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Understanding species-environment relationships at large spatial scales is required for the prioritization of conservation areas and the preservation of landscape connectivity for large carnivores. This endeavour is challenging for jaguars (Panthera onca), given their elusiveness, and the local nature of most jaguar studies, precluding extrapolation to larger areas. We developed an occupancy model using occurrence data of jaguars across five countries of Central America, collected from camera-trap studies of 2–12 months' duration, deployed over an area of 14 112 km 2 from 2005 to 2018. Our occupancy model showed that habitat use of jaguars increased with primary net productivity and distance to human settlements, and distance to rivers. Detection of the species was related to survey effort and research team identity. Within the jaguar extent of occurrence, 73% was deemed suitable for the species, with 47% of it lying within Jaguar Conservation Units (JCU) and 59% of JCU land being legally protected. Suitable areas were divided into four distinct clusters of continuous habitat shared across country borders. However, large areas of predicted low habitat suitability may constrict connectivity in the region. The reliability of these spatial predictions is indicated by the model validation using an independent dataset (AUC = 0.82; sensitivity = 0.766, specificity = 0.761), and concordance of our results with other studies conducted in the region. Across Central America, we found that human influence has the strongest impact on jaguar habitat use and JCUs are the main reservoirs of habitat. Therefore, conservation actions must focus on preventing habitat loss and mitigating human pressure, particularly within the clusters of continuous areas of high suitability, and on restoring habitat to foster connectivity. The long-term persistence of jaguars in the region will depend on strong international cooperation that secures jaguar populations and their habitat across Central American borders.

We estimated jaguar density and tenure, and investigated ranging behavior, using camera traps across the Maya Forest Corridor, a human-influenced landscape in central Belize that forms the only remaining connection for jaguar populations inhabiting two regional forest blocks: the Selva Maya and the Maya Mountain Massif. Jaguars were ubiquitous across the study area. Similar to the neighboring Selva Maya, mean density ranged from 1.5 to 3.1 jaguars per 100 km2, estimated by spatial capture-recapture models. Cameras detected almost twice as many males as females, probably reflecting detection bias, and males ranged more widely than females within the camera grid. Both sexes crossed two major rivers, while highway crossings were rare and male-biased, raising concern that the highway could prevent female movement if traffic increases. Jaguars were more transient where the landscape was fragmented with settlements and agriculture than in contiguous forest. Compared with jaguars in the protected forests of the Maya Mountains, jaguars in central Belize displayed a lower potential for investment in intraspecific communication, indicative of a lower quality landscape; however, we did detect mating behavior and juveniles. Tenure of individuals was shorter than in the protected forests, with a higher turnover rate for males than females. At least three-quarters of reported jaguar deaths caused by people were male jaguars, and the majority was retaliation for livestock predation. Jaguars seem relatively tolerant to the human-influenced landscape of central Belize. However, intensification of game hunting and lethal control of predators would threaten population persistence, while increased highway traffic and clear-cutting riparian forest would severely limit the corridor function. Our results show that the viability of the corridor, and thus the long-term survival of jaguar populations in this region, will depend on appropriate land-use planning, nonlethal control of livestock predators, enforcement of game hunting regulations, and wildlife-friendly features in future road developments.

We estimated jaguar density and tenure, and investigated ranging behavior, using camera traps across the Maya Forest Corridor, a human-influenced landscape in central Belize that forms the only remaining connection for jaguar populations inhabiting two regional forest blocks: the Selva Maya and the Maya Mountain Massif. Jaguars were ubiquitous across the study area. Similar to the neighboring Selva Maya, mean density ranged from 1.5 to 3.1 jaguars per 100 km2, estimated by spatial capture-recapture models. Cameras detected almost twice as many males as females, probably reflecting detection bias, and males ranged more widely than females within the camera grid. Both sexes crossed two major rivers, while highway crossings were rare and male-biased, raising concern that the highway could prevent female movement if traffic increases. Jaguars were more transient where the landscape was fragmented with settlements and agriculture than in contiguous forest. Compared with jaguars in the protected forests of the Maya Mountains, jaguars in central Belize displayed a lower potential for investment in intraspecific communication, indicative of a lower quality landscape; however, we did detect mating behavior and juveniles. Tenure of individuals was shorter than in the protected forests, with a higher turnover rate for males than females. At least three-quarters of reported jaguar deaths caused by people were male jaguars, and the majority was retaliation for livestock predation. Jaguars seem relatively tolerant to the human-influenced landscape of central Belize. However, intensification of game hunting and lethal control of predators would threaten population persistence, while increased highway traffic and clear-cutting riparian forest would severely limit the corridor function. Our results show that the viability of the corridor, and thus the long-term survival of jaguar populations in this region, will depend on appropriate land-use planning, nonlethal control of livestock predators, enforcement of game hunting regulations, and wildlife-friendly features in future road developments.

Exploitation of key consumers can have major consequences for community and ecosystem functioning. Limpets are key grazers exploited in regions such as Macaronesia, southern Africa, Chile and California. Here we describe a field experiment designed to simulate human exploitation of British limpets that are unexploited and used as model populations. Our aim was to evaluate the effects of size-selective harvesting on the composition of the rocky shore community of non-target species. Limpet populations were subjected to simulated exploitation of large size classes for 18 mo at 2 locations in the southwest of England, by systematic removal at 2 different intensities: low and high exploitation compared with unexploited plots. The exploitation of limpets led to establishment of Fucus spp. to differing degrees at each location, but while variation in percentage cover of Fucus spp. decreased over the course of the experiment in unmanipulated control plots, it increased in plots with either low or high exploitation. Multivariate analyses showed that communities at the 2 locations responded differently to the same intensity of exploitation: unmanipulated controls were similar to low-exploitation treatments at Constantine, while at Trevone low-exploitation treatments were similar to high-exploitation treatments. This was mainly due to increases in percentage cover of F. vesiculosus var. evesiculosus with exploitation, indicating that site-specific differences in assemblage structure and the size structure of the harvested populations will determine its assemblage-level responses. Therefore, reductions in density of grazers may have divergent consequences for different rocky shore communities.

Agent-based models can predict system-level properties of populations from stochastic simulation of fine-scale movements. One important application to conservation lies in their ability to consider the impact of individual variation in movement and decision-making on populations under future landscape changes. Here, we present a spatially explicit agent-based simulation of a population of jaguars (Panthera onca) in a mixed forest and farmland landscape in Central America that demonstrates an application of least-cost modelling, a description of the way that agents move through their environment, to equilibrium population dynamics. We detail the construction and application of the model, and the processes of calibration, sensitivity analysis and validation with empirical field data. Simulated jaguars underwent feeding, reproduction, and mortality events typical of natural populations, resulting in realistic population dynamics and home range sizes. Jaguar agents located inside protected forest reserves exhibited higher fitness (fecundity, energy reserves, age and age of mortality) as well as lower energy- and habitat-related mortality than jaguar agents located outside these reserves. Changes in fecundity directly affected the dynamics of simulated populations to a larger degree than either mortality or agent–agent interactions. Model validation showed similar patterns to camera traps in the field, in terms of landscape utilisation and the spatial distribution of individuals. The model showed less sensitivity to socially motivated and fine-scale movements, apart from those directed towards feeding and reproduction, but reflected the interactions and movement of naturally occurring populations in this region. Applications of the model will include testing impacts on population dynamics of likely future changes in landscape structure and connectivity.

Sex change, or sequential hermaphroditism, occurs in the plant and animal kingdoms and often determines a predominance of the first sex. Our aim was to explore changes in sex ratios within the range of the species studied:Patella vulgataandPatella depressa. The broad-scale survey of sex with size of limpets covered a range of latitudes from Zambujeira do Mar (southern Portugal) to the English Channel. Indirect evidence was found for the occurrence of protandry inP. vulgatapopulations from the south of England, with females predominating in larger size-classes; cumulative frequency distributions of males and females were different; sex ratios were biased towards males and smallest sizes of males were smaller than the smallest sizes of females. In contrast in Portugal females were found in most size-classes ofP. vulgata. InP. depressapopulations from the south coast of England and Portugal females were interspersed across most size-classes; size distributions of males and females and size at first maturity of males and females did not differ.P. depressadid, however, show some indications of the possibility of slight protandry occurring in Portugal. The test of sex ratio variation with latitude indicated thatP. vulgatasex ratios might be involved in determining the species range limit, particularly at the equatorward limit since the likelihood of being male decreased from the south coast of England to southern Portugal. Thus at the southern range limit, sperm could be in short supply due to scarcity of males contributing to an Allee effect.

Millions of people throughout the tropics consume wild meat. Overhunting reduces food security for people and large predators, yet little is known of the impact of hunting in systems where people and predators target the same prey species. We collate published data on predator diet in Belize with interview data about the consumption of wild and domestic meat by Belizeans, to compare the wild-meat diets of humans, jaguarsPanthera oncaand pumasPuma concolorand assess the sustainability of the combined offtake by humans and jaguars. Six wild mammal species (nine-banded armadilloDasypus novemcinctus, pacaCuniculus paca, collared peccaryPecari tajacu, white-lipped peccaryTayassu pecari, red brocket deerMazama americanaand white-tailed deerOdocoileus virginianus) comprised 7% of the animal-protein meals eaten by Belizeans. Overall, 80% of these meals were eaten by 20% of interviewees, suggesting a necessary role of wild meat for the minority. The same species were found in 69 and 86% of jaguar and puma scats, respectively. We estimate a national annual harvest of c. 4,000 tonnes of these six wild mammals by humans and jaguars, of which 78% is hunted by people. Sustainability is difficult to evaluate because prey population data are lacking in Belize. However, simple models suggest that a sustainable harvest at this rate would require higher prey population densities than averages recorded in hunted Neotropical forests. We emphasize the need for robust regional estimates of game species densities, to improve assessments of sustainability and inform hunting regulations. We recommend that the requirements of predators as well as those of people be considered when assessing wild meat harvests.

Activity patterns of top predators are adapted for efficient predation, whereas their prey must contend with the conflicting demands of acquiring resources and avoiding predators. Here we analyse the activity of jaguars (Panthera onca) and pumas (Puma concolor) in relation to their most important prey species, armadillos (Dasypus novemcinctus) and pacas (Agouti paca) respectively, in the Cockscomb Basin Wildlife Sanctuary, Belize using large-scale camera-trap data. Jaguars and pumas have similar 24 h activity patterns as armadillos and pacas, both burrow-dwelling species, and negligible overlap with less frequently consumed prey species such as red brocket deer (Mazama americana) and peccaries. Activity of armadillos and pacas varied with moon phase, with reduced activity during periods of brighter illumination, perhaps as a predator-avoidance strategy. Across the study area, moon phase had no overall influence on jaguar and puma activity; however at locations associated with armadillos, jaguar activity declined with brighter illumination, perhaps indicating a shift to alternative prey during full moon when armadillos avoided foraging above ground. No such relationship was found for pumas and moon phase at locations associated with pacas.

Little is known about the long-term consequences of grazing effects on microphytes. This study tested for density-dependent responses to grazer removal on the biomass (Chlorophyll a: ‘Chla’) and composition of natural high rocky-shore biofilms over a 7-month period. Gastropod snails Melarhaphe neritoides graze entirely within circular halos generated in biofilms surrounding their refuges. The experiment crossed 3 levels of original snail density per halo with 3 levels of grazing intensity (generated by 100%, 50% and 0% snail removal). Areas inside halos from which all snails had been removed sustained significantly higher Chla than never-grazed control areas outside the halos. This effect of grazing history was still present after 7 months, suggesting that past grazing had an enduring positive influence on biofilm biomass. Against expectation, Chla-biomass was not increased by removing snails, regardless of original grazer density. Half- and fully-grazed halos peaked to a higher Chla than ungrazed halos in spring. Grazing did not affect the presence of major biofilm taxonomic groups, although it did alter their relative contributions. Never-grazed areas were covered by thick biofilm detritus and had proportionally more filamentous cyanobacteria than grazed areas, which sustained abundant clusters of coccoid cyanobacteria and lichen within micro-pits inaccessible to snail radulae. The study shows that effects of grazing history are not exclusive to macrophytic systems. Grazers boosted the concentration of micro-autotrophs relative to non-Chla biofilm constituents, probably by removing an unproductive biofilm canopy and facilitating light and nutrient penetration for new growth.

Jaguars Panthera onca coexist with pumas Puma concolor across their entire range. In areas where they occur together their coexistence may be facilitated by differences in diet. This study compared food habits of jaguars and pumas in Belize, Central America, across a protected lowland rainforest and the neighbouring human-influenced landscape. Diets were determined from 362 jaguar scats and 135 puma scats, identified by genetic analysis. In the protected forest, dietary breadths were low for jaguars and pumas and showed little overlap. In this habitat each relied heavily on a single medium-sized (5–10 kg) prey species: armadillos Dasypus novemcinctus for jaguars, and pacas Agouti paca for pumas. Both cats also took larger prey (>10 kg), mainly white-lipped peccaries Tayassu pecari by jaguars and red brocket deer Mazama americana by pumas. In unprotected fragmented lands, jaguar scats rarely contained large wild prey species; rather, a diet of relatively small wild prey was supplemented with larger domestic species. Pumas did not take domestic species and were scarce outside the protected forest, possibly indicating competition with humans for pacas and deer, which are also prized game species in the region. This study is the largest analysis to date of sympatric jaguar and puma diets in both forest and farmland. We suggest that jaguar predation on cattle may be reduced by ensuring that game hunting is sustainable and potentially by augmenting forests within the human matrix with large wild ungulates. The supplementation could benefit both of the cat species, and the local game hunting economy.

Understanding the functional significance of shelter for animal populations requires knowledge of the behavioural mechanisms that govern the dynamics of shelter use. Exploitation of shelters may be impeded by mutual interference, yet interference competition can be difficult to distinguish from exploitation competition. We used bullheads (Cottus gobio) as a model system of mobile fish to investigate the effect of intraspecific competition on shelter use. A series of field experiments was conducted under controlled conditions of shelter availability and population density. For each experiment, the location of each individual fish was observed over a period of 10 days. We then constructed a continuous-time Markov-chain model for the movement of fish between shelters and the open stream, which explicitly parameterised exploitation competition and interference competition for shelter and which accounted for two different size-classes of fish. By using a stochastic rather than a deterministic model, we were able to account for the distribution of fish across shelters, and not just the average occupation. Analysis of the model showed strong evidence of exploitation competition, which was highly dependent on body size, and an increased departure rate from shared shelters. Over and above exploitation, interference competition limited the ability of unsheltered fish to colonise vacant shelters at high population densities. Different formulations of the interference competition were compared using the Akaike Information Criterion. The formulation that best fitted the observations modelled interference competition as an increasing function of average shelter occupancy rather than population density per se.

An electrofishing survey of daytime shelter microhabitat use of bullhead Cottus gobio in a southern English chalk stream revealed positive selection for moderate water velocity, vegetation cover and coarse substrata. Water depth, other forms of cover, shade and substratum embeddedness had no significant influence on the distribution of fish. Microhabitat use was size-dependent, with patches occupied by adult fish containing coarser substrata and less blanket weed (Cladophora algae) than those occupied by smaller juvenile conspecifics. Differences in substratum use between size-classes were less pronounced in parts of the stream shaded by the tree canopy. In laboratory tanks stocked at low fish density, both juveniles and adults favoured use of cobbles over pebbles. The response of fish to increased conspecific density was size-dependent; juveniles reduced use of the coarse substratum whereas adults maintained their predominance in this habitat. An apparently greater shift by juveniles when in the presence of adults was significant at a alpha = 0.10 only, as was an apparent reduction in interactions between size-classes under low light intensity. The displacement of small juvenile fish from the preferred cobble substratum is consistent with the hypothesis that intraspecific competition contributes to the size-related microhabitat shift observed in the field. Although there was a tendency for the strength of competition to be reduced at low light levels, the mechanism by which tree canopy cover affects microhabitat use remains uncertain.

Ecological theory predicts that genetic variation produced by sexual reproduction results in niche diversification and provides a competitive advantage both to facilitate invasion into genetically uniform asexual populations and to withstand invasion by asexual competitors. We tested the hypothesis that a large group of diverse clones of Daphnia obtusa has greater competitive advantage when invading into genetically uniform populations of this species than a smaller group with inherently less genetic diversity. We compared competitive outcomes to those of genetically uniform groups of small and large size invading into genetically diverse populations. Genetically diverse invaders of initially large group size increased their representation by more than those of initially small size; in contrast, genetically uniform invaders of initially large group size diminished on average by more than those of initially small size. These results demonstrate an advantage to the genetic variation produced by sexual reproduction, both in invasion and resisting invasion, which we attribute to competitive release experienced by individuals in genetically diverse populations.

The frozen niche variation hypothesis proposes that asexual clones exploit a fraction of a total resource niche available to the sexual population from which they arise. Differences in niche breadth may allow a period of coexistence between a sexual population and the faster reproducing asexual clones. Here, we model the longer term threat to the persistence of the sexual population from an accumulation of clonal diversity, balanced by the cost to the asexual population resulting from a faster rate of accumulation of deleterious mutations. We use Monte-Carlo simulations to quantify the interaction of niche breadth with accumulating deleterious mutations. These two mechanisms may act synergistically to prevent the extinction of the sexual population, given: (1) sufficient genetic variation, and consequently niche breadth, in the sexual population; (2) a relatively slow rate of accumulation of genetic diversity in the clonal population; (3) synergistic epistasis in the accumulation of deleterious mutations.

1. Movements of hedgehogs, Erinaceus europaeus L., were analysed in relation to roads by recording their nocturnal foraging trajectories in urban areas adjacent to major road systems. Four male and four female hedgehogs at each of two sites were each tracked over five replicate trajectories of more than 3 h, using radio-telemetry and direct observation. 2. Frequency of road crossings and use of habitat were compared to simulated random trajectories. For each observed trajectory, 100 trajectories were simulated with the same distribution of speeds as observed, but with random direction. 3. Observed trajectories had lower rates of crossing large but not small roads than simulated, indicating that hedgehogs treat large roads as barriers during nightly foraging activities. Most hedgehogs were never observed to cross roads, whereas almost all simulated trajectories did cross both large and small roads. 4. Crossing behaviour differed by site, but not by sex. 5. Roads and road verges had the lowest rank in a habitat preference analysis at both sites, while playing fields, gardens and urban areas were preferred habitats. These results are discussed in relation to the regional scale preference for urban areas, and the attraction to road verges while dispersing, shown by hedgehogs.

Levins’ model of metapopulation dynamics is modified to incorporate variable degrees of density dependence in the per capita exploitation of resource patches. We demonstrate a simple means of testing for this density dependence in a sample of metapopulations, each at its equilibrium balance of local colonization to extinction. The fraction of habitable unoccupied patches equilibrates to a constant number under the null model of density independent colonization, and to a constant proportion under strong density dependence. We compare the null model to two density dependent alternatives, using data on exploitation of nest boxes by collared flycatchers Ficedula albicollis. The analysis shows how predicted trends in the equilibrium unoccupied fraction are similar for both spatial interference and net immigration. This needs to be recognized, since the null hypothesis of a constant unused resource applies also to the dynamics of consumable resources, where it is expressed in a constant stock of uneaten prey at the dynamic equilibrium of predators to prey.

The activity patterns of red foxes (Vulpes vulpes L.) living and breeding in urban areas of Oxford, and the interactions between individuals, were analysed from detailed radio-tracking data on 17 adults. Foxes were nocturnal and active during the night for a mean of 6h 52min min, irrespective of the time of year. The number of active/resting periods increased in autumn and winter, and in winter and spring the night was characteristically divided into several short cycles of activity of 2–2 1/2 h each, interspersed with similar periods of rest. The foxes occupied mutually exclusive group ranges and group members remained within 50m of each other for up to one-third of the time spent active at night. The implications of fox spatial relationships for rabies transmission are discussed.

The diet of red foxes ( Vulpes vulpes ) inhabiting the city of Oxford, England, was analyzed from 1,939 feces collected October 1980–February 1984. The dry weight of undigested remains comprised scavenged food (37%), earthworms ( Lumbricus terrestris , 27%), mammals (16%), fruits (9%), birds (8%), other invertebrates (2%), and domestic stock (1%). No single category of food occurred in more than 50% of the samples. Eighty-one types of food were indentified, including five orders of birds, 14 species of small mammals, and 14 species of fruits. The composition of the diet varied monthly and seasonally. Small mammals peaked in late winter, lagomorphs in April, and birds in June; fruits constituted a large proportion of the diet in autumn. Occurrence in feces of fruits, Passeriformes, Coleoptera, and invertebrate larvae correlated strongly with seasonal variations in indices of the abundance of these prey, suggesting that they were taken in proportion to their availability. Columbiformes, lagomorphs, and rodents showed no such direct relationship, indicating that foxes selected for or against these foods in some way not directly related to their abundances as censused.

Population dynamics of the coypu, Myocastor coypus, were studied in central-West France. This species has recently colonized temperate regions despite physiological sensitivity to cold weather. Live-trapping over three years demonstrated that increasing population densities from summer into autumn were associated with a faster population turn-over, homogeneous dispersion, and reduced rates of weight gain. Densities fell by 71% over a cold winter in which canals froze for 20 consecutive days, and by 69% over a mild winter with a flood of 5 weeks duration. Mortality was high in the coldest weather, and 45% of those surviving had frost lesions. A scarcity of males after the cold winter (up to 1♂: 3.3♀) was matched in a nearby population at artificially low density, where dispersing males predominated after the flood. The effect of the cold winter on reproductive output was to synchronize littering in summer, at a time of rich food supply. It was concluded that a flexible response to winter conditions enabled coypus to minimize the effects of extreme events and maximize their colonizing potential.

The frozen niche variation hypothesis proposes that asexual clones exploit a fraction of a total resource niche available to the sexual population from which they arise. Differences in niche breadth may allow a period of coexistence between a sexual population and the faster reproducing asexual clones. Here, we model the longer term threat to the persistence of the sexual population from an accumulation of clonal diversity, balanced by the cost to the asexual population resulting from a faster rate of accumulation of deleterious mutations. We use Monte-Carlo simulations to quantify the interaction of niche breadth with accumulating deleterious mutations. These two mechanisms may act synergistically to prevent the extinction of the sexual population, given: (1) sufficient genetic variation, and consequently niche breadth, in the sexual population; (2) a relatively slow rate of accumulation of genetic diversity in the clonal population; (3) synergistic epistasis in the accumulation of deleterious mutations.

Why sex prevails in nature remains one of the great puzzles of evolution. Sexual reproduction has an immediate cost relative to asexual reproduction, as males only express their contribution to population growth through females. With no males to sustain, an asexual mutant can double its relative representation in the population in successive generations. This is the widely accepted 'twofold cost of males'. Many studies have attempted to explain how sex can recoup this cost from fitness benefits associated with the recombination of parental genotypes, but these require complex biological environments that cycle over evolutionary timescales. In contrast, we have considered the ecological dynamics that govern asexual invasion. Here we show the existence of a threshold growth rate for the sexual population, above which the invasion is halted by intraspecific competition. The asexual population then exerts a weaker inhibitory effect on the carrying capacity of the sexual population than on its own carrying capacity. The stable outcome of this is coexistence on a depleted resource base. Under these ecological circumstances, longer-term benefits of sex may eventually drive out the asexual competitor.

Blackwell and Macdonald (2000) have re-analysed models by Doncaster and Woodroffe (1993) for badger territory configurations, and drawn opposite conclusions in suggesting that sett locations are not the crucial factor in determining territory shapes and sizes. Doncaster and Woodroffe had constructed Dirichlet tessellations around badger main setts and compared their borders with the locations of actual border latrines. A close correspondence at some sites provided direct evidence that territory size and configuration could be determined solely from the locations of main setts. In contrast, Blackwell and Macdonald use the latrine locations to define Dirichlet tessellations, in order to compare the centres of these modelled territories to actual sett locations. Their method employs statistical techniques that avoid some complications in the way the original model was compared to alternatives. However, because their analysis pre-determines the size and shape of territories from latrine sites, it cannot test hypotheses about factors regulating size and shape. In this respect their conclusions overinterpret the analysis, which can only test the hypothesis that Dirichlet centres associate with sett locations. Here I describe two consequences of this limitation. Firstly, any test of an exact coincidence between Dirichlet centres and setts is necessarily sensitive to underlying structure in the mosaic of habitats across which border latrines are situated, and to missing data on latrine sites. These influences can explain the observed displacement of centres from setts reported by Blackwell and Macdonald. Secondly, alternative tests of non-random association between centres and setts can provide indirect evidence for a role in territory configuration of some single point feature at least in the vicinity of the sett, if not the sett itself. A simple test of this sort indeed confirms a strong pairing of centres with setts at two out of three study sites.

Potential competitors that eat each other can engender patterns of spatial segregation similar to those produced by competition, and distinguishable only by field manipulation. This paper reports the results of a perturbation experiment to test the factors responsible for small-scale discontinuities in the distribution of a common insectivore. Populations of hedgehogs (Erinaceus europaeus) were monitored following their introductions into an area where they had been absent, and into a neighbouring area where they were known to persist. The two sites had a similar availability of preferred habitat, and the growth rates of introduced hedgehogs were similar. The density of badgers (Meles meles), larger members of the same guild, appears to produce differences in mortality and dispersal, which returned the populations close to their original levels within 2 months of the transplant.

Coypus (Myocastor coypus Molina) have recently colonized temperate regions of Europe in large numbers, originating from populations indigenous to subtropical regions of South America. Observations of coypu behavior in the wild and in enclosures under a temperate climate showed a preference for close proximity to water and frequent swimming bouts. Little change was observed in the semiaquatic habit in winter, despite high mortality during this period, particularly among young and adult male coypus. Evidence for constraints on thermal adaptation was sought from measurements in a thermostatic chamber of the resting metabolic rate (RMR) of young coypus caught from wild populations in France and of the body (Tb) and skin (Tsk) temperatures as a function of ambient temperature (Ta). A light heterothermic response with deep Tb falling by 0.8 degree C and stabilizing at a new level of 36.7 degrees C was observed in water and air at Ta below the lower critical temperatures. In common with other semiaquatic mammals, RMR (2.94 W/kg) was high relative to terrestrial mammals of equivalent body mass. Minimal thermal conductance was 0.10 W.kg-1.degree C-1 in air for Ta between -10 and +20 degrees C, and conductance varied in water from 0.24 to 1.18 W.kg-1.degrees C-1 for Ta between 5 and 35 degrees C. The physiological adaptations to cold and particularly the high insulative value of the fur (80-90% of the insulation) help to explain the successful extension of the coypu's range to temperate regions. Energetic costs were nevertheless high in cold water, suggesting that social factors may be implicated in severe winter mortality, particularly dominance hierarchy regulating the persistent use of water bodies even under freezing conditions.

A central problem in conservation biology is how to determine the amount of suitable habitat required for a population to persist. The critical minimum is what Lande (1987) terms the 'extinction threshold'. Lawton et al. (1994) and Nee (1994) have pointed out the fundamental equivalence of this quantity to the 'eradication threshold' used in epidemiology (Anderson and May 1991). The eradication threshold defines the maximum fraction of a susceptible population that an immunisation programme can afford to miss, while still succeeding in eradicating the disease. This has been shown to equal in magnitude the uninfected fraction of the susceptible population; in other words, it takes the same value as the unused amount of the disease's limiting resource (Anderson and May 1991). For a conservation biologist, the eradication threshold would define the smallest amount of suitable habitat or limiting resource that can sustain a population of animals. Lawton et al. (1994) give the example of a metapopulation consisting of local populations distributed among discrete patches. The metapopulation is at equilibrium when a local population colonises just one other patch before going extinct. Not all patches are occupied at equilibrium. This scenario parallels the epidemiological case of a human population of which some fraction are not immune to the disease and are either carrying it or susceptible to it. Some fraction, h, of the patches are habitable, and a fraction x* among these are unoccupied at equilibrium though susceptible to colonisation. By the simple device of presenting the equilibrium fraction of occupied patches as h x*, it follows that this reaches zero (extinction of the metapopulation) when h equals x*. In other words, the minimum fraction of patches required to avoid extinction, h, is simply x*, the unoccupied but susceptible fraction at equilibrium. Nee (1994) likewise demonstrates how the eradication threshold of a predator is equal in magnitude to the uneaten fraction of limiting prey. A population well buffered against extinction is thus one that occupies the majority of habitable patches; or it is one that maintains the equilibrium density of limiting prey well below what it would be in the absence of predation. Conversely, a population that is at risk of extinction in the event of a small reduction in habitable patches or prey is one whose members occupy few of the habitable patches at equilibrium, or make little impact on the density of their prey. Such situations can arise if the habitat is highly fragmented and dispersal incurs a substantial mortality risk. Equally a predator might make little impact on prey density if the prey have effective defences against predation (they are present in numbers, but difficult to catch). It is interesting to note that highly disturbed environments are likely to be inhabited by species that use the majority of suitable habitat, whereas historically undisturbed environments will support species that are less efficient in this respect. Knowledge of the unused fraction thus provides a way of indexing environmental disturbance. Most of the species-specific details that are commonly sought in conservation studies, such as migration rates between patches, foraging efficiency for limiting prey, birth rates, death rates, etc. are superfluous to this estimate of minimum habitat requirements (Nee 1994). This conclusion has obvious consequences for field research on rare species: the essential priority in conservation studies is to determine accurately what constitutes the limiting resource or the suitable habitat. Unfortunately, this is often the most difficult objective to realise in practice (see Caughley and Sinclair 1994 for examples). Several factors may combine to regulate population size (Sinclair 1989). Even if their combined influence points towards certain types of habitat as being more suitable than others, defining exactly what

1. Principal environmental factors predicting local variations in hedgehog abundance were sought from surveys of 58 fields of grazing pasture at six sites of 12-15 km 2 in Oxfordshire, UK. Comparable surveys were additionally conducted on 31 mown grass playing fields in the same region. Complementary information on presence or absence of hedgehogs was obtained from a questionnaire survey of farmers. 2. Presence or absence of hedgehogs and their abundance in the pasture fields correlated with the magnitudes of five environmental variables. In a Principal Components Analysis, pasture fields in which hedgehogs were present were grouped together along a predator axis, characterized by indicators of badger activity and distance from town, and a resource axis, characterized by indices of earthworm availability

This paper reports the results of a field experiment to identify factors regulating local variations in population sizes of a common insectivore. A low density population of hedgehogs Erinaceus europaeus was artificially increased in numbers while simultaneously a high density population was reduced. Subsequent dispersal, mortality and natality were monitored in complete censuses of the total populations, and compared to a control population of transplanted hedgehogs at unchanged density. Predation on hedgehogs was principally by badgers Meles meles which forage for substantially similar foods to hedgehogs, and was significantly higher in the expanded population during the first 2 wk after transplant than in the control, which nevertheless suffered a high overall mortality

This paper describes the responses of three species of rodents (Apodemus sylvaticus, Microtus agrestis and Clethrionomys glareolus) and a shrew (Sore.x araneus) to traps tainted with the faecal odour of a predator, the Red fox. The rodents generally avoided traps bearing fox odour, but readily entered traps marked with rodent odour, whereas shrews entered all traps equally. Among the rodents, avoidance of fox odour was strongest in male A. sylvaticus and C. glareolus and least in M. agrestis and female A. sylvaticus. Fox droppings were found principally along paths and in open habitats where, of the rodents mentioned, they were most likely to be encountered by A. sylvaticus. It was suggested that avoidance of fox faecal and urinary odours in this species, especially by the active males, would reduce the time spent in areas frequented by foxes, and hence reduce the chance of encountering the predator itself. In contrast, M. agresis would seldom encounter fox droppings in its sub-surface runways, so avoidance of fox faecal odour would do little to reduce its chance of encountering the predator. Avoidance by the rodents of the faecal odour of badger, a predator not present in the study areas, was only slightly less marked than their avoidance of fox faecal odour. It was postulated that similar chemicals eliciting avoidance in rodents may commonly occur in the faeces and urine of carnivores.

Male and female strategies were compared for wild–living populations of coypu (Myocastor coypus Molina) censused during two years in marshlands of central–west France. In a habitat composed of a canal network bisecting pasture fields typically 0–5 ha in size, coypu movements were largely restricted to stretches of open water, though males explored further from water than females. Adults occupied home ranges with a mean size of 3–82 ha or 1. 19 km of canal, males on average moving faster over a larger area and using a greater length of canal than females. Movements within partially shared ranges were most positively coordinated between male–female pairs, while male–male interactions were less frequent. Juvenile coypus were largely absent from the late winter population. Synchronization of litters in March–April resulted in a peak of juveniles in early summer. The sex ratio of juveniles and sub–adults reversed from a male bias in summer to a female bias in autumn. Population densities peaked in November at 4 ha, with a significant female bias (1M: 1–6F). In the same month, a neighbouring population at lower density (1 ha-l after treatment with rodenticide) was significantly male biased (2–7M:lF) and may therefore have been acting as a sink for males dispersing from the high density population. Transients comprised 63% of the population. Females were resident longer than males, 22% of females remaining at least 5 months against 6% of males. Dispersal was recorded only for males aged 6 months or older. The general result, of exploratory behaviour amongst males contrasting with the establishment of longer term home ranges by females, is discussed in terms of male reproductive success and the capacity for females to influence nutrient supply to their litters.

(1) Ramsey Island (260 ha), Dyfed, Wales was surveyed by random quadrat sampling for ants' nests, and twelve variables of the habitat associated with each nest. (2) Nine species of ants from four genera were found. The average nest density was 0.057 m-2, with a maximum of 0 61 m-2. The distributions of the five commonest species are analysed in detail. (3) Nest dispersion is highly contagious (conforming to a logarithmic model), resulting from high nest densities in a few favourable sites. There is incomplete segregation of each species in the habitat, indicated by a random distribution of species packing. (4) Three physical and nine vegetational variables of the habitat are considered singly and in combination as niche dimensions. The variables are compared in a correlation matrix, and three principal components extracted. (5) The first component, representing an exposure factor differentiates the exposed coastal habitat of Lasius alienus F6rster from the sheltered sites of L. niger L. in heath and grassland vegetation. The second representing a drainage factor separates these two species from Myrmica scabrinodis Nylander and M. sabuleti Meinert. The third represents altitude and differentiates Lasius flavus F. from the other Lasius species, as well as Myrmica sabuleti from M. scabrinodis. (6) The nest dispersions of all Ramsey's ants are compared, and explained by specific and generic differences in nest building and foraging behaviour. The canopy effect of vegetation and the importance of rabbit grazing are discussed. (7) It is concluded that the dispersion and density of nests are broadly determined by the pattern of habitats on Ramsey and the factors influencing them, particularly exposure, moisture and rabbit grazing. The most widely distributed ants are generalist in their physical and vegetational resource requirements and can built a variety of nest structures. Lasius flavus typifies this group as it is able to nest at high and low densities in a range of habitats, either as the dominant species or in co-existence with as many as four other species.

SUMMARY (1) Populations of four species of small mammals, Apodemus sylvaticus, Clethrionomys glareolus, Microtus agrestis and Sorex araneus, were censused using live traps and hair sampling tubes in fifty discrete patches of habitat within the City of Oxford. (2) Habitats were classified as woodland, scrub, orchard, long grass, short grass, allotment, detached, and semi-detached house garden using ordination methods and subjective criteria. (3) Apodemus sylvaticus occurred in all habitats and in 84% of patches, and reached maximum densities (c. 70-80 ha-1) in scrub. (4) Clethrionomys glareolus occurred in all habitats except allotment, and achieved maximum abundance (< 30 ha-') in woodland. (5) Microtus agrestis and Sorex araneus were largely absent from cultivated gardens, allotments and short grass, and were most abundant (c. 50-66 ha-~) in long grass and scrub.