Hibernation

Because they live at such extremely high altitudes, S. beldingi have evolved specific adaptations to avoid cold weather and the food shortage that occur during the winter. All of the behaviors exhibited by S. beldingi are profoundly affected by the most obvious of these adaptations, hibernation. Incredibly, S. beldingi must hibernate for approximately 8 months out of the year (Sherman and Morton 1979). This means that they are only above ground for four to five months out of the year!

The times that S. beldingi go into hibernation depend on their age, sex, and the altitude at which they live. At higher altitudes, males go into hibernation between late July (Loehr and Risser 1977) and early September (depending on the elevation, followed by females in late September (Sherman and Morton 1979, Turner 1972). All juveniles go into hibernation after their parents. Female juveniles go into hibernation when they are 13 weeks old, and juvenile males when they are 10 weeks old (Holekamp 1986). It seems that this occurs when the grass begins to dry out and turn brown, not when it is cold. This way the squirrels avoid the hot, dry end of summer (Turner 1972).

S. beldingi sleep away the winter in burrows in the ground called a hibernacula. Males hibernate alone, but females are though to share their burrow system (but not necessarily their hibernculum) often hibernate in groups including their relatives (Sherman and Morton 1979, Mateo 2000). The date of emergence in the spring depends on the spring weather and the snow pack. Males emerge first in February at lower elevations and by the end of April in higher elevations, often having to dig out of the snow (Sherman and Morton 1979, Morton and Gallup 1975, Turner 1972). When they emerge, they are instantly ready to mate (Sherman and Morton 1979). The females emerge approximately two weeks later, once the snow around their hibernaculas has melted (Sherman and Morton 1979). Female emergence is spread out over several weeks, and thus so is parturition (Morton and Gallup 1975).

Food!

In alpine and sub alpine meadows, food is not always plentiful, especially in early spring before the snow has melted. Food is an especially precious to S. beldingi because they must have enough resources to supply them with nutrients for their eight-month hibernation. Unlike many other rodents, S. beldingi do not cache food. Instead, they accumulate fat reserves (Loehr and Risser 1977, Sherman and Morton 1979). As a result, S. beldingi must eat A LOT of food in the four months that they are above ground. . In fact, before they go into hibernation, their body weight almost doubles, and their fat content increase fifteen fold (Sherman and Morton 1979)! Consequently, S. beldingi spend 40% of the summer feeding (Loehr and Risser 1977). Luckily, during the months they are above ground, the food is more plentiful and the climate is suitable (Loehr and Risser 1977). Interestingly, S. beldingi only use three fourths of their fat reserves so that they still have fat left over in case of severe weather after spring emergence (Sherman and Morton 1979)

S. beldingi feeds by standing on its back paws and manipulating food with its front paws (Loehr and Risser 1977). S. beldingi are mainly herbivores, and their choice foods are flowers and seeds(Sherman and Morton 1979). Despite this, they will eat a variety of other foods in order to gain enough weight. S. beldingi have been know to eat insects, eggs, carcasses, infant S. beldingi, and small mammals (young males will kill and eat voles and mice, possibly to increase their fat content, and give them greater reproductive success) (Sherman and Morton 1979). In the late summer, seeds make up about 75% of the squirrel's diet (thus why they are called Spermophilus, which means seed lovers) (Turner 1972).

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***Note: This page was created by a student for an undergraduate class (Animal Behavior, BIO 323) at Davidson College***