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Indiana bat

Indiana bat. Photo by USFWS; Andrew King



Indiana Bat Calendar


<July - September>

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Different species of bats have different echolocation calls.  Here’s one example.  Bat biologists look at pictures of bat sounds, called sonograms, to distinguish among bat species.

Most bat echolocation calls are beyond the range of human hearing.  A bat detector is a device tha converts bat echolocation calls to frequencies audible to humans.  See a bat detector in use in this video.
Forty-two years ago today, the first Indiana bat maternity colony was discovered when a dead elm tree was bulldozed in a hedgerow in Wayne County, Indiana.  An Indiana bat maternity colony had been roosting under the bark of this tree.  Some of the bats were killed and these were identified as Indiana bats.

Before discovering the first maternity colony, we didn't know anything about Indiana bat maternity colonies or where pups were born. Today, the location of over 320 maternity colonies has been documented in 17 states. However, the location of most colonies is not known.
Indiana bat mothers nurse their pups from birth through early volancy (the time when pups begin to fly).  Indiana bat pups become volant within 3 to 5 weeks of birth.  Pups are born beginning in June and extending into July, so by now most Indiana bat pups have been weaned. 

Bat pups grow quickly, so female bats have to produce a lot of milk.  Pound for pound, a mother Mexican free-tailed bat produces more than five times as much milk as an average Holstein cow.

After bat pups learn to fly, they are weaned and begin foraging for insects.  Newly-volant pups likely forage with their mother and gradually become more independent, buthe pups still return to roost with the colony. 

Researchers estimate the size of maternity colonies by conducting emergence counts. They count the number of bats that emerge from roost trees at dusk. The results of emergence counts change throughout the summer depending on how many trees a colony is using. Colony size can nearly double when pups are born. 
Counting bats emerging from a roost tree may sound easy, but it is actually quite challenging to make accurate counts. A typical Indiana bat maternity colony has 50 to 100 females, so after pups are born there can be 200 bats emerging from a primary roost tree. That is a lot of bats to count, especially in the low light of dusk and often under the canopy of trees.
Once young Indiana bats are flying, colonial clustering behavior diminishes. Bats become less gregarious and the colony uses more alternate roosts. The entire colony is less likely to be found together in the same tree, possibly because there is less need for the adult females to cluster for heat and to nurture their young.
In addition to needing insect prey, bats also need drinking water. During drought, familiar water sources may dry up and make it difficult for bats to find water.  In arid portions of the Western United States, availability of drinking water can be limiting for bats.
Bats generally drink while flying, swooping down to a water source and lapping up water with their tongue as they skim past.   Standing by a lake or pond in a forested area can be a good place to view bats at dusk.  Bats often drink before beginning a night of foraging.
Lakes, ponds, streams, and even road ruts that fill with water in forested areas are used as water sources by Indiana bats.  There are usually enough water sources for Indiana bats, although drought or degradation of water sources can be a problem for local populations.
Good water quality is important to bats.  Water contaminated with pesticides or other chemicals can harm or kill bats.  Contaminated water also affects insect prey. Bats can be affected if pesticides reduce their food supply of insects or they can be poisoned if they eat insects that have taken up pesticides.
Here are some stunning photos of bats swooping low over a garden pond, enjoying an evening drink at their favorite watering hole  
Bats can sense when the echolocation signal that bounces back to them comes from a large, smooth surface, such as water.  Thirsty bats instinctively associate this signal with a water source.  Researchers have found that the smooth surface of a metal plate can fool thirsty bats .
Unfortunately bats often cannot distinguish a good quality water source from a bad one.  Pits containing contaminated waste water from oil and gas operations can poison bats and other living organisms.  The U.S. Fish and Wildlife Service works to make sure these pits do not become death traps for bats and other wildlife.
Today’s bat fact will be of particular interest to Star Wars fans.  Scientists have discovered a species of bat new to science … named the Chewbacca Bat.  Check out the pictures to decide if you think the bat deserves to share the name of the beloved Star Wars character.
Most of us know that bats provide awesome ecological services, especially controlling insect populations.  Some other benefits are less well known.  There are many examples of researchers, inspired by bats, making advancements in the fields of medicine and human health.  We’ll explore some examples this week.
New research from the University of Southampton has shown that people who are blind or visually impaired have the potential to use echolocation, similar to that used by bats and dolphins, to determine the location of an object.
The American Heart Association reported that vampire bat saliva contains a potent clot-busting substance that could help stroke patients. A drug, called Draculin, is being developed from an enzyme that is a natural blood thinner used by the bats to increase their target’s blood flow.
Surgical hypothermia (lowering body temperature) is sometimes used during open heart surgery on humans. While this technique has been used since the 1950’s, scientists hope that understanding how the heart of a bat functions at low temperatures could help improve these surgeries and lower associated risks.
Bats tailor their ultrasound signals to individual targets.  For instance, a bat may emit an ultrasound squeak that enables the bat to distinguish a flying insect, rather than a falling leaf.  Scientists hope to mimic this aspect of bat echolocation to locate and identify tumors hidden deep inside the human body.   
Researchers discovered that vampire bats have specialized sensors near the nose that are extremely sensitive to heat.  These allow the bat to sense changing body temperatures associated with blood flow, similar to human receptors that sense heat and pain.  Studying these sensors may lead to treatments for human ailments like chronic pain and inflammation. 
Bats have inspired many technological innovations.  For example, scientists at the University of Michigan College of Engineering are developing a six-inch robotic spy plane, modeled after a bat.
Researchers from Boston University used recent advances in computational techniques and thermal imaging to examine flight behavior of bats in unprecedented detail and to provide quantifiable measurements of flight dynamics.  Their models of bat flight may lead to a new generation of biologically-inspired unmanned aircraft.
A new invention uses technology inspired by bat radar to check the condition of buried water pipes.  The SewerBatt system features a small speaker inserted down a manhole that plays a tone, mimicking a bat echolocation signal.  The system analyzes the resulting echo to locate cracks, blockages or other structural defects along the pipe. 
A blind college student successfully rode a mountain bike down a trail with the help of bat-inspired technology that provides advanced warning of obstacles in the path so the rider can steer around them.  His mountain bike was outfitted with a device which aids in mobility by emitting ultrasonic waves, the same way bats and dolphins navigate by echolocation. 
Bat wings are highly articulated, with more than two dozen independent joints and a thin flexible membrane covering them. Researchers studying bat wings and bat flight say that the results suggest that the highly maneuverable mammals may be a model for tiny flying machines. 
Check out the hairy tongue of the Pallas's long-tongued bat and the way that they use their long tongue to get nectar from deep inside flowers.  Scientists think this discovery has the potential to help design new medical instruments for use in surgery.
In the heat of August most of us probably haven’t starting making preparations for the winter ahead, but for Indiana bats it is critical that those preparations start while insect prey is still abundant. Bats are busy foraging to put on weight to prepare for fall migration and for the winter ahead.
Last updated: June 10, 2014