Malagasy flying foxes, among the world’s largest fruit bats, may be getting smaller. Researchers compared skull and teeth measurements from 121 specimens held in nine museums in the United States and Europe, covering roughly 150 years of history.
The study, published in the Journal of Mammalogy, found a notable change around the 1980s. Bats collected before that period had skulls that were, on average, 6 percent longer than those collected afterward. The researchers say the shift coincides with the expansion of commercial hunting in Madagascar.
Emily Cornelius Ruhs, a Field Museum post-doctoral researcher and the study’s lead author, began the project after hearing that older flying fox skeletons appeared larger than bats observed in the field. Field Museum scientist Steven Goodman subsequently examined specimens in several collections and recorded measurements from 12 skull and dental features.
Before the 1980s, the bats were generally hunted on a small scale for family or village consumption. Commercial hunting later made flying foxes more available in markets and on restaurant menus, increasing pressure on their populations. Ruhs said climate change and deforestation may also have played a role, but the timing of the size change points toward hunting as a possible cause.
The findings do not establish that hunting directly made the bats smaller. One possibility is that hunters preferentially target larger, mature animals because they provide more meat. Researchers have not determined whether the change has a genetic basis or whether larger bats are simply being removed before they can reproduce effectively.
Malagasy flying foxes are classified as vulnerable. Researchers estimated that Madagascar had about 300,000 of the animals in the early 2000s, with the population since falling by roughly two-thirds. Because the bats generally produce only one pup per year, removing sexually mature and reproductively active individuals could affect the population’s long-term viability.
The consequences may extend beyond the bats. The species is considered a keystone animal because it disperses seeds from large fruits, including figs, across the landscape. Ecologists say this process supports plant reproduction and forest regeneration. Changes in the bats’ population, size or mouth structure could potentially affect their ability to process and disperse larger fruits and seeds.
Researchers say conservation efforts should address hunting pressure, while recognizing that flying foxes are an important food and income source for many people in Madagascar. Ruhs said the study raises questions about how hunting should be regulated and who should be responsible for protecting the populations in the future.
Sources: Smithsonian Magazine.