IN THE undergrowth of a New Zealand forest, one thing stirs. A small, fuzzy animal is scurrying over tree roots and thru leaf litter, foraging for bugs and fruit. It scuttles with an odd gait, as if on stilts. Is it a mouse? A hen? No, it’s a bat. The New Zealand lesser short-tailed bat, or pekapeka-tou-poto, to be exact.

Bats first took to the skies about 52 million years in the past, and so they have stayed there ever since. Among the many world’s 1300 or so species, not certainly one of them is flightless. Most can’t even stroll very nicely, which is why many people could be shocked by the behaviour of the pekapeka-tou-poto, a bat as comfy on the bottom as it’s within the air.

However precisely why there aren’t any flightless bats is an evolutionary thriller. The opposite nice group of flying vertebrates, birds, have developed to be flightless a number of occasions globally. They typically achieve this on distant islands, resembling these of New Zealand, the place there’s little hazard from ground-based predation (not less than till people come alongside – roast dodo anybody?). In these circumstances, flightlessness is an efficient adaptation as a result of flying is energetically pricey.

Because the world’s most terrestrial bat, the pekapeka-tou-poto has lengthy appeared key to explaining the curious absence of flightless bats. However analysis over the previous 20 years has revealed a shock: many different species of bat also can stroll. Some may even…