Behaviour of hibernating little brown bats experimentally inoculated with the pathogen that causes white-nose syndrome

Pathogens can affect host behaviour in ways that influence disease transmission as well as survival and fitness for both host and pathogen. Hibernating bats with white-nose syndrome (WNS) show a number of unusual behaviours including increased frequency of arousal from torpor, altered roosting behaviour and premature emergence. However, mechanisms underlying these patterns are not understood, and the behaviour of bats with WNS has not been examined systematically. Three hypotheses could explain increased arousal frequency. Bats may arouse to (1) groom in response to skin infection, (2) drink to offset dehydration or (3) increase activity, possibly in an attempt to access resources, avoid a source of infection or limit the risk of infecting relatives. We tested these hypotheses with captive little brown bats, Myotis lucifugus, inoculated with Pseudogymnoascus destructans, the fungus that causes WNS. In contrast to predictions of all three hypotheses, bats inoculated with the fungus tended to be less active than controls during arousals from torpor and did not increase grooming or visits to the water source in their enclosures. However, bats showed a dramatic reduction in clustering behaviour as infection progressed. Reduced activity and clustering could represent adaptive, maladaptive or pathological responses. Reduced activity could be an energy-saving mechanism or a pathological consequence of infection while reduced clustering could have beneficial or detrimental consequences for transmission, energetics, water balance and survival. Our results highlight the need for studies of host behaviour to understand dynamics of wildlife infectious diseases.