Historical agricultural land-use legacies affect the contemporary abundance of small mammals

Background/Question/Methods

Anthropogenic disturbances such as agricultural land use can cause significant, persistent changes to plant communities. However, it remains less well known whether changes in vegetation caused by historical land use lead to changes in animal abundance. For example, although habitat selection and foraging by small mammals is influenced by a variety of factors including the density and type of ground cover, it is unknown whether the abundance of small mammals is altered by legacies of historical land use. Moreover, although small mammals also respond to contemporary disturbances, such as timber thinning, it is unknown whether the response of small mammal populations to such contemporary disturbances is modified by past land use. We use a landscape-level experiment to evaluate how the abundance of small mammals is affected by past agricultural land use as well as contemporary disturbance (tree thinning, a common restoration tool for herbaceous plants). Between July 2012 and January 2014, we sampled small mammal populations in longleaf pine woodlands that differed in canopy cover (thinned or unthinned) and land-use history (sites used for agriculture >60 years ago or sites with no known history of agricultural land use). 

Results/Conclusions

Our results suggest that past agricultural land use interacts with contemporary disturbance to produce significant changes in the abundance of small mammals. Over four trapping sessions, 4,536 trap nights generated 152 unique captures. The two most common species we captured were cotton mice (Peromyscus gossypinus) and oldfield mice (Peromyscus polionotus). The responses of these two species to the canopy-thinning treatment depended on agricultural history. Within post-agricultural habitats, we captured more P. gossypinus individuals in unthinned patches than in thinned patches. Within habitats with no history of agricultural land use, the pattern was reversed: we captured more P. gossypinus individuals in thinned patches than in unthinned patches. Significantly more P. polionotus individuals were captured in thinned patches than in unthinned patches, regardless of land-use history. Overall, captures of small mammals were nearly three times greater in newly restored longleaf habitats than unrestored habitats. These results illustrate that the response of small mammals to contemporary disturbances such as tree thinning can be modified by persistent legacies of past land use. Given the substantial portions of the terrestrial biosphere modified by human agricultural disturbance, our research highlights the importance of accounting for land-use history when interpreting patterns of animal abundance.