June 22, 2006
Big Bats Show Puzzling Fondness for Small Places
By Ed Stoddard
ANALASOA, Madagascar -- The startled bats resemble a flock of demonic ravens as they take to the sky, their huge wings spreading over the green canopy of the forest."They must be disturbed by our presence," said conservation biologist Dr. Richard Jenkins as scores of Madagascar's flying foxes squealed their displeasure at the human intrusion.
With wingspans of a meter (3.3 ft) or more, the bats are surprisingly big but their chosen home is small. This ecological oddity intrigues scientists like Jenkins and highlights the importance of protecting small and isolated habitats.
Protected areas are one of the key themes of a conservation conference this week in Madagascar, an Indian Ocean island off Africa's east coast. But while ecologists are mostly discussing large spaces, the bats focus attention on the small.
Measuring just a few hectares, the bats' roosting place is an island of indigenous forest in a sea of introduced pine trees, planted there for large-scale commercial harvesting.
Their ancestors also displayed a fondness for islands.
"The theory holds that the flying foxes came out of southeast Asia by hopping islands," explained Jenkins.
Known as fruit bats because of their dietary preference, flying foxes are found in Australia and Pacific and Indian Ocean islands as well as Madagascar.
Evolving into different species as they moved from island to island, the flying foxes colonized ecosystems right up to Pemba Island off Tanzania's coast. But they gave the mainland a miss.
"They seem to prefer small fragments of habitat. Why they don't have a foothold in mainland Africa is a mystery," said Jenkins, who heads a local green NGO called Madagasikara Voakajy, which means Madagascar Conserved.
Some wonder if small areas kept the bats safe from predators likely to focus on larger territories. Others think the topography might have made it easier to find their way home.
No one really knows why the bats prefer narrow strips of habitat separated from larger siblings by the ocean or a forest of exotic pines.
ORTHODOXY UPSIDE DOWN
Like a bat when it sleeps, this turns ecological orthodoxy upside down.
Accepted science holds that fragmentation of natural habitats is bad -- many species have disappeared when their habitat has been diced up by human activities like farming.
Most recorded extinctions over the past few centuries have also occurred on islands, an indication of the fragility of small populations living in isolation.
"Most of the endemic animals depend on intact forest. If it becomes fragmented, they lose species," said Jenkins.
But the big bats are exceptions to the rule.
"There are some species which choose not to live in the big forest. We are not challenging the notion that fragmentation is bad, but the notion that fragments have no ecological value," said Jenkins.
Large protected areas, like the 16,000 hectare (39,500 acre) Mantadia park roughly a 25-km (15.5 mile) bat flight from the pine plantation, have no flying foxes.
The bats can fly such distances, and may even disperse seeds to larger areas of habitat far from their roosts.
Fidinirina Andriamanalina is studying the bats' range and is in charge of a program that has seen eight of the animals radio-collared -- a delicate task involving capture with nets.
"This group moves about mostly between here and another location where they roost," he said, as he held up a large antenna. But much more work needs to be done to determine their nocturnal foraging movements.
Jenkins, a laid-back Welshman, says some baobab forests in the west of Madagascar, the world's fourth largest island, are almost exclusively pollinated by flying foxes.
This shows that while the bats may appear to be cut off from other habitats, they do in fact have a link to them.
In the pine plantation, there are about eight small areas - the smallest is only two hectares (5 acres) - which 3,000 to 4,000 of the flying foxes call home.
"We call them orphaned forests because they have been abandoned," said Jenkins.
Poor communities in the area have "adopted" the bats.
"We used to hunt them for meat. But we have had awareness programs explaining the importance of the bats and now we don't kill them," said villager Namisoa Ravelonirina as she cradled a baby on her hip.
Jenkins hopes the wider green community will also adopt his orphans and include them in bigger conservation plans, including Madagascar's own drive to triple its protected areas.