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Eric Schauber -- Research
I am interested in the causes and consequences of fluctuating animal populations within the broader context of ecological communities. These fluctuations can lead to changes in the magnitude of community interactions such as predation, competition, and disease transmission. A mechanistic understanding what causes booms and busts in animal abundance may allow humans to predict ecological consequences and make management and conservation decisions accordingly.
Some of my major areas of current research are:
Space-use and Epizootiology of White-tailed Deer
Diseases are an increasingly important consideration in wildlife management. Chronic wasting disease and bovine tuberculosis are emerging diseases in white-tailed deer (Odocoileus virginianus) populations in various parts of North America. The establishment and potential effects of these diseases in free-ranging deer populations depend on the frequency and pattern of contacts among individual deer. Global positioning system (GPS) collars provide a fantastic tool for obtaining high-resolution data on the movements and interactions of individual deer. Because GPS collars can determine the locations of deer with high precision in space and time, we can examine the simultaneous locations of multiple deer to determine how frequently they come in close proximity. We are currently using these data to assess how patterns of contact vary depending on whether deer are in the same social group or not, and whether simple measures of home-range overlap could be used as a "short cut" index of potential contacts. This project is a collaboration with Clay Nielsen, and two Ph.D. students are involved: Lene Kjær will be using data on deer movements to construct an individual-based simulation model; Charles Anderson will be focusing on the relationship between landscape characteristics, deer abundance and distribution, and vulnerability of deer to hunting.
Many of my research interests spin off from a general interest in masting (the intermittent production of large seed crops, especially by trees) and the fluctuations is causes in animal populations and communities. Masting appears to be an evolved strategy that some plants use to ensure that some of their offspring will escape seed consumers (like squirrels and birds) and successfully germinate. Oak trees (Quercus spp.) are a well-known and important group of masting species in North America. Acorn production by oaks varies greatly among years, which means an unpredictable food supply for many wildlife species that feed on acorns (like squirrels, deer, mice, and many others). A bumper crop of acorns attracts white-tailed deer into oak stands, and causes the abundance of acorn-eating rodents like white-footed mice (Peromyscus leucopus) to increase the following summer.
White-footed mouse
These effects on wildlife can translate into indirect effects on a variety of species and ecological processes, for example:
Gypsy moth (Lymantria dispar) Population Dynamics
White-footed mice are major predators on gypsy moth pupae, so a big acorn crop means lots of mice and low survival of gypsy moths. Thus, acorns may indirectly control the initiation of destructive gypsy moth outbreaks in eastern forests.
Gypsy Moth Caterpillar
The blacklegged ticks (Ixodes scapularis) that carry Lyme disease feed on deer in their adult stages, but often feed on mice and other small mammals when immature. White-footed mice are particularly important hosts for the ticks and also an excellent reservoir of the bacterium that causes Lyme-disease (Borrelia burgdorferi). A bumper acorn crop brings deer into oak forests in autumn, where the adult ticks feed on deer blood and lay eggs. The immature ticks hatch the following summer, just when white-footed mice are reaching peak densities. Many of the larval ticks that feed on white-footed mice become infected with B. burgdorferi, and can infect humans the following year during their nymphal and adult stages. As a consequence, incidence of Lyme disease in the northeast may be higher 1.5 years after a large acorn crop. If this relationship holds, it may enable prediction of peaks in Lyme disease risk more than one year ahead of time.
Generalist Predators: Space Use and Prey Populations
I am interested in ways that the space use of predators (especially generalists) determines their impact on prey populations. There is a growing body of theory relating to the relationship between spatial heterogeneity and stability of predator-prey systems, particularly those involving specialist predators or parasitoids. However, many predators feed on > 2 prey species, so predators may remain abundant even as one prey species approaches extinction. With a generalist predator, spatial heterogeneity in predation risk may be even more important than the specialist-predator case, because a prey species cannot take refuge in rarity. In a collaborative project with Brett Goodwin, Clive Jones, and Rick Ostfeld funded by the National Science Foundation, I am examining how persistence of gypsy moth populations may be enhanced by the synergistic effects of (1) spatial heterogeneity in the risk of predation by white-footed mice and (2) limited dispersal distances of gypsy moth caterpillars. This project involves mathematical and simulation models, using parameter values estimated from field data collected at the Institute of Ecosystem Studies in Millbrook, New York.
Another intriguing complication in predator-prey interactions involving generalist predators is that the abundance and distribution of one prey species may influence the predator’s impact on other prey. This indirect interaction between prey species can be positive (apparent mutualism) if an abundant prey diverts predators away from rare prey or negative (apparent competition) if an abundant prey increases predator abundance thereby increasing predation risk for rare prey. One of my graduate students, Saleen Richter is examining how weasels use space in response to the distribution of primary prey, and how this impacts survival of alternative prey.
Comments and Questions:
schauber@siu.edu
Department of Zoology E-mail:
zoology@zoology.siu.edu
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Last Updated: 25-Jul-05 / ems