It is safe to say that Tracie and I love bats. Fortunately for us Costa Rica has massive diversity when it comes to these flying mammals. Scientists have identified around 240 mammals in Costa Rica of which 113 are bats. The Osa Peninsula has the highest bat diversity in the country with 80 identified species.
Even so, bats can be elusive during the Night Tour. Most of our sightings are fleeting views of bats flying by at breakneck speed. At times we are also approached by insectivorous bats capitalizing on the insects attracted by our headlamps.
Occasionally we are fortunate enough to encounter roosting bats which we can observe in detail. These prized encounters, although usually brief, are always memorable. By far the most memorable bat encounter we have had is with the Wrinkle-faced Bat, Centurio senex.
This bat is so different from other bats it is the only member of its genus: Centurio. The binomial name is derived from the Latin words centurio, meaning 100, and senex, meaning old or aged, because its face looks like that of a 100 year old person.
It is not known why these bats evolved such a wrinkly face, but it is though that perhaps the wrinkles act as canals to channel juices into the bat’s mouth as it feeds on ripe fruit.
Male bat’s faces are wrinklier than the females’ faces and they also have chin folds which they stretch over their faces while roosting. A swollen ridge along the bat’s foreheads prevents the face mask from slipping and, incredibly, the masks are complete with transparent “window panes” over the area covering the eyes!!
Wrinkle-faced Bats have a very short and wide skull which allows them to apply about 20% more force in their bite compared to other similarly sized bats. Scientists believe that this allows Wrinkle-faced Bats to feed on harder fruits than other frugivorous bats. They also have pouches in their mouth where they can store spare fruit.
Another impressive feature about these bats are their massive thumbs. It seems this is an obvious adaptation which allows the bat to grip and feed on large fruit, although their feeding habits are poorly understood. Very little is actually known about these handsome bats. Roosts are rarely found and scientists think they may roost high in the canopy.
The facial features of the Wrinkle-faced Bat make it one of the most unusual mammals in Costa Rica. Some may say they have a face only a mother could love. To us, though, their unique looks represent the beauty and diversity awaiting discovery in the tropical rainforest.
LaVal, R. & Rodríguez, B. 2002 Murciélagos de Costa Rica / Bats Editorial INBio
Wainwright, M. 2002 The Natural History of Costa Rican Mammals Zona Tropical