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Behavioral and ecological interactions of fossa, raptors, and lemurs in southeastern Madagascar: A multiple-predator approach

Predation has long been recognized as a significant factor mediating the structure and dynamics of animal populations and communities. Predation may not only alter rates of prey mortality, but also directly drive prey species' behavioral pattern community greater than would be expected by simply summing or multiplying single predator predation rates. In contrast, prey that s and decisions. My research focuses on the direct and indirect effects of predation on prey communities in the context of multiple predator theory.

While most prey species face more than one functional type of predator, such as aerial and terrestrial predators on primates, traditional studies of predator-prey dynamics have only focused on single predator-single prey interactions. The few studies that have been performed on multiple predator systems indicate that the effect of multiple predators at the population level (e.g density, population size) of prey cannot be predicted by a linear extrapolation of the results of single predator-single prey studies. These deviations from an independent, linear summation of single predator effects are termed "emergent multiple predator effects." Recent reviews of multiple predator effects on predation rates (e.g. prey mortality or survival) found some cases of pure additivity, but more commonly, emergent effects such as risk enhancement (greater than expected predation rates) or risk reduction (less than expected predation rates).

Emergent multiple predator effects may be behaviorally mediated. Prey that employ very specific anti-predator responses may actually increase their risk of predation in a multiple predator employ general anti-predator tactics may actually reduce their expected predation rates as behavior effective against one predator will be effective against all.

I conduct my research in Madagascar as predation has been a major topic of debate for ecologists interested in understanding 1) the origins and maintenance of social behavior in primates, in general, and 2) the unique features of lemur social systems in particular, including female dominance and cathemerality. 

Additionally, understanding the interactions between lemurs and their multiple predators has management implications.  Lemur anti-predator behavior may lead to emergent effects in a multiple predator environment.  The complex anti-predator behaviors of lemurs may lag changes in predator populations that are occurring in Madagascar at a rapid rate due to human-induced habitat loss and fragmentation.  Changing predator populations will have lethal and sub-lethal impacts on lemurs and may result in local extinctions of endangered species of lemurs if predators are confined to small patches of isolated forests holding such lemur species. Finally, many species of both the lemur prey and their predators are threatened and endangered, so understanding the basic forces that influence their population numbers and dynamics is critical to successful conservation and potential reintroduction efforts.

Past studies of the lemurs of Madagascar demonstrated that they were potentially subject to predation from a diverse group of predators (including raptors, the terrestrial fossa, Cryptoprocta ferox, and constrictor snakes such as Sanzinia madagascariensis), yet little was known about the details of any of these ecological interactions before I began my studies of raptor predation.  

To understand how predation structures lemur groups and impacts the management of lemur populations, I adopt three approaches in my research:  1) direct studies of diurnal and nocturnal raptor predators and carnivores to quantify lemur predation rates, 2) comparisons of primate predation rates across species and correlations with life history characteristics, and 3) experimental manipulations of lemur predation risk to explore the existence of trade-offs that might lead to emergent multiple predator effects.  My dissertation research and publications focused primarily on the effects of diurnal raptors on lemur populations.  New studies now underway will focus on carnivore population dynamics and carnivore impacts on lemurs in the eastern rainforests in and around Ranomafana National Park.

For more information on all aspects of Ranomafana National Park, see Dr. Patricia Wright’s (my Ph.D. co-advisor), Institute for Conservation of Tropical Environment’s (ICTE) website

For more information on the impacts of predation on primate population’s, see the web site of Dr. Charles Janson (my Ph.D. co-advisor)

Department of Fisheries and Wildlife Sciences
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Email: Department of Fisheries and Wildlife