Diversity vs. sustenance: How mammalian diversity and abundance correlate with agricultural practices

Background/Question/Methods

Wildlife habitat continues to be converted into agricultural land to satisfy the demand of growing human populations. These conversions typically cause severe reductions in biodiversity. Therefore, understanding which agricultural practices best mitigate the effects of food production on surrounding biodiversity is a critical conservation concern. Although significant literature has explored the relationship between agricultural practices and insect diversity (especially pests and pollinators), less work has focused on the relationship between these practices and vertebrate species. We investigated how agricultural practices relate to mammalian diversity and abundance on 13 diverse farms in the North Carolina Piedmont. On each farm, 20 Sherman live traps were used to sample small mammal populations, and one camera trap was used to sample large mammal populations. For 9 weeks, Sherman traps were opened every other evening and checked the following morning. Open trap lines alternated between two sets of farms. Each captured mammal was identified to species and marked with an ear tag. For 14 weeks, camera traps were deployed, and all photos were identified to species. Species diversity, abundance, and Shannon indices were then compared to pesticide use, farm size, and crop diversity.

Results/Conclusions

A total of 58 individual small mammals were captured with the Sherman traps, with 25 instances of recapture. Four mammalian species were captured with the Sherman traps (Mus musculus, Sigmodon hispidus, Peromyscus leucopus, and Microtus pennsylvanicus), and 7 were captured with the camera traps, not including domesticated species (Canis latrans, Didelphis virginiana, Mephitis mephitis, Odocoileus virginianus, Procyon lotor, Sylvilagus floridanus, and Urocyon cinereoargenteus). Increasing pesticide use, increasing farm size, and decreasing crop diversity were correlated with decreasing small mammal species diversity and abundance. Of these three metrics, pesticide use had the largest effect on small mammal diversity and abundance, while the greatest small mammal diversity and abundance was found on farms that either did not use pesticides or only used organic pesticides. Results suggest that eliminating conventional pesticides will best conserve mammalian diversity on agricultural land.