Rafinesque’s Big-Eared Bat - Corynorhinus rafinesquii
By Hilda Flamholtz, SC Master Naturalist
Photo by John Grego
Rafinesque’s Big-Eared Bat (Corynorhinus rafinesquii) is a medium sized bat (3-4 inches long, 10-12 inches from wing-tip to wing-tip). It weighs less than or equal to ½ ounce. The fur is gray or dark brown on the back and white on the belly. The nose has two glands protruding on either side of it. The ears are huge in proportion to the overall size of the bat: when laid back against the body, they are almost half the length.
This bat emerges later in the evening than most bats, emerging after it is completely dark. It eats primarily moths, but may eat other insects like beetles, mosquitoes, and flies when moths are scarce. It gleans insects off vegetation more often than catching insects in flight. Sometimes the prey is very large, so the bat usually has a night roost where it can take large prey and eat it at leisure. Mating occurs in fall or winter and one pup is born each May/June. Pups can fly by 3 weeks of age.
Rafinesque’s big-eared bats roost in colonies which may consist of 3 or 4 up to a hundred. They do not migrate. In winter, they hibernate near the entrances of well-ventilated caves or mines. In summer, they are found roosting in abandoned buildings in forested areas, caves or dead trees. Colonies are larger in the northern part of their range where there are more caves and abandoned mines. When approached, the bats rotate their ears. This is probably a defensive mechanism to keep track of intruders.
There have been significant efforts to study the habits of Rafinesque’s big-eared bats. However, the species has proven to be particularly difficult to catch in mist nets. One study played the social calls of the species in an attempt to attract the bats, but it seemed to have the opposite effect. A theory is that the bats might need virtual silence in order to hear and detect the small noises of prey on vegetation so they may avoid their fellow bats when hunting.
Rafinesque’s big-eared bats are rare or endangered in their entire range. They were once thought to inhabit the entire Southeastern United States north to southern Virginia and Illinois; west to eastern Oklahoma and Texas. However, the current range shows significant gaps within that area. For example in North and South Carolina and Georgia, Rafinesque’s big-eared bats are found in the coastal plain and the mountains, but no longer in the Piedmont. The biggest reason for this decline is believed to be loss of habitat: older forest trees being cut down, abandoned buildings demolished, and trails leading visitors to desirable caves causing disturbance. Pesticides used to control insects, like gypsy moths, can also be detrimental to these bats.
In an effort to better understand the bats and protect them, surveys have gone on to determine where Rafinesque’s are living. Land has been conserved where possible to allow contiguous forest habitat for the bats. In some cases, tunnels have been gated to reduce human disturbance while allowing free passage for the bats. After it was determined that some Rafinesque’s big-eared bats live in I-beam and T-beam bridges, consideration was given to modifying bridges under re-construction to provide good habitat for bats. Also, training for pest control and wildlife control operators has been provided to show how to exclude bats from negative impact.
These bats play a key role in controlling our insect populations, so it is important to continue efforts like these and others to protect them.
Stokes: Beginner’s Guide to Bats, by Kim Williams, Rob Mies and Donald & Lillian Stokes
Peterson Field Guides Mammals of North America, by Fiona A Reid
SC Department of Natural Resources article: Colonial Cavity Roosting Bats, by Mary Bunch, Susan Loeb, Wendy Hood, Mary K. Clark, and Travis Perry;http://www.dnr.sc.gov/cwcs/pdf/colonialbats.pdf
SC Department of Natural Resources article on Rafinesque’s Big-eared Bats in Ace Basin;http://www.dnr.sc.gov/marine/mrri/acechar/specgal/rafbat.htm