Research

My research program uses population dynamics framed in an ecological context, and cutting-edge technology, to ultimately promote conservation of wildlife species. I have a particular focus on rare or elusive high-profile species, such as large cats, that are notoriously difficult to study and about which we have little information on population status in the wild. I use new and evolving techniques and analyses to obtain demographic information that can then be used in population modeling to conserve species. As part of a collaborative project, I have pioneered a camera-trapping technique using infra-red, remotely-triggered, motion-sensitive cameras arrayed across a landscape, that "capture" animals on film. The capture histories of each individual are analyzed with mark-recapture statistics to estimate the demographic parameters population size, density, survival and recruitment of the target population. This research has produced the first density estimates of jaguar populations across four different study sites in Central and South America, and provides new information for management and reserve design. These promising results have led me to new research projects employing modified and similar techniques for determining population densities of ocelots in Belize, leopards in Tanzania, and white-tailed deer in the Piedmont of Virginia.

My work in population dynamics has two main foci: Parameter Estimation (e.g. population size, survival, and recruitment) such as that described above, and Population Viability Analysis (PVA). Following the collection of demographic data, I predict wildlife population trends and threats into the future. I use mathematical models to conduct population simulations under various management scenarios in an attempt to determine long term viability. This can produce surprising results and redefine management strategies. For example, my PVA work on Serengeti cheetahs revealed that an increase in the local lion population created the largest threat to cheetah viability, because lions kill cheetah cubs. The implications for large predator management become complicated by such findings because a reserve designed for one large predator may not benefit other predators living within the reserve boundaries. This has led to a new focus on studying cheetah populations in both woodland areas (in addition to plains areas) and in areas outside national parks (but within game reserves) where lions are hunted as game by humans. Areas where lions are hunted may be better for cheetah conservation.

My population dynamics research is grounded in the ecological context of how top predators coexist within ecosystems. I have expanded my Serengeti predator research to examine coexistence between the jaguars, pumas, and ocelots in Central America to determine whether predators limit each other in heavily forested environments to the same extent they limit each other in open plains ecosystems. Large predator conservation is important because the disappearance of top predators has been linked to trophic cascades, where mid-sized predators increase when released from competition and decimate their prey which can then change vegetation structure. Therefore ecosystem-wide effects can occur with the loss of top predators.

I link my population work with animal behavior, for example, through an intensive examination of cheetah home range and movement patterns. This link has, in the process, used novel techniques to examine site fidelity (e.g. linearity indices) and has determined that these wide-ranging cats actually do establish true home ranges, which replaces the previously-assumed notion of random migration patterns across a landscape. This finding has implications for programs of reintroduction or translocation and raises new questions about the cheetah's ability to survive in and acclimate to a new location. Their exhibition of homing behavior greatly complicates current conservation efforts.

My research continues to evolve as methods and technology advance. I have two new projects in occupancy modeling. First, I will use new camera techniques to create detection histories from presence/absence data (as opposed to an individual capture history for each animal from traditional camera-trapping studies) for Sumatran tigers in order to predict tiger occurrence across a landscape. This is an important expansion of the remote camera technique to provide information necessary for conservation of species that occur in abundances too low to conduct traditional mark-recapture analyses for population estimates. Second, I plan to use acoustic detectors, arrayed across a landscape, and designed to detect and record bat calls to establish detection histories for target bat species in Virginia. In this case, identification of individual bats is not possible, and yet we need information on bat distribution to effectively manage these populations. Using habitat variables as covariates will allow modeling the probability of bat species occurrence across the landscape and provide for better bat conservation. By combining new technology in remote detection with occupancy modeling, I am expanding my research to new species and new methods of analyses with real-world applications.

Because many of the species I study exist outside the United States, I have numerous international collaborations with particularly strong ties to the Institute of Zoology in London (ZSL) where I collaborate with Drs. Sarah Durant and Chris Carbone. We are developing protocols for country-wide carnivore surveys (including remote camera surveys) in Tanzania, East Africa as part of the mandate dictated by the Convention on Biodiversity. I was recently made a Research Associate at ZSL. I collaborate with Dr Sybille Klenzendorf of the World Wildlife Fund (WWF) on tiger conservation in Sumatra, Drs. Andy Noss and Scott Silver from the Wildlife Conservation Society, Mario DiBetitti from the National Research Council of Argentina, and Drs. Joanne Earnhart and Eric Lonsdorf on jaguar population size estimation and PVA. Along with my international collaborations, I have numerous collaborations within my own department and use my expertise in population dynamics to advise/consult on projects such as salamander abundance and survival, small mammal mark-recapture, and horseshoe crab surplus production modeling. Additionally I have strong ties with the Conservation Management Institute (CMI) and have been instrumental in Virginia TechÕs co-management of a tropical field station, Las Cuevas Research Station in Belize, Central America. Many of the projects mentioned above would not be possible without the hard work and dedication of the numerous graduate students in my lab and as well as the commitment and involvement of other collaborators.

© tboy 2006