Student Spotlight - Stephanie Seto

Small Mammal Response to Oak Loss

by Stephanie Seto

Fall 2008 

Large-scale lteration of forest ecosystems due to disease could result in dramatic changes in community and ecosystem structure and composition.  Black Rock’s oak loss project [Ed. Note: See “Oak Research Update,” p. 6] provides a unique opportunity to observe the effects of this type of ecosystem change on the small mammal community.

Many small mammal species depend on oak trees as an important source of food and habitat, and thus oaks can be important factors for fitness and survival.  Relationships between oaks and small mammals can even affect the risk of Lyme disease transmission since its prevalence is determined by interactions among acorns, white-footed mice, gypsy moths, deer, and ticks.

For my master’s thesis, I am studying the effects of oak loss on the small mammal community, specifically whether loss of oaks or other trees will cause a change in the relative abundances of species and/or changes in species’ diets. Using the oak project study plots, I am trapping small mammals, collecting insects, analyzing fecal matter to determine mammal diets, and using data from vegetation surveys to explore the relationship between oaks and small mammal communities.

I collect general morphological data on the animals I trap and then tag them so I can make abundance estimates and discover whether any travel from plot to plot. I will compare my small mammal data to data obtained before the study plots were treated and also look at differences between the control and altered plots.

This study is unique in that it examines the interactions between a dominant tree species in a forest ecosystem and small mammals. If the population of one species is altered, this could result in changes in other species.  For example, a loss of oaks will deplete the white-footed mouse’s food source (acorns) and could thereby lower the density of mice in that area. The change in vegetative composition will also change insect composition, thus also potentially affecting the diet of some small mammals.

I am still early in my research, but I have so far captured white-footed mice, Eastern chipmunks, red-backed voles, woodland voles, short-tailed shrews, masked shrews, Northern flying squirrels, Southern flying squirrels, and long-tailed weasels. I predict that the relative abundances of species will be different in the treated plots than in the control and pretreatment plots. Small mammal species composition will change in altered oak habitat as some species supplement their diets with other forage while other species move elsewhere. The data from this study will contribute to a better understanding of the complex interactions between plant and animal species in eastern forest ecosystems. 

Stephanie Seto is in her second year of Columbia University’s Conservation Biology MA program.