New Zealand is home so some pretty unusual animals, including the world’s only walking bats: the greater short-tailed bat (Mystacina robusta) and the lesser short-tailed bat (Mystacina tuberculate.)
The Lesser Short-Tailed Bat
As the sun slips beneath the horizon, blanketing New Zealand in darkness. A small head pokes out from a narrow rock crevice. The lesser short-tailed bat’s bright, tiny eyes peer into the deeper shadows, looking for signs of danger before the small, winged creature slips out of the roost. Dried leaves crackle beneath it’s folded up wings as it ambles across the forest floor. Long, pointed ears swivel from side to side as it sends and receives echolocation signals that not only help it navigate the dark forest, but also identify food sources.
The forest dwelling lesser short-tailed bat can only be found in New Zealand and the surrounding islands. While this is the only remaining mammal that’s native to New Zealand, that’s far from the only thing that makes the species unique. It has several traits that make it stand out from all other bat species.
To begin with, the lesser short-tailed bat walks. When it emerges from its roost for a night of hunting, it walks on its back legs and uses its folded-up wings for support, with the result being an odd-looking shuffle that serves the bat well. While the bat is capable of flight, they truly seem to prefer walking across the forest floor. Although no one knows exactly why New Zealand’s bats started walking, most feel that it’s in response to the lack of native mammal predators, which is why many believe that so many of the native birds are also flightless.
The lesser short-tailed bat has developed a unique anatomy in response to its terrestrial lifestyle. The thick 6-8 cm (2.3-3.14 in) long body is covered with greyish-brown, short, thick fur (the fur is considerably thicker than that of most other bat species, including the ones that live in cold northern climates.) The underside is covered in a paler coloured fur that’s just as thick. When the bat is walking, they don’t just fold their wings, but actually roll them up, rather like an umbrella, this allows the bat the freedom to use its forearms as braces. The wing membranes are a bit thicker than other bat species and the bat’s fingers are designed in such a way that when the wing is rolled, the first phalanx fold to the outside. The species is the only microbat that has a small talon on their thumb, which is attached to the bat’s claw. Stiff bristle like whiskers sprint from the bat’s nose. The bat’s short, thick feet are covered with small grooves that also adorn the animal’s powerful legs. Although it’s not as long or as mobile as nectar feeding bats, the lesser short-tailed bat’s tongue does have extendable tissue and there are small papillae on the end of it which allow the bat to sip nectar.
Those who are lucky enough to spot this extremely rare bat, will marvel at how smoothly it navigates the debris strewn ground, and how quickly it races, squirrel like, up tree trunks before scurrying across branches.
Research indicates that the walking bats evolved to fulfil the role of mice and rats which until recently weren’t found in New Zealand and which now represent invasive species that are taking a huge toll on the native ecology.
Fulfilling the role of rodent certainly explains the lesser short-tailed bat’s diet. It is one of the only known bat species that’s an omnivore. It eats pretty much anything it encounters and doesn’t seem to have a preference if the food is an insect, nectar, or piece of fruit. The bat is credited with being the primary pollinator of New Zealand’s woodrose (Dactylanthus spp.)
While the lesser short-tailed bat prefers walking when it’s foraging for food, it’s not flightless. The bats do fly, though they tend to stay close to the ground and don’t enjoy the same amount of speed or agility as other types of microbats.
Like most bats, the lesser short-tailed bat bears just one pup a year. The pups mature quickly. They’re ready to start learning how to fly when their about a month old and are fully grown between eight and twelve weeks. The species uses a lek (singing) courtship routine. Between the months of February and April, males select a nice tree branch and sing about their love. Researchers have noticed that an interested female will travel as far as 10km (6.2ml) while she’s searching for a mate.
The Greater Short-Tailed Bat
Little is known about the greater short-tailed bat. They were primarily spotted on New Zealand’s Solomon Islands and Big South Cape, though fossils suggests that there was a time when they were also present on both North and South Islands.
Like its lesser short-tailed cousin, the greater short-tailed bat was believed to have dined on a wide assortment of food options and hunted primarily by stalking along the ground. The last time anyone has laid eyes on any representative of the species was in 1965. While it’s believed that the laughing owls took a huge toll on this bat population, experts believe that what finally drove the greater short-tailed bat into extinction was the accidental infestation of ship rats to Big South Cape Island. The introduction of the rats had a massive impact on the island’s ecology. Shortly after the infestation, the greater short-tailed bat disappeared as did many of the flightless birds that called the island home. The ship rat invasion has the distinction of being the first recorded time in history when rats were pinpointed as the cause of the extinction of another species. In addition to the greater short-tailed bat, rats also led to the extinction of both the Stead’s bush wren and the Stewart Island Snipe. The rats continue to have a devastating impact on the region’s ecology, leading conservationists to discuss some extremely drastic options, including gene editing as an eradication method.
The Greater short-tailed bat is believed to be extinct. The New Zealand Department of Conservation considers the lesser short-tailed bat to be a Species of Highest Conservation Priority and they’re committed to doing everything they can to preserve the species. In addition to exploring ways to manage the rat problem and preserve the bat’s preferred habitat, research programs designed to learn as much about the species, including its social behavior are currently underway.
Want more beautiful bat facts, check out 60 Beautiful Bat Facts, available 1/8/18
Schira, Jess “60 Beautiful Bat Facts.” 8 January 2018