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Behavioural Ecology (behavioural + ecology)
Selected AbstractsPredator control of ecosystem nutrient dynamicsECOLOGY LETTERS, Issue 10 2010Oswald J. Schmitz Abstract Predators are predominantly valued for their ability to control prey, as indicators of high levels of biodiversity and as tourism attractions. This view, however, is incomplete because it does not acknowledge that predators may play a significant role in the delivery of critical life-support services such as ecosystem nutrient cycling. New research is beginning to show that predator effects on nutrient cycling are ubiquitous. These effects emerge from direct nutrient excretion, egestion or translocation within and across ecosystem boundaries after prey consumption, and from indirect effects mediated by predator interactions with prey. Depending on their behavioural ecology, predators can create heterogeneous or homogeneous nutrient distributions across natural landscapes. Because predator species are disproportionately vulnerable to elimination from ecosystems, we stand to lose much more from their disappearance than their simple charismatic attractiveness. [source] A landscape theory for food web architectureECOLOGY LETTERS, Issue 8 2008Neil Rooney Abstract Ecologists have long searched for structures and processes that impart stability in nature. In particular, food web ecology has held promise in tackling this issue. Empirical patterns in food webs have consistently shown that the distributions of species and interactions in nature are more likely to be stable than randomly constructed systems with the same number of species and interactions. Food web ecology still faces two fundamental challenges, however. First, the quantity and quality of food web data required to document both the species richness and the interaction strengths among all species within food webs is largely prohibitive. Second, where food webs have been well documented, spatial and temporal variation in food web structure has been ignored. Conversely, research that has addressed spatial and temporal variation in ecosystems has generally ignored the full complexity of food web architecture. Here, we incorporate empirical patterns, largely from macroecology and behavioural ecology, into a spatially implicit food web structure to construct a simple landscape theory of food web architecture. Such an approach both captures important architectural features of food webs and allows for an exploration of food web structure across a range of spatial scales. Finally, we demonstrated that food webs are hierarchically organized along the spatial and temporal niche axes of species and their utilization of food resources in ways that stabilize ecosystems. [source] A Quantified Ethogram for Oviposition in Triturus Newts: Description and Comparison of T. helveticus and T. vulgarisETHOLOGY, Issue 4 2005Karen M. Norris Female newts of the genus Triturus deposit and wrap their eggs individually in the submerged leaves of aquatic macrophytes. Although this behaviour has previously been described, the different elements of the oviposition process have not been fully characterized nor any attempt made to quantify the behavioural elements. The study examined the oviposition behaviour of the two similarly sized species, Triturus helveticus and T. vulgaris on a standardized substrate macrophyte, Rorippa nasturtium,aquaticum. Continuous focal sampling was used to develop a baseline of discrete behavioural elements enabling quantification and comparison of oviposition behaviour between the two species. The results showed that the same pattern of elements was followed for each egg laid and the same key elements of the process were present in each newt species. Although these are broadly similar in size, there were striking differences in certain aspects of the oviposition sequence between the two species. Key findings were that leaf sniffing and leaf flexing and a measure of the duration of ovipositing were all significantly greater in females of T. helveticus and females of T. vulgaris laid significantly more eggs than those of T. helveticus in a standard observation period. The work presented here defines a baseline ethogram and shows how it can be used to reveal quantifiable differences in closely related species. This demonstrates its value in furthering our understanding of oviposition , a key aspect of female behaviour currently understudied in Triturus behavioural ecology, despite its intrinsic interest and value in understanding recruitment and maintenance of populations. [source] Learning of foraging skills by fishFISH AND FISHERIES, Issue 3 2003Kevin Warburton Abstract This chapter outlines the relationships between a number of key factors that influence learning and memory, and illustrates them by reference to studies on the foraging behaviour of fish. Learning can lead to significant improvements in foraging performance in only a few exposures, and at least some fish species are capable of adjusting their foraging strategy as patterns of patch profitability change. There is also evidence that the memory window for prey varies between fish species, and that this may be a function of environmental predictability. Convergence between behavioural ecology and comparative psychology offers promise in terms of developing more mechanistically realistic foraging models and explaining apparently ,suboptimal' patterns of behaviour. Foraging decisions involve the interplay between several distinct systems of learning and memory, including those that relate to habitat, food patches, prey types, conspecifics and predators. Fish biologists, therefore, face an interesting challenge in developing integrated accounts of fish foraging that explain how cognitive sophistication can help individual animals to deal with the complexity of the ecological context. [source] Non-lethal effects of predation in birdsIBIS, Issue 1 2008WILL CRESSWELL Predators can affect individual fitness and population and community processes through lethal effects (direct consumption or ,density' effects), where prey is consumed, or through non-lethal effects (trait-mediated effects or interactions), where behavioural compensation to predation risk occurs, such as animals avoiding areas of high predation risk. Studies of invertebrates, fish and amphibians have shown that non-lethal effects may be larger than lethal effects in determining the behaviour, condition, density and distribution of animals over a range of trophic levels. Although non-lethal effects have been well described in the behavioural ecology of birds (and also mammals) within the context of anti-predation behaviour, their role relative to lethal effects is probably underestimated. Birds show many behavioural and physiological changes to reduce direct mortality from predation and these are likely to have negative effects on other aspects of their fitness and population dynamics, as well as affecting the ecology of their own prey and their predators. As a consequence, the effects of predation in birds are best measured by trade-offs between maximizing instantaneous survival in the presence of predators and acquiring or maintaining resources for long-term survival or reproduction. Because avoiding predation imposes foraging costs, and foraging behaviour is relatively easy to measure in birds, the foraging,predation risk trade-off is probably an effective framework for understanding the importance of non-lethal effects, and so the population and community effects of predation risk in birds and other animals. Using a trade-off approach allows us to predict better how changes in predator density will impact on population and community dynamics, and how animals perceive and respond to predation risk, when non-lethal effects decouple the relationship between predator density and direct mortality rate. The trade-off approach also allows us to identify where predation risk is structuring communities because of avoidance of predators, even when this results in no observable direct mortality rate. [source] Breeding birds on small islands: island biogeography or optimal foraging?JOURNAL OF ANIMAL ECOLOGY, Issue 2 2006GARETH J. RUSSELL Summary 1We test MacArthur and Wilson's theory about the biogeography of communities on isolated habitat patches using bird breeding records from 16 small islands off the coasts of Britain and Ireland. 2A traditional examination of patterns of species richness on these islands suggests that area and habitat diversity are important predictors, but that isolation and latitude have a negligible impact in this system. 3Unlike traditional studies, we directly examine the fundamental processes of colonization and local extinction (cessation of breeding), rather than higher-order phenomena such as species richness. 4We find that many of MacArthur and Wilson's predictions hold: colonization probability is lower on more isolated islands, and extinction probability is lower on larger islands and those with a greater diversity of habitats. 5We also find an unexpected pattern: extinction probability is much lower on more isolated islands. This is the strongest relationship in these data, and isolation is the best single predictor of colonization and extinction. 6Our results show that examination of species richness alone is misleading. Isolation has a strong effect on both of the dynamic processes that underlie richness, and in this system, the reductions in both colonization and extinction probability seen on more distant islands have opposing influences on species richness, and largely cancel each other out. 7We suggest that an appropriate model for this system might be optimal foraging theory, which predicts that organisms will stay longer in a resource patch if the distance to a neighbouring patch is large. If nest sites and food are the resources in this system, then optimal foraging theory predicts the pattern we observe. 8We advance the hypothesis that there is a class of spatial systems, defined by their scale and by the taxon under consideration, at which decision-making processes are a key driver of the spatiotemporal dynamics. The appropriate theory for such systems will be a hybrid of concepts from biogeography/metapopulation theory and behavioural ecology. [source] Hunting for large carnivore conservationJOURNAL OF APPLIED ECOLOGY, Issue 6 2009Adrian Treves Summary 1. Carnivores are difficult to conserve because of direct and indirect competition with people. Public hunts are increasingly proposed to support carnivore conservation. This article reviews scientific evidence for the effectiveness of public hunts of large carnivores in attaining three common policy goals: stable carnivore populations, preventing conflict with carnivores (property damage and competition over game) and building public support for carnivore conservation. 2. Sustainable exploitation of stable wildlife populations has a solid, scientific foundation but the theory and its predictions must be adapted to complex patterns of carnivore behavioural ecology and population dynamics that demand years of landscape-level monitoring to understand fully. 3. A review of the evidence that hunting prevents property damage or reduces competition for game reveals large gaps in our understanding. Reducing the number of large carnivores to protect hunters' quarry species seems straightforward but we still know little about behavioural and ecological responses of the contested prey and sympatric meso-predators. For reducing property damage, the direct effect , numerical reduction in problematic individual carnivores , presents numerous obstacles, whereas the indirect effect , behavioural avoidance of humans by hunted carnivores , holds more promise. 4. Scientific measures of public support for carnivore-hunting policies are almost completely lacking, particularly measures of attitudes among hunters before and after controversial wildlife is designated as legal game species. Moreover, illegal killing of carnivores does not appear to diminish if they are designated as game. 5.Synthesis and applications. Sustainable hunting to maintain stable populations is well understood in theory but complex life histories of carnivores, and behavioural changes of hunters and the carnivores they stalk may result in unsustainable mortality for carnivores. The direct impact of hunting on carnivore damage to property is unclear and even doubtful given the inability or unwillingness of hunters to remove specific individuals selectively. However, hunters may indirectly deter carnivores from people and their property. The assumption that hunters will steward carnivores simply because they have in the past helped conserve other game species requires more study as preliminary results suggest it is incorrect. Policy-makers may achieve support for policy if they mesh utilitarian and preservationist values held by the general public. A number of opposed hypotheses should be disentangled before researchers confidently inform policy on sustainable hunting to prevent conflicts and build public support for carnivore conservation. [source] Daytime variation in T-cell-mediated immunity of Eurasian kestrel Falco tinnunculus nestlingsJOURNAL OF AVIAN BIOLOGY, Issue 5 2006Jesús Martínez-PadillaArticle first published online: 15 AUG 200 Host-parasite interactions are central in evolutionary and behavioural ecology. In the last few years, skin injections of the mitogen Phytohaemagglutinin (PHA) have become one of the most important and widely used in-vivo assays of immune function in birds. However, there are no studies of the circadian variation suggesting that care should be taken interpreting results when using this technique. This 3-year study assessed PHA responses as a function of daylight time in 310 Eurasian kestrel Falco tinnunculus nestlings at 24 days of age in Central Spain. I found that T-cell-mediated immunity was positively related to nestling mass and varied among years. Controlling for these variables, I also found that T-cell-mediated immunity decreased with the hour of sampling, and that this pattern was consistent between years. In addition, I found that at the end of the day only, T-cell-mediated immunity decreased with brood size. Parasites seem not to be behind this pattern, but I suggest that the cumulative effect of sibling competition during the day might explain the decrease of cellular immunity with the hour of sampling. Thus, I strongly recommend that future studies of cellular immunity should control for this potential source of variation when nestling self-maintenance is evaluated by the PHA-induced skin-swelling response. [source] Biology, ecology and status of Iberian ibex Capra pyrenaica: a critical review and research prospectusMAMMAL REVIEW, Issue 1 2009PELAYO ACEVEDO ABSTRACT 1The Iberian ibex Capra pyrenaica is endemic to the Iberian Peninsula and of the four subspecies originally recognized, recent extinctions mean that only two now persist. Recent genetic analyses have cast doubt on the generally accepted taxonomy of the species, where four subspecies were distinguished by coat colour and horn morphology, and propose the distinction of two subspecies based on their mitochondrial DNA sequence polymorphism. These analyses make clear the need for a comprehensive revision that integrates genetic and morphological approaches resulting in a definitive description and differentiation of the subspecies. 2Studies of ibex behavioural ecology and health status are scarce and generally descriptive. They should be implemented in an integrative way, taking into account the ecological requirements of the species, current population status, the presence of other sympatric wild and domestic ungulates, and the type of hunting regime and management in their distribution areas. 3A natural expansion of the species is currently taking place. Ibexes are present and well established in all the main mountain ranges of the Spanish Iberian Peninsula, and have recently expanded their range into the north of Portugal. Other authors estimated a total population of more than 50 000 individuals 10 years ago, distributed over more than 60 000 km2, with an average population density of 2.7 ibex/km2. However, these estimates were obtained prior to the species' recovery from recent epizootics of sarcoptic mange and should be updated. Survey methods, mainly direct count-based methods, should be adjusted to suit mountainous conditions, where it is difficult to estimate accurately the surveyed surface. 4A series of threats to ibex conservation have been identified, such as population overabundance, disease prevalence and potential competition with domestic livestock and invasive ungulates, along with negative effects of human disturbance through tourism and hunting. 5Applied ecological issues focused on the proper management of populations should be prioritized, along with the identification of current threats based on empirical, ecological data obtained from populations living in various ecological conditions in different regions. [source] Sensory and behavioural responses of the stable fly Stomoxys calcitrans to rumen volatilesMEDICAL AND VETERINARY ENTOMOLOGY, Issue 3 2007P. JEANBOURQUIN Abstract Analysis of volatiles from rumen digesta by gas chromatography linked antennogram recordings from Stomoxys calcitrans (L) (Diptera: Muscidae) antennal receptor cells revealed about 30 electrophysiologically active constituents, the most important of which is dimethyl trisulphide with a sensory threshold in the femtogram range. The behavioural responses of S. calcitrans to five chemostimulants (dimethyl trisulphide, butanoic acid, p -cresol, oct-1-en-3-ol and skatole) were tested in a wind tunnel where activation and attraction of hungry flies to rumen volatiles were recorded. Dimethyl trisulphide, butanoic acid and p -cresol were found to attract S. calcitrans. This sensitivity to rumen volatile constituents, that also occur in animal wastes used for oviposition by Stomoxys spp., as well as in flowers used by stable flies as sources of nectar is discussed in the context of the behavioural ecology of these flies. [source] Extension of ideal free resource use to breeding populations and metapopulationsOIKOS, Issue 1 2000C. Patrick Doncaster The concept of an ideal and free use of limiting resources is commonly invoked in behavioural ecology as a null model for predicting the distribution of foraging consumers across heterogeneous habitat. In its original conception, however, its predictions were applied to the longer timescales of habitat selection by breeding birds. Here I present a general model of ideal free resource use, which encompasses classical deterministic models for the dynamics in continuous time of feeding aggregations, breeding populations and metapopulations. I illustrate its key predictions using the consumer functional response given by Holling's disc equation. The predictions are all consistent with classical population dynamics, but at least two of them are not usually recognised as pertaining across all scales. At the fine scale of feeding aggregations, the steady state of an equal intake for all ideal free consumers may be intrinsically unstable, if patches are efficiently exploited by individuals with a non-negligible handling time of resources. At coarser scales, classical models of population and metapopulation dynamics assume exploitation of a homogeneous environment, yet they can yield testable predictions for heterogeneous environments too under the assumption of ideal free resource use. [source] A simple method for measuring colour in wild animals: validation and use on chest patch colour in geladas (Theropithecus gelada)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2008THORE J. BERGMAN Adaptive hypotheses about colour variation are widespread in behavioural ecology, and several methods of objective colour assessment have been proposed and validated for use in a wide variety of taxa. However, to date, the most objective and reliable methods of assessing colour are not readily applied to wild animals. In the present study, we present a simple method for assessing colour in unrestrained, wild subjects using digital photography. The method we describe uses a digital camera, a colour standard, and colour analysis software, and can be used to measure any part of the visible colour spectrum. We demonstrate that the method: (1) is accurate and precise across different light conditions; (2) satisfies previous criteria regarding linearity and red, green, and blue equality; and (3) can be independently validated visually. In contrast with previous digital methods, this method can be used under natural light conditions and can be readily applied to subjects in their natural habitat. To illustrate this, we use the method to measure chest colour in wild geladas (Theropithecus gelada). Unique among primates, geladas have a red patch of skin on their chest and neck, which, for males, is thought to be a sexually selected signal. Offering some support to this hypothesis, we found differences in chest ,redness' for males across different age groups, with males in their reproductive prime exhibiting the reddest chests. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 94, 231,240. [source] Social influences on mammalian circadian rhythms: animal and human studiesBIOLOGICAL REVIEWS, Issue 3 2004Ralph E. Mistlberger ABSTRACT While light is considered the dominant stimulus for entraining (synchronizing) mammalian circadian rhythms to local environmental time, social stimuli are also widely cited as,zeitgebers'(time-cues). This review critically assesses the evidence for social influences on mammalian circadian rhythms, and possible mechanisms of action. Social stimuli may affect circadian behavioural programmes by regulating the phase and period of circadian clocks (i.e. a zeitgeber action, either direct or by conditioning to photic zeitgebers), by influencing daily patterns of light exposure or modulating light input to the clock, or by associative learning processes that utilize circadian time as a discriminative or conditioned stimulus. There is good evidence that social stimuli can act as zeitgebers. In several species maternal signals are the primary zeitgeber in utero and prior to weaning. Adults of some species can also be phase shifted or entrained by single or periodic social interactions, but these effects are often weak, and appear to be mediated by social stimulation of arousal. There is no strong evidence yet for sensory-specific nonphotic inputs to the clock. The circadian phase-dependence of clock resetting to social stimuli or arousal (the,nonphotic'phase response curve, PRC), where known, is distinct from that to light and similar in diurnal and nocturnal animals. There is some evidence that induction of arousal can modulate light input to the clock, but no studies yet of whether social stimuli can shift the clock by conditioning to photic cues, or be incorporated into the circadian programme by associative learning. In humans, social zeitgebers appear weak by comparison with light. In temporal isolation or under weak light-dark cycles, humans may ignore social cues and free-run independently, although cases of mutual synchrony among two or more group-housed individuals have been reported. Social cues may affect circadian timing by controlling sleep-wake states, but the phase of entrainment observed to fixed sleep-wake schedules in dim light is consistent with photic mediation (scheduled variations in behavioural state necessarily create daily light-dark cycles unless subjects are housed in constant dark or have no eyes). By contrast, discrete exercise sessions can induce phase shifts consistent with the nonphotic PRC observed in animal studies. The best evidence for social entrainment in humans is from a few totally blind subjects who synchronize to the 24 h day, or to near-24 h sleep-wake schedules under laboratory conditions. However, the critical entraining stimuli have not yet been identified, and there are no reported cases yet of social entrainment in bilaterally enucleated blind subjects. The role of social zeitgebers in mammalian behavioural ecology, their mechanisms of action, and their utility for manipulating circadian rhythms in humans, remains to be more fully elaborated. [source] | ||||||||||||||||||||||