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winter, are different in structure and location.Pre-winter dens are usually near favoriteroosting or feeding areas and consist primarilyof hollow trees. Winter dens are generally rockcrevices in steep-sloped areas and located awayfrom their preferred roosting or feeding sites. Astring of below freezing temperature daysstimulates porcupines to enter a permanentden. Where rock crevices are used for dens,porcupines commonly come out to feed atnight.Although porcupines prefer rock crevices forwinter dens, if these are not available, caves,live hollow trees, hollow logs, human outbuildings,and thickly branched crowns of evergreensare suitable substitutes. Den use by porcupinesis not mandatory, and some animals remainoutside all year. This is especially true in areaswhere evergreens are abundant and no suitablerock crevices are available. Hemlock, Douglasfir, white spruce, yellow pine, and white fir arefavorite trees for winter survival. In addition toproviding shelter, these conifer trees alsoprovide a convenient food source.Porcupines do not use bedding or nesting materialin the den but, instead, prefer a dry floor devoid ofleaves and debris. Large accumulations of fecesoccur since dens are used year after year. In moist,temperate climates, feces are decomposed by mites;however, in dry, arid climates, accumulated fecesform into an extremely hard concrete-like mass.Two factors influence springtime exit from aden: a series of days where temperatures areabove freezing and decreased snow pack. Inareas of deep, fluffy snow where travel isdifficult, porcupines leave den sites only whensnow pack diminishes.Porcupines are nocturnal animals and active allyear. However, much time is spent resting intrees called "rest trees." Use of a den or rest treeis evident by the presence of broken quills,recent scats, and the pungent odor of urine.Rest trees are a critical component of theirhabitat, even during adverse winter weather

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16y ago

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