Bats

Order: Chiroptera

Bats have received a bad reputation as being blood suckers, carriers of disease and "flying rats," All of these descriptions are wrong and fail to grasp the beauty, wonder and benefits of bats. 

There are over 40 species of bats in the United States and all of them are beneficial to people. Most bats feed on insect pests and some bats even help in pollination.  Scientists study bats to further expand our understanding of flight, sound, sonar and evolutionary biology.  Even bat guano is an important resource and fertilizer!  So before you tell scary stories about bats, remember how much they help make our lives better every day!

 

Bats swarm

Description:  Bats are the only mammals that can fly. Instead of arms or hands, they have wings. The wings have a bone structure similar to the human hand. Between the bones are flaps of skin.

Bats have fur on their bodies and sometimes the head. The wings do not have fur. Bats can be a range of colors from red to tan, brown or gray.

A bat's ears are very important because bats use them to hunt food. The ears tend to be large and noticeable. Many times the ears will stick up on the side of the head. The Allen's big-eared bat has ears so long that they make up two thirds of its body length! 

A bat's nose can be very useful characteristic for identifying a bat species. Some are small and simple, others are shaped like a pig's nose and some even have noses shaped like leaves.


Size:  The smallest bat in the U.S. is the western pipistrelle bat which grows to about 2 1/2 - 3 1/2 inches long with an 8-inch wingspan. The largest bat in the U.S. is the greater mastiff bat. It can grow as long as 7 inches or more with a wingspan of 21 to 23 inches.

Bats are very light weight to make it easier to fly. The western pipistrelle bat weighs less than a penny, while the greater mastiff bat weighs about 2 oz.


Diet:  The majority of bats in the U.S. are insectivores. They hunt at night and eat flying insects such as mosquitoes, beetles and moths, many of which are considered pests. Bats provide an important ecological service by eating tons of insects.  In a single midsummer night, the 20 million Mexican free-tailed bats from Bracken Cave in central Texas eat more than 200 tons of insects!

Not all bats eat insects. Some live on a diet of nectar and fruit. Bats that feed on nectar also serve as pollinators to nighttime blooming plants.

Vampire bats do exist, but there are none in the U.S. The closest vampire bats are found in Mexico.


Typical Lifespan:  Despite being small, bats can have a relatively long lifespan. Bats that make it to adulthood can live into their teens; a rare few into their twenties. The hard part is making it to adulthood, because there is a high mortality rate for young bats. 


Habitat:  Bats can be found in almost every type of habitat. They live in deserts, woodlands, suburban communities, caves, and some are even found in cities.

Bats make their homes (roosts) in a variety of different structures. They can use trees, caves, cracks in buildings, bridges, and even the attic of a house!  The largest urban colony of bats in the U.S. lives under Austin, Texas' Congress Avenue Bridge during the summer.  The Congress Avenue Bridge becomes a temporary home to over 1.5 million Brazilian free-tailed bats!

Bats typically prefer warmer temperatures and they have several ways of dealing with the cold. Some bats, including the big brown bat and the eastern red bat, hibernate in caves and trees to survive the winter. They can sometimes be seen flying around on warm winter days. Many bats migrate to warmer climates or even to a nearby cave.


Range:   Bats are found throughout the U.S., Puerto Rico and the Virgin Islands. The Hawaiian hoary bat is the only native, terrestrial mammal on the Hawaiian Islands. Bats can even be found in Alaska!


Communication:  Insect-eating bats hunt using a type of natural sonar called echolocation. They emit a high-frequency sound (undetectable to people) that bounces off of surrounding objects. When a sound hits an object, or better-yet an insect, it bounces back and returns to the bat. Using special sensory organs, the bat can determine where the insect is located and how far away. Everything happens so quickly that a bat can make almost instant turns and maneuvers to catch a flying insect. A bat's echolocation system is so advanced and precise that scientists study bats to make sonar equipment for ships.


Life History and Reproduction:  Bats are mainly nocturnal, and your best chance of spotting one in flight is at dawn and dusk. They fly very quickly and can make fast maneuvers.  It can be a real challenge to identify species of bats when they are in flight.

Bats congregate in large roosts during their winter hibernation/migration. In the fall and winter months, many species breed so that the offspring are born in the late spring. The births are timed with the return of insect prey.

Bats can have more than one offspring at a time. The babies are born furless, blind and without the ability to fly. They are completely dependent on their mother. However, it only takes a few weeks for the young bats to develop and start to fly.


Threats to Bats:

  • Disease - White-nosed Bat Syndrome
  • Habitat Loss  
  • Pollutants  - Pesticides and Insecticides 
  • Fear - Bats are highly misunderstood and this can cause people to harm bats and their roosts

Several bat species are on the Endangered Species List including, the Gray Bat, Hawaiian Hoary Bat, Indiana Bat, Lesser Long-nosed Bat, Mexican Long-nosed Bat, Ozark Big-eared Bat, and the Virginia Big-eared Bat.

 

Resources:

Night Friends: Bats of the Americas On-line Activity Guide (PDF) 

 

Sources:

Bat Conservation International

U.S. Fish and Wildlife Service

University of Michigan's Animal Diversity Web

Defenders of Wildlife

Stoke's Beginner's Guide to Bats.  Williams, K., R. Mies, D. Stokes and L. Stokes. Boston: Little, Brown and Company, 2002. 

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