Bats conquer Antarctica

There are no fossil records of bats in Antarctica, yet paleobiogeography suggests that they were once present, when Antarctica was a temperate forest. After more than 40 million years, this successful group of mammals has made their return to the icy continent, not so much icy anymore. 

At the moment, bats are the only land mammals present in Antarctica, except the semiaquatic newotter. Moreover, only one lineage was able to colonize this cold and empty land: all 4 species of antarctic bats are vesper bats of the Myotinae subfamily, derived from a myotis-like bat that diverged from the south american clades about 4 million years ago.

The most generalistic species is surely the willow myotis (Criomyotis gigas) a medium-sized myotis that commonly rest in large hollow willows. Winter colonies are small, rarely reaching 200 individuals, while summer colonies can exceed 40.000 individuals. Willow myotis typically hunts its prey over the water surface of rivers and lakes: midges, flies, mayflies, caddisflies and moths cover most of their diet during the warm season.

Another interesting species of bat is the nesthief (Cuniculumyotis aviphyla) a myotis species that is strongly correlated to the presence of ground tyrants: the entire cycle of wintering and nursing is made inside of the abandoned burrows of these large birds. Burrows are an optimal microclimate, with a high level of humidity and relatively stable temperature. Prey are captured near the resting areas but, since ground tyrants can be found everywhere, the hunting ground of the nesthief is extremely variable, from the coastal forests to the edge of shrub tundra.