Hanging by a Thread - Rodrigues fruit bat - Brief Article

Animals, Sept, 2000 by Lisa Capone

Ask a scientist what he or she likes best about science, and the answer is often the thrill of unexpected discovery. Go looking for one thing, and you sometimes stumble upon another. It was through such serendipity that the rare Rodrigues fruit bat made U.S. newspaper headlines in the mid-1990s.

Thomas H. Kunz of Boston University's Center for Ecology and Conservation Biology was conducting unrelated research in 1991 at the Lubee Foundation, a bat conservation and research station in Gainesville, Florida, when something surprising occurred in another cage. A Rodrigues fruit bat (Pteropus rodricensis) was trying to give birth in the wrong position--hanging by her feet and thumbs, sometimes with her head down--and having difficulty. What made this birth remarkable, however, wasn't the mother's struggle with her delivery but the help she was getting from another female--a bat midwife, so to speak.

For nearly three hours, Kunz and Lubee director John Seyjagat observed the pair until the mother produced a healthy pup. During that time, the "midwife" cued the mother several times to switch to the typical feet-down birthing position by adopting this position and straining as if she were giving birth herself The midwife bat also fanned the mother with her wings and licked her to stimulate birth. It was the first time one bat was seen helping another to give birth. Since then, Seyjagat reports, Lubee keepers have observed older females assisting young mothers with delivery on numerous occasions. And while scientists don't know for sure, Kunz suggests bat midwifery isn't an anomaly restricted to captive populations.

"There is no reason to doubt, in our minds, that this is something that occurs regularly [in the wild]," says Kunz. He and Seyjagat published their findings in the Journal of Zoology in 1993.

The Lubee Foundation is one of seven North American institutions participating in a Rodrigues fruit bat Species Survival Plan. The first captivebreeding program for the species was established on the Channel Islands off the coast of France by the Jersey Wildlife Preservation Trust in 1976, when the species was its closest yet to extinction.

Wild Rodrigues fruit bats live only on Rodrigues Island, an isolated, volcanic speck of land in the western Indian Ocean, often battered by cyclones. Severe deforestation linked to both tropical storms and the human impacts of habitat destruction and hunting had reduced the bat population there to 70 by 1975. The population rebounded to 1,000 in 1981. Now 1,500 to 2,000 Rodrigues fruit bats range in the wild, says Kim Whitman, curator of large mammals for the Philadelphia Zoo. But since they are clustered in a single area located in a "cyclone belt," the population is considered extremely vulnerable. The species is listed as endangered by the U.S. Fish and Wildlife Service and the ICUN-World Conservation Union and is also protected by the Convention on International Trade in Endangered Species of Wild Fauna and Flora.

In Golden Bats and Pink Pigeons, naturalist Gerald Durrell describes them: "The leather, umbrella-like wings were dark chocolate brown, while the fur on the bodies and heads ranged from bright, glittering yellow, like spun gold, to a deep fox red. They were, without a doubt, the most colorful and handsome fruit bats I had ever seen." Medium-sized members of the family Pteropodidae, Rodrigues fruit bats weigh about 13 ounces and have a three-foot wingspan. Colonial, gregarious animals with good eyesight, they feed at night on fruits, nectars, and other plant materials. Like other fruit bats, they suck the nectar of fruits and spit out the pulp.

While Rodrigues fruit bats can live up to 15 years in captivity, little is known of their longevity in the wild. Adults reach sexual maturity at one and a half to two years. Males defend territories and breed with several females, which usually give birth to one pup each per year.

Noting that islands are home to many threatened species, Kunz points out that P. rodricensis is among the rarest of old-world fruit bats. Its difficulties are inextricably tied to deforestation: its preferred habitat, the upper-canopy trees of dense rainforests, is losing ground to agriculture, human settlement, and tourism. Measuring 5 by 11 miles, Rodrigues is also home to 35,000 people.

"Today the rainforest is pretty much destroyed. Largely because of deforestation, it's a pretty denuded island currently," says Kunz. The International Union for Conservation of Nature and Natural Resources classifies it "as one of the most florally devastated islands in the world."

While upland forests are harvested for lumber and fuel wood or cleared for farming and grazing, coastal mangrove swamps are often destroyed by developers bent on creating beach areas for a growing tourism industry, Kunz says. Bat conservation is focused on restoring the island's forests. Whitman carried out an educational program on the island in 1995. Since then, the Philadelphia Zoo and the American Zoo and Aquarium Association have hired a local woman to teach islanders about habitat protection and bat conservation and to help with locally based environmental projects.