Gray Squirrels and Acorns
November 24, 2015
It’s fairly well known that gray squirrels hoard or cache acorns. The details, however, are not as well known: How do they find the acorns? Are the acorns of all oak species equally relished by squirrels? What effect does it have on a forest? How do they protect their cache?
Though they recover and eat more than half of them (estimated at 74%), many are left underground to germinate and grow into young oak trees. These squirrels also protect their cache through what is termed deceptive behavior.
According the ScienceDirect article, “Cache Protection Strategies of a Scatter-Hoarding Rodent: Do Tree Squirrels Engage in Behavioral Deception?” by Michael A. Steele, Sylvia L. Halkin, et.el. (2006), gray squirrels “adjust their behavior” when their cache is threatened, “displaying three kinds of pilferage-averting behavior: (1) covering sites where nothing had been cached (deceptive caching; (2) caching nuts in sites that were either out of view of or inaccessible to observers (behind obstacles, under bushes, in tree nests and cavities, in stumps and in muddy areas); and (3) eating nuts rather than caching them.” The authors also noted, however, that this deceptive behavior occurs infrequently.
On November 24, 2015, I watched a squirrel dig up an acorn (see photos below). He held it, in his hands, in his mouth, but didn’t eat it. Instead, he moved to another spot on the same lawn, within a few feet from where he dug it up, and set it within the grass, in a shallow hole. Then, he ran away.
Was this a deceptive strategy? Or, did this squirrel pilfer another squirrel’s acorn and then bury it as his own? Why did he plant it again so close to where he found it? Why didn’t he eat it?
Red oak acorns have more tannin than the acorns of white oaks, so, in the study for the above article, the authors noticed that many squirrels would eat the top half of the acorn and toss the rest away. This is because the tannins are found at the bottom of the acorn. The acorn, with only the bottom half remaining, is still able to germinate. So, acorns have their own defensive strategies. This squirrel’s acorn seems to be from a white oak, but it’s too hard to be sure. The ScienceDirect article about the dissemination of acorns by gray squirrels allowed them to speculate on the extent to which squirrels aid in the growth of forests. It was interesting to watch this behavior in progress, though it’s a bit frustrating because I’ll never know for sure what this squirrel was actually doing.
