Pathogens may influence hibernation patterns

Hibernating mammals typically arouse from torpor several times each winter. For very short periods — usually 24 hours or less — their body temperatures temporarily return to normal.

These arousals are energetically very expensive, so why do they occur?

Angie Luis and Peter Hudson hypothesized that hibernating mammals may need to temporarily fire up important parts of their immune systems to fight off infections.

Using a simple mathematical model, Luis & Hudson predicted the temporal pattern of arousals expected under different conditions.

Model results closely resembled observed arousal patterns when pathogens were assumed to be capable of growing at low temperatures — as several bacterial species indeed are.

This finding supports the hypothesis that temporary arousals may have evolved — at least in part — to help animals control pathogens.