The Great Red Island: A Future for its Bats?

With much of Madagascar defoliated, conservationists the world over are scrambling to preserve what is left so that the island’s unique fauna can survive . . .

by James M. Hutcheon

The scene is a balmy beachfront at sunset. The location is the Masoala Peninsula of Madagascar. The village of Ambanizana rests behind a screen of trees. From our vantage point the sounds of village life are barely audible over the surf crashing on the tree–lined shore. Night is falling rapidly as we sit awaiting the arrival of the fanihy, the Madagascar flying fox (Pteropus rufus).

Finally we see them: Soaring high above on oceanic wind currents are the flying foxes. Quiet shadows come gliding in. They land with a rustle of wings and a slap of wet leaves as they begin to scramble through the branches of Terminalia catappa, a beachfront tree that grows thickly in this area. By dawn the ground beneath the trees will be littered with the remnants of the night’s feast. The role this large bat plays in the dynamics of the forest is what Michelle Zjhra and I have come here to study.

The island of Madagascar has been a source of intense interest to naturalists for several centuries. About 2,000 miles long and 350 miles across at its widest point, the island separated from mainland Africa over 100 million years ago, its relative isolation allowing for the evolution of unique and endemic plant and animal groups. It was also one of the last major land masses to be colonized by humans, with people arriving as recently as 2,000 years ago. Although Madagascar lies only about 250 miles from mainland Africa, it appears that the major wave of human colonization came from Indonesia.

Madagascar, the Great Red Island, has long evoked images of mystery, adventure, spice, and pirates. The stories of Sinbad tell of that hero’s encounter with the mythical Roc on Madagascar. The reality of the island’s rich natural heritage is as dramatic and exciting as the legends surrounding it.

Madagascar seems to be a zoogeographical composite, where representatives of diverse ranges come together in a unique setting. Taken as a whole, this suggests a rich evolutionary story, which is still not well understood. Some of its most well-known endemic residents are the lemurs, a primitive group of primates that shows a tremendous diversity in habitat, body size, and appearance. Like many of Madagascar’s endemic mammals, however, lemurs are rapidly facing danger of extinction due to habitat loss and hunting pressures. Since the arrival of humans, a number of taxa have gone extinct, including the largest known lemur, the koala lemur (Megaladapis).

Far less known than Madagascar’s famous lemurs are its bats. About 28 species of bats, representing seven families, inhabit the islands. One of the families, Myzopodidae, consists of a single species: the Old World sucker-footed bat (Myzopoda aurita) is named for the “suction cup” on its thumb and is found mostly on Madagascar. Once believed to be extremely rare, recent work has suggested that it is more common than was thought. Like most of Madagascar’s bats, very little is known of its ecology. It has been rumored to roost in the fronds of the traveler’s palm (Ravenalla madagascariensis), the national plant of Madagascar.

It is interesting to note that a remarkably similar bat, the New World sucker-footed bat (Thyroptera tricolor) is found in Central and South America. Aside from the suction cups on their thumbs, these two bats are actually dissimilar in a number of ways, even differing in the form and structure of their odd adaptation, perhaps an example of convergent evolution.

Madagascar is also home to three species of flying foxes, all of which are endemic to the island. The Madagascar rousette bat (Rousettus madagascariensis) is the smallest and apparently the most common of the three. Recent work at the Molecular Systematics Laboratory at the University of Wisconsin Zoological Museum suggests that this bat has strong affinities with a group of rousette bats that are found on the African mainland.

In contrast, the Madagascar flying fox, the largest of the fruit bats found on the island, is certainly of Asian or Indonesian origin. The genus Pteropus, found from Australia and the Pacific islands to Southeast Asia and India, represents something of a distributional anomaly and poses a nagging biogeographical puzzle. Although it occurs on Madagascar and on Mafia and Pemba Islands, only 6 and 18 miles, respectively, from the mainland coast of Africa, it is not found on the African continent itself. This is especially intriguing since these bats routinely travel this far in a single night’s foraging.

The Malagasy straw-colored fruit bat (Eidolon dupraeneum) is Madagascar’s third flying fox. Until recently this bat was considered to represent an extension of the range of the African straw-colored fruit bat (E. helvum), but recent studies have suggested that it is, in fact, a distinct species. Another example of discontinuous distribution is Peter’s sheath-tailed bat (Emballonura atrata). The other members of this genus are found in Southeast Asia and in the South Pacific. Although Madagascar lies in relatively close proximity to Africa, this bat is another example of faunal affinities with Indonesia.

The Masoala, where we conducted our research, is a rainy and heavily forested peninsula in the northeastern corner of Madagascar. It represents one of the last large tracts of pristine forest remaining on the island. Our work last year from June through August was conducted in roughly the equivalent of winter in Madagascar. Characterized by high rainfall, the period is one of relative poverty in terms of total diversity of fruiting and flowering plants. Nevertheless, our work showed it to be the home of at least nine separate species of bats during this season and likely more at other times of the year. Previous mammal lists for the Masoala had recorded only two bats.

Tracking and observing a flying nocturnal animal is fraught with difficulties. While studying the habits of bats requires some sleepless nights on the part of field workers, it also requires developing an eye for the crucial signs of bat visitation upon which these studies often rely. In our work on the Madagascar flying fox, we spent long nights observing these bats feeding on fruit, and early mornings walking through the forest in search of evidence of feeding from the previous night. Bat feeding sign is not subtle: usually a mess of fruit and flower parts strewn on the forest floor beneath a tree marks their visit. Seeds that have been gnawed upon, and the fruit pericarp, which has been chewed and spat out, are in abundance.

Our initial studies have indicated that T. catappa plays a crucial role in the diet of the flying foxes of Madagascar, acting as a staple source of food during the rainy season. With low overall fruiting and flowering during this period, frugivores such as flying foxes may be stressed for food resources. Because catappa trees fruit continuously, they represent a valuable resource for flying foxes at a difficult time of year. Some nights we observed them traveling from 12 to 18 miles down the coast in search of catappa fruit.

Terminalia catappa is generally considered a water-dispersed genus, but the abundance of this tree, and its clear importance in the diet of flying foxes, suggests that perhaps, at least on the Masoala Peninsula, an interaction between plant and animal indeed exists. Since the catappa seeds were virtually always found beneath the tree following a bat visit, it is unlikely that the Madagascar flying fox plays a major role in the tree’s seed dispersal. However, a very strong possibility exists that this bat could play an important role as a pollinator of this tree. The terminal erect inflorescences of the blossom are typical of other bat-pollinated flowers. Inadvertent pollination by the bats as they scramble through the foliage in search of fruits would result in greater fruit production, which in turn would lead to an increase in seed litter and eventually more trees upon which to feed.

The broader role of flying foxes in the pollination and dispersal of the forest plants is not so clear. It is very likely, however, that their role is far from insignificant. As Madagascar has a comparatively small number of bird and mammal pollinators, it is likely that bats play an important role in the ecosystem. Unfortunately, almost no data exist on plants visited by Madagascar’s flying foxes. While there is much suggestive evidence that bats are crucial to forest propagation, the role of bats as pollinators and seed dispersers has been largely unstudied in Madagascar. Our work on determining the components of the flying fox’s diet is adding to our understanding of how bats interact with the complex forests of Madagascar.

While understanding the role of bats in an ecosystem is often essential in initiating conservation efforts, education is key to ensuring success. Whenever possible, we talked to the villagers about the important role fanihy may play in forest dynamics. Because local people ultimately determine the success or failure of any conservation project, we felt obligated to share with the community in which we were living the information we were gathering.

During the course of our study, we also tried to determine the extent of local knowledge about bats and how they were perceived by people. For the most part, very little was known, which is not surprising given these people’s fear of night and the forest. Interestingly, we found that the local dialect had three words for bats, which seemed to be based on size. The word fanihy was unambiguously applied to the flying foxes; manavy was used to describe small bats. Finally, we learned the word andrehy. Exactly which bats this referred to was unclear. It seemed to apply to medium-sized bats, but locals we spoke with weren’t in agreement as to which medium-sized bats were andrehy.

Because of their high visibility and easily disturbed roost sites, Madagascar’s flying foxes are at great risk. In addition to enormous habitat pressures, these animals are also hunted in some areas, as their meat is considered a delicacy. These problems, coupled with the fanihy’s official, but largely misunderstood, designation as crop pests, have rendered the flying fox’s future on Madagascar uncertain.

The tragedy of much of the world’s tropics is exemplified by Madagascar. Roughly 80 to 90 percent of the island’s original vegetation has been destroyed. Numerous conservation and development organizations are feverishly working with local people to preserve what is left, but the ever-increasing demands of population, culture, and industry have made this a continually uphill battle. Madagascar’s human population is approximately 12 million and increasing at a rate of 3 percent a year. This means that the population will double in 22.5 years. Whether sustainable methods of agriculture and forestry can be introduced in light of this pressure remains to be seen.

Photos taken from orbiting satellites show the ocean surrounding Madagascar to be red, due to the washing of the island’s crimson soils into the sea–a direct result of the massive deforestation. The metaphor of a bleeding island is tragically accurate, for with those soils, the lifeblood of Madagascar’s rich biodiversity washes away. It is possible, however, to find glimmers of hope in much of the conservation work that is being accomplished.

Until recently, the Madagascar flying fox received little attention from conservation groups. Efforts are now underway by the Xerces Society and Wildlife Conservation International to have the forest on the Masoala Peninsula set aside as a natural reserve that will be managed by the local people. That the Malagasy government is working with conservation groups to have this large tract of forest preserved is encouraging. For us, the most exciting aspect is the fact that bats are now being considered seriously in the conservation and management plan, a first in Madagascar and rare enough anywhere.

The inclusion of bats in the conservation framework is a hopeful sign for the future of this living laboratory of evolution. The attention drawn to bats and their current inclusion in conservation efforts was, in large part, made possible by BCI’s assistance with this pilot project. Obviously a great deal more research must be conducted before we are to understand fully the role of bats in Madagascar’s last large forest. Given the high degree of endemism among the island’s flora, the role is likely to be critical. Certainly if the Masoala is to be preserved, bats will prove to be an essential component.

Dusk continues to fall. Only the top arc of the sun is visible on the horizon, painting the sky a vivid crimson and orange. Audible above the roar of the surf is the chattering of the feeding bats. The majestic and mysterious fanihy of the Great Red Island soar out into the night and an uncertain future.

(Bio)
James M. Hutcheon is a graduate student at the University of Wisconsin in the Department of Zoology. His doctoral work includes looking at evolutionary patterns and adaptive radiations of the bats of the Indian Ocean. BCI helped to sponsor the work that he and his wife, Michelle Zjhra, conducted in Madagascar.