Appearance
The Rafinesque’s big-eared bat is an elusive, medium sized bat that weights 7-13 grams (about the weight of two quarters) and has gray to brown fur on its back with light tan fur on its belly. This bat is known for its long, distinctive ears, which can measure over an inch in length and distinguish the species from other bats in Florida. The species is also characterized by two fleshy lumps on either side of its nose, a feature which gives the genus its name: Corynorhinus, meaning “club-nosed.”
Behavior
Like every other species of bat in Florida, the Rafinesque’s big-eared bat is insectivorous, meaning it eats primarily insects. This bat eats mainly moths, which make up to 90% of its diet, though it is known to prey upon many other soft-bodied insects including mosquitoes, beetles, and flies. The species uses echolocation to find its prey, frequently emitting high-pitched calls and listening to the echo to home in on an insect’s exact location. Rafinesque’s big-eared bats will catch insects in flight like many other bat species, a behavior known as “hawking.” It is also one of the few bat species in Florida that will also target and pick insects directly off vegetation or the ground, a behavior called “gleaning” (Florida Bat Conservancy 2005). Unlike most bats, which are crepuscular (meaning only active at twilight and/or dawn), Rafinesque’s big-eared bat is fully nocturnal, actively flying and hunting from sunset to sunrise. They typically stay within 1 km of their roosting spots (Menzel, Menzel, and Ford 2001). These bats like to roost in relatively small colonies, with winter colonies ranging from 14-49 individuals and summer colonies reaching over 100 bats (Hurst and Lacki 1999). Rafinesque’s big-eared bats tend to mate in the fall, with females giving birth to a single pup in late May or early June (Florida Bat Conservancy 2005). They live up to ten years in the wild.
Habitat
The Rafinesque’s big-eared bat prefers specific types of habitats that do not occur evenly throughout is range, including karst features, such as rock shelters and caves, and mature forests, such as cypress gum swamps and bottomland hardwood forests (Bayless, Clark and Stark 2011). The species usually roosts in hollows, cavities, or under loose bark of relatively large living or dead trees averaging almost 60 feet tall (21 meters) and 3.5 feet (110 cm) in diameter. They prefer to roost in living trees due to the more stable conditions, which helps them better control their temperature (Trousdale 2011). They also prefer trees in stands with mostly closed canopies and with many other roost-appropriate trees nearby. While they do not always return to the same roost tree each night, they do return to the same cluster of trees (Trousdale 2011). While they most often roost in trees, they will also readily roost in abandoned forest buildings, in caves entrances, under bridges, in culverts and in bat houses (Florida Bat Conservancy 2005).
Threats
Deforestation and habitat loss to development are the most serious threats to Rafinesque’s big-eared bats, due to the loss of natural roosting areas. Climate change is predicted to have a negative impact on this species. As climate change may cause insects to emerge less in sync with the end of bat hibernation, reducing the bats food sources as they need to recover (Weller et al. 2009).
An additional threat Rafinesque’s big-eared bats may face is the disease called white-nose syndrome (WNS). WNS is caused by the fungus Pseudogymnoascus destructans, and has spread across North America (U.S. Fish and Wildlife Service [USFWS] 2020). White-nose syndrome causes widespread death in some cave bat populations by disrupting hibernation and , causing individuals to wake more frequently and use up fat reserves (Frick et al. 2010, 2015; Lorch et al. 2011; Warnecke et al. 2012). While Rafinesque’s big-eared bats have been documented with fungal spores on their bodies, they are not yet known to suffer symptoms of White Nose Syndrome. This disease primarily affects other cave-dwelling species and has appeared in every other state in the southeast region. While it has not yet appeared in Florida, FWC continues to monitor the state’s caves for the disease.
Conservation and Management
The Rafinesque's big-eared bat is one of Florida's Species of Greatest Conservation Need. These bats are monitored with the other bat species in Florida as part of the Long-term Bat Monitoring Program, which seeks to keep track of bat populations throughout the state. The program achieves this by placing ultrasonic detectors across the state that pick up and record echolocation calls of nearby bats. Rafinesque’s big-eared bats are particularly difficult to monitor because the low intensity of their echolocation calls means they are rarely detected by the ultrasonic detectors. The challenge of recording their echolocation calls has given them the nickname “whisper bats”. Currently, there are many research gaps on this species’ ecology, behaviors, and response to management activities (Loeb, Lacki and Miller 2011). In addition, FWC performs yearly surveys of caves to check for the fungus that causes white-nose syndrome.
It is illegal to remove bats from structures or to otherwise handle them directly in the state of Florida. If you have bats in your house or other structure, please see our Living With Bats page to learn how to properly evict them.
How You Can Help
We are always glad to have volunteer help with our bat conservation work, particularly with the Long-term Bat Monitoring Program in which volunteers help place and monitor our acoustic detectors. If you are interested in volunteering with this program or in helping in other ways, please visit our Bat Force website to learn more.
References
Bayless, Mylea, et al. "Distribution and Status of Eastern Big-Eared Bats." Conservation and Management of Eastern Big-Eared Bats The Synamious (2011): 13-26. Document.
Florida Bat Conservancy. "Rafinesque's big-eared bat." 2005. Florida Bat Conservancy. https://www.floridabats.org/rafinesques-big-eared-bat.html. 4 December 2019.
Hurst, Tracey E. and Michael J. Lacki. "Roost Selection, Population Size, and Habitat Use by a Colony of Rafinesque's Big Eared Bats." The Ameican Midlands Naturalist (1999): 363-371. Document.
Loeb, Susan C., Michael J. Lacki and Darren A. Miller. "Conservation and Management of Eastern Big-eared Bats: An Introduction." Conservation and Management of Eastern Big-eared Bats A Symposium (2011): 1-12. Document.
Menzel, Michael A., et al. "Home Range and Habitat Use of Male Refibnesque's Big Eared Bats (Corynorhinus rafinesquii)." The American Midlands Nautralist (2001): 402-408. https://bioone.org/journals/The-American-Midland-Naturalist.
Trousdale, Austin W. "Ecology of Tree-roosting Rafinesque's big-eared bats in the Eastern United States." Conservation and Management of Eastern Big-eared bats The Synampious (2011): 27-38. Document.
Vanderwolf, K.J., D. Malloch, and D.F. McAlpine, 2015. Fungi associated with over-wintering tricolored bats, Perimyotis subflavus, in a white-nose syndrome region of eastern Canada. Journal of Cave and Karst Studies, 77(3): 145-151.
Weller, T.J., P.M. Cryan, and T.J. O’Shea. 2009. Broadening the focus of bat conservation and research in the USA for the 21st century. Endangered Species Research 8:129-145.