Art Credit: Sahina Irvin
Appearance
The velvety free-tailed bat is a medium sized bat with a wingspan of 10-12 inches and a weight of 0.4-0.5 ounces (11-15 grams; Goodwin and Greenhall 1961). This species gets its name from both its dense, reddish-brown to black colored fur and from its tail that extends out from the uropatagium, or tail membrane. This bat can be distinguished from the similar Brazilian free-tailed bat by its ears, which are joined at the base and pointed forward (USDA).
Behavior
Velvety free-tailed bats are insectivorous, which means they eat insects such as moths, beetles, flies, and flying ants (Emrich et al. 2013). Because velvety free-tailed bats have long, narrow wings that are more suited for speed than maneuvering (Emrich et al. 2013), they tend to fly at higher altitudes, in open areas, above tree canopies, and near water sources (Voigt and Holderied 2012, Fenton et al. 1998). While hunting, velvety free-tailed bats use a technique known as “aerial hawking,” which means they catch insects in the air (Voigt and Holderied 2012). These bats increase their hunting success by travelling in small groups and eavesdropping on the echolocation calls of nearby bats to help locate productive feeding grounds (Gager et al. 2016). They are crepuscular, meaning they are most active at twilight and just before sunrise (Esbérard and Bergallo 2010).
Because most of their range is tropical, the reproductive cycle Velvety Free-tailed Bats seems to be driven by wet-dry season cycle and changes in rainfall rather than the typical four-season cycle found further from the tropics (Silva-Duarte et al. 2023). They mate in the dry season and give birth to a single pup at the beginning of the rainy season between June and September.
Habitat
The velvety free-tailed bat is found across much of Central and South America, as well as in the Caribbean. Velvety Free-tailed bats were not discovered in the continental United States until the mid-1990s, where they are only found in the Florida Keys and the Dry Tortugas. Across much of its range, this species will roost in many areas in hardwood forests, including hollow trees, palm fronds, rock crevices and caves (USDA). However, in Florida, they have only been found to be roosting in man-made structures, including attics and crawl spaces, giving them the nickname “House Bats” (University of Florida). They are colonial roosters, forming groups as large as 50-300 individuals.
Threats
The main threat to this species is likely human development and the resulting destruction of its forest habitat. This is mitigated somewhat by these bats’ ability to comfortably roost in human structures, but we don’t fully understand how deforestation will impact them yet (Barquez et al. 2015).
This species is also under threat from a recently discovered virus called Alphacornonavirus. Although the virus does not appear to have severe effects on infected individuals, it may lower their body weights (Lau et al. 2012).
Conservation and Management
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 calls of nearby bats.
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
Barquez, R., Rodriguez, B., Miller, B. & Diaz, M. 2015. Molossus molossus. The IUCN Red List of Threatened Species 2015: e.T13648A22106602.
Emrich, M.A., E.L. Clare, W.O.C. Symondoson, S.E. Koenig, and M.B. Fenton. 2013. Resource partitioning by insectivorous bats in Jamaica. Molecular Ecology 23:3648-3556.
Esbérard, C. E. L., & Bergallo, H. G. (2010). Foraging activity of the free-tailed bat Molossus molossus (Chiroptera; Molossidae) in southeastern Brazil. Brazilian Journal of Biology, 70, 1011-1014.
Fenton, M. B., Rautenbach, I. L., Rydell, J., Arita, H. T., Ortega, J., Bouchard, S., ... & Vonhof, M. J. (1998). Emergence, echolocation, diet and foraging behavior of Molossus ater (Chiroptera: Molossidae) 1. Biotropica, 30(2), 314-320.
Gager, Y., O. Gimenez, M.T. O’Mara, and D.K.N. Dechmann. 2016. Group size, survival and surprisingly short lifespan in socially foraging bats. BMC Ecology 16:1-12.
Goodwin, G.G. and A.M. Greenhall. 1961. A review of the bats of Trinidad and Tobago. Bulletin of the American Museum of Natural History 122:195-301.
Marks, C. S., and G. E. Marks. Bats of Florida. 2006. University Press of Florida. Gainesville, Fl. 176 pp.
Lau, S. K. P., Li, K. S. M., Tsang, A. K. L., Shek, C.-T., Wang, M., Choi, G. K. Y., … Yuen, K.-Y. (2012). Recent Transmission of a Novel Alphacoronavirus, Bat Coronavirus HKU10, from Leschenaults Rousettes to Pomona Leaf-Nosed Bats: First Evidence of Interspecies Transmission of Coronavirus between Bats of Different Suborders. Journal of Virology, 86(21), 11906–11918.
Silva-Duarte, L., Herrera-Sarmiento, M. M., Serrano-Cardozo, V. H., & Ramírez-Pinilla, M. P. (2023). Reproductive activity and diet of an urban population of Pallas' free-tailed bats Molossus molossus (Molossidae). Acta Chiropterologica, 25(2), 237-250.
Simmons, J., M. Ferragamo, T. Haresign, J. Fritz. Aug 1996. Representation of Perceptual Dimensions of Insect Prey During Terminal Pursuit by Echolocating Bats. Biological Bulletin, 191:(1): 109-121.
University of Florida. Florida’s Bats: Velvety Free-Tailed Bat. University of Florida IFAS Extension. Retrieved from http://edis.ifas.ufl.edu/uw425#FIGURE%202.
USDA. Velvety Free-Tailed Bat. USDA: United States Department of Agriculture Forest Service. Retrieved from https://www.fs.usda.gov/detail/elyunque/learning/nature-science/?cid=fsbdev3_042947
Voigt, C. C., & Holderied, M. W. (2012). High manoeuvring costs force narrow-winged molossid bats to forage in open space. Journal of Comparative Physiology B, 182, 415-424.