Progress 10/01/10 to 09/30/15
Outputs
Target Audience:Academics and interested public Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Opportunities for undergraduates, graduates and postdocs to get involved in research. How have the results been disseminated to communities of interest?Many of my publications get media attention What do you plan to do during the next reporting period to accomplish the goals?Continue to work on chrarismatic species of wide public interest
Impacts
What was accomplished under these goals?
Until quite recently, the idea that meat eating mammals might kill and eat other carnivores was completely new although there had been anecdotal reports in the popular literature. Now, however, we realize that what is called intraguild predation, essentially a form of interspecific competition, is very widespread in nature and affects many aspects of the biology of middle-sized carnivores living in the same area as larger carnivorous mammals. These are seen in their activity patterns and behavior designed to avoid larger carnivores, their careful use of particular habitats, and the defenses of mid-sized carnivores designed to deter attack, such as the noxious spray of skunks. But they are also seen in population responses: here mesopredators live at relatively low densities where large apex predators are still found, and conversely show population eruptions where larger predators have been eliminated and provide no longer keep them in check. These ecological phenomena have ramifications for both conservation and agriculture. Where large carnivores no longer live due to human persecution, mid-sized carnivores live in large populations and can be very effective pest control agents keeping rodents in check. Conversely, where large carnivores still live as, for example, in national parks, mid-sized carnivores such as wolverines remain rare and find it difficult to coexist with other carnivore guild members. My research over the last 5 years has investigated many of these issues involving the ecology, evolution, and applied consequences of interspecific competition.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2011
Citation:
Caro, T., J. Darwin, T. Forrester, C. Ledoux-Boom and C. Wells. 2011. Conservation in the anthropocene. Conservation Biology 26, 185-188.
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Caro, T. 2013. The colours of extant mammals. Seminars in Cell and Developmental Biology 24:542-552.
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Caro, T, T. Stankowich, C. Kiffner, and J. Hunter. 2013. Are spotted skunks
conspicuous or cryptic? Ethology, Ecology and Evolution 25, 144-160.
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Caro, T. 2013. Trends in mortality of mammals on roads in northern California. Southwestern Naturalist 58, 440-445.
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Progress 10/01/13 to 09/30/14
Outputs
Target Audience: Academics. lay persons Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? I have trained one graduate and two diversity undergraduates to score pelage coloration patterns quantitatively and to map thermal isocline maps on to carnivore geographic range maps. How have the results been disseminated to communities of interest? No. Still being analyzed. What do you plan to do during the next reporting period to accomplish the goals? We want to develop a non-lethal protocol for reducing coyote predation on domestic cats and other carnivores using aversive learning rather than killing coyotes which are a key predator in California ecosystems.
Impacts
What was accomplished under these goals?
We are developing a large carnivore data base that focuses on the extent to which carnivores are predated by other carnivores, and independent variables including temperature, snowpack, vegetation type, group size, and external coloration patters. We hope to relate these to the extent of interspecific predation caused by members of the same guild.
Publications
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Progress 01/01/13 to 09/30/13
Outputs
Target Audience: Academics. lay persons Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? We have trained a graduate student in GIS mapping skills of geographic ranges of carnivores and birds-of-prey worldwide. How have the results been disseminated to communities of interest? Through a peer reviewed high impact factor journal What do you plan to do during the next reporting period to accomplish the goals? Investigate the ecological factors underlying intraspecific variation in external appearance and severity of defenses in striped skunks, of interest to both dog owners nationwide and to the scientific community.
Impacts
What was accomplished under these goals?
Mammals have evolved several morphological and behavioral adaptations to reduce the risk of predation but we know little about ecological factors that favor their evolution. For example, some mammalian carnivores have the ability to spray noxious anal secretions in defense, whereas other species lack such weaponry but may instead rely on collective vigilance characteristic of cohesive social groups. Using extensive natural history data on 181 species in the Order Carnivora and we created a new estimate of potential predation risk from mammals and birds-of-prey and used comparative phylogenetic methods to assess how different sources of predation risk and other ecological variables influence the evolution of either noxious weaponry or sociality in this taxon. We demonstrate that the evolution of enhanced spraying ability is favored by increased predation risk from other mammals and by nocturnality but that the evolution of sociality is favored by increased predation risk from birds-of-prey and by diurnality, which may allow for enhanced early visual detection. These results suggest that noxious defenses and sociality are alternative antipredator strategies targeting different predator guilds under different lighting conditions.
Publications
- Type:
Journal Articles
Status:
Awaiting Publication
Year Published:
2014
Citation:
Ecological drivers of antipredator defenses in carnivores
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Progress 01/01/12 to 12/31/12
Outputs
OUTPUTS: A phylogenetically controlled quantitative analysis of pelage coloration in the carnivore group that includes seals, walruses and sea lions was published in the journal Behavioral Ecology. A methodological paper describing how to construct preliminary hypotheses about animal coloration was published in the journal Ethology, Ecology and Evolution. A novel way of thinking about illegal hunters as apex predators was published in European Journal of Wildlife Research and serves as a yardstick with which to compare prey preferences of large carnivores. PARTICIPANTS: Stankowich, Mesnick and Costa are colleagues at the California State Long Beach, the National Oceanic and Atmospheric Administration, and the University of California at Santa Cruz respectively; Kiffner was a postdoctoral colleague with me; Melville is an amateur naturalist; the others are graduates or undergraduates at UC Davis. TARGET AUDIENCES: My refereed articles are targeted at a wide academic audience including behavioral ecologists, sensory ecologists, ecologists and those working on human-wildlife conflict issues PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Carnivores are not only terrestrial but amphibious too. The pinnipeds (seals, sea lions, fur seals and walrus) principally live in sea water and even freshwater environments but they must haul out on land or ice to give birth. They are therefore subject to predation on land and in the sea during some period of their lives. In collaboration with colleagues very experienced with this taxonomic group, we systematically documented external coloration in pinnipeds showing that it varies enormously across species from uniform white to black or brown, and from solid coloration to subtle spotted or bold markings. Moreover, coat color differs by sex and age in several species, with neonates having different color and patterning from their parents. We explored the functional significance of these color patterns controlling for phylogenetic relationships. We found strong evidence for background matching both on land - because species in which adults or pups have white pelage live in arctic regions and are subject to terrestrial predation - and also at sea because spotted species forage in well-lit shallow waters on-shelf, and dark species forage in dark waters off-shelf. Species give birth to black offspring in places lacking terrestrial predators, on islands or in caves, where selection on camouflage is relaxed. In species where males and females differ in coloration, species are highly polygynous and copulate on land. Interspecific predation by other carnivores, such as polar bears, have shaped pinnipeds' external appearance. Although coloration patterns can be investigated comparatively as in the pinniped study, most investigations of how prey coloration "manages" predatory behavior are conducted using model insect prey but such studies are impractical or unethical in rare mammals. We investigated the function of the striking markings in such a mammal, the giant anteater, using photography and simple experiments with models. These methods gave insight into markings on different parts of the body and suggested they may serve different functions in this species including warning coloration and disruptive coloration. These methods are readily applicable to studies of interspecific competition in carnivores. Knowledge about predatory habits of several top carnivores is reasonably well known but far less is known about the prey preferences of human hunters, now an apex predator in many ecosystems. Since human hunting is very circumscribed in USA, we worked in an African ecosystem applying the same analytical techniques to humans' prey preferences as have been used in animal studies. Specifically, we compared stated preferences for different species with that reportedly hunted and related them to known prey densities in the area. We found that hunters would like to kill large species but instead hunt opportunistically when they cannot realize these preferences and so end up taking smaller species than would be expected. We found that a surprising amount of rarer species are taken. Our study helps to unveil novel information that wildlife managers can use to predict what hunters' are likely to extract most from protected areas.
Publications
- Caro, T, Stankowich, T., Mesnick, S.L., Costa, D.P. and Beeman, K. 2012. Pelage coloration in pinnipeds: functional considerations. Behavioral Ecology 23: 765-774.
- Caro, T. and Melville, C. 2012 Investigating colouration in large and rare mammals: the case of the giant anteater. Ethology, Ecology and Evolution 24: 104-115.
- Martin, A., Caro, T. and Kiffner, C. 2012. Prey preferences of bushmeat hunters in an East African savannah ecosystem. European Journal of Wildlife Research DOI 10.1007/s10344-012-0657-8
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Progress 01/01/11 to 12/31/11
Outputs
OUTPUTS: A wide ranging review of coloration in all mammals was published in an edited book called "Animal Camouflage" published by Cambridge University Press, and a quantitative analysis of warning (black and white) coloration in terrestrial carnivores was published in the journal Evolution. PARTICIPANTS: Ted Stankowich and Matthew Cox are colleagues at the University of Massachusetts TARGET AUDIENCES: My book chapter is targeted at both an academic audience and the informed lay reader. Of all the chapters in the semi-popular book, it is the one that stimulates wonder of the natural world because it discusses well known, identifiable and charismatic species with photographs. It has the potential to make people appreciate their natural history better and thereby become more committed conservationists. The journal article targets evolutionary biologists interested in ecological issues. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Several species of terrestrial carnivores have bold contrasting color patterns that in some species advertise noxious anal secretions. For example, in California two species of skunks are prominent predators of waterfowl and carriers of disease. We found that boldly colored species using these defenses are stocky and live in exposed habitats, like marshes and agricultural landscapes, where other forms of anti-predator defense are limited. White dorsa (backs) are found in sprayers that are primarily nocturnal, horizontal stripes are found in species that can spray secretions accurately, and facial stripes are found in burrowing species that typically leave only their heads exposed to attack, such as American badgers. Despite finding that warning coloration has evolved more than once in terrestrial carnivores, the companion wide ranging review of all mammals shows that this sort of conspicuous coloration is relatively uncommon. Rather, contrasting coloration has evolved for a number of other reasons unrelated to avoiding interspecific predation from carnivores including intra and interspecific communication. Research into the function and evolutionary origins of animal coloration, particularly mammalian coloration, serves three clear purposes for the people of California. First, detailed natural historical accounts, as seen for example in wildlife TV and movies, encourages people to consider the natural world more thoughtfully and to ask questions about animals rather than simply regarding them as agricultural pests. In particular, children learn about the colors of mammals such as zebras and giant pandas from a very early age. Animal coloration, not just its description but the reasons for it, has an ambassadorial role for the natural world for young people. Second, comparative (across species) information on such a readily-graspable issue as external coloration gives the public an entry point into appreciating species diversity and for caring about species that are listed in California, such as the wolverine, San Francisco garter snake and tiger salamander. Third, many of the principal conservation issues in this country, including those in California, hoist their petard on charismatic uniquely colored mammals such as the black-footed ferret, the spirit bear, the killer whale and San Joaquin kit fox. Understanding why these species are colored in the way that they are can only add to appreciation and determination to conserve these species and the ecosystems in which they live. Research into animal coloration is therefore an entry point into the world of natural history and conservation and is central to awarding a species the status of flagship species in conservation efforts.
Publications
- Caro, T. 2011. Black and white coloration in mammals: review and synthesis. In: Animal Camouflage: Mechanisms and Function, edited by M. Stevens and S. Merilaita. Cambridge University Press, Cambridge. Pp. 298-332 .
- Stankowich, T., Caro, T and M. Cox. 2011. Bold coloration and the evolution of aposematism in terrestrial carnivores. Evolution 65: 3090-3099.
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Progress 01/01/10 to 12/31/10
Outputs
OUTPUTS: A review of the conservation effects of loss of top predators have been collated in a chapter of a book that I have published called "Conservation by Proxy" available from Island Press. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: My book describing the use of surrogate species in conservation biology deals specifically with the import of top predators being used as keystone species in conservation programmes: in management, restoration and in ecosystem protection. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
A large number of studies have both indicated that there are severe conservation consequences of removing top predators from ecosystems. These predators are therefore termed keystone species in some contexts and are used as an ecological and political lever in conservation programs. I collate and synthesize these attempts in one chapter of my new book discussing the following issues: mesopredator release in temperate ecosystems, ecological meltdown in the neotropics, keystone introductions, removing invasive species, problems with using keystone species as a conservation tool, and reasons for continuing to use keystone species.
Publications
- Conservation by Proxy: Indicator, Umbrella, Keystone, Flagship, and Other Surrogate Species. Monograph by Tim Caro. Island Press (2010) 374 pp.
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Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: Ecological and distributional data on American carnivores was analyzed to determine which carnivores experience most inter-specific competition and predation from other members of their guild. This was published in the peer reviewed journal Etholgy, Ecology and Evolution. Experimental fieldwork conducted in ten study sites across northern California was carried out to understand how California carnivores interact with each other in the wild. The work was published in the peer reviewed journal, Behavioral Ecology. This work was then picked up in the following on the TV stations: ABC 7 channel (SF), Discovery Channel, Discovery Channel Canada TV (Daily Planet); and in the following newspapers: the Vancover Sun (BC), USA Today, the Daily Democrat, UC Davis Aggie (twice), and UC Davis Magazine. PARTICIPANTS: Dr Jennifer Hunter, former graduate student with Caro, now a post-doctoral fellow with the Audubon Society, California. TARGET AUDIENCES: In order to disseminate findings most widely, my students and I publish in peer reviewed journals but follow this up at every opportunity to reach the public, including through TV networks and newspaper and magazine articles as noted above. We have shown for the first time how the iconic species, the striped skunk, manages to coexist and deter other carnivores with whom it lives in the wild by using remote controlled cameras, instead of relying on anecdotal stories of pet dogs suffering from interacting with skunks. And we have broadened these findings to show that skunk species in general face more potential competition from other sympatric carnivores than do the rest of the other American carnivore families showing the necessity of evolving warning coloration. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
It is generally accepted that warning signals in animals function to deter predatory attacks, however, this idea has never been investigated systematically in mammals. We mapped the geographic distributions of species of American carnivores on to each other and estimated inter-specific competition and predation through shared ecologies. We found that procyonids appear to avoid contact with other carnivores through arboreality, and that mephitids do this through noxious secretions. In experimental work we examined the relative importance of specific visual cues that wild predators use to recognize defended animals. We used taxidermy models of striped skunks and gray foxes to investigate this in ten wilderness sites across northern California. Skunk mounts were natural or dyed gray fox colors, and fox mounts were natural or dyed skunk colors. Video cameras that were set up at baited mounts showed that mammalian carnivores approached black-and-white models more hesitantly than gray models and, in addition, reacted negatively to skunk shaped models suggesting both skunk shape and coloration is important. In areas where skunks were most abundant, other carnivores were least likely to visit black-and-white models and were more hesitant in approaching skunk shapes. These findings suggest that prior experience and the frequency with which warningly colored prey are encountered in a landscape are important predictors of predator avoidance and inter-specific interactions among carnivores.
Publications
- Hunter J. and Caro, T. 2008. Inter-specific competition and predation in American carnivore families. Ethology, Ecology and Evolution, 20, 295-324. Hunter J.S. 2009. Familiarity breeds contempt: effects of striped skunk color, shape, and abundance on wild carnivore behavior. Behavioral Ecology, 20, 1315-1322.
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: Although it is assumed that black and white coloration in skunks is a form of warning coloration informing would-be predators that skunks are dangerous to handle, the function of black and white coloration in other carnivores and in mammals is far less understood. I therefore surveyed, collated and synthesized information on contrasting coloration in 5000 species of terrestrial mammals focusing on black and white pelage. After briefly reviewing alternative functional hypotheses for coloration in mammals, I examined nine color patterns and combinations on different areas of the body and for each mammalian taxon tried to identify the most likely evolutionary drivers of contrasting coloration. These results have been published in a peer reviewed high-impact journal. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: In order to generalize findings about the evolutionary impact of interspecific predation on carnivores, specifically on their morphology (coloration), to mammals in general, and then additionally show how contrasting animal signals (coloration) functions in nature, I set up predictions as to how contrasting coloration might be adaptive based on classic hypotheses about coloration in animals. I then examined a large number of mammals, separating them by different sorts of coloration found on the body, and then tested these predictions systematically. The results give scientists a broad understanding of the diversity of selective forces driving conspicuous coloration in carnivores and in mammals more generally. Since publication, the manuscript has been requested as a book chapter too, eventually also giving the public access to these findings. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
The meta-analysis revealed that aposematism (warning coloration) and perhaps conspecific signaling are the most consistent explanations for black and white pelage in mammals. Background matching may explain white pelage. Evidence for contrasting coloration being involved in crypsis through pattern blending, disruptive coloration or serving other functions, such as signaling dominance, lures, reducing eye glare, or in temperature regulation have barely moved beyond anecdotal stages of investigation. Sexual dichromatism is limited in mammals and its basis is unclear. Astonishingly, the functional significance of pelage coloration in most large charismatic black and white mammals that were new to science 150 years ago still remains a mystery.
Publications
- Caro, T. 2009. Contrasting coloration in terrestrial mammals. Philosophical Transactions of the Royal Society, 364, 537-548.
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Progress 01/01/07 to 12/31/07
Outputs
Skunks are presumed to be warningly colored, or aposematic, to advertise their noxious anal secretions. Nonetheless, different species of skunks are colored in different ways - striped skunks have bold longitudinal blazes of black and white; spotted skunks have white spots on a black background - but we do not know why. The function of these different pelage types was investigated by observing the rate at which stuffed skunk models disappeared from human view at night, and reappeared in the morning. Eight observers recorded the rate at which a spotted skunk model, a striped skunk model, a spotted skunk dyed brown, a spotted skunk dyed to resemble a striped skunk and a bobcat model (classically cryptic) disappeared from sight. Normal spotted skunks disappeared very rapidly along with the bobcat and brown spotted skunk suggesting that spotted skunk body coloration is cryptic not aposematic at a distance. These findings question classic ideas that skunks always advertise
themselves to larger predators.
Impacts
Understanding the function of coloration in animals is a growing discipline but conducted mostly in insects and birds, not mammals. That skunks advertise themselves has been taken for granted, never questioning why they need to fend off predators using noxious secretions and advertisements. Previous research addressed interspecific competition from other carnivores in driving pelage coloration in these mesopredators; this research shows that the situation is more complicated, with some skunk species opting for camouflage rather than advertisement, suggesting advertisement is not a fail-safe strategy despite skunks being so well defended. These findings have implications for the extent to which predators avoid each other and defend themselves.
Publications
- Caro T, Merilaita S, Stevens M. 2007 In press. The colours of animals: from Wallace to the present day. I. Cryptic colouration. In: Natural Selection and Beyond: the Intellectual Legacy of Alfred Russel Wallace. Ed by C. Smith and G. Beccaloni. Oxford University Press.
- Caro T, Hill G, Lindstrom L, Speed M. 2007 In press. The colours of animals: from Wallace to the present day. I. Conspicuous colouration. In: Natural Selection and Beyond: the Intellectual Legacy of Alfred Russel Wallace. Ed by C. Smith and G. Beccaloni. Oxford University Press.
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Progress 01/01/06 to 12/31/06
Outputs
Since many mammalian carnivores scavenge meat as well as kill prey themselves, food-stealing or kleptoparasitism is common among both new world and old world carnivores. In the course of these interactions, smaller carnivores are sometimes killed and even eaten by larger competitors. Factors affecting the probability of large carnivores discovering and stealing the prey of smaller carnivores were investigated in an in depth study where direct behavioral observations were possible. Counterstrategies used by smaller carnivores to escape predation were also investigated. Principles derived from these detailed observations appear to operate in north American carnivores too as determined by a major cross-species meta-analysis.
Impacts
Knowledge of the pattern and extent of interspecific competition between mammalian carnivores has a direct impact on how top carnivores are used as tools in conservation biology. Use of carnivores as flagship or umbrella species is called into question where meso-carnivore (mid-sized species) populations are likely to be eradicated by larger carnivores, for example, in wolf reintroduction programs in the USA or where large carnivores such as mountain lions in California are allowed to flourish. The ramifications of using top predators in conservation has been point-by-point detailed in a major review.
Publications
- Hunter JS, Durant SM, Caro TM 2007. To flee or not too flee: scavenger avoidance by cheetahs in Serengeti National Park. Behavioral Ecology and Sociobiology.
- Hunter JS, Durant SM, Caro TM 2007. Patterns of scavenger arrival at cheetah kills in Serengeti National Park, Tanzania. African Journal of Ecology.
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Progress 01/01/05 to 12/31/05
Outputs
To understand the potential for interspecific predation and food-stealing (kleptoparasitism) in American carnivores, geographic ranges of 77 species of terrestrial carnivores have been overlaid on each other.This gives a coarse measure of the potential for interspecific competition.Next, dietary specialization, habitat, activity pattern and height in the canopy were added to the database to give finer resolution for the potential for interspecific competition.The most carnivorous families (Felidae and Mustelidae) appeared under severest competition pressure.Mephitidae (the skunk family) was under particularly high predation pressure, but Procyonidae (the raccoons) were under very low predation pressure.Species with black and white coloration were under great risk of predation compared to other species.
Impacts
These findings show, for the first time, that north and south American carnivores are under high risk of predation from members of their own guild.Thus our attempts to conserve large carnivore species in heavily protected areas may be detrimental to population sizes of middle-sized carnivores. Thus there are conservation merits in partially or lightly protected land use areas on the two continents.
Publications
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Progress 01/01/04 to 12/31/04
Outputs
Interspecific competition among carnivores is seen as an important ecological factor structuring carnivore communities but it can also have important consequences for conservation. For example, large carnivores are often umbrella species with large area requirements, which if given sufficient habitat area, will bring other species under protection. Their presence, however, may reduce or even extirpate smaller carnivore species on which they prey or from whom they steal food. Similarly flagship species, such as mountain lions or jaguars, may attract conservation attention and funding to an area, but their presence will adversely affect sympatric smaller carnivore species. This is an example of how knowledge of basic ecological processes informs conservation agenda.
Impacts
Use of large carnivores as a conservation short cut to delineate protected areas or to act as a magnet for conservation attention has unforseen difficulties brought to light by knowledge of interspecific predation between carnivores. Centering conservation efforts around large predators that prey on meso-carnivore species that perforce live at low densities is a dangerous conservation gambit because it handicaps our efforts to conserve middle-sized carnivores. Conservation strategies must also focus on conserving less than pristine areas where large carnivores have been extirpated including agricultural areas in the Central Valley of California.
Publications
- Caro, T.M. 2003. Umbrella species: critique and lessons from East Africa. Animal Conservation 6: 171-181.
- Caro, T.M., Engilis, Jr, A. Fitzherbert, E., and Gardner. T. 2004. Preliminary assessment of the flagship species concept at a small scale. Animal Conservation 7: 63-70.
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Progress 01/01/03 to 12/31/03
Outputs
Research has shown that competition between different species of carnivore is common and often centers around stealing kills (or kleptoparasitism) because most carnivores scavenge as well as capture prey for themselves. In turn, middle-sized or mesocarnivores employ counter strategies that reduce the likelihood of their kills being found by larger competitors. These include hunting during times of competitor inactivity, hiding carcasses, dragging carcasses into high cover, and starting to eat extremely quickly, all of which have been shown to increase the amount of meat that they can ingest. Surprisingly, mesocarnivores appear relatively relaxed about being vigilant when they are feeding, perhaps to maximize time spent eating meat.
Impacts
Interspecific competition in carnivores is thought to be an important ecological factor in keeping middle-sized and small carnivore populations at low levels and to be implicated in their endangerment. The phenomenon appears widespread having been documented in North America, Europe and Africa. These new results, however, suggest that the potential for interspecific competition may in reality have far less of an impact on mesocarnivores' resource intake, and that its consequences have been exaggerated. If so, this is a welcome sign for conservation of rare and endangered mammalian carnivores.
Publications
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Progress 01/01/02 to 12/31/02
Outputs
Competition between different mammalian carnivore species appears common and can take many forms. These include one species killing and eating members of another species, one species stealing prey that another species has killed, competition over the same prey base, and simply avoiding other carnivores in space and time. Focusing on one aspect of competition, food stealing or kleptoparasitism, we are examining the counterstrategies that weaker carnivore species employ to avoid losing their prey carcasses to scavengers. These include hunting during midday when other carnivores are inactive, dragging a carcass into vegetation where it is unlikely to be found, and driving away avian scavengers away that attract attentions of more formidable terrestrial carnivores to the kill site.
Impacts
Interspecific competition between carnivores can limit population sizes of weaker carnivore species. The phenomenon appears widespread having been documented for North American, European and African species pairs. Unusually, the conservation problem is ecological and this is not caused by humans raising difficult issues for the conservation community because it forces us to evaluate which species are more important than others and can even force consideration of management strategies that actively reduce larger competitors.
Publications
- Caro, T.M. and Stoner C.J. 2003 in press. The potential for interspecific competition among African carnivores. Biological Conservation.
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Progress 01/01/01 to 12/31/01
Outputs
Interspecific competition between carnivores has conservation significance because it can reduce population sizes of endangered carnivores and have top down effects on species consumed by middle-sized or small carnivores. The general importance of interspecific competition as an ecological factor for carnivores is, however, unknown and its conservation significance may have been inflated by intensive research conducted on a few vulnerable species. We therefore examined the potential for interspecific competition across carnivores on one continent, Africa, as a means by which we could refine our techniques before embarking on the carnivores of North America. We calculated, for each of 70 carnivore species there, the number of other carnivore species that overlapped it in geographic range, habitat, and diet, and that could potentially kill the species in question. The average carnivore in Africa shares some of its geographic range and habitat with 26 other species
suggesting competition could be pervasive. More specifically, carnivores may have to share food resources with 22 other carnivore species, on average, although the potential for food stealing is low. The average African carnivore may be vulnerable to predation by 15 other species although it is unlikely to be eaten by other carnivores. The novelty of these crude analyses is that they indicate that exploitative competition and interspecific killing are unlikely to be restricted to the few selected carnivores highlighted in the current literature but instead are of potential widespread importance for carnivores on that continent.
Impacts
Increasingly, interspecific competition between carnivores is seen as important factor limiting carnivore population sizes. This has a number of conservation implications. For example, reserves cannot necessarily be designed simply to protect large carnivores because medium-sized carnivores will suffer; they may need different reserves. Also, given that the presence of large carnivores can reduce medium-sized carnivore populations, this allows the latter's prey base to flourish; thus large carnivore presence can be seen as a factor that promotes biodiversity at other trophic levels. Thus, the extent to which interspecific competition is important in carnivores needs to be understood.
Publications
- No publications as yet 2001.
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Progress 01/01/00 to 12/31/00
Outputs
This project was approved as of 10/01/00, and progress has not been reported for the first 3 months.
Impacts
(N/A)
Publications
- No publications reported this period
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