Smile For the Camera: Patterns of Mammal Abundance in Great Hill Forest Through Four Years of Camera Trapping

Snapshot USA is a nationwide camera trapping project aiming to determine biodiversity and abundance of animal populations across all 50 states. Since 2019, participants have used camera traps to document wildlife every September and October, coinciding with animal activity patterns and North American academic year starts. Understanding biodiversity through long-term monitoring is an important topic to study, because the knowledge obtained can help track populations and better understand wildlife responses to disturbances. Since Snapshot USA participants use the same methods and trapping season, the information we collect can be directly compared to other Snapshot USA locations. At Great Hill Forest in Bridgewater, MA, our Snapshot USA array has used 8-10 unbaited cameras each year, spaced at least 100 meters apart, during September and October, starting in 2019 and continuing to present. For this study, we are focused on four years of data on wild mammals (humans, domesticated mammals, and birds were removed from the data set). We estimated relative abundance for each species detected using a relative abundance index (RAI), and explored the changes in RAI over time. Over four years, we detected 15 species of terrestrial mammals. Most species were detected every year, however one species (striped skunks) were only detected in one year (2020). Our most abundant mammal was the eastern gray squirrel and in all four years, eastern gray squirrels, eastern chipmunks, and white-tailed deer were consistently the top three most abundant species. Interestingly, gray fox abundance was high in 2019 and 2020, but nearly zero in 2021 and 2022, while red fox showed the opposite pattern. This suggests replacement of gray foxes by red foxes, perhaps due to competition for food. This thesis documents these and other patterns in mammal abundance at one location, and we have outlined several potential follow up studies: (1) to compare the patterns at our site to other Snapshot USA locations within New England to check for consistency; (2) generate hypotheses to explain the fluctuating patterns we uncovered, and test those using ecological modeling approaches. (3) explore local patterns of seasonal abundance using the larger Bridgewater data set of continuous camera trap monitoring since September 2019