By Matt Walker
Editor, Earth News
A monastic male awaits a mate
A monastic species of bat is mystifying zoologists.
The bat, known as the sucker-footed bat, lives in Madagascar, and although it has long been known, its ecology is only just being researched.
But new studies of the bat have revealed a curious phenomenon; they have yet to reveal a single female sucker-foot bat, despite having caught or sighted hundreds of males.
No-one knows where the females live, or why they sexually segregate this way.
Details of the monastic bat are published in the Journal of Zoology.
The sucker-footed bat (Myzopoda aurita) is named after the sucker-like structures on the ends of its limbs.
Males roost in Ravenala leaves
Originally is was thought that bats with these structures literally use them as suckers to stick to vertical surfaces; now scientists know that they stick via a process of wet adhesion, the same forces that stick wet paper to a window.
Studies are also revealing that the bat mainly dines on beetles and moths.
But the real mystery surrounds the no-show of female sucker-footed bats.
Professor Paul Racey of the University of Aberdeen and colleagues based in Madagascar, including at the University of Antananarivo, have being netting sucker-footed bats around the village of Kianjavato in southeastern Madagascar for several years.
Previously, the bat species was listed as 'vulnerable' by the International Union for Conservation of Nature (IUCN), because only a few individuals had been caught in Madagascar.
But the discovery of a population at an agricultural research station in Kianjavato, near Ranomafana National Park, meant the bat's conservation status could be downgraded to 'least concern' and studies into its ecology could begin.
So far, after netting sucker-footed bats during four visits a year, for several years, Prof Racey's team have yet to catch a female.
"We have netted enough times and in enough different places at Kianjavato to be sure they are not there," Prof Racey told the BBC. "We have netted up and down the valley and not found anything.
"We have also found a new population nearer the coast 100km away, but all males."
At Kianjavato, the researchers have so far located 133 roosts of sucker-footed bats, which roost in the partially unfurled leaves of the so-callled Traveller's tree (Ravenala madagascariensis), a well-known plant in Madagascar that looks much like a banana tree.
Each roost contained between nine and 51 individual males.
"My research assistant Mahefa Ralisata emailed this morning to say she had just netted another 26 males at Kianjavato, no females," says Prof Racey.
Despite this monastic lifestyle, male sucker-footed bats evidently find and meet females.
Juvenile males arrive at Kianjavato twice a year, and as juvenile bats do not migrate long distances, due to the fact their wing bones haven't fully grown, they must have been born close by.
Because the species appears adapted to roost in Ravenala leaves, the females are also likely roosting somewhere close in secondary forest.
One reason the females may segregate is that they prefer to live in adjacent, but much better quality habitats.
Females of another bat species, the Daubenton's bat, live in different places in the UK to males, living along better quality lower reaches of river that may better support them during pregnancy and lactation.
Prof Racey expects the mysteriously missing female sucker-footed bats to be doing something similar.
Something else is peculiar about the sucker-footed bat: none of those yet captured and released have been found to carry any parasites on their bodies.
This is extremely rare, as almost all wild mammals carry so-called ectoparasites, such as fleas or ticks.
But "no parasites is easily explained by the roosting habits in the partially unfurled leaves of Ravenala," explains Prof Racey.
These leaves are too smooth for arthropod parasites to stick to, so they cannot crawl onto the bats.
That may be one reason why the monastic male bats choose Ravenala trees to roost in.