Ancient Dental Records Suggest Nectar-Drinking Bat Was Actually Omnivorous

Fossil teeth can reveal an ancient species' deepest, darkest secrets. In a recent study, researchers from Stony Brook University used a single fossilized molar to reveal that the oldest known nectar-drinking bat, scientifically known as Palynephyllum antimaster, was probably omnivorous.

Researchers were able to unravel the species' eating habits based on a skull model developed using evidence provided in dental measurements. To estimate the animals' skull length, researchers measured the same molars and skulls of other living nectar-feeding bats. Using this information, they were then able to estimate the bat's bite force and body size, and interpret its diet and omnivorous transition, according to a news release.

"A longstanding hypothesis holds that species shift to nectar feeding gradually, by first eating a mix of insects and nectar, but this has not been tested with fossils," Liliana Dávalos, one of the study researchers and a professor in the Department of Ecology and Evolution at Stony Brook University, said in the release.

For their study, researchers examined Palynephyllum molars collected from the Miocene of La Venta, Colombia. Twelve million years ago -- when Palynephyllum glided through the skies -- this area of South America was home to a wide variety of species. Similar to other modern nectar-drinking relatives, the fossil molars were narrow and their cusps were reduced and flattened. The evolution of cusp morphology in response to methods of feeding makes mammalian molars an important indicator of what was being eaten. 

"Our analyses show that Palynephyllum could not have fed exclusively on nectar, and it likely supplemented its diet with protein-rich insects, which supports this hypothesis," Dávalos added. 

Foraging solely for nectar, which is basically sugar water, is extremely physiologically demanding and requires special metabolic adaptations in order to rapidly convert sugar into energy. However, for that reason, a switch from protein-rich insects to carbohydrate-rich nectar diets is a valuable indication of evolutionary behaviors and body size changes.  

"We came up with a way to visualize what this animal looked like based on rigorous statistical methods," Laurel Yohe, lead author and Ph.D. candidate in Stony Brook's Department of Ecology and Evolution, explained. "In biology, there are different levels at which we find variation, and it is important to keep track of them. There is measurement variation, variation among species and individuals, and the samples cannot be assumed to be independent because the organisms are related to one another through common descent. Our models and estimations account for all of that."

Their study was recently published in the Royal Society's journal Biology Letters.

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