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Deception abounds in nature. Some species are first-rate con-artists. Angler fish with fins that mimic squiggling morsels that lure unsuspecting prey. Carnivorous pitcher plants that emit the aroma of rotting [...]

I present a framework for ecology and evolution laboratory exercises using artificial caterpillars made from modeling clay. Students generate and test hypotheses about predation rates on caterpillars that differ in appearance or 'behavior' to understand how natural selection by predators shapes distribution and physical characteristics of organisms. Key Words: Behavior; foraging; herbivore; inquiry; predation., Ecological and evolutionary processes determine the patterns and organization of communities of organisms around us. Yet these processes can be challenging to explore in a classroom setting because they often [...]

Group incidence and size are described for recruit parrotfishes, wrasses, and damselfishes on Hawaiian reefs over 3 years (2006-2008) at sites spanning the archipelago (20-28°N, 155-177°W). Coral-poor and coral-rich areas were surveyed at sites with both low (Hawaii Island) and high (Midway Atoll) predator densities, facilitating examination of relations among predator and recruit densities, habitat, and group metrics. Predator and recruit densities varied spatially and temporally, with a sixfold range in total recruit densities among years. Group ([greater than or equal to]2 recruits) metrics varied with time and tracked predator and recruit densities and the proportion of schooling species. Groups often included heterospecifics whose proportion increased with group size. A non-saturating relationship between group size and recruit density suggests that the anti-predator benefits of aggregation exceeded competitive costs. Grouping behavior may have overarching importance for recruit survival-even at high recruit densities-and merits further study on Hawaiian reefs and elsewhere., Author(s): Edward E. DeMartini [sup.1] , Todd W. Anderson [sup.2] , Alan M. Friedlander [sup.3] , James P. Beets [sup.4] Author Affiliations: (1) grid.466960.b, 000000040601127X, NOAA Fisheries, Pacific Islands Fisheries [...]

Abstract Archaeological investigations of human predation pressures on shellfish usually rely on measurements of complete shell specimens. However, most archaeological shell assemblages consist predominantly of broken shells, limiting measurable sample [...]

Sea spiders are one of the few marine invertebrates whose males care exclusively for offspring. The costs of parental care, however, have never been addressed for any species of pycnogonid. Costs may be significant for brooding sea spiders of Achelia simplissima, since males carry up to 12 egg masses simultaneously and actively aerate those eggs by moving their ovigerous legs back and forth. This study explored four potential costs to males as a result of parental care: predation, dislodgment, movement and feeding patterns, and frequency of epibionts. Brooding males were found to experience significantly higher frequencies of predator attacks and epibionts, as well as a lower rate of movement compared with nonbrooding males. Interestingly, brooding males were harder to dislodge than nonbrooding males and experienced no change in feeding frequency as a result of parental care. This is the first study to provide evidence that parental care may be costly for male pycnogonids in terms of individual survival and future reproductive success., Author(s): Zair P. Burris [sup.1] Author Affiliations: (1) grid.170202.6, 0000 0004 1936 8008, Oregon Institute of Marine Biology, University of Oregon, , PO Box 5389, 97420, Charleston, OR, USA Introduction [...]

We tested whether ingesting toxic algae by heterotrophic prey affected their nutritional value to crab larval predators, using toxic algal strains that are either ingested directly by larval crabs or rejected by them. Ingestion of toxic strains of the dinoflagellates Alexandriumandersoni and A. fundyense by the rotifer Brachionusplicatilis was confirmed. Rotifers having ingested either algal type for five days were fed to freshly hatched larvae of three crab species, with larval survival and stage durations determined. For both algal/rotifer treatments in all three crab species, larvae fed algae directly died during the first zoeal stage, while those fed rotifers that had been fed either algal strain survived to the experiment's end (zoeal stage 3). Survival was lower, and stage duration longer, for larvae fed rotifers cultured on toxic algae when compared to those fed non-toxic algae. The role of toxic algae in the planktonic food web may be influenced by its direct or indirect ingestion by larval crabs., Author(s): Rachel Garcia [sup.1] , Stephen Sulkin [sup.1] , Miranda Lopez [sup.1] Author Affiliations: (1) grid.281386.6, 0000000121657413, Shannon Point Marine Center, Western Washington University, , 1900 Shannon Point Road, 98221, [...]

Increasing concerns about the ecological impacts of ongoing and possibly worsening blooms of the toxic, carcinogenic cyanobacteria Lyngbya majuscula in Moreton Bay, Australia, led us to assess differences in meiofaunal prey assemblages between bloom and non-bloom substrates and the potential dietary impacts of dense L. majuscula blooms on the omnivorous benthivore, the Eastern Long-finned Goby, Favonigobius lentiginosus and the obligate meiobenthivorous juveniles of Trumpeter Whiting, Sillago maculata. Marked differences in invertebrate communities were found between sandy and L. majuscula bloom foraging substrates, with copepods significantly more abundant (18.49% vs. 70.44% numerical abundance) and nematodes significantly less abundant (55.91% vs. 1.21% numerical abundance) within bloom material. Gut analyses showed that bentho-planktivorous fishes exposed to L. majuscula in captivity had consumed a significantly greater quantity of prey by both total number (P < 0.0019) and volume (P < 0.0006) than fish exposed to sand treatments. Thus, it is likely for such fishes that L. majuscula blooms increase rates of prey encounter and consumption, with consequent changes in trophic relationships through shifts in predator-prey interactions between small benthivorous fishes and their meiofaunal prey., Author(s): Ben L. Gilby [sup.1] , Dana D. Burfeind [sup.1] [sup.2] , Ian R. Tibbetts [sup.1] Author Affiliations: (1) grid.1003.2, 0000000093207537, School of Biological Sciences, The University of Queensland, , [...]

To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1600-0706.2010.18547.x Byline: F. A. Jones, L. S. Comita Abstract: Negative density-dependent demographic processes operating at post-dispersal seed, seedling, and juvenile stages are the dominant explanation for the coexistence of high numbers of tree species in tropical forests. At adult stages, the effect of pollinators and pre-dispersal fruit predators are often dependent on the density or abundance of flowers and fruit in the canopy, but each have opposite effects on individual realized reproduction. We studied the effect of density on total and mature fruit set and pre-dispersal predation rates within individual tree canopies in a common canopy tree species, Jacaranda copaia in a 50-ha forest census plot in central Panama. We sampled all reproductive sized trees in the plot (n = 188) across three years and estimated fruit set and predation rates. Population-wide pre-dispersal seed predation averaged between 6-37% across years. Using linear mixed effects models, we found that increased density and fecundity of conspecific neighbours increased focal tree fruit set, but also the rate of pre-dispersal predation. An interaction between individual and neighbourhood fruit production predicted lower predation rates at high individual and neighbourhood fecundities, which suggests predator satiation at high fruit abundance levels. However, the rate at which fruit set increased with conspecific neighbour fruit production was greater than the rate at which fruit were lost to predation, resulting in an overall positive effect of neighbour density on mature fruit production in focal trees. Our results run counter to the expectation of a uniformly negative effect of density across all life stages in tropical trees and suggest further exploration of the role of spatial clumping, pollen dispersal limitation, and predation at pre-dispersal adult stages in maintenance of species diversity in plant communities. Author Affiliation: (1)Smithsonian Tropical Research Inst., Apartado 2072 Balboa, Ancon, Republic of Panama, and: Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot, Berks, SL5 7PY, UK (2)Dept of Ecology, Evolution and Environmental Biology, Columbia Univ., 1200 Amsterdam Avenue, New York, NY 10027, USA Article History: Paper manuscript accepted 26 March 2010 Article note: F. A. Jones, Smithsonian Tropical Research Inst., Apartado 2072 Balboa, Ancon, Republic of Panama, and: Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot, Berks, SL5 7PY, UK. E-mail: f.jones@imperial.ac.uk

Animal beauty provides a significant aesthetic reason for protecting nature. Worries about aesthetic discrimination and the ugliness of predation might make one think otherwise. Although it has been argued that aesthetic merit is a trivial and morally objectionable basis for action, beauty is an important value and a legitimate basis for differential treatment, especially in the case of animals. While the suffering and death of animals due to predation are important disvalues that must be recognized, predation's tragic beauty has positive aesthetic value that can be appropriately aesthetically appreciated.

Folivory has been accepted as the general dietary pattern for colobines. However, recent ecological studies have revealed that extensive seed eating is found in some colobine species. The ripeness of foraged seeds is also reported to differ between seed eaters. As seeds are generally stress-limited and may pose greater mechanical demands, seed-eating species are predicted to exhibit morphological features adaptive for seed predation. In addition, species that feeds on seeds from unripe fruits with hard pericarp is predicted to exhibit increased leverage for anterior dentition. To test these hypotheses, we compared the craniodental morphology of seed-eating Asian colobines (Presbytis rubicunda and Trachypithecus phayrei) with those of species that rarely exploit seeds (Presbytis comata, Trachypithecus obscurus, and Semnopithecus vetulus). The results show that the seed-eating colobines possess a masticatory system with enhanced leverage at postcanine bite points. The sclerocarpic forager P. rubicunda also exhibits markedly greater masticatory leverage at anterior dental bite points, while the mature-seed-eating T phayrei shows no such advantage for canine and incisor use. These observations suggest that P. rubicunda is well adapted to husking the resistant pericarps of unripe fruits, using the anterior dentition and to gain access to the immature seeds, whereas such sclerocarpic feeding behavior may be less important for T phayrei. Our findings indicate that the distinctive craniodental variations of colobines may be linked to mature and/or immature seed eating and suggest the significance of seed predation for the evolution of colobine monkeys. DOI 10.1002/ajpa.21213 KEY WORDS ecomorphology; masticatory apparatus; bite force; seed eating

To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1600-0706.2009.17953.x Byline: Takefumi Nakazawa, Takeshi Miki, Toshiyuki Namba Abstract: The persistence of intraguild predation (IGP), the prey-predator interaction between competing species, is puzzling because simple IGP models readily predict species extinction. In this study, we explored a mathematical model incorporating predator-specific defense adaptation of basal prey against intraguild prey and intraguild predator. The model explicitly described the dynamics of the defense effort against each predator under the assumption that anti-predator defense was associated with reducing effort allocated to reproduction. The model predicted that defense adaptation (i.e. the ability to reallocate defense effort) would facilitate coexistence, particularly when system productivity is high; at low productivity, coexistence would be facilitated or inhibited depending on initial effort allocation prior to defense adaptation. In addition, we found that three-species dynamics became more stable at higher adaptation rates. The results suggest that common behavioral changes, such as predator-specific defense adaptation, have significant implications for the community structure and dynamics of IGP systems. Author Affiliation: (1)Center for Ecological Research, Kyoto Univ., 509-3, 2-chome, Hirano, Otsu, JP-520-2113 Shiga, Japan (2)Inst. of Oceanography, National Taiwan Univ., No.1, Sec.4, Roosevelt Rd., TW-10617 Taipei, Taiwan (3)Dept of Biological Science, Graduate School of Science, Osaka Prefecture Univ., Gakuen-cho 1-1, Naka-ku, JP-599-8531 Sakai, Japan Article History: Paper manuscript accepted 20 July 2009 Article note: T. Nakazawa, Center for Ecological Research, Kyoto Univ., 509-3, 2-chome, Hirano, Otsu, JP-520-2113 Shiga, Japan. E-mail: tknkzw@ntu.edu.tw

Abstract--Diet, gastric evacuation rates, daily ration, and population-level prey demand of bluefin tuna (Thunnus thynnus) were estimated in the continental shelf waters off North Carolina. Bluefin tuna stomachs were collected [...]

The extent to which community processes can be generalized from local field studies to larger spatial scales remains a contentious issue. The search for broad generality can be hampered when species interactions vary geographically, a common phenomenon attributed to a wide range of underlying ecological factors. Less attention has been directed toward understanding the additional role that evolutionary processes may play in modifying the way that pairs of species interact over large spatial scales. Here we examine whether marked geographic variation in the interaction between a predatory snail (Nucella canaliculata) and an intertidal mussel (Mytilus californianus) arises from phenotypic plasticity or fixed genetic differences among snail populations. Over a three-year period, we reared snails from eight populations in California and Oregon, USA, through two laboratory generations and tested whether family lines differed in their ability to drill M. californianus. Remarkably, F2 generation snails from Oregon sources were generally unable to drill mid-sized Mytilus californianus (5-7 cm long), whereas snails from California readily drilled this prey. Because snails were raised through two generations on a common diet (Mytilus trossulus), these differences among populations likely have a genetic basis. Snails from California and Oregon readily interbred and produced viable offspring in the laboratory, suggesting that populations belong to a single biological species. Field surveys of mussel beds revealed striking geographic variation in predation that closely matched the observed differences in the drilling capacity of N. canaliculata. Drilled M. californianus were common at all sites in California and included many large mussels (>10 cm long). In contrast, drilled M. californianus were rare on the central Oregon coast and consisted mostly of small mussels ( Key words: biogeography; California coast, USA; local adaptation; mussel beds; Mytilus californianus; Nucella canaliculata; Oregon coast, USA; population connectivity; predator--prey interactions; rocky intertidal communities; snails.

The prediction of the effects of disturbances in natural systems is limited by the general lack of knowledge on the strength of species interactions, i.e., the effect of one species on the population growth rate of another, and by the uncertainty of the effects that may be manifested via indirect pathways within the food web. Here we explored the consequences of changes in species populations for the remaining species within nine exceptionally well-characterized empirical food webs, for which, unlike the vast majority of other published webs, feeding links have been fully quantified. Using the inverse of the Jacobian matrix, we found that perturbations to species with few connections have larger net effects (considering both direct and indirect pathways between two species) on the rest of the food web than do disturbances to species that are highly connected. For 40% of predator-prey links, predators had positive net effects on prey populations, due to the predominance of indirect interactions. Our results highlight the fundamental, but often counterintuitive, role of indirect effects for the maintenance of food web complexity and biodiversity. Key words: connectance; food webs; indirect effects; inverse Jacobian matrix; linkage density; press perturbation; specialization.

To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1600-0706.2009.16921.x Byline: Daan J. Gerla, Matthijs Vos, Bob W. Kooi, Wolf M. Mooij Abstract: When does community assembly lead to a predictable species composition and when does this process depend on chance events, such as the timing of species arrivals? We studied the combined effects of enrichment and predation on the occurrence of priority effects, i.e. dependency on the timing of arrival, using a model of a small food web consisting of a predator, two competing prey and interference through allelopathy. Our analysis shows the conditions under which priority effects can occur. In the system we studied, the interfering species has to be the weaker resource exploiter of the two consumers, or it has to be more susceptible to predation. When it is the weaker resource exploiter, a minimum level of nutrient input is required for interference to be strong enough to cause a priority effect. When the interfering species is more susceptible to predation, a priority effect actually requires predation, which in itself also requires a minimum level of nutrient inflow. However, the priority effect disappears when predation pressure rises above a threshold value, also when the two competitors are equally preferred by the predator. This is so because predation reduces population densities and thereby the strength of interference. Our analyses make clear how the effects of resources and predation can combine to result in the absence or presence of priority effects during community assembly. Article History: Manuscript Accepted 30 January 2009 Article note: D. J. Gerla (d.gerla@nioo.knaw.nl) and W. M. Mooij, Netherlands Inst. of Ecology (NIOO-KNAW), Centre for Limnology, Rijksstraatweg 6, NL-3631 AC Nieuwersluis, the Netherlands. - M. Vos, Netherlands Inst. of Ecology (NIOO-KNAW), Centre for Estuarine and Marine Ecology, Korringaweg 7, NL-4401 NT Yerseke, the Netherlands. Present address for MV: Dept of Ecology and Ecosystem Modeling, Inst. of Biochemistry and Biology, Univ. of Potsdam, Am Neuen Palais 10, DE - 14469 Potsdam, Germany. - B. W. Kooi, Dept of Theoretical Biology, Faculty of Earth and Life Sciences, Vrije Univ., De Boelelaan 1085, NL-1081 HV Amsterdam, the Netherlands.

One challenge to the idea that animals have a moral right to life claims that any such right would require us to intervene in the wild to prevent animals from being killed by predators. I argue that belief in an animal right to life does not commit us to supporting a program of predator-prey intervention. One common retort to the predator challenge contends that we are not required to save animals from predators because predators are not moral agents. I suggest that this retort fails to overcome the predator challenge. I seek to articulate a more satisfactory argument explaining why we are not required to save wild prey from predators and how this position is perfectly consistent with the idea that animals have a basic right to life., Among the moral rights that some philosophers have wanted to attribute to nonhuman animals is the right to life. If animals have a right to life, then it must be [...]

To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1600-0706.2008.16382.x Byline: Julia Lehmann, Robin Dunbar Abstract: Despite the fact that all African great apes have overlapping diets, they differ substantially in both biogeographical distribution and social organisation: Gorilla lives in relatively small, cohesive groups within a small biogeographical area while Pan is much more widely distributed and lives in large, fluid groups in which the members are rarely all together. In this study we use a modelling approach to identify possible causes and consequences of these differences. We use a time budget model which is based on the relationship between time available for various activities, group size, body mass and climate. We demonstrate the importance of body mass as a critical determinant for maximum ecologically tolerable group size as well as ape distribution patterns. In addition, we show that predation pressure may play a strong role in limiting the distribution of smaller-bodied apes (Pan). Predation pressure appears to be especially important if the apes opt for a fission-fusion strategy because it obliges them to maintain larger (sub-) groups. In effect, the apes appear to face a tradeoff between solving the predation problem by increasing body size (at the expense of reduced ecological flexibility) and going for ecological flexibility (but at some cost in terms of how they handle predation). Article History: Manuscript Accepted 4 September 2008 Article note: J. Lehmann (j.lehmann@roehampton.ac.uk) and R. Dunbar, Brit. Acad. Centenary Res. Project, School of Biological Sciences, Univ. of Liverpool, Liverpool, L69 7ZB, UK. JL also at: School of Human and Life Sciences, Roehampton Univ., Whitelands College, London, SW15 4JD, UK. RD also at: Inst. of Cognitive and Evolutionary Anthropology, Univ. of Oxford, Oxford, OX2 6PE, UK.

Food habits of cougars (Puma concolor) in North America have been documented for western populations in the United States, Canada and Mexico. Most studies assessed diets of cougars occupying typical habitats, and within established populations. We evaluated food habits of cougars in prairie and agricultural landscapes in the Dakotas (regions that had been devoid of the species for roughly a century) located well outside of known resident populations. We obtained stomach and gastrointestinal (GI) tracts from 14 cougars (10 male; 4 female) from 2003-2007, and evaluated contents via frequency of occurrence (%) of various prey items. Deer (Odocoileus spp.) had the highest frequency of occurrence (50.0%). Other native mammalian prey included jackrabbit (Lepus townsendii, L. californicus), porcupine (Erethizon dorsatum), beaver (Castor canadensis), badger (Taxidea taxus), mink (Mustela vison) and rodent species (e.g., vole). No domestic livestock species were documented as part of the cougar diet in the Dakotas, although remains of domestic housecat (Felis silvestris) were found in GI tracts of two animals. Based on our results, cougars occupying non-typical, newly recolonized habitats were successfully adapting predation techniques for capture of natural and newly confronted prey species. The wide range of prey encountered suggested that prey was being obtained opportunistically in prairie and agricultural landscapes of the Dakotas., INTRODUCTION Cougars (Puma concolor) are obligate carnivores that consume deer-sized prey throughout their range in the western hemisphere (Logan and Sweanor, 2000). As such, how cougars meet their dietary needs [...]

That some animals need to prey on others in order to live is lamentable. While no one wants predators to die of starvation, a world in which no animal needed to prey on others would, in some meaningful sense, be a better world. Predation is lamentable for four primary reasons: (1) predation often inflicts pain on prey animals; (2) it often frustrates prey animals' desires; (3) anything other than lamentation--which would include relishing predation as well as being indifferent to it--is in tension with sensitivity to many other forms of hardship and suffering; and (4) lamenting is demanded by the virtues of compassion and gentleness. One can lament predation even while acknowledging respects in which predation is genuinely praiseworthy. One can esteem admirable traits developed through and displayed in predation without esteeming the mechanism through which they are developed or the activity in which they are displayed. In addition, appreciating the check on population that predation provides does not preclude lamenting predation. While holding these positions does involve (in some sense) opposing nature itself and failing to appreciate predators for exactly what they ate, doing so does not disqualify a person as an environmentalist. Finally, one can lament predation without being logically committed thereby to preventing or disrupting it.

The disturbance associated with nest monitoring raises concerns about the validity of the estimated nest success and the well-being of the populations under study. Observer activity may attract or deter predators to or from bird nests, thus decreasing or increasing nest success. Results of previous studies related nest success to frequency of nest visits or estimated survival over rechecking intervals of different length. Such studies usually cannot reveal the underlying mechanism through which predation rate is influenced, because the timing of predation remains unknown. I measured, using data loggers, the exact survival times of 747 nests of 11 songbird species in fragmented woodland in the Czech Republic in 2001-2003 and analyzed the temporal relationship between predation and observer visits. I found only a short-term observer effect that lowered the hazard of predation during 2 h after a visit but did not appreciably affect the overall nest success. The timing of nest visits and the short duration of the effect imply that predators were deterred from the nests directly by the observer's presence, rather than by long-lasting cues (scent trails, damage to vegetation), and that diurnal predators (mainly corvids) responded to observer presence. This effect was consistent across years but differed between species groups. Deterrence of avian predators was profitable for a heterogeneous 'warbler' group of species with limited nest- defense ability (model-averaged hazard ratio: 0.38; 95% confidence interval: 0.12-1.25), but it had little effect on thrushes (Turdus spp.; 1.01; 0.28-3.68). I support the view that predation on songbird nests is not increased by repeated observer visits, especially in situations where nest densities and background human disturbance are high. Key words: Cox-Andersen-Gill model, disturbance, nest predators, nest success, observer effect, passerines, survival time analysis, timing. El disturbio asociado al monitoreo de los nidos suscita preocupacion sobre la validez de la estimacion del exito de los nidos y sobre el bienestar de las poblaciones bajo estudio. La actividad del observador puede atraer o alejar a los depredadores, disminuyendo o incrementando el exito de los nidos. Los resultados de estudios previos relacionaron el exito de los nidos con la frecuencia de visitas a estos, o estimaron su supervivencia mediante visitas realizadas a intervalos de diferente duracion. Estos estudios usualmente no pueden revelar el mecanismo subyacente a traves del cual se influencia la tasa de depredacion, debido a que no se conoce cuando sucede la depredacion. Utilizando aparatos registradores de datos, medi el tiempo exacto de supervivencia de 747 nidos de 11 especies de aves canoras en bosques fragmentados en la Republica Checa entre 2001 y 2003, y analice la relacion temporal entre la depredacion y las visitas de observadores. Encontre solo un efecto de corto plazo del observador, que disminuyo el riesgo de depredacion en las 2 h posteriores a las visitas, pero no afecto de modo apreciable el exito general de los nidos. La temporalidad de las visitas al nido y la corta duracion del efecto implican que los depredadores fueron disuadidos del nido directamente por la presencia del observador mas que por los rastros de su actividad, y que principalmente los depredadores diurnos (corvidos) respondieron a la presencia del observador. Este efecto fue consistente a traves de los anos pero difirio entre grupos de especies. La disuasion de los depredadores de aves fue beneficiosa para un grupo heterogeneo de especies de 'reinitas' con una limitada habilidad de defensa del nido (cociente de riesgo promedio del modelo: 0.38; intervalo de confianza del 95%: 0.12-1.25), pero tuvo poco efecto en las especies de Turdus (1.01; 0.28-3.68). Apoyo la idea de que la depredacion de los nidos de las aves canoras no se ve incrementada por las visitas repetidas de un observador, especialmente en situaciones donde las densidades de los nidos y las condiciones generales de disturbio humano son altas.

Brood parasitism and predation are two factors that limit seasonal fecundity in grassland songbirds. We removed Brown-headed Cowbirds (Molothrus ater) in a switchback experiment to examine the effects of brood parasitism and nest predation on the productivity of Dickcissels (Spiza americana). Nesting Dickcissels were monitored at four study plots in northeast Kansas in a two-year study. Brown-headed Cowbirds were captured with drop-in traps at two removal plots, two unmanipulated plots were reference plots, and treatments were reversed between years. To evaluate the effect of Brown-headed Cowbird removals, we compared the percentage of nests parasitized, rates of multiple parasitism, clutch size, daily nest survival rates, and overall productivity per nest between removal and reference plots. Removals of Brown-headed Cowbirds successfully reduced the probability of parasitism and rates of multiple parasitism, but only in one of two years. Brown-headed Cowbirds did not appear to contribute to nest losses, given that few nests were abandoned because of cowbird activity and that the probabilities of nest parasitism and nest survival declined simultaneously over the breeding season. Overall, nest productivity showed no difference between treatments in either year, despite reduced rates of parasitism at removal plots in 2004. High rates of nest predation minimized the potential benefits of Brown-headed Cowbird removals for increasing productivity of Dickcissels. Our results demonstrate that removals can reduce parasitism levels but that the success of removal programs may vary annually, particularly in regions where Brown-headed Cowbirds and nest predators are abundant. Management actions that minimize parasitism and predation by modifying habitat structure may provide better alternatives to programs based on removals. Key words: Brown-headed Cowbird, Dickcissel, fecundity, management, Molothrus ater, productivity, Spiza americana. El parasitismo y la depredacion de la nidada son dos factores que limitan la fecundidad estacional en las aves canoras de pastizal. Removimos individuos de Molothrus ater para examinar experimentalmente los efectos del parasitismo de la nidada y de la depredacion de nidos sobre la productividad de Spiza americana. Monitoreamos individuos de S. americana que estaban anidando en cuatro parcelas de estudio en el noreste de Kansas durante dos anos. Los individuos de M. ater fueron capturados con trampas en dos parcelas de remocion y dos parcelas no manipuladas sirvieron de referencia; los tratamientos fueron revertidos entre los anos. Para evaluar el efecto de la remocion de M. ater, comparamos el porcentaje de nidos parasitados, las tasas de parasitismo multiple, el tamano de la nidada, las tasas de supervivencia diaria de los nidos y la productividad total por nido entre las parcelas de remocion y las de referencia. La remocion de M. ater redujo con exito la probabilidad de parasitismo y las tasas de parasitismo multiple, pero solo en uno de los dos anos. Esta especie de parasito no parecio contribuir a las perdidas de nidos, dado que pocos nidos fueron abandonados como consecuencia de su actividad y a que las probabilidades de parasitismo y de supervivencia de los nidos disminuyeron a lo largo de la estacion reproductiva. En total, la productividad de los nidos no mostro diferencias entre los tratamientos en ninguno de los anos, a pesar de las tasas reducirlas de parasitismo en las parcelas de remocion observadas en 2004. Las altas tasas de depredacion de nidos minimizaron los beneficios potenciales de la remocion de M. ater, que apuntaban a incrementar la productividad de S. americana. Nuestros resultados demostraron que la remocion puede reducir los niveles de parasitismo, pero que el exito de los programas de remocion puede variar anualmente, particularmente en las regiones donde M. ater y los depredadores de nidos son abundantes. Las acciones de manejo que minimizan el parasitismo y la depredacion mediante la modificacion de la estructura del habitat pueden brindar mejores alternativas que los programas basados en la remocion.

The bank vole Myodes (= Clethrinomys) glareolus, a multiway artificial selection experiment is employed to study the predatory behavior and the ability to cope with herbivores diet in a wild rodent. The presence of a genetic variation in the traits related to the locomoter behavior and food habits in the rodent is also demonstrated.

To purchase or authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.2007.0030-1299.15989.x Byline: Bart Vervust, Irena Grbac, Raoul Van Damme Abstract: We investigated the possible role of variation in predation pressure in the phenotypic divergence of two island populations of the Italian wall lizard, Podarcis sicula. In 1971, ten adult specimens from the island of Pod Kopiste (Adriatic Sea, Croatia) were transported to the island of Pod Mrcaru, 3.5 km east, where they founded a new population. Although the two islands resemble each other in general physiognomy (size, elevation, microclimate) and in the absence of terrestrial predators, lizards from the newly established population are now on average larger and have shorter hind limbs. They also exhibit lower maximal sprint speed as measured on a racetrack, and fatigue faster when chased in a torus track. In the field, lizards from the original population of Pod Kopiste respond to a simulated predatory attack by fleeing at larger approach distances and by running further from the predator than lizards from Pod Mrcaru. These changes in morphology, behaviour and performance may result from the relaxed predation intensity on the latter island. Our analysis of the structural features of the microhabitats suggests that the vegetation on Pod Mrcaru offers more protection to lizards. Also, plasticine models of lizards, laid out on the islands, less often exhibited signs of being attacked by birds on Pod Mrcaru than on Pod Kopiste. Our findings provide an example of how changes in (possibly a single) environmental factor may simultaneously produce responses in behaviour, morphology and whole-animal physiology, and this on a surprisingly small spatial and temporal scale. Article History: Manuscript Accepted 30 April 2007 Article note: B. Vervust (bart.vervust@ua.ac.be) and R. Van Damme, Laboratory for Functional Morphology, Dept of Biology, Univ. of Antwerp, Universiteitsplein 1, BE-2610 Wilrijk, Belgium. - I. Grbac, Croatian Natural History Museum, Demetrova 1, 10000 Zagreb, Croatia.

Competition is predicted to affect the expression of inducible defenses, but because costs of behavioral and morphological antipredator defenses differ along resource gradients, its effects on defenses may depend on the traits considered. We tested the predictions from different defense models in tadpoles of the common frog Rana temporaria, which exhibit both types of defenses. In an outdoor experiment, we exposed the tadpoles to nonlethal predators (Aeshna dragonfly larvae) and to a gradient of intraspecific competition. Morphological responses did not follow any of the expected patterns, since investment in defense was not affected by resource level. Instead, tail depth decreased in the absence of predators. Behavioral defenses followed a state-dependent model. Overall, the defense strategy of the tadpoles revealed a shift from morphological and behavioral defenses at low tadpole density to morphological defense only at high density. This difference probably reflects the different efficiency of the defenses. Hiding is an effective means of defense, but it is unsustainable when resources are scarce. Morphological responses become more important with increasing density to compensate for the increase in behavioral risk-taking. Our results indicate that competition can strongly affect reaction norms of inducible defenses and highlight the importance of integrating ecological parameters that affect the cost benefit balance of phenotypic plasticity. Key words: competition; costs; inducible defenses; phenotypic plasticity; predation; tadpole.

The role played by chemical defenses secreted by insects in determining predator birds' prey selection is analyzed. Secreted defenses make the insects unpalatibile and help predators to discriminate between palatable and unpalatable insects.

Edge effects are caused by the penetration of abiotic and biotic conditions from the matrix into forest interiors. Although edge effects influence the biogeography of many tropical organisms, they have not been studied directly in primates. Edge effects are particularly relevant to lemurs due to the loss of 80-90% of forests in Madagascar. In this study, data are presented on how biotic edge effects influenced the distribution and density of lemurs in the Vohibola III Classified Forest in southeastern Madagascar. In total, 415 lemur surveys were conducted during June-October 2003 and May--September 2004 along six 1,250-m transects that ran perpendicular to the forest edge. Data were also collected on lemur food trees along the six transects (density, height, diameter at breast height, area, volume, and distance to forest edge). Four nocturnal species (Avahi laniger, Cheirogaleus major, Lepilemur microdon, and Microcebus rufus) and four diurnal species (Eulemur rubriventer, Eulemur fulvus rufus, Hapalemur grisesus griseus, and Propithecus diadema edwardsi) were sighted during surveys. Regression analyses of lemur densities as a function of distance to forest edge provided edge tolerances for A. laniger (edge-tolerant), M. rufus (edge-tolerant), E. rubriventer (edge-tolerant or omnipresent), and H. g. griseus (omnipresent). The density and distribution of M. rufus and their foods trees were correlated. Edge-related variations in food quality and predation pressures may also be influencing lemurs in Vohibola III. Tolerance for edge effects may explain, in part, how lemurs have survived extreme habitat loss and forest fragmentation in southeastern Madagascar. KEY WORDS forest fragmentation; diet; food quality; predation; protected areas

The bacterium Vibrio cholerae, like other human pathogens that reside in environmental reservoirs, survives predation by unicellular eukaryotes. Strains of the O1 and O139 serogroups cause cholera, whereas non-O1/non-O139 strains cause human infections through poorly defined mechanisms. Using Dictyostelium discoideum as a model host, we have identified a virulence mechanism in a non-O1/non-O139 V. cholerae strain that involves extracellular translocation of proteins that lack N-terminal hydrophobic leader sequences. Accordingly, we have named these genes 'VAS' genes for virulence-associated secretion, and we propose that these genes encode a prototypic 'type VI' secretion system. We show that vas genes are required for cytotoxicity of V. cholerae cells toward Dictyostelium amoebae and mammalian J774 macrophages by a contact-dependent mechanism. A large number of Gram-negative bacterial pathogens carry genes homologous to vas genes and potential effector proteins secreted by this pathway (i.e., hemolysin-coregulated protein and VgrG). Mutations in vas homologs in other bacterial species have been reported to attenuate virulence in animals and cultured macrophages. Thus, the genes encoding the VAS-related, type VI secretion system likely play an important conserved function in microbial pathogenesis and represent an additional class of targets for vaccine and antimicrobial drug-based therapies. Dictyostelium discoideum | type VI secretion | virulence-associated secretion

In many birds, breeding males display bright colors, sing, and engage in active territory defense; whereas females are less conspicuous. Therefore, it is sometimes assumed that in the breeding season males suffer higher predation than females. Several studies have reported, however, higher female predation rates, which suggests that traits other than coloration and mate-acquisition behaviors are important in determining predation rates for the sexes. Theoretical and empirical work suggests that foraging behavior and foraging rate are major determinants of predation risk. Here, we examine this possibility in a study of breeding Eurasian Blackbirds (Turdus merula) and predation on them by Eurasian Sparrowhawks (Accipiter nisus). Female Eurasian Blackbirds foraged more than males and foraged closer to the ground, both early and late in the breeding season. On the basis of this observation, we predicted that females should suffer higher predation than males. Of 98 Eurasian Blackbirds taken in 33 Eurasian Sparrowhawk territories during four years, 56 were females and 42 males. On the basis of the male-biased sex ratio in the population, female Eurasian Blackbirds suffered higher predation risk than males. For breeding birds, these results indicate a trade-off between foraging effort and predation rate, which is of importance for sexual dichromatism (selection for female crypsis), population sex ratio, and behaviors of the sexes. Received 5 February 2004, accepted 27 June 2005. Key words: Accipiter nisus, crypsis, Eurasian Blackbirds, Eurasian Sparrowhawks, feeding, predator, sex, songbirds, Turdus merula. Chez de nombreux oiseaux, les males reproducteurs presentent des couleurs vives, produisent des chants, et s'engagent dans une defense active du territoire, alors que les femelles sont moins voyantes. Par consequent, il est parfois considere qu'au cours de la saison de reproduction, les males sont plus affectes par la predation que les femelles. Neanmoins, plusieurs etudes ont rapporte un taux de predation plus eleve chez les femelles, ce qui suggere que des traits autres que la coloration et le comportement d'acquisition d'un partenaire jouent un role important dans la determination du taux de predation pour chacun des sexes. Les travaux theoriques et empiriques suggerent que le comportement et le taux de quote alimentaire sont des elements cles en ce qui concerne le risque de predation. Nous examinons cette possibilite dans une etude sur la reproduction de Turdus merula et sur leur predation par Accipiter nisus. Les femelles Turdus merula consacrent plus de temps a la quote alimentaire que les males et se tiennent a proximite du sol, que ce soit tot ou tard dans la saison de reproduction. En se basant sur cette observation, nous avons predit que les femelles devraient etre moins affectees par la predation que les males. Parmi les 98 Turdus merula collectes dans 33 territoires de Accipiter nisus au cours de 4 annees, 56 etaient des femelles et 44 des males. En se basant sur ce sex-ratio biaise dans le sens des males, les femelles Turdus merula etaient plus affectes par la predation que les males. Pour les oiseaux reproducteurs, ces resultats indiquent un compromis entre les efforts de quete alimentaire et la taux de predation, ce qui joue un role important dans le dichromatisme sexuel (selection pour le camouflage de la femelle), le sex-ratio de la population, et les comportements des deux sexes.

We assessed the reproductive success of the California Clapper Rail (Rallus longirostris obsoletus), an endangered subspecies restricted to San Francisco Bay, and the relative importance of predation, flooding, and contaminants as factors affecting that success. Our study was conducted in six tidal marshes in the northern and southern reaches of San Francisco Bay. This assessment, conducted in four breeding seasons (1991, 1992, 1998, 1999), determined that productivity of California Clapper Rails was much reduced over the natural potential. Only 69% of clapper rail eggs whose viability could be assessed were viable. Hatchability of eggs in North Bay and South Bay marshes was 65% and 70%, respectively. Only 45% of the nests successfully hatched at least one egg. Despite mean clutch sizes of 6.7 and 6.9 in the North and South bays, respectively, clapper rails produced only 1.9 and 2.5 young per nesting attempt. Flooding was a minor factor, reducing the number of eggs available to hatch by only 2.3%. Predation on eggs was a major factor affecting nest success, reducing productivity by a third. Failed eggs were examined for abnormal development and contaminant concentrations. Contamination appeared to adversely influence California Clapper Rail reproductive success, as evidenced by deformities; embryo hemorrhaging; embryo malpositions; a depressed rate of hatchability; excess concentrations of mercury, barium, and chromium over known avian embryotoxic thresholds; and a correlation of deformities with elevated concentrations of some trace elements in eggs that failed to hatch. Mercury was the only significant contaminant common to all marshes. Received 19 November 2003, accepted 28 April 2005. Key words: California Clapper Rail, contaminants, mercury, nest predation, Rallus longirostris obsoletus, San Francisco Bay. Evaluamos el exito reproductivo de Rallus longirostris obsoletus, una subespecie amenazada restringida a la bahia de San Francisco, y la importancia relativa de la depredacion, las inundaciones y los contaminantes como factores que afectan su exito reproductivo. Nuestro estudio fue realizado en seis pantanos mareales en los extremos norte y sur de la bahia de San Francisco. Esta evaluacion, realizada en cuatro epocas reproductivas (1991, 1992, 1998, 1999), determino que la productividad de R. l. obsoletus fue muy reducida con respecto a su potencial natural. Solo el 69% de los huevos cuya viabilidad pudo ser determinada fueron viables. La capacidad de eclosionar de los huevos en los pantanos del norte y el sur de la bahia fue del 65% y 70%, respectivamente. Aunque los tamanos medios de las nidadas fueron 6.7 y 6.9 en el norte y el sur, respectivamente, las aves solo produjeron 1.9 y 2.5 pichones por intento de nidificacion. Las inundaciones fueron un factor poco importante, pues redujeron el numero de huevos disponibles para eclosionar solo en un 2.3%. La depredacion de los huevos fue un factor importante que afecto el exito de nidificacion, reduciendo la productividad en un tercio. Los huevos que fracasaron fueron examinados en busca de evidencia de desarrollo anormal y para medir las concentraciones de contaminantes. La contaminacion parecio influenciar negativamente el exito reproductivo, como lo evidencian las deformidades, hemorragias en los embriones, posiciones inadecuadas de los embriones, disminucion en la habilidad de eclosionar, concentraciones en exceso de mercurio, bario y cromo por encima de los umbrales toxicos conocidos para los embriones de las aves y una correlacion de las deformidades con concentraciones elevadas de algunos elementos halladas en los huevos que no eclosionaron. El mercurio fue el unico contaminante significativo que estuvo presente en todos los pantanos.

Abstract: The paper investigates conditions under which endogenous cyclic behavior may be observed within the context of Predator-Prey (Lotka-Volterra) Models. The analysis also establishes conditions under which such behavior is [...]

The optimal harvesting of prey in a predator-prey ecosystem when predator conservation is considered important is analyzed. The behavior of the system is studied and conditions for optimal control are discussed.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2004.12.002 Byline: G. Sancho (a), C.R. Fisher (b), S. Mills (c), F. Micheli (d), G.A. Johnson (e), H.S. Lenihan (f), C.H. Peterson (e), L.S. Mullineaux (c) Abstract: This study investigates predation by the vent zoarcid fish Thermarces cerberus through gastrointestinal analyses of 27 specimens collected with the submersible ALVIN at vents at 9[degrees]50'N on the East Pacific Rise. T. cerberus fed most frequently on gastropod mollusks (mainly Lepetodrilus elevatus) and amphipod crustaceans (mainly Ventiella sulfuris). Species found occasionally in high abundance included the swarming amphipod Halice hesmonectes and the snail Cyathermia naticoides. Other items also found in gastrointestinal tracts, but in very low numbers, included polychaete worms, crustaceans and unidentified tissue clumps. The comparison between the size distribution of L. elevatus limpets ingested by T. cerberus and those found attached to vestimentiferan tubes suggest that the fish may selectively prey on large limpets. If the selective removal of large Lepetodrilus spp. limpets by T. cerberus does occur, then it would have potential community-level consequences at hydrothermal vents, since these mobile gastropods appear to inhibit the settlement of sessile vent species, including tube-building worms. Our results suggest possible direct and indirect effects of T. cerberus on benthic community structure at hydrothermal vents on the East Pacific Rise. Author Affiliation: (a) College of Charleston, Grice Marine Laboratory, 205 Fort Johnson, Charleston SC 29412, USA (b) Pennsylvania State University, University Park PA 16802, USA (c) Woods Hole Oceanographic Institution, Woods Hole MA 02543, USA (d) Stanford University, Hopkins Marine Station, Pacific Grove CA 93950, USA (e) University of North Carolina at Chapel Hill, Institute of Marine Sciences, Morehead City NC 28557, USA (f) Bren School of Environmental Science and Management, University of California, Santa Barbara CA 93106, USA

Fossilized ichthyosaur offers a prehistoric 'Kinder Surprise' for researchers. Fossilized ichthyosaur offers a prehistoric 'Kinder Surprise' for researchers., Author Affiliations: A fossilized marine reptile's bellyful of a second, slightly smaller marine reptile is visible as a block protruding from its abdomen. Credit: Ryosuke Motani Huge chunk of rock [...]

Byline: R.S. Cantrell (1), C. Cosner (1) Keywords: Reaction-diffusion; Interacting particle systems; Hydrodynamic limits; Population dynamics; Spatial models; Scaling; Lotka-Volterra; Ratio-dependence; Competition; Predator-prey; Hawk-Dove game Abstract: We use a scaling procedure based on averaging Poisson distributed random variables to derive population level models from local models of interactions between individuals. The procedure is suggested by using the idea of hydrodynamic limits to derive reaction-diffusion models for population interactions from interacting particle systems. The scaling procedure is formal in the sense that we do not address the issue of proving that it converges instead we focus on methods for computing the results of the scaling or deriving properties of rescaled systems. To that end we treat the scaling procedure as a transform, in analogy with the Laplace or Fourier transform, and derive operational formulas to aid in the computation of rescaled systems or the derivation of their properties. Since the limiting procedure is adapted from work by Durrett and Levin, we refer to the transform as the Durrett-Levin transform. We examine the effects of rescaling in various standard models, including Lotka-Volterra models, Holling type predator-prey models, and ratio-dependent models. The effects of scaling are mostly quantitative in models with smooth interaction terms, but ratio-dependent models are profoundly affected by the scaling. The scaling transforms ratio-dependent terms that are singular at the origin into smooth terms. Removing the singularity at the origin eliminates some of the unique dynamics that can arise in ratio-dependent models. Author Affiliation: (1) Department of Mathematics, University of Miami, Coral Gables, FL, 33124, USA Article History: Registration Date: 01/01/2003 Online Date: 20/08/2003 Article note: Research partially supported by NSF grants DMS 99-73017 and DMS 02-11367 Received: 2 July 2001

Black ratsnakes (Elaphe obsoleta obsoleta) prey extensively on both birds (eggs and nestlings) and mammals. There is conflicting evidence, however, regarding whether the snakes specialize on birds during the birds' nesting season or whether predation on birds is opportunistic. We tested these alternatives by determining seasonal dietary patterns from 81 fecal samples collected from black ratsnakes in eastern Ontario over 4 y. We also used these data to determine how diet varies with snake size. Birds occurred in the snakes' diet from May through August, but the occurrence of birds never exceeded that of mammals in any month. This pattern was the same as that previously reported for black ratsnakes in Kansas and supports the hypothesis that black ratsnakes prey on birds opportunistically. Relative to smaller individuals, larger ratsnakes preyed on larger species of mammals and reduced their consumption of smaller species of mammals. The reduction in the consumption of small prey by large snakes was due to diet diversification rather than specialization. However, because larger snakes continued to include small prey in their diet, predation patterns on birds and mammals suggest that ratsnakes are opportunistic predators.