The internal body temperature of spiders is variable and tends to fluctuate with their environment. This means that the cold temperatures of winter pose a challenge. Spiders meet this challenge in one of several ways. A majority (as many as 85%) of species crawl under the leaf litter, shut their metabolism way down and become dormant; some species mate, lay eggs and die; and some remain active.
It is not unusual to come across tiny active spiders on top of the snow, especially on sunny winter days. If it’s particularly cold, they may have their legs pulled in and appear lifeless. When their body is sufficiently warmed up, they will resume crawling across the snow.
The metabolism rate of spiders that remain active through the winter is elevated, making starvation as big a threat as freezing. They must find food (springtails and other invertebrates) in order to sustain themselves. Some of these spiders can remain active until their body temperature is 25 F degrees when they will go dormant like other spiders. They cannot survive If their internal temperature drops to 19 F. degrees. (Source, Vermont Center for Ecostudies) (Photo: active spider surviving despite loss of one leg)
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