Squirrels are famously conspicuous on North American college campuses, and conversations about these charismatic rodents abound in (non-scientific) venues of discourse. The positioning of researchers at colleges and universities offers opportunity for the study of sciurids in human-dominated landscapes, but cross-campus studies have been inhibited by a lack of baseline information across these habitats. To establish an inventory of squirrel species on college and university campuses across the USA and Canada, we employed a crowdsourcing approach similar to citizen science but with a targeted data collection strategy. Reports of squirrel species presence and absence were sought from faculty experts at post-secondary institutions across the continent, resulting in species lists for 536 campuses. This crowdsourcing approach not only amplified data acquisition beyond what could be accomplished by a single research team, but importantly also engaged a network of science faculty interested in squirrel-focused research. Reports were used to establish maps of species distributions and diversity across campuses. We used contingency analyses to assess how competition between key species pairings effects their cohabitation of the same campuses. We broadly assess regional trends of campus species diversity and highlight historical changes in species distributions that should be monitored into the future.
Results/Conclusions
We find that squirrels are (almost) ubiquitous on campuses across the continental USA and Canada, appearing on 95% of surveyed campuses. Only a select few species are common across these habitats, namely the eastern gray squirrel (Sciurus carolinensis – on 62% of surveyed campuses), eastern fox squirrel (Sciurus niger, 38%), eastern chipmunk (Tamias striatus, 35%), North American red squirrel (Tamiasciurus hudsonicus, 26%), and woodchuck (Marmota monax, 25%). Competition between eastern gray and eastern fox squirrels results in campus partitioning: contingency analyses reveal that they are significantly less likely than expected to cohabit campuses, and the eastern fox is more sensitive to the presence of the eastern gray than vice versa. The invasion of the West Coast by eastern gray and fox squirrels has corresponded with the decline of the native western gray squirrel (Sciurus griseus), but surprisingly, contingency analysis does not support the conclusion that competition with eastern Sciurus is the primary factor discouraging western grays from using campus habitats. This inventory of campus squirrel distributions can serve as a baseline for longitudinal studies within and across these habitats and may be opportunely combined with initiatives to engage students and the public.