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7 Foods and Feeding
- Johns Hopkins University Press
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What do squirrels eat? “Practically everything” would be the glib answer to this question. Anyone who has observed squirrels in a backyard or city park knows that the stereotypic image of a squirrel eating only nuts is not the complete picture. Squirrels do not have a reputation for being discriminating and given the opportunity seem to eat almost anything—including candy bars, chicken wings, cookies, and even leftover pizza. In official terms, squirrels are omnivorous , meaning that they eat both vegetable and animal matter. Re- flecting this, squirrel species across the world have varied and, sometimes, unique diets. The foods eaten by squirrels can vary by season, in response to availability . This seasonal availability of food also can vary annually, and it most certainly varies geographically. In the early spring in the temperate zone, tree squirrels (Sciurus carolinensis, S. niger, and S. vulgaris) and flying squirrels (Glaucomys volans and Pteromys volans) may feed on a diverse variety of buds, flowers, young shoots, and the like. In the summer, insects can make up a large percentage of their diet. In the autumn, nuts and seeds become the conspicuous source of food. In some species of squirrels, pine cones make up a large proportion of the diet. Abert’s squirrel (Sciurus aberti) eats primarily seeds from the Ponderosa pine. The North American red squirrel (Tamiasciurus hudsonicus) and Douglas’ squirrel (Tamiasciurus douglasii) also feed primarily on pine cones, most notably western hemlock, spruce, and Douglas fir cones for Douglas’ squirrel, and Lodgepole pine and Ponderosa pine cones for the North American red squirrel in the western United States. Chapter 7 Foods and Feeding Squirrels do not hesitate to take advantage of opportunity and make use of an abundant resource if it is available. A perfect example of this can be seen during the appearance of the 13- and 17-year cicadas in the United States, when squirrels will gorge themselves, to the exclusion of all other food, on this seemingly infinite food supply. In other cases, squirrels seek out special resources that they need. Chris Smith, at the University of Kansas , observed pregnant and lactating North American red squirrels gnawing on bones and antlers. Presumably these squirrels gain minerals, such as calcium, which is inadequately represented in their normal diet, from the bones, which helps in the growth and development of young. Harmon Weeks and Charles Kirkpatrick looked at sodium (Na) intake in fox squirrels (Sciurus niger) and woodchucks (Marmota monax). Both species of squirrels are known to lick road salt, and woodchucks are known to eat the salt-laden gravel along the side of the road. Weeks and Kirkpatrick found that both squirrels had peaks in their intake of sodium, with fox squirrels having two peaks (April and September) and woodchucks having one peak (May/June). Sodium is an essential element in the diet, presumably deficient in the diets of these squirrels at this time of year. Some ground squirrels, such as chipmunks, have diets very similar to those of temperate tree squirrels. Other ground squirrels, such as the marmots , feed extensively on the vegetative parts of plants. Marmots prepare for hibernation by storing energy in their body fat, not by hoarding seeds and nuts. Body fat can only be metabolized when it is liquid, and for hibernators this requires unsaturated fats. Saturated fats are solid at hibernation temperatures and cannot be metabolized. Consequently, marmots and other ground squirrels feed on plants containing unsaturated fats, in California ground squirrels sample a piece of pizza left by a generous human. Squirrels are notorious for some unusual eating habits, tastetesting candy bars, birthday cake, and even chicken wings. Photo © Gregg Elovich, www.scarysquirrel.org Foods and Feeding 103 [54.242.75.224] Project MUSE (2024-03-19 08:30 GMT) 104 Squirrels: The Animal Answer Guide particular, the fatty acid linoleic acid, which they can metabolize while hibernating and when coming out of hibernation. They carefully select food plants that provide them with the proper amount of these fatty acids—not too much and not too little—to permit their hibernating behavior. Many species of squirrels feed on mushrooms and other fungi. Small subterranean truffles are a favorite food of northern flying squirrels (Glaucomys sabrinus), Abert’s squirrels (Sciurus aberti), and many fox squirrels. The North American red squirrel (Tamiasciurus hudsonicus), Abert’s squirrels , the Eurasian red squirrel, and the Japanese squirrel (Sciurus lis) will collect mushrooms of many kinds, hang them up on tree limbs to dry, and then...