Rafinesque’s big-eared bat

Rafinesque's big-eared bats / Cory Holliday ©

Corynorhinus rafinesquii

The Rafinesque’s big-eared bat’s western range is the bottomland hardwood forests of east Texas. It is one of 10 species of bats that can be found on Trinity River National Wildlife Refuge, where an estimated 140 bats form the largest known maternal colony in Texas.

Rafinesque’s are found in older growth bottomland hardwood forests of the southeast United States. They thrive in mature forests that have plenty of mature, hollow, roost-trees. The trees serve as sanctuaries where they spend winters in a kind of hibernation called torpor and raise their young in the spring. The mature flooded forests have plenty of space between trees, providing perfect foraging habitat for the bats to prey on primarily moths during the night. Rafinesque’s have rabbit-like ears that are essential for echolocation during hunting and navigating through the forest at night.

In the winter they hunker down in the trees while they go into torpor, a special behavior, in which they lower their body temperature to save energy. They drop their body temperature to a level so low, they are actually cold to the touch and cannot move. Bothering a bat is never a good idea because they can bite and may carry diseases fatal to humans. Also, bothering any animal in torpor decreases their chance of surviving the winter as they expend vital energy trying to get away from you.

These bats have a social structure that keeps the males and females apart except during the breeding season in early fall. The females do not actually fertilize the egg until early spring. At that point the breeding females form an all-female maternal colony to raise their young.

Each female will give birth to one pup per year. The pup is flightless until it is three weeks old. Within two months they are fully grown and can only be recognized as a young bat due to the color of their fur, which is darker than an adult bats’.

Population declines for this species could be related to a number of reasons. First of all, the Rafinesque’s depend on mature bottomland hardwood forests. Most forests in the southeast U.S. are all relatively young with few trees being over 50 years old. Secondly, their food source, insects, may possibly be contaminated with heavy metals or other forms of contaminants. Finally, with a female only producing one young per year, any loss of pups can drive the population to lower levels in just a few short years.

The U.S. Fish and Wildlife Service classifies this bat as a Candidate II Species of Concern, meaning it is on the watch list for the Endangered Species Act. Texas Parks and Wildlife Department lists the bat as a threatened species.

How the refuge is helping the Rafinesque’s big-eared bat:
In addition to keeping the abandoned building in which the bats were discovered, the refuge, in a partnership with a grant from Bat Conservation International, has also erected two experimental bat towers. These experimental cinderblock towers mimic large hollow trees and create a habitat suitable for the maternal colony. The bats often move from structure to structure, utilizing all three during the year.

A three-year refuge study was conducted to find out more about the bats’ habits. Using radio-telemetry and banding, they were followed from their artificial roosts to their winter roosts. These winter roosts turned out to be various trees not far from the artificial roosts. Additionally, the refuge studied the temperature and humidity in the trees that were discovered by radio-telemetry. Data collected will compare the temperature and humidity from within the bat towers and house to try to find what drives the bats’ movements and what they require to continue reproducing.

How you can help bats:  

  • Build a bat house and place it on your property. 
  • Or, build a pond or a garden in your yard. The bats appreciate a garden where tasty insects are unwanted. You will appreciate it too! Add a pond and watch bats skim a sip of water on it during the night. 
  • Learn more at Bat Conservation International