The Evolution of Scatterhoarding Behavior and Behavioral Adaptations of Eastern Gray Squirrels (Sciurus carolinensis)

Abstract

We investigated the evolution of scatterhoarding behavior (storing food for future use) and behavioral adaptations of eastern gray squirrels (Sciurus carolinensis). First, we simulated the evolution of scatterhoarding compared to nonhoarding behavior at different levels of predation risk, food availability, and foraging efficiency. We found that scatterhoarding behavior was most likely to be adaptive when both predation and the amount of food were low. Further, predation risk could greatly impact the presence of scatterhoarding behavior in a population, regardless of food availability and how easily it could be found. Next, we conducted a range-wide citizen science based study (2019 – 2022) on geographic variation in scatterhoarding behavior of eastern gray squirrels (n = 4540 squirrels) We found that squirrels decreased their investment in hoarding behavior as winters get milder and as the need for scatterhoarded food to survive winter lessened. We also conducted small-scale studies on behavioral adaptations of eastern gray squirrels in a forest in Auburn, Alabama. We monitored 793 artificially scatterhoarded seeds over two scatterhoarding seasons and discovered that a multiyear supply of scatterhoarded food is possible, as 2.9% of all seeds (n = 23) were useful to hoarders at the end of the second scatterhoarding season. We also took a closer look at pilferage rates and selective pilfering of different seed types. We determined that scatterhoarders selectively pilfer seeds based on seed species and treatment (seeds with embryo artificially removed or whole seeds) and prefer to pilfer seeds commonly perceived as more valuable. Finally, by using tagged, germinating acorns, we found evidence that hoarders use seedlings as cues of food belowground and they may use other seed and seedling characteristics to determine how to handle the seed after digging it up.