by Carl Strang
Those who dislike tree squirrels regard them as rats with bushy tails. Those bushy tails are important in many ways, however. They provide insulation when wrapped around the animal in its nest, and they also are used in communication. Two studies in 2014 focused on tail communication and, in one case, vocalizations. Both studies are ongoing but incomplete, as my notes indicate, but I include them here to remind us that these common animals have something to teach us if we pay attention.
University of Miami. 2014. “Predicting the predator threatening a squirrel by analyzing its sounds and tail movements.” ScienceDaily, <www.sciencedaily.com/releases/2014/10/141021125943.htm>. This article describes Ph.D. thesis work by Thaddeus McRae on the vocal and visual signals given by tree squirrels in the presence of various predators. “He measured the response of three distinct squirrel sounds: the “kuk” (a short bark), the “quaa” (a longer squeal) and the “moan” (a whistling sound). He also looked for specific patterns for tail motions in combination with these noises. The “twitch” involves a controlled movement in an arc shape, while the “flag” can take the shape of an arc, figure eight, circle or squiggle.” The article does not say which signals are associated with which predators, so future publications by this author will need to be found.
Pardo, Michael A., Scott A. Pardo, and William M. Shields. 2014. Eastern gray squirrels (Sciurus carolinensis) communicate with the positions of their tails in an agonistic conflict. Am. Midl. Nat. 172:359-365. They filmed squirrels’ aggressive interactions at feeders, determining dominance (who chases who) and tail position (tightness of bend, 5 levels varying from straight up to sharply bent; and portion bent, 3 levels varying from straight to tip-only bent, to bent about in the middle). Degree of aggression ranged from none to continuing a chase after a subordinate flees. Degree of aggressiveness by the dominant was influenced by the subordinate’s tail position as well as by the dominant’s. For instance, a dominant with a tightly bent tail showed the lowest aggression when the subordinate bent a large portion of its tail. When the dominant bent a small portion of its tail and the subordinate’s tail was loosely bent, the dominant showed low aggression, but this shifted to the highest level when it bent a large portion of its tail and the subordinate’s was tightly bent.