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66 Behavior and Social Interactions Their voice is not often heard, but is at once recognized as the husky barking of a big squirrel. Usually it is a soft chuff, chuff, repeated at intervals of a few seconds and only becoming animated when some enemy is sighted and other members of the family are to be warned. —V. Bailey, Mammals of New Mexico, 1931 Introduction Behavior of the tassel-eared squirrels has been a focus of many researchers , with one of the first observations made in 1894: “It had a loud ‘barking ’ call and feeds on cones of Pinus ponderosa, and usually builds its nest of branches in some lightning-blasted trees” (ref. 1). Much of a squirrel’s day is spent searching for and consuming food items, grooming fur, and resting on tree branches. Tassel-eared squirrels hideintreesbyflatteningonbranches,wheretheymayremainmotionless for an hour or more, making it very difficult to observe them by looking up into the tree from below. If squirrels are encountered on the ground, they quickly move away. If the squirrels are in a tree and are disturbed, they will bark, cluck, or growl, fluff or flick their tails, and foot thump. Daily Activity Diurnal animals, tassel-eared squirrels rise with the sun and are back in their nests by sundown (ref. 2, 3, 4). There is an account of a Kaibab squirrel pushing the limit of being diurnal: “I have no documentation of just when squirrels retire for the night but vividly recall one summer evening on road E-6 when the tail of one ground foraging Kaibab 6 B e h a v i o r a n d S o c i a l I n t e r a c t i o n s 67 squirrel was seemingly caught up in the golden glow by the horizontal rays of the sun then sinking beyond the hulk of Matthes peninsula” (ref. 5). One report from Colorado states that tassel-eared squirrels leave their nests about forty minutes after sunrise and return to nest for the evening about three hours before sunset (ref. 6). This same report included the amount of time spent outside the nest with the available daylight by season (table 6.1). The amount of time spent in different behaviors varied with the seasons and also depended on the foods available to the squirrels during a particular season. For example, when squirrels were eating seeds from pine cones, they spent more time in nesting behavior and when squirrels were eating inner bark, they spent less time in nesting behavior (ref. 2, 6, 7). Squirrel behaviors were categorized by William Austin in 1990 based on 296 hours of observations of squirrels during the four seasons over two years (table 6.2). He found that female squirrels foraged more actively in the summer and fall than did males, whereas males were more active in the winter months than females. Females also demonstrated a wider range of foraging activities and choices of food items (ref. 7). Hall followed a Kaibab squirrel for two successive days from dawn to dusk. That squirrel spent approximately one-third of its time on maintenance and two-thirds in active behavior (ref. 3). A one-year study on the behavior of Abert’s squirrels in Flagstaff, Arizona, concluded —just as Hall had with the Kaibab squirrel—that squirrels spent about one-third of their day in maintenance activities. They most often conducted maintenance behaviors in the branches of pine trees rather than on the ground. They spent more time in July and August doing maintenance activities than in the other ten months of the year. Social interactions occurred whenever a squirrel met another squirrel. The amounts of time squirrels spent in the other behavior categories varied seasonally. As temperatures increased, food handling and foraging activities increased, to a point: less foraging time was spent as ambient temperatures increased beyond 210 C. Foraging time increased in the fall and winter while the amount of time spent on maintenance decreased. During the spring and summer with the increase in day length, a reversal was detected, possibly because these seasons offer a much larger variety of foods with higher caloric values. When squirrels are on the ground they spend more time beneath blackjack pines where hypogeous fungi are more common rather than beneath yellow pines, which are more isolated with less available cover (ref. 8, 9). Blackjack ponderosa pine trees are less than 150 years old and have dark bark. [18.218...

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