Mexican Free Tail Bat in Florida

08.09.2005 - Here we have a Mexican Free Tail Bat, Tadarida brasiliensis. Why is it not Tadarida mexiciensis? Perhaps for the same reason the Norway Rat, Rattus norvegicus is not called the Rattus newyorkseweregicus - when it comes to taxonomical nomenclature, it's first come, first serve. Whoever discovers the species gets to name it. That's why a type of louse found on owls is named the Strigiphilus garylarsoni, because Gary Larson himself discovered this species, and he is a vain man, and he also closely resembles the organism that bears his name, in both appearance and behavior. The point here is that the scientific name of a species does not necessarily describe the traits of the animal (unlike gorilla gorilla, whose name leaves little to ponder).

Thus it is with the Mexican Free-Tail bat. It's not only from Brazil. It also is not only from Mexico. In my personal experience, it's only from the attics of people with big mouths and small pocketbooks. In truth, it's from most of South America, Central America, and southern North America, Florida included. In fact, I call the bat the Brazilian Free Tail, as do most biologists and other people in my field that I've encountered. A Google search of the two competing names, and they are competing as much as Brontosaurus and Apatosaurus are competing, yields 500,000 results for "Brazilian Free Tail Bat", 1,270,000 results for "Mexican Free Tail Bat" and 0 results for "David Seerveld is dashingly handsome". So it appears that Mexican wins out, which is largely the reason I created this page: in case anyone wants to do a little online research about the bat, and possibly find an expert for removal of Mexican Free-Tail bats in Florida or elsewhere. Plus see a fine photo of two handsome mugs smiling for the camera.

In this particular photo by the way, we see a bat that I caught at a customer's home. One would normally never see me handling a bat in this manner. First of all, my bat exclusions are done with a minimum of stress put upon the animal. The bats are never physically touched - they are removed in a safe and gentle way. Secondly, bats are very fragile. The wings are actually analogous to hands, with a thin membrane stretched across the finger bones. As with any flying animal, the bones are thin and light, and anyone who handles a bat without the gentle touch of a dentist could break these bones. Third, no one should pick up a bat, because if you encounter one on the ground, it may be rabid, and the only chance it'll bite and infect you is if you pick the dang thing up. Fourth, if you must pick up a bat, there's no reason to spread the wings out as I have above.

So then, why am I holding the bat? Well, it came from inside a customer's bedroom of course, and I had no choice but to remove it by hand, and once I had it in hand, I had no choice but to take the best bat-holding photo that I could muster, and bats look more impressive with the wings out. But I was extremely gentle, and when the photo shoot was over, I threw the bat up into the air, and off it flew to Brazil, where it belongs.

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Mexican free-tailed bats - also called Brazilian free-tailed bats - are one of the most fascinating species of bat. Although endemic to the Americas, they are one of the most prevalent bat species in North America. You’ve probably heard of Bracken Cave, north of San Antonio, Texas, where an estimated 20 million bats of this species form the largest bat colony in the world. In this post, we’re going to talk about the Mexican free-tailed bat and their presence in Florida.

Appearance
The Mexican free-tailed bat (Tadarida brasiliensis) is a medium-sized bat, spanning about 9 cm in length. Interestingly, their tail accounts for almost half of their total length, hence the name ‘free-tailed” bats. They weigh between 7 to 12 g. However, females have an additional 1 to 2 g of fat used to store up energy for gestation and nursing. They have broad, black forward-pointing ears and wrinkled lips, with gray or reddish-brown to dark brown fur. Their wings are long and narrow, making them suited for fast flight patterns.

Speed
They are referred to as the jets of bats, reaching speeds of up to 100 mph (161 km/h).

Habitat
Although Mexican free-tailed bats primarily roost in caves, they are highly adaptable and can live in several kinds of structures with warmth and darkness. This is particularly true of bats in Florida that prefer man-made structures. A common explanation for this behavior is that Florida’s caves typically contain water, which raises humidity above their tolerance level. But because buildings are not as large as caves, they do not roost in the millions in Florida. Instead, their colony size typically consists of a few hundred bats to thousands.

Reproduction
Baby bats (pups) are usually born during the summer, where they roost in the highest regions of the building or cave because it is warmer. This bat species roost in large colonies because it allows their pups to remain behind in warmth and safety while the mother leaves the roost to feed. Amidst the thousands of pups, it is thought that a mother locates her pup by recognizing its call.

Diet
Mexican free-tailed bats are insectivores, preying on moths, ants, flies, dragonflies, beetles, wasps, and so on. They use a sophisticated system of echolocation to track down their prey.

Migration
Mexican free-tails migrate typically south towards Mexico and Central America during the winter. However, the south-eastern free-tailed bat subspecies do not because the seasonal temperature variation is minimal in Florida and that allows for warmth and all-year availability of food. They also do not hibernate during the winter, but instead, fall into a state of torpor that allows them to conserve energy by slowing down their bodily functions.

Predators
From time to time, animals like snakes, owls, cats, raccoons, and many others gain access to their roosting site. Pups are typically vulnerable, especially if they fall, as they make for an easy meal.

Life Span
They are thought to live up to 18 years.