The Mexican free-tailed bat, Tadarida brasiliensis, has a tail
that extends a third past the tail membranes; the tails of most
bats are limited to within the tail membrane. Bats are the only
mammals that can fly, and fossil evidence shows that they have existed
for more than 50 million years.
100 million Mexican free-tailed bat (Tadarida brasiliensis)
living in Central Texas caves consume approximately 1,000
tons of insects nightly, according to Bat Conservation International.
(photo courtesy of Merlin D. Tuttle - Bat Conservation International,
What Do They Look Like
Mexican Free-tailed Bats are small bats at 3 ½ to 4 ½
inches long. They have a total wingspan of 12 to 14 inches. Mexican
Free-tailed Bats weigh 0.4 to 0.5 ounces. Their colors vary from
dark reddish brown to gray. They have wide black ears that point
forward. Mexican Free-tailed Bats have wrinkly lips and long, thin
wings. They have double talons on their thumb and toe claws. Mexican
Free-tailed Bats are very fast fliers. Bats are nocturnal animals,
and they do their feeding at night. They use echolocation, a system
of sending out signals and listening for the echoes, to find food
and to navigate as they fly. Male Mexican Free-tailed Bats live
as long as 18 years. Females live around 13 years.
free-tailed bats (Tadarida brasiliensis) exiting Bracken Bat
Cave in southern Comal County, Texas.
Image credit: Ann Froschauer / U.S. Fish and Wildlife Service.
Habitats of Mexican Free-tailed Bats
Mexican Free-tailed Bats are the most common bats found in the southwestern
U.S., numbering 120-150 million. Mexican Free-tailed Bats are also
found throughout Mexico, Central America, and the northernmost parts
of South America. The largest group of Mexican Free-tailed Bats
in the U.S. lives near San Antonio, Texas, where as many as 20,000,000
are located in a single cave. The Carlsbad Caverns in New Mexico
are well known for their population of Mexican Free-tailed Bats.
At their peak population, they numbered at 8-9 million bats, but
the number ranges in the low hundreds of thousands now.
Mexican Free-tailed Bats live in several different climates.
They can be found in desert climates as well as juniper and pine
forests that are at 9,000 feet above sea level and higher. Female
Mexican Free-tailed Bats form maternity colonies and live in buildings,
abandoned mines, limestone caves, and under bridges. If a number
of bats are found living in a building, they will be female bats.
Smaller colonies of males can be found in hollow trees.
They often live near areas of still water that attract the insects
that they eat. Most Mexican Free-tailed Bats migrate to Mexico and
Central America during the winter, although sometimes older males
will remain in one place throughout the year. After migration, Mexican
Free-tailed Bats will return to their roost from the previous year
if at all possible. Sometimes, their former habitat is destroyed
due to natural or man-made causes and they have to find a new home.
What Do They Eat
Mexican Free-tailed Bats eat mosquitoes, moths, beetles, and other
insects. They can eat up to 50% of their bodyweight in insects per
day. Large colonies of Mexican Free-tailed Bats can eat several
tons of insects each night. Many of the insects that they eat are
harmful to crops, so bats are considered beneficial for the environment.
Some of the harmful insects that Mexican Free-tailed Bats eat are
the cotton boll worm moths and the corn ear-worm moth. Both of these
moths can destroy acres of crops, and the bats keep the numbers
of these destructive pests down.
Mexican Free-tailed Bats eat just after dusk each night and
just before dawn in the morning; after the sun rises, they return
to their roost until it goes down again. The bats will fly as far
as 150 miles looking for food. These bats use echolocation to find
insects. They emit signals, and then listen to the echo bounce back,
which enables them to determine where insects are. They also use
echolocation to locate bodies of still water where insects are abundant.
And no, these bats are not blind, they can see fine, but they use
echolocation to help assist them.
free-tail bat pup resting after a meal.
(photo by Mary Cummins, Animal Advocates)
Mexican Free-tailed Bats mate in the fall. Females and males join
together in large gatherings in caves, where they mate; the females
outnumber the males, so the males will mate with several females.
The females store the sperm while they hibernate. When they wake
up in the spring, they fertilize one egg. Female bats will form
maternity colonies in the spring. They have their babies in the
summer, with each mother having just one pup, and the babies all
live together in the hottest part of their shelter. The mothers
do not stay in the same roost as the babies, but they feed them
and take care of them.
The babies are unable to fly for several weeks, and they are
totally dependent on their mothers until they are able to fly. There
are many predators of bats, including snakes, cats, raccoons, and
owls. If a baby bat falls to the floor of a cave, it will be left
there as the mother will not risk getting snatched up by a predator.
Once the babies are old enough to fly, they will join the rest of
the colony on their nightly hunts. At about 8 months old, the babies
will be mature and will mate during the fall.
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