Madagascar is losing its forests at a perilous pace. The loss of these native ecosystems threatens much of the island's remarkably diverse and often unique wildlife, and little is being done officially to reverse this trend. But graduate student Ryszard Oleksy cites a powerful natural tool for helping to regenerate these fragmented forests: the Madagascan flying fox.
|The Madagascan flying fox. Photo courtesy of Ryszard Oleksy.
This bat feeds on the fruits of many plants and scatters the seeds over wide areas, notably including cleared lands. But the species, found only on Madagascar, has virtually no legal protection and is, in fact, listed as a game animal. Oleksy, a Ph.D. candidate at the University of Bristol in the United Kingdom, says the bats are hunted and persecuted throughout the island, which lies off southeastern Africa.
"Reliable information about the Madagascan flying fox and its contributions to restoring damaged forests should, I hope, convince local people and government officials to protect these beleaguered bats," he said.
He used a BCI Student Research Scholarship to confirm the importance of these flying foxes for long-range seed dispersal. He also demonstrated that bat-processed seeds – those that are eaten by bats, passed through the gut and dispersed in droppings – are significantly more likely to germinate than seeds that come directly from fruit.
Oleksy tested a total of 2,400 seeds of a native fig tree, Ficus grevei. He compared the germination success of seeds extracted from bat feces with those from ripe fruit by distributing them in laboratory dishes under different conditions: seeds grown on plain filter paper; on soil treated to remove all organisms; and on untreated soil.
By far the most dramatic effect was among seeds grown on paper, with no soil substrate. Among bat-processed seeds, an average of 11.7 seeds (out of 20) germinated in each dish, compared to just 3.3 germinated seeds from ripe fruit.
Oleksy suggests this difference might be caused by bits of feces that likely remain on the processed seeds and act as fertilizer to promote germination. Considering that bats defecate in flight and scatter seeds not only on the ground but also on vegetation, bits of manure around the seeds may very well increase the chances for germination and seedling establishment.
He reports no significant differences in germination of seeds sown on the two soil treatments. Generally, germination success on the soil treatments was lower than on filter paper.
Part of the explanation may be that Ficus grevei
is what's called a "strangler tree" – one that initiates germination on the bark of another tree, then gradually send its roots to the ground. Dispersal by flying bats increases the opportunities for seeds to be deposited on other trees, Oleksy said, and the residual manure provides a good start for germination.
Among other topics, Oleksy also studied bats' seed-dispersing potential by attaching GPS tags on 18 flying foxes to track their travels while foraging.
He found that a bat can travel as far as six miles (10 kilometers) from a feeding site in just 12 minutes and can, in one night, disperse seeds from three different fig trees. He also determined that bats disperse most seeds within about three hours of eating, although a few may be retained much longer.
Clearly, Oleksy concludes, the Madagascan flying fox is an extremely efficient long-distance seed disperser. "My results suggest that Madagascan flying foxes may serve as 'stepping stones' that begin the forest-regeneration process and attract other seed-dispersing animals to build on that foundation to protect wildlife biodiversity and the economic health of local people."BCI Members can read the whole story of Ryszard Oleksy's pioneering research in the Summer 2013 issue of BATS magazine. And you can help BCI support such important student research and other vital conservation efforts around the world at www.batcon.org/donate