World's Largest Bats Shrinking Due to Human Hunters, Study Finds

The largest flying fox fruit bats in the world are shrinking in size, and researchers suspect human hunters are responsible, according to a new study.

Scientists at Chicago's Field Museum compared flying fox specimens collected over the past 150 years with those found in more recent fieldwork in Madagascar. Their findings, published in the Journal of Mammalogy, indicate a significant decrease in the body size of these bats, particularly starting around 1980.

Dr. Emily Ruhs, the study's lead author, initially explored environmental factors like temperature or habitat changes to explain the size discrepancy. However, her colleague Dr. Steve Goodman, a biologist who has worked in Madagascar for nearly 40 years, proposed a different hypothesis.

Goodman observed that historical museum specimens from the late 18th and 19th centuries were considerably larger than the bats encountered in modern times. He noted that flying foxes are considered a "vermin" species in Madagascar due to their consumption of commercially important fruits and are hunted for food on a large scale in some areas.

"Many of these animals were of monster size compared to animals we handle today," Goodman said. "Hence, the idea was formed that they have diminished in body size as a result of recent heavy hunting pressure and they are not living as long as they did in decades past."

To investigate, Goodman examined 121 Madagascar flying fox specimens from natural history museums across the United States and Europe, measuring their skulls and teeth. Ruhs then analyzed this data statistically.

"We saw a clear drop in size starting around 1980, when we believe bat hunting became more commercialized," Ruhs stated. She initially doubted her analysis, but the trend proved consistent.

The study suggests that larger bats, being easier targets and providing more meat, are more likely to be hunted. If older, larger, breeding-age bats are disproportionately targeted, it could impact the overall flying fox population.

While the research establishes a correlation between commercialized hunting and the bats' shrinking size, the authors acknowledge that other factors may also contribute. These include deforestation, climate change, and alterations in the fruit season.

"I don’t think there’s any one cause that explains it all," Ruhs noted. However, she emphasized that human-driven pressure appears to be a primary driver.

The researchers stress the importance of protecting these bat populations, which serve as a vital food source in parts of Madagascar. They recommend enhanced protection measures, particularly at breeding sites, to prevent population collapse, citing the need for robust enforcement of new national laws.

The study also underscores the continuing scientific value of historical museum collections, with Ruhs adding, "We can still get a lot of information from these bat specimens that were collected in the 1800s."