Ugly bats are built to bite
A face that only a mother could love conceals a skull with a surprisingly powerful jaw.
With a strangely naked face covered in skin flaps and a wide, foreshortened skull, the head of the rarely seen, fruit-eating, wrinkle-faced bat (Centurio senex) has been an enigma to biologists for a long time.
Now, a team led by Elizabeth Dumont at the University of Massachusetts in Amherst has discovered that the oddly-shaped skulls include jaws that are more powerful than not just other fruit bats but also much larger predatory bats, which need to be able to sink their teeth into tough hides.
"When I first saw them I thought, oh my god, these are just too weird to be real," says Dumont.
Their fascination with the species led Dumont and her colleagues to question whether the bizarre skulls helped the bats to strengthen their bite in some way. To explore this, they set up nets every evening for a week around fruit trees in a remote region of southern Mexico where wrinkle-faced bats had been reported to be present. The researchers caught 26 wrinkle-faced bats and brought them to a nearby base camp where they measured the bats' bite strength using a piezoelectric device. Some of the creatures were also filmed for a short time while eating fruits of different hardness.
The researchers report in the Journal of Zoology1 that the bats had an average maximum bite force of 10.9 newtons, which is roughly 20% stronger than that of any other known bat of the same size and approaches the strength of some of the strongest predatory bats. The team also report that the bats can easily eat hard fruits, such as apples, that do not grow in their region.
Dumont and her team suggest that the strong bite hints that either the bats are eating hard fruits in their habitat without anyone knowing about it or, that their ability to eat hard fruits is a characteristic that they evolved long ago during a time period when soft fruits were not as plentiful.
The bats' strong bite and their ability to eat hard fruit is surprising because the species was thought to live on soft fruits. "The problem is we don't really know what they are eating," says Dumont. "These guys are really rare and studying their feeding habits is a challenge. We were really lucky to catch so many, another team went out to the same location a year later and found nothing."
Blaire Van Valkenburgh, a palaeontologist at the University of California, Los Angeles, who specializes on the evolution of feeding, says that it is frustrating not to have more information on what the bats eat in the wild. "Hyenas have large bite forces that allow them access to a wider array of foods, such as bone and flesh, than other carnivores. Clearly [wrinkle-faced bats] must be eating something that few competitors can — I wish I knew what that was," Van Valkenburgh says.
- Dumont, E. R., Herrel, A., Medellín, R. A., Vargas-Contreras, J. A. J. Zool. advance online publication doi:10.1111/j.1469-7998.2009.00618.x (2009).