There’s a really cool recent paper about white nose syndrome in bats that links temperature and humidity, bat fat stores, and arousal from torpor to predict the regions in the US where white nose syndrome should cause bat mortality. In short, it’s normal for bats to periodically arouse from torpor, and each arousal event uses up a huge chunk of the bats’ energy reserves for winter. Infection with Pd increases the number of arousal events, which increases bats’ energy expenditure and decreases the probability that bats will survive the whole winter on their energy reserves – especially in areas with long winters. Bigger bats with more fat reserves are more likely to survive, which might explain why bigger species like the big brown bat have experienced smaller declines than small species like the little brown bat.
That’s right, you guys. It’s not survival of the fittest. It’s survival of the FATTEST.
Also, remember how European bats are infected by Pd, but seem tolerant of their infections? Well, using the climate-body fat-arousal model, Hayman et al. (2015) showed that European bats should be able to make it through the winter just fine given their fat reserves, even when they’re infected by Pd. So now we know why European bats are doing so well, while North American bats (with relatively low energy reserves) are doing so poorly! Ahhhhhhhhhhhmazing.
I do apologize for any nightmares that this cartoon causes…
Hayman, T.S., J.R.C. Pulliam, J.C. Marshall, P.M. Cryan, and C.T. Webb. 2016. Environment, host, and fungal traits predict continental-scale white-nose syndrome in bats. Sci. Adv. 2: e1500831.