Less than one percent of North America’s historic tallgrass prairie remains today, making it one of the most endangered ecosystems on Earth. Currently, one of the biggest threats to tallgrass prairies is invasion by nonnative plants. Granivorous small mammals, such as mice, voles, and squirrels, affect plant community assembly at the seedling/establishment phase, which is when many invasive plants exert competitive dominance over native plants. Thus, understanding small mammal populations may offer insight into the spread of invasive plants. Conversely, removing invasive plants may reduce food availability to small mammals, altering their abundance or diversity. The goal of this study was to characterize the small mammal community at a restored prairie, understand the relationship between small mammal and nonnative plant abundance, and determine the impacts from herbicide control of red clover (Trifolium pratense, a common invasive plant) on small mammal diversity.
Sherman traps were used to capture small mammals at 14 sites at Nachusa Grasslands, a 1,400 hectare restored prairie in Franklin Grove, IL. Each site received 100 trap nights four times per year from 2013-2017. Captured individuals were PIT tagged to track movements and avoid duplicate counts. At half the sites T. pratense was removed by spot spraying with broadleaf herbicide.
Results/Conclusions
820 unique individuals comprising ten different species were caught over four years. The most common species were Peromyscus maniculatus, P. leucopus, and Microtus ochrogaster. P.maniculatus was the most abundant for all years except 2017, when M. ochrogaster abundance spiked, presumably signaling the start of a “boom” phase in population size. Site age (time since restoration began) had a positive but weak effect on mammal diversity. Sites where T. pratense was treated with herbicide did not have significantly different small mammal diversity. Data on the correlation between small mammal and nonnative plant abundance are forthcoming. These findings suggest that small mammals are able to survive on other food sources, even during aggressive herbicide regimes. Given the magnitude of small mammal population fluctuations, it may be valuable to consider their population abundance when trying to anticipate plant invasions.