Invasion of an emerging infectious disease, white-nose syndrome, eliminates continental differences in sociality and alters distributional patterns of its hosts
Sociality in animals varies across orders of magnitude from solitary animals to colonies composed of millions of individuals. What drives such large variation in social organization remains poorly understood, but is important for explaining macroecological patterns of abundance and distribution. We investigated the impacts of an emerging infectious disease on social group size and distributional patterns. We compared sizes of 1,078 colonies of 16 species of hibernating bats across two continents (North America and Europe) before and after emergence of white-nose syndrome (WNS), a multi-host disease of hibernating bats that emerged in North America in 2006.
On average, colony sizes before disease arrival in North America were four-fold larger than in Europe, even after accounting for habitat and climatic factors that could influence group size. WNS emergence reduced winter colony sizes by 10-fold within five years of arrival. Colony sizes of bats in eastern North America are no longer significantly different than colony sizes of ecologically and taxonomically similar species throughout Europe, where the disease has likely been present for millennia. Declines from WNS have resulted in local extinction of 6 to 69% in six species of North American bats. Local extinction rates were driven by both rarity prior to disease invasion and susceptibility to disease mortality. Patterns of sociality and distribution result from complex biotic and abiotic interactions and our results suggest that disease emergence may be an important driver of macroecological patterns.