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HIBERNATION / AESTIVATION - Editorial Comment

Raccoons do not hibernate, however they may sleep for several days to as long as a month or more at a time during winter. Juvenile raccoons in northern areas may lose as much as 50% of body weight over the winter, but this is reduced for urban raccoons. Even in southern areas in which raccoons remain active all year round, there is a winter weight loss averaging about 16%.

(References are available in detailed literature reports below)

Hibernation / Aestivation

• Raccoons do not hibernate (B405.w1, B147), however during very cold spells a raccoon may sleep for a month or more at a time. (J59.16.w2, B180.w1)
• To prepare for winter, raccoons in more northern parts of their range store up to 30% of body weight in fat. (B403.27.w27)
• The winter sleep can last for up to four months, during which time raccoons must live on accumulated body fat, as very little food is consumed during waking periods. (B403.27.w27)
• Despite not hibernating, raccoons have a long winter sleep, or torpor, from which they wake on warm days, or if disturbed. (B402.6.w5, B403.27.w27, B405.w1, J59.16.w2)
  • Torpor appears to be induced by the first heavy snowfall of the winter, and to last from November through to March or April in northern regions.
  • Body temperature during winter torpor does not drop below 35°C. 
  • While in winter sleep, the heartbeat of raccoons does not decline. 
  • Metabolic rate stays high during winter torpor.
  • Raccoons live off their fat reserves during the winter.

  (B147, B403.27.w27, B402.6.w5)

• Raccoons will forage during warmer parts of the winter, but do not need to eat, as they store up to a third of their body weight in fat during the autumn and can survive all winter without extra food. (B180.w1)
• In the northern parts of the United States and southern Canada raccoons are inactive throughout the winter. While temperature remains below freezing raccoons stay in a den. When the temperature rises they may move dens. (B285.w2, B147)
• During cold winters raccoons experience some of the physical changes brought on by hibernation, including the increase in size of the islets of Langerhans that is often seen in true hibernators. (B402.6.w5)
• Winter denning is often communal, with more than 23 raccoons being found in the same den. (B285.w2, B180.w1)

Winter weight loss:

• During northern winters, raccoons of all ages (adults, yearlings and juveniles) may lose up to 50% of their autumn body weight. (B403.27.w27, B405.w1)
• Despite rural raccoons losing up to 50% of their body weight in winter, urban raccoons lose a much lower percentage of weight, from 10 to 24%. (J40.67.w2)
• In southern parts of their range raccoons remain active all year, (B405.w1, B147) however a weight loss is still experienced during the winter, with a maximum loss in on study of 32% and an average loss of 16-17%. (B403.27.w27)