Modeling the colonization of Hawaii by hoary bats (Lasiurus cinereus)

The Hawaiian archipelago, the most isolated cluster of islands on Earth, has been colonized successfully twice by bats. The putative lava tube bat of Hawaii is extinct, whereas the Hawaiian Hoary Bat, Lasiurus cinereus semotus, survives as an endangered species. We conducted a three-stage analysis to identify conditions under which hoary bats originally colonized Hawaii. We used FLIGHT to determine if stores of fat would provide the energy necessary to fly from the Farallon Islands (California) to Hawaii, a distance of 3,665 km. The Farallons are a known stopover and the closest landfall to Hawaii for hoary bats during migrations within North America. Our modeling variables included physiological, morphological, and behavioral data characterizing North American Hoary Bat populations. The second step of our modeling process investigated the potential limiting factor of water during flight. The third step in our modeling examines the role that prevailing trade winds may have played in colonization flights. Of our 36 modeling scenarios, 17 (47 %) require tailwind assistance within the range of observed wind speeds, and 7 of these scenarios required <10 m s^-1 tailwinds as regularly expected due to easterly trade winds. Therefore the climatic conditions needed for bats to colonize Hawaii may not occur infrequently either in contemporary times or since the end of the Pleistocene. Hawaii's hoary bats have undergone divergence from mainland populations resulting in smaller body size and unique pelage color.