Changing Reproductive Phenology of the Eastern Gray Squirrel (Sciurus carolinensis) Due to Climate Change in New England

Abstract

Generalist species of great abundance are often overlooked as data sources showing how climate change affects local ecosystems. While there is a lack of studies in peer-reviewed literature, decades of quantitative data about these species have been collected by conservation medicine and wildlife rehabilitation organizations. Using 20 years of data from the Center for Wildlife of Cape Neddick, Maine, I analyzed trends in reproductive phenology of the eastern gray squirrel (Sciurus carolinensis) that correlate with climate change. Using the approximate birth dates of neonate and juvenile eastern gray squirrels admitted as patients, I analyzed the timing of two seasonal birth pulses from 2004 through 2024. Compared to 2004, the first and second birth pulses had shifted 8.8 (95% CI: 3.2, 14.3) and 5.9 (2.5, 9.3) days earlier, respectively, by 2024. Births overall have expanded earlier in the spring, gradually lengthening the reproductive season by 37.6 (-6.8, 82.0) days. Should current trends continue, the changing breeding phenology of the eastern gray squirrel may affect the greater ecosystem. Additionally, these findings demonstrate the potential value of existing data from wildlife rehabilitation and conservation medicine organizations in understanding the effects of climate change, describing dynamics in local ecosystems, and informing conservation.