinction rate at low density. 3. A stochastic model of the process revealed how the critical density below which population growth is negative depends on the mechanistic details of the predator–prey interaction. 4. The ubiquity of predator–prey interactions and saturating functional responses suggests predator-driven Allee effects are potentially important in determining extinction risk of a large number of species. [ABSTRACT FROM AUTHOR]

1. We established complex marine communities, consisting of over 100 species, in large subtidal experimental mesocosms. We measured the strength of direct interactions and the net strength of direct and indirect interactions between the species in those communities, using a combination of theoretical and empirical approaches. 2. Theoretical predictions of interaction strength were derived from the interaction coefficient matrix, which was parameterised using allometric predator–prey relationships. Empirical estimates of interaction strength were quantified using the ln-ratio, which measures the change in biomass density of species A in the presence and absence of species B. 3. We observed that highly connected species tend to have weak direct effects and net effects in our experimental food webs, whether we calculate interaction strength theoretically or empirically. 4. We found a significant correlation between our theoretical predictions and empirical estimates of direct effects and net effects. The net effects correlation was much stronger, indicating that our experimental communities were dominated by a mixture of direct and indirect effects. 5. Re-calculation of the theoretical predictions of net effects after randomising predator and prey body masses did not affect the negative relationship with connectance. 6. These results suggest that food web topology, which in this system is constrained by body mass, is overwhelmingly important for the magnitude of direct and indirect interactions and hence species importance in the face of biodiversity declines. [ABSTRACT FROM AUTHOR]

1. Population dynamics of insect host–parasitoid systems are important in many natural and managed ecosystems and have inspired much ecological theory. However, ecologists have a limited knowledge about the relative strengths of species interactions, abiotic effects and density dependence in natural host–parasitoid dynamics. Statistical time-series analyses would be more informative by incorporating multiple factors, measurement error and noisy dynamics. 2. We use a novel maximum likelihood and model-selection analysis of a state-space model for host–parasitoid dynamics to examine 21 years of annual census data for woolly bear caterpillars ( Platyprepia virginalis) and their locally host-specific tachinid parasitoids ( Thelaira americana). 3. Caterpillar densities varied by three orders of magnitude and were driven by density dependence and precipitation from the previous March but not detectably by parasitoids, despite variable and sometimes high (>50%) parasitism. 4. Fly fluctuations, as estimated from per cent parasitism, were affected by density dependence and precipitation from the previous July. There was marginal evidence that host abundance drives fly fluctuations as a generic linear effect but no evidence for classical Nicholson–Bailey coupling. 5. The state-space model analysis includes new methods for likelihood calculation and allows a balanced consideration of effect magnitude and statistical significance in a nonlinear model with multiple alternative explanatory variables. [ABSTRACT FROM AUTHOR]

1. Body size differences among coexisting related species are common, but the actual effect of these differences in mitigating interspecific interactions, such as resource competition and reproductive interference, is poorly understood. 2. Local assemblages of the ground beetle genus Carabus (subgenus Ohomopterus) typically consist of two or more species of varying sizes. Through foraging and mating experiments using four Ohomopterus species in parapatry and sympatry, we examined whether interspecific body size differences are effective in partitioning food resources or reducing reproductive interference. 3. Because larval Ohomopterus feed exclusively on earthworms, body size differences may be related to partitioning earthworms of different sizes. However, larvae did not exhibit differences in selectivity or attack success on earthworms of different sizes based on larval body size, indicating little possibility of partitioning food by body size. 4. In contrast, interspecific mating behaviours, such as mate recognition, mounting, and copulation, were hindered when body size differences were large; copulation was frequently accomplished between parapatric species with smaller body size differences. 5. These results suggest that body size differences between species effectively reduce reproductive interference, rather than resource competition. Although body size differences in coexisting closely related species have been considered to function in resource partitioning, they may function primarily in reproductive isolation and thereby facilitate coexistence of species. [ABSTRACT FROM AUTHOR]

1. Factorial analysis of variance (anova) with unbalanced (non-orthogonal) data is a commonplace but controversial and poorly understood topic in applied statistics. 2. We explain thatanova calculates the sum of squares for each term in the model formula sequentially (type I sums of squares) and show howanova tables of adjusted sums of squares are composite tables assembled from multiple sequential analyses. A differentanova is performed for each explanatory variable or interaction so that each term is placed last in the model formula in turn and adjusted for the others. 3. The sum of squares for each term in the analysis can be calculated after adjusting only for the main effects of other explanatory variables (type II sums of squares) or, controversially, for both main effects and interactions (type III sums of squares). 4. We summarize the main recent developments and emphasize the shift away from the search for the ‘right’anova table in favour of presenting one or more models that best suit the objectives of the analysis. [ABSTRACT FROM AUTHOR]

1. In studies on the effect of competition in plant communities two terms are used to describe its effects: the absolute reduction in growth of an individual as a consequence of the presence of another one is called intensity , while the relative impact of competition on an individual as a proportion of the impact of the whole environment is called importance. One school of thought is that the role of competition remains constant across productivity gradients, while the other is that it decreases with increasing severity. J.B. Grace (1991. A clarification of the debate between grime and tilman. Functional Ecology, 5, 583–587.) suggested that the apparent contradiction might be solved if we acknowledge that the two schools are discussing different aspects of competition: the intensity of competition might remain constant while its importance declines with increasing severity. 2. There are no studies that compare intensity and importance of competition in bird populations between areas that differ in quality or productivity and hence it is not possible to make predictions how intensity or importance of competition would vary between them. 3. I compared variation in intensity and importance of competition of three demographic variables between five plots that differ strongly in quality for great Parus major L . and blue tit Cyanistes caeruleus (L.). 4. Both intensity and importance of competition are larger in great than in blue tit populations meaning that the effect of competition on demographic variables is stronger in great than in blue tits and that the contribution of competition to variation in these variables is relatively higher in great than in blue tits. 5. Intensity of competition is higher in low quality than in high quality plots for both species, a result not expected from studies in plant communities. 6. Importance of competition varies strongly between plots. It is larger in oak-dominated plots than in mixed deciduous plots. 7. In birds breeding density increases with habitat quality but is limited by territorial behaviour. As a result competition for food is reduced in high quality habitats resulting in a reduction of competition intensity in high quality sites in which birds breed at high densities. 8. It can be predicted that in studies of territorial species density dependent effects on reproduction are more likely to be detected in low quality sites explaining in part differences in results between studies. [ABSTRACT FROM AUTHOR]

1. Linking the movement and behaviour of animals to their environment is a central problem in ecology. Through the use of electronic tagging and tracking (ETT), collection of in situ data from free-roaming animals is now commonplace, yet statistical approaches enabling direct relation of movement observations to environmental conditions are still in development. 2. In this study, we examine the hidden Markov model (HMM) for behavioural analysis of tracking data. HMMs allow for prediction of latent behavioural states while directly accounting for the serial dependence prevalent in ETT data. Updating the probability of behavioural switches with tag or remote-sensing data provides a statistical method that links environmental data to behaviour in a direct and integrated manner. 3. It is important to assess the reliability of state categorization over the range of time-series lengths typically collected from field instruments and when movement behaviours are similar between movement states. Simulation with varying lengths of times series data and contrast between average movements within each state was used to test the HMMs ability to estimate movement parameters. 4. To demonstrate the methods in a realistic setting, the HMMs were used to categorize resident and migratory phases and the relationship between movement behaviour and ocean temperature using electronic tagging data from southern bluefin tuna ( Thunnus maccoyii). Diagnostic tools to evaluate the suitability of different models and inferential methods for investigating differences in behaviour between individuals are also demonstrated. [ABSTRACT FROM AUTHOR]

1. Dispersal of individuals between habitat patches depends on both the propensity to emigrate from a patch and the ability to survive inter-patch movement. Environmental factors and individual characteristics have been shown to influence dispersal rates but separating the effects of emigration and dispersal mortality on dispersal can often be difficult. In this study, we use a soil mite laboratory system to investigate factors affecting emigration and dispersal mortality. 2. We tested the movement of different age groups in two-patch systems with different inter-patch distances. Differences in immigration among age groups were primarily driven by differences in emigration but dispersal mortality was greater for some groups. Immigration declined with increasing inter-patch distance, which was due to increasing dispersal mortality and decreasing emigration. 3. In a second experiment, we compared the dispersal of recently matured males and females and tested the impact of food availability during the developmental period on their dispersal. Dispersal was found to be male biased but there was no significant sex bias in dispersal mortality. There was some evidence that food availability could affect emigration and dispersal mortality. 4. These results demonstrate that both emigration and dispersal mortality can be affected by factors such as individual age and resource availability. Understanding these effects is likely to be important for predicting the fitness costs and population consequences of dispersal. [ABSTRACT FROM AUTHOR]

1. We examined the influence of local weather conditions on reproductive success, timing of breeding and survival in a population of a multi-brooded ground nesting passerine (woodlark Lullula arborea) over 35 years. 2. Woodlarks laid larger clutches when rainfall was low and temperature high during the egg-laying and pre-laying period. Nest success increased with higher temperatures during the nesting period. In successful nests, the number of chicks fledged per egg laid was greater when weather was drier during the brood stage. 3. Although woodlarks bred earlier in years with warmer early spring temperatures, with the onset of breeding varying by 25 days, there was no significant advance in the onset of breeding over the 35 years of study, due to considerable inter-annual variability, and no overall trend, in weather. 4. Simulation modelling of annual reproductive output demonstrated that earlier breeding could increase productivity by 23·5% in the warmest compared to the coldest year, due to birds having more nesting attempts. Other effects of weather on productivity affected breeding output to a lesser extent. 5. Effects of weather on productivity were minor compared to an increased rate of nest predation through the period of study, which reduced productivity by 49·8% by 2004 compared to 1971. 6. Turning points analysis identified three distinct demographic periods: from1971 to 1988 the population grew slowly, during 1988–1999 the population grew rapidly, but after 1999 the population declined. Increased population growth after 1988 was associated with higher first-year survival rates (estimated using a population model). Population decline after 1999 was caused by a combination of reduced productivity (resulting from increased nest failure rates attributed to predation) and lower first-year survival rates, that appear unrelated to winter temperature. 7. Climate change (long-term changes in weather) did not explain the marked changes observed in the population trajectory over 35 years. We suggest that understanding effects of both climate and habitat change on populations is essential in predictive population modelling. [ABSTRACT FROM AUTHOR]

1. Notwithstanding the growing amount of literature emphasizing the link between habitat, life-history traits and behaviour, few empirical studies investigated the combined effect of these parameters on individual predation risk. We investigated direct and indirect consequences of habitat composition at multiple spatial scales on predation risk by red foxes on 151 radio-monitored roe deer fawns. We hypothesized that the higher resource availability in fragmented agricultural areas increased predation risk because of: (i) shorter prey movements, which may increase predictability; (ii) larger litter size and faster growth rates, which may increase detectability in species adopting a hiding neonatal anti-predator strategy. The sharing of risky habitat among littermates was expected to promote whole-litter losses as a result of predation. 2. The landscape-scale availability of agricultural areas negatively affected pre-weaning movements, but did not influence growth rates or litter size. Predation risk was best described by the interplay between movements and fine-scale habitat fragmentation: a higher mobility increased the encounter rate and predation risk in highly fragmented home ranges, while it reduced predation risk in forest-dominated areas with clumped resources because of decreased predictability. This is one of the first demonstrations that movement patterns can be an efficient anti-predator strategy when adjusted to local conditions. 3. In accordance with previous studies documenting the existence of family effects (i.e. non-independence among siblings) in survival, littermates survived or died together more often than expected by chance. In addition, our study specifically demonstrated the occurrence of behaviourally mediated family effects in predation risk: after a fox killed one fawn the probability of a sibling being killed within a few days rose from 20% to 47%, likely because of the win-stay strategy (i.e. return to a previously rewarding site) adopted by the predator. Hence, the predator’s hunting strategy has the potential to raise fawn mortality disproportionately to predator abundance. 4. There is increasing evidence that fawns inhabiting highly productive predator-free habitats are granted lifetime fitness benefits; these potential advantages, however, can be cancelled out when predation risk increases in the very same high-productivity areas, which might thus turn into attractive sinks. [ABSTRACT FROM AUTHOR]

1. Inducible defences of prey and inducible offences of predators are prevalent strategies in trophic interactions with temporal variation. Due to the inducible properties of the functional traits themselves, which drive the dynamic predator–prey relationship on an ecological time-scale, predator and prey may reciprocally interact through their inducible traits (i.e. reciprocal phenotypic plasticity). 2. Although overwhelming evidence of the stabilizing effect of inducible traits in either species on community dynamics forcefully suggests a critical ecological role for reciprocal plasticity in predator–prey population dynamics, our understanding of its ecological consequences is very limited. 3. Within a mathematical modelling framework, we investigated how reciprocal plasticity influences the stability of predator–prey systems. 4. By assuming two types of phenotypic shift, a density-dependent shift and an adaptive phenotypic shift, we examined two interaction scenarios with reciprocal plasticity: (i) an arms-race-like relationship, in which the defensive prey phenotype is more protective against both predator phenotypes (i.e. normal and offensive) than the normal prey phenotype, and the offensive predator is a more efficient consumer, preying upon both prey phenotypes (i.e. normal and defensive), than the normal predator and (ii) a matching response-like relationship, in which the offensive predator consumes more defensive prey and fewer normal prey than the normal predator. 5. Results of both phenotypic shift models consistently suggest that given the used set of parameter values, the arms-race-like reciprocal plasticity scenario has the largest stability area, when compared with the other scenarios. In particular, higher stability is achieved when the prey exhibits a high-performance inducible defence. Furthermore, this stabilization is so strong that the destabilizing effects of enrichment may be eliminated, even though the higher flexibility of plasticity does not always stabilize a system. 6. Recent empirical studies support our model predictions. Clear-cut examples of reciprocal phenotypic plasticity show an arms-race-like relationship in which prey species exhibit induced high-performance defences. We may need to re-examine reported predator–prey interactions in which predator or prey exhibits inducible plasticity to determine whether arms-race-like reciprocal plasticity is a general ecological phenomenon. [ABSTRACT FROM AUTHOR]

1. Movement behaviour has become increasingly important in dispersal ecology and dispersal is central to the development of spatially explicit population ecology. The ways in which the elements have been brought together are reviewed with particular emphasis on dispersal distance distributions and the value of mechanistic models. 2. There is a continuous range of movement behaviours and in some species, dispersal is a clearly delineated event but not in others. The biological complexities restrict conclusions to high-level generalizations but there may be principles that are common to dispersal and other movements. 3. Random walk and diffusion models when appropriately elaborated can provide an understanding of dispersal distance relationships on spatial and temporal scales relevant to dispersal. Leptokurtosis in the relationships may be the result of a combination of factors including population heterogeneity, correlation, landscape features, time integration and density dependence. The inclusion in diffusion models of individual variation appears to be a useful elaboration. The limitations of the negative exponential and other phenomenological models are discussed. 4. The dynamics of metapopulation models are sensitive to what appears to be small differences in the assumptions about dispersal. In order to represent dispersal realistically in population models, it is suggested that phenomenological models should be replaced by those based on movement behaviour incorporating individual variation. 5. The conclusions are presented as a set of candidate principles for evaluation. The main features of the principles are that uncorrelated or correlated random walk, not linear movement, is expected where the directions of habitat patches are unpredictable and more complex behaviour when organisms have the ability to orientate or navigate. Individuals within populations vary in their movement behaviour and dispersal; part of this variation is a product of random elements in movement behaviour and some of it is heritable. Local and metapopulation dynamics are influenced by population heterogeneity in dispersal characteristics and heritable changes in dispersal propensity occur on time-scales short enough to impact population dynamics. [ABSTRACT FROM AUTHOR]

1. Social network analyses tend to focus on human interactions. However, there is a burgeoning interest in applying graph theory to ecological data from animal populations. Here we show how radio-tracking and capture–mark–recapture data collated from wild rodent populations can be used to generate contact networks. 2. Both radio-tracking and capture–mark–recapture were undertaken simultaneously. Contact networks were derived and the following statistics estimated: mean-contact rate, edge distribution, connectance and centrality. 3. Capture–mark–recapture networks produced more informative and complete networks when the rodent density was high and radio-tracking produced more informative networks when the density was low. Different data collection methods provide more data when certain ecological characteristics of the population prevail. 4. Both sets of data produced networks with comparable edge (contact) distributions that were best described by a negative binomial distribution. Connectance and closeness were statistically different between the two data sets. Only betweenness was comparable. The differences between the networks have important consequences for the transmission of infectious diseases. Care should be taken when extrapolating social networks to transmission networks for inferring disease dynamics. [ABSTRACT FROM AUTHOR]

1. Modern theories of species coexistence recognize the importance of environmental heterogeneity. 2. Despite the existence of many observational studies, few experimental studies have evaluated the extent to which, and mechanisms by which, fixed spatial heterogeneity increases community diversity and alters community structure. 3 In experimental protist communities, we found that non-spatial mechanisms unrelated to heterogeneity were responsible for a large component of baseline diversity. Above this baseline, fixed spatial heterogeneity produced small but predictable increases in metacommunity diversity through species sorting, while heterogeneity and dispersal together altered local community structure (composition and relative abundance) through mass effects. 4. Our study illustrates that heterogeneity is not always the strongest driver of diversity, while experimentally demonstrating mechanisms by which heterogeneity alters community structure. [ABSTRACT FROM AUTHOR]

1. Body size is positively correlated with fecundity in various animals, but the factors that counterbalance the resulting selection pressure towards large size are difficult to establish. Positively size-dependent predation risk has been proposed as a selective factor potentially capable of balancing the fecundity advantage of large size. 2. To construct optimality models of insect body size, realistic estimates of size-dependent predation rates are necessary. Moreover, prey traits such as colouration should be considered, as they may substantially alter the relationship between body size and mortality risk. 3. To quantify mortality patterns, we conducted field experiments in which we exposed cryptic and conspicuous artificial larvae of different sizes to bird predators, and recorded the incidence of bird attacks. 4. The average daily mortality rate was estimated to vary between 4% and 10%. In both cryptic and conspicuous larvae, predation risk increased with prey size, but the increase tended to be steeper in the conspicuous group. No main effect of colour type was found. All the quantitative relationships were reasonably consistent across replicates. 5. Our results suggest that the size dependence of mortality risk in insect prey is primarily determined by the probability of being detected by a predator rather than by a size-dependent warning effect associated with conspicuous colouration. Our results therefore imply that warningly coloured insects do not necessarily benefit more than the cryptic species from large body size, as has been previously suggested. [ABSTRACT FROM AUTHOR]

1. The geographical pattern in Fennoscandian small rodent population dynamics with a southern noncyclic and a northern cyclic region, and with latitudinal gradients in density-dependent structure, cycle period length and spatial synchrony within the northern cyclic region, has been widely publicized and interpreted in the ecological literature. However, the time-series data on which these inferences have been established are relatively short and originate from a specific time period (mostly around 1970–90). Hence, it can be questioned whether the geographical population dynamics patterns are consistent over time (i.e. whether they are stationary). 2. Here we analyse an almost century long (1880–1976) panel of fox bounty time series including 18 counties of Norway, thus spanning the whole range of latitudes of Fennoscandia (i.e. 15 latitudinal degrees). These fox time series mirror the dynamics of their dominant small rodent prey, in particular, with respect to cycle period length and spatial synchrony. 3. While we found some evidence consistent with previous analyses showing a clearly patterned dynamics according to latitude, such patterns were not stationary on a longer time-scale. In particular, we observed a shift from an extensively synchronous (i.e. regionalized) 4-year cycle north of 60°N just after the ‘Little Ice Age’ (1880–1910) to a diversification of cycle period length (3–5 years) and eventually, partial loss of cyclicity and synchronicity in later periods. Incidents of loss of cyclicity appeared to be preceded by changes in cycle period (i.e. period lengthening and shortening). 4. These results show that the dynamics of Fennoscandian small rodents, and their associated guild of predators, are more prone to change than previously acknowledged. [ABSTRACT FROM AUTHOR]

1. When studying speciation, researchers commonly examine reproductive isolation in recently diverged populations. Polymorphic species provide an opportunity to examine the role of reproductive isolation in populations that may be in the process of divergence. 2. We examined a polymorphic population of Plethodon cinereus (red-backed salamanders) for evidence of sympatric ecological separation by colour morphology. Recent studies have correlated temperature and climate with colour morphology in this species, but no studies have looked at differences in diet or mate choice between colour morphs. We used artificial cover objects to assess salamander diet, mating preference and surface activity over a 2-year period at a field site in north-eastern Ohio. 3. We detected differences in diet between two colour morphs, striped and unstriped. The diets of striped individuals were significantly more diverse and were made up of more profitable prey than the diets of unstriped salamanders. 4. Opposite sex pairs were made up of individuals of the same colour morph and striped males were found more often with larger females than were unstriped males. 5. We corroborate findings of earlier studies suggesting that the unstriped form is adapted to warmer conditions. Unstriped individuals were the first to withdraw from the forest floor as temperatures fell in the late fall. We found no evidence that the colour morphs responded differently to abiotic factors such as soil moisture and relative humidity, and responses to surface temperatures were also equivocal. 6. We conclude that the two colour morphs exhibit some degree of ecological separation and tend to mate assortatively, but are unlikely to be undergoing divergence given the observed frequency of intermorph pairings. [ABSTRACT FROM AUTHOR]

1. Although theory predicts a positive relationship between oviposition preferences and the developmental performance of offspring, the strength of this relationship may depend not only on breeding site quality, but also on the complex interactions between environmental heterogeneity and density-dependent processes. Environmental heterogeneity may not only alter the strength of density dependence, but may also fundamentally alter density-dependent relationships and the preference–performance relationship. 2. Here I present results from a series of field experiments testing the effects of environmental heterogeneity and density-dependent feedback on offspring performance in tree-hole mosquitoes. Specifically, I asked: (i) how do oviposition activity, patterns of colonization and larval density differ among habitats and among oviposition sites with different resources; and (ii) how is performance influenced by the density of conspecifics, the type of resource in the oviposition site, and the type of habitat in which the oviposition site is located? 3. Performance did not differ among habitats at low offspring densities, but was higher in deciduous forest habitats than in evergreen forest habitats at high densities. Oviposition activity and larval densities were also higher in deciduous forests, suggesting a weak preference for these habitats. 4. The observed divergence of fitness among habitats with increasing density may select for consistent but weak preferences for deciduous habitats if regional abundances vary temporally. This would generate a negative preference–performance relationship when population densities are low, but a positive relationship when population densities are high. 5. This study demonstrates that failure to recognize that fitness differences among habitats may themselves be density-dependent may bias our assumptions about the ecological and evolutionary processes determining oviposition preferences in natural systems. [ABSTRACT FROM AUTHOR]

1. Changing plant composition in a community can have profound consequences for herbivore and parasitoid population dynamics. To understand such effects, studies are needed that unravel the underlying behavioural decisions determining the responses of parasitoids to complex habitats. 2. The searching behaviour of the parasitoid Diadegma semiclausum was followed in environments with different plant species composition. In the middle of these environments, two Brassica oleracea plants infested by the host Plutella xylostella were placed. The control set-up contained B. oleracea plants only. In the more complex set-ups, B. oleracea plants were interspersed by either Sinapis alba or Hordeum vulgare. 3. Parasitoids did not find the first host-infested plant with the same speed in the different environments. Sinapis alba plants were preferentially searched by parasitoids, resulting in fewer initial host encounters, possibly creating a dynamic enemy-free space for the host on adjacent B. oleracea plants. In set-ups with H. vulgare, also, fewer initial host encounters were found, but in this case plant structure was more likely than infochemicals to interfere with the searching behaviour of parasitoids. 4. On discovering a host-infested plant, parasitoids located the second host-infested plant with equal speed, demonstrating the effect of experience on time allocation. Further encounters with host-infested plants that had already been visited decreased residence times and increased the tendency to leave the environment. 5. Due to the intensive search of S. alba plants, hosts were encountered at lower rates here than in the other set-ups. However, because parasitoids left the set-up with S. alba last, the same number of hosts were encountered as in the other treatments. 6. Plant composition of a community influences the distribution of parasitoid attacks via its effects on arrival and leaving tendencies. Foraging experiences can reduce or increase the importance of enemy-free space for hosts on less attractive plants. [ABSTRACT FROM AUTHOR]

1. Social species in the spider genus Anelosimus predominate in lowland tropical rainforests, while congeneric subsocial species occur at higher elevations or higher latitudes. 2. We conducted a comparative study to determine whether differences in total biomass, insect size or both have been responsible for this pattern. 3. We found that larger average insect size, rather than greater overall biomass per se, is a key characteristic of lowland tropical habitats correlating with greater sociality. 4. Social species occupied environments with insects several times larger than the spiders, while subsocial species nearing dispersal occupied environments with smaller insects in either high or low overall biomass. 5. Similarly, in subsocial spider colonies, individuals lived communally at a time when they were younger and therefore smaller than the average insect landing on their webs. 6. We thus suggest that the availability of large insects may be a critical factor restricting social species to their lowland tropical habitats. [ABSTRACT FROM AUTHOR]

1. There is increasing evidence that density-independent weather effects influence life-history traits and hence the dynamics of populations of animals. Here, we present a novel statistical approach to estimate when such influences are strongest. The method is demonstrated by analyses investigating the timing of the influence of weather on the birth weight of sheep and deer. 2. The statistical technique allowed for the pattern of temporal correlation in the weather data enabling the effects of weather in many fine-scale time intervals to be investigated simultaneously. Thus, while previous studies have typically considered weather averaged across a single broad time interval during pregnancy, our approach enabled examination simultaneously of the relationships with weekly and fortnightly averages throughout the whole of pregnancy. 3. We detected a positive effect of temperature on the birth weight of deer, which is strongest in late pregnancy (mid-March to mid-April), and a negative effect of rainfall on the birthweight of sheep, which is strongest during mid-pregnancy (late January to early February). The possible mechanisms underlying these weather–birth weight relationships are discussed. 4. This study enhances our insight into the pattern of the timing of influence of weather on early development. The method is of much more general application and could provide valuable insights in other areas of ecology in which sequences of intercorrelated explanatory variables have been collected in space or in time. [ABSTRACT FROM AUTHOR]

1. The role of climate variability in determining the spatial and temporal patterns of numerical fluctuations is a central problem in ecology. The influence of the North Atlantic Oscillation (NAO) index on the population dynamics and spatial synchrony of the green spruce aphid Elatobium abietinum across the UK was shown. 2. Fifteen overlapping time series within the UK were analysed; we used nonparametric models for determining the feedback nonlinear structure and the climatic effects. The spatial synchrony of these populations and the relationship between synchrony and NAO was estimated. 3. From the 15 time series across the UK, 11 showed positive and significant NAO effects. In most of the cases the NAO effects were nonlinear showing strong negative effects of low values. The NAO variation improve the explained variance of the first-order feedback models in 14·5%; ranging from 0% to 48%. All data showed strong-nonlinear (concave) feedback structure. In most of the localities the explained variance by the first-order feedback was about 50–60%. 4. The spatial synchrony of the per capita growth rates and residuals is high across long distances for those populations affected by NAO. The correlation function predicts a spatial scale of synchrony of about 350–400 km for NAO influenced populations. 5. We think that simple population theoretical models describing the link between NAO fluctuations and green spruce aphid dynamics may be fundamental for predicting and simulating the consequences of different climatic scenarios of the future. [ABSTRACT FROM AUTHOR]

1. Aposematism is a widely used antipredator strategy in which an organism possesses both warning coloration and unprofitable characters. Theoretical evidence suggests that aposematic colour should develop when high opportunity costs imposed by crypsis force an organism to engage in conspicuous behaviours. Hence, it is expected that ontogenetic colour change (OCC) in larval insects should include aposematism when foraging needs compel behavioural modifications that preclude a continued state of crypsis. 2. To test this idea, I first investigated whether OCC in caterpillars of the panic moth Saucrobotys futilalis was indicative of a switch from cryptic to aposematic coloration. I then examined the context of panic moth OCC as it related to foraging patterns and behavioural conspicuousness. 3. Early Saucrobotys instars are a cryptic green, but later instars become progressively more orange and develop black spots. Early instar larvae forage cryptically on the inner parenchyma of silked-together host plant leaves to avoid predation, but are rapidly forced to engage in conspicuous foraging behaviours as they outgrow the resources afforded by their shelters. Both coloration and behaviour reach maximal conspicuousness in final instar larvae. 4. As predicted, OCC encompassed a change from crypsis to aposematism in Saucrobotys. Aposematic function was demonstrated by changes in both antipredator behaviour patterns and effectiveness of predator deterrence in early and late instars. Moreover, increased opportunity costs of crypsis and behavioural conspicuousness coincided with the onset of aposematic coloration. 5. This pattern of OCC suggests that aposematic coloration in Saucrobotys develops as a response to constraints imposed by crypsis. Moreover, my study illustrates the importance of the study of ontogenetic patterns in determining how behaviour, morphology, and predator responses interact to influence the initial evolution of phenomena such as aposematism. [ABSTRACT FROM AUTHOR]

1. Pairs of European Triturus newt species of similar size tend not to co-occur syntopically, suggesting that similarity in body size is associated with competitive interactions that prevent coexistence. I tested this hypothesis with an experiment involving larvae of four species in 675-L artificial ponds. 2. There were strong interactions between most species pairs. Even the small T. helveticus had a clear impact on the larger T. alpestris. Pairs of species with different body sizes did not interact less strongly. 3. A standard increase in competitor biomass ( c. 2 g mass at metamorphosis) caused 42% lower expected survival from hatching to 1 year of age, regardless of whether the species were of similar or different size. In most cases this resulted from delayed metamorphosis, reduced size at emergence, and slightly lower larval survival. 4. A standard increase in competitor density (0·74 individuals m−2) caused a greater reduction in expected 1-year survival when the competitor was larger (18% decline) than when both species were of similar size (6% decline), primarily because the very large T. cristatus consumed the smallest species. 5. These findings suggest that species interactions during the larval stage cannot explain distribution patterns of same- and different-sized Triturus. [ABSTRACT FROM AUTHOR]

1. Large-scale habitat loss is frequently identified with loss of biodiversity, but examples of the direct effect of habitat alterations on changes in vital rates remain rare. Quantifying and understanding the relationship between habitat composition and changes in vital rates, however, is essential for the development of effective conservation strategies. 2. It has been suggested that the decline of woodland caribou Rangifer tarandus caribou populations in North America is precipitated by timber harvesting that creates landscapes of early seral forests. Such habitat changes have altered the predator–prey system resulting in asymmetric predation, where predators are maintained by alternative prey (i.e. apparent competition). However, a direct link between habitat condition and caribou population declines has not been documented. 3. We estimated survival probabilities for the threatened arboreal lichen-feeding ecotype of woodland caribou in British Columbia, Canada, at two different spatial scales. At the broader scale, observed variation in adult female survival rates among 10 distinct populations (range = 0·67–0·93) was best explained by variation in the amount of early seral stands within population ranges and population density. At the finer scale, home ranges of caribou killed by predators had lower proportions of old forest and more mid-aged forest as compared with multi-annual home ranges where caribou were alive. 4. These results are consistent with predictions from the apparent competition hypothesis and quantify direct fitness consequences for caribou following habitat alterations. We conclude that apparent competition can cause rapid population declines and even extinction where changes in species composition occur following large scale habitat change. [ABSTRACT FROM AUTHOR]

1. Predators impose costs on their prey but may also provide benefits such as protection against other (e.g. nest) predators. The optimal breeding location in relation to the distance from a nesting raptor varies so as to minimize the sum of costs of adult and nest predation. We provide a conceptual model to account for variation in the relative predation risks and derive qualitative predictions for how different prey species should respond to the distance from goshawk Accipiter gentilis nests. 2. We test the model predictions using a comprehensive collection of data from northern Finland and central Norway. First, we carried out a series of experiments with artificial bird nests to test if goshawks may provide protection against nest predation. Second, we conducted standard bird censuses and nest-box experiments to detect how the density or territory occupancy of several prey species varies with distance from the nearest goshawk nest. 3. Nest predation rate increased with distance from goshawk nest indicating that goshawks may provide protection for birds’ nests against nest predation. Abundance (or probability of presence) of the main prey species of goshawks peaked at intermediate distances from goshawk nests, reflecting the trade-off. The abundance of small songbird species decreased with distance from goshawk nests. The goshawk poses little risk to small songbirds and they may benefit from goshawk proximity in protection against nest predation. Finally, no pattern with distance in pied flycatcher territory (nest box) occupation rate or the onset of egg-laying was detected. This is expected, as flycatchers neither suffer from marked nest predation risk nor are favoured goshawk prey. 4. Our results suggest that territory location in relation to the nest of a predator is a trade-off situation where adult birds weigh the risk of themselves being predated against the benefits accrued from increased nest survival. Prey species appear able to detect and measure alternative predation risks, and respond adaptively. From the prey perspective, the landscape is a mosaic of habitat patches the quality of which varies according to structural and floristic features, but also to the spatial distribution of predators. [ABSTRACT FROM AUTHOR]

1. Although the home range is a fundamental ecological concept, there is considerable debate over how it is best measured. There is a substantial literature concerning the precision and accuracy of all commonly used home range estimation methods; however, there has been considerably less work concerning how estimates vary with sampling regime, and how this affects statistical inferences. 2. We propose a new procedure, based on a variance components analysis using generalized mixed effects models to examine how estimates vary with sampling regime. 3. To demonstrate the method we analyse data from one study of 32 individually marked roe deer and another study of 21 individually marked kestrels. We subsampled these data to simulate increasingly less intense sampling regimes, and compared the performance of two kernel density estimation (KDE) methods, of the minimum convex polygon (MCP) and of the bivariate ellipse methods. 4. Variation between individuals and study areas contributed most to the total variance in home range size. Contrary to recent concerns over reliability, both KDE methods were remarkably efficient, robust and unbiased: 10 fixes per month, if collected over a standardized number of days, were sufficient for accurate estimates of home range size. However, the commonly used 95% isopleth should be avoided; we recommend using isopleths between 90 and 50%. 5. Using the same number of fixes does not guarantee unbiased home range estimates: statistical inferences differ with the number of days sampled, even if using KDE methods. 6. The MCP method was highly inefficient and results were subject to considerable and unpredictable biases. The bivariate ellipse was not the most reliable method at low sample sizes. 7. We conclude that effort should be directed at marking more individuals monitored over long periods at the expense of the sampling rate per individual. Statistical results are reliable only if the whole sampling regime is standardized. We derive practical guidelines for field studies and data analysis. [ABSTRACT FROM AUTHOR]

1. Time and energy are key currencies in animal ecology, and judicious management of these is a primary focus for natural selection. At present, however, there are only two main methods for estimation of rate of energy expenditure in the field, heart rate and doubly labelled water, both of which have been used with success; but both also have their limitations. 2. The deployment of data loggers that measure acceleration is emerging as a powerful tool for quantifying the behaviour of free-living animals. Given that animal movement requires the use of energy, the accelerometry technique potentially has application in the quantification of rate of energy expenditure during activity. 3. In the present study, we test the hypothesis that acceleration can serve as a proxy for rate of energy expenditure in free-living animals. We measured rate of energy expenditure as rates of O2 consumption ( ) and CO2 production ( ) in great cormorants ( Phalacrocorax carbo) at rest and during pedestrian exercise. and were then related to overall dynamic body acceleration (ODBA) measured with an externally attached three-axis accelerometer. 4. Both and were significantly positively associated with ODBA in great cormorants. This suggests that accelerometric measurements of ODBA can be used to estimate and and, with some additional assumptions regarding metabolic substrate use and the energy equivalence of O2 and CO2, that ODBA can be used to estimate the activity specific rate of energy expenditure of free-living cormorants. 5. To verify that the approach identifies expected trends in from situations with variable power requirements, we measured ODBA in free-living imperial cormorants ( Phalacrocorax atriceps) during foraging trips. We compared ODBA during return and outward foraging flights, when birds are expected to be laden and not laden with captured fish, respectively. We also examined changes in ODBA during the descent phase of diving, when power requirements are predicted to decrease with depth due to changes in buoyancy associated with compression of plumage and respiratory air. 6. In free-living imperial cormorants, ODBA, and hence estimated , was higher during the return flight of a foraging bout, and decreased with depth during the descent phase of a dive, supporting the use of accelerometry for the determination of activity-specific rate of energy expenditure. [ABSTRACT FROM AUTHOR]

1. Data from a long-term study of Papio hamadryas ursinus (L.) in the De Hoop Nature Reserve, Western Cape, South Africa, were used to test the assumptions and predictions of Altmann's model of maternal time budgets. 2. Female baboons’ feeding time was below model predictions, and there was no evidence for a consistent increase in feeding time with infant age. In addition, female feeding time was not significantly higher than observed baseline feeding times for nonlactating females. 3. Female baboons reduced activity levels in the first few months post-partum, as reflected in significant increases in resting time, and there was some indication that females lost body mass over the course of lactation. When feeding demand was high, females sacrificed social time, and conserved resting time. 4. Females increased vigilance levels during the first 4 months of infant life and were more vigilant overall during lactation than when nonlactating. There was a negative relationship between feeding time and vigilance, but a positive relationship between resting time and vigilance. 5. Female baboons at De Hoop appear to cope with the energetic costs of lactation by reducing activity levels, although this cannot compensate completely for increased energetic costs. This may not be so much an ‘energy-sparing’ strategy as a response to threats presented by infanticidal males in this population. Females therefore trade-off feeding time against vigilance. [ABSTRACT FROM AUTHOR]

1. Ecosystem alterations can affect the abundance, distribution and diversity of plants and animals, and thus potentially change the relative strength of bottom-up (the plant resource) and top-down (natural enemies) trophic forces acting on herbivore populations. 2. The hypothesis that alterations of the forest ecosystem associated with precommercial thinning have contributed to the increased severity of outbreaks of Neodiprion abietis (Harris), a sawfly defoliator, through the reduction of trophic forces acting on N. abietis larvae, was tested using exclusion techniques. 3. The relative contributions to N. abietis larval mortality of bottom-up and top-down forces both increased with increasing levels of defoliation and were both reduced by thinning. The reduction of bottom-up and top-down forces caused a 58% mean increase in N. abietis larval survival in thinned compared with untreated stands, which is less than would be expected by the sum of the effects of thinning on each source of mortality. Evidence indicates that the partly compensatory, partly additive nature of the mortality associated with trophic forces in the system under study is responsible for this discrepancy. 4. To our knowledge, this is the first study to show the impact of ecosystem alterations on the balance between bottom-up and top-down forces acting on an eruptive herbivore population along a gradient of host-plant defoliation, and how this can lead to increased outbreak severity. It is stressed that accurate estimates of the relative contributions of bottom-up and top-down forces to mortality cannot be obtained if the additive or compensatory nature of the mortality associated with these trophic forces is overlooked. [ABSTRACT FROM AUTHOR]

1. Using data on breeding birds from a 35-year study of Florida scrub-jays Aphelocoma coerulescens (Bosc 1795), we show that survival probabilities are structured by age, birth cohort, and maternal family, but not by sex. Using both accelerated failure time (AFT) and Cox proportional hazard models, the data are best described by models incorporating variation among birth cohorts and greater mortality hazard with increasing age. AFT models using Weibull distributions with the shape parameter > 1 were always the best-fitting models. 2. Shared frailty models allowing for family structure greatly reduce model deviance. The best-fitting models included a term for frailty shared by maternal families. 3. To ask how long a data set must be to reach qualitatively the same conclusions, we repeated the analyses for all possible truncated data sets of 2 years in length or greater. Length of the data set affects the parameter estimates, but not the qualitative conclusions. In all but three of 337 truncated data sets the best-fitting models pointed to same conclusions as the full data set. Shared frailty models appear to be quite robust. 4. The data are not adequate for testing hypotheses as to whether variation in frailty is heritable. 5. Substantial structured heterogeneity for survival exists in this population. Such structured heterogeneity has been shown to have substantial effects in reducing demographic stochasticity. [ABSTRACT FROM AUTHOR]

1. Functional response models (e.g. Holling's disc equation) that do not take the spatial distributions of prey and predators into account are likely to produce biased estimates of predation rates. 2. To investigate the consequences of ignoring prey distribution and predator aggregation, a general analytical model of a predator population occupying a patchy environment with a single species of prey is developed. 3. The model includes the density and the spatial distribution of the prey population, the aggregative response of the predators and their mutual interference. 4. The model provides explicit solutions to a number of scenarios that can be independently combined: the prey has an even, random or clumped distribution, and the predators show a convex, sigmoid, linear or no aggregative response. 5. The model is parameterized with data from an acarine predator–prey system consisting of Phytoseiulus persimis and Tetranychus urticae inhabiting greenhouse cucumbers. 6. The model fits empirical data quite well and much better than if prey and predators were assumed to be evenly distributed among patches, or if the predators were distributed independently of the prey. 7. The analyses show that if the predators do not show an aggregative response it will always be an advantage to the prey to adopt a patchy distribution. On the other hand, if the predators are capable of responding to the distribution of prey, then it will be an advantage to the prey to be evenly distributed when its density is low and switch to a more patchy distribution when its density increases. The effect of mutual interference is negligible unless predator density is very high. 8. The model shows that prey patchiness and predator aggregation in combination can change the functional response at the population level from type II to type III, indicating that these factors may contribute to stabilization of predator–prey dynamics. [ABSTRACT FROM AUTHOR]

1. Growth models for body mass and length were fitted to data collected from 1842 sea otters Enhydra lutris shot or live-captured throughout south-west Alaska between 1967 and 2004. Growth curves were constructed for each of two main year groups: 1967–71 when the population was at or near carrying capacity and 1992–97 when the population was in steep decline. Analyses of data collected from animals caught during 2004, when the population density was very low, were precluded by a small sample size and consequently only examined incidentally to the main growth curves. 2. Growth curves demonstrated a significant increase in body mass and body length at age in the 1990s. Asymptotic values of body mass were 12–18% higher in the 1990s than in the 1960s/70s, and asymptotic values for body length were 10–11% higher between the same periods. Data collected in 2004 suggest a continued increase in body size, with nearly all data points for mass and length falling significantly above the 1990s growth curves. 3. In addition to larger asymptotic values for mass and length, the rate of growth towards asymptotic values was more rapid in the 1990s than in the 1960s/70s: sea otters reached 95% of asymptotic body mass and body length 1–2 years earlier in the 1990s. 4. Body condition (as measured by the log mass/log length ratio) was significantly greater in males than in females. There was also an increasing trend from the 1960s/70s through 2004 despite much year-to-year variation. 5. Population age structures differed significantly between the 1960s/70s and the 1990s with the latter distribution skewed toward younger age classes (indicating an altered lx function) suggesting almost complete relaxation of age-dependent mortality patterns (i.e. those typical of food-limited populations). 6. This study spanned a period of time over which the population status of sea otters in the Aleutian archipelago declined precipitously from levels at or near equilibrium densities at some islands in the 1960s/70s to < 5% of estimated carrying capacity by the late 1990s. The results of this study indicate an improved overall health of sea otters over the period of decline and suggest that limited nutritional resources were not the cause of the observed reduced population abundance. Our findings are consistent with the hypothesis that the decline was caused by increased killer whale predation. [ABSTRACT FROM AUTHOR]

1. Size variation is a ubiquitous feature of animal populations and is predicted to strongly influence species abundance and dynamics; however, the factors that determine size variation are not well understood. 2. In a mesocosm experiment, we found that the relationship between mean and variation in wood frog ( Rana sylvatica) tadpole size is qualitatively different at different levels of competition created by manipulating resource supply rates or tadpole density. At low competition, relative size variation (as measured by the coefficient of variation) decreased as a function of mean size, while at high competition, relative size variation increased. Therefore, increased competition magnified differences in individual performance as measured by growth rate. 3. A model was developed to estimate the contribution of size-dependent factors (i.e. based on size alone) and size-independent factors (i.e. resulting from persistent inherent phenotypic differences other than size that affect growth) on the empirical patterns. 4. Model analysis of the low competition treatment indicated that size-dependent factors alone can describe the relationship between mean size and size variation. To fit the data, the size scaling exponent that describes the dependence of growth rate on size was determined. The estimated value, 0·83, is in the range of that derived from physiological studies. 5. At high competition, the model analysis indicated that individual differences in foraging ability, either size-based or due to inherent phenotypic differences (size-independent factors), were much more pronounced than at low competition. The model was used to quantify the changes in size-dependent or size-independent factors that underlie the effect of competition on size-variation. In contrast to results at low competition, parameters derived from physiological studies could not be used to describe the observed relationships. 6. Our experimental and model results elucidate the role of size-dependent and size-independent factors in the development of size variation, and highlight and quantify the context dependence of individual (intrapopulation) differences in competitive abilities. [ABSTRACT FROM AUTHOR]

1. Attempts to identify the prevalence and nature of density dependence in ecological populations have often used statistical analysis of ecological time-series of population counts. Such time-series are also being used increasingly to parameterize models that may be used in population management. 2. If time-series contain measurement errors, tests that rely on detecting a negative relationship between log population change and population size are biased and prone to spuriously detecting density dependence (Type I error). This is because the measurement error in density for a given year appears in the corresponding change in population density, with equal magnitude but opposite sign. 3. This effect introduces bias that may invalidate comparisons of ecological data with density-independent time-series. Unless census error can be accounted for, time-series may appear to show strongly density-dependent dynamics, even though the density-dependent signal may in reality be weak or absent. 4. We distinguish two forms of measurement error, both of which have serious consequences for detecting density dependence. 5. First, estimates of population density are based rarely on exact counts, but on samples. Hence there exists sampling error, with the level of error depending on the method employed and the number of replicates on which the population estimate is based. 6. Secondly, the group of organisms measured is often not a truly self-contained population, but part of a wider ecological population, defined in terms of location or behaviour. Consequently, the subpopulation studied may effectively be a sample of the population and spurious density dependence may be detected in the dynamics of a single subpopulation. In this case, density dependence is detected erroneously, even if numbers within the subpopulation are censused without measurement error. 7. In order to illustrate how process variation and measurement error may be distinguished we review data sets (counts of numbers of birds by single observers) for which both census error and long-term variance in population density can be estimated. 8. Tests for density dependence need to obviate the problem that measured population sizes are typically estimates rather than exact counts. It is possible that in some cases it may be possible to test for density dependence in the presence of unknown levels of census error, for example by uncovering nonlinearities in the density response. However, it seems likely that these may lack power compared with analyses that are able to explicitly include census error and we review some recently developed methods. [ABSTRACT FROM AUTHOR]

1. Communities of competing sessile organisms are often modelled using Markov chains. Sensitivity analysis of the stationary distribution of these models tells us how we expect the abundance of each organism to respond to changes in interactions between species. This is important for conservation and management. 2. Markov models for such communities have usually been formulated in discrete time. Each column of the discrete-time transition matrix must sum to 1 (column stochasticity). Sensitivity analysis therefore involves defining a pattern of compensation that maintains column stochasticity as a single transition probability changes. There is little biological theory about the appropriate compensation pattern, but the usual choices involve changing only the elements of a single column of the transition matrix. 3. I argue that if the underlying dynamics occur in continuous time, each transition probability is the net outcome of direct and many indirect interactions. 4. Determining the consequences of changing a single direct interaction will often be of interest. I show how this can be achieved using a continuous-time model. The resulting discrete-time compensation pattern is quite different from those that have been considered elsewhere, with changes occurring in many columns. 5. I also show how to determine which direct interactions are being changed under any discrete-time compensation pattern. [ABSTRACT FROM AUTHOR]