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Mexican free-tailed bats leaving Bracken Cave.

Mexican free-tailed bats leaving Bracken Cave.. Photo by USFWS; Ann Froschauer



Indiana Bat Calendar


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Researchers have identified a new genus of bat after discovering a rare specimen in South Sudan. The bat's strikingly beautiful and distinct pattern of spots and stripes has been compared to the markings of a badger
Bats are arriving back at maternity sites.  Many people look forward to bats returning to traditional roosts on their property, but some bats take up residence in places they’re not wanted.  Over the next few days we’ll offer tips for what to do when a bat gets in your home.
A bat will occasionally fly into a home through an open door or window. When this happens, the bat’s primary goal is to escape safely back outside. These bats will usually leave on their own if a window or door to the outside is opened and interior entrances are closed.  Homeowner’s Guide to Bats
Most bats cannot take flight from the ground. So, a bat that is on the floor or ground cannot fly until it gets on an elevated perch from which to launch.  Here are suggestions on dealing with bats flying in your home.  Remember to NEVER risk a bite by handling a bat with bare hands.
Seven years ago today, the first Indiana bat maternity roost was found at Great Swamp National Wildlife Refuge in New Jersey. 250 bats were counted emerging from this tree.
Sometimes colonies of bats roost in attics or other spots where a homeowner does not want them.  Bat Conservation International and Organization for Bat Conservation provide humane and effective bat exclusion tips. State natural wildlife agencies are also a good source of information.
Bats often roost in buildings during periods when they give birth and raise their pups. Exclusions should not be used until young bats can fly; otherwise pups will be trapped inside, away from their mothers, and die of starvation. See tips on timing exclusion activities.
What species of bat is roosting in your house?  In the eastern U.S., if you have bats roosting in your home or barn in the summer, they are most likely little brown bats or big brown bats.
Indiana bats rarely roost in occupied buildings.  There are hundreds of records of Indiana bat colonies found in trees but only a handful of cases of Indiana bats roosting in buildings.
Install a backyard bat house to help conserve bats and your bat tenants will pay you back with some wonderful benefits.  They will put a dent in insect pest populations and you'll enjoy watching them come and go from the home you provided.  Bat Conservation International and others have more on bat houses.
Several states have “citizen science” projects that monitor bat populations by having volunteers conduct emergence counts, which means they count bats emerging from a building or bat house.  Examples include Pennsylvania’s Appalachian Bat Count and Vermont Bats Summer Maternity Roost Monitoring Program.
More than 40 different tree species have supplied roosts for Indiana bats.  Which trees are used depends on the local availability of trees with suitable structure.  Trees that maintain thick slabs of peeling bark when they die, like many ashes and oaks, provide good maternity colony roosting habitat.
Indiana bat roost trees are usually deciduous in the Midwest.  Primary roost trees are trees used frequently and by large numbers of bats.  They are usually large dead or dying trees.  In Indiana, primary roosts are often in eastern cottonwood although Indiana bats use many tree species.
Indiana bats also sometimes roost under the naturally peeling bark of living trees, especially shagbark hickory.  Shagbark hickory is a valuable component of roosting habitat because as a living tree with peeling bark  it provides roost sites for many years whereas dead trees lose their bark or fall over after a few years.
While male Indiana bats save energy by using torpor, females are more likely to save energy by clustering.  The energy demands of pregnancy and lactation are one reason that maternity colonies form.  By roosting in groups female bats can take advantage of shared body heat to help stay warm during cool periods.
Indiana bats are likely to use pine trees as maternity roosts in the southern part of their range.  For example, in the Great Smoky Mountains National Park, researchers found Indiana bats taking up residence in pines that died after a southern pine beetle infestation.
Indiana bats are now well beyond the hibernation season.  So, does that mean that the bats maintain a constant body temperature during summer?  No, because bats actually continue to use periodic torpor bouts to save energy, particularly during cold spells in spring and summer.
How does torpor, used in summer by bats, differ from hibernation?  Torpor is a short term reduced body temperature, usually in response to cool temperatures or low food availability.  Both torpor and hibernation involve a controlled reduction in body temperature but hibernation is more extended.
During spring and summer, if temperatures drop and foraging conditions are poor, bats can go into torpor to save energy.  Males are more likely to use torpor than females.  Females may not use torpor because of pregnancy and lactation (milk production) energy demands.
If a pregnant female bat uses torpor to deal with cold or lack of food, the pregnancy will be longer because torpor also slows embryo development.  After giving birth, a lactating female is not likely to use torpor because she has to be out foraging to maintain milk production for her growing pup.
Happy Father’s Day.  Is your father hanging out in his “man cave” today?  That’s where many male Indiana bats spend the day as well.  While some males migrate and spend the summer near maternity colonies, many males forgo migration and stay near their hibernacula.  These males may use the caves intermittently throughout summer.
There are no documented occurrences of a female Indiana bat successfully giving birth and raising a pup alone without communal benefits of a maternity colony.  You may have heard the African proverb: "It takes a village to raise a child."   In the case of Indiana bats, it takes a colony to raise a pup.
Indiana bats give birth to a single pup, rarely twins, in June or early July.  Births occur in the maternity roost tree. The timing of births is later in the northern portions of the range compared with the southern portion.
Gestation is the time from egg fertilization to the birth of young in animals.  In most mammals gestation is more-or-less constant for a given species.  In humans gestation is 9 months. The African elephant’s 22-month gestation is the longest known in mammals. Tomorrow, find out the gestation period for Indiana bats.
The gestation period in Indiana bats generally lasts from 50 to 60 days.  Cool weather and use of torpor by pregnant bats can lengthen gestation.  One study in Ohio showed births extending over two weeks within one colony.
Indiana bats are mostly hairless and blind at birth.  A bat pup is totally dependent on its mother’s milk until it is able to fly and forage on its own, which will take weeks.  While we don’t have a picture of an Indiana bat pup to share, here is video of newborn pipistrelle bat pups which shows what they look like at birth.
In spite of the fact that the pups are large in comparison to the mother (about ¼ or more of the mother’s weight at birth), females must carry the pups in flight if they need to switch roost trees.  Female bats have been observed flying with pups attached to a teat and clinging to their belly.
Producing milk for her pup is the most energy demanding phase of reproduction for female bats.  They must eat twice as much or more when lactating.  This increased energy demand means that the female bats must spend more time foraging or must find higher quality foods.
Female bats may eat more than half of their body weight in insects per night to keep up with the energy demands of lactation.  But, a female bat must balance the need to spend time foraging with the needs of her pup.  She must return to the roost tree periodically during the night to feed her pup.
Do baby bats play? That depends on how you define “play.” We know that baby bats are inquisitive and explore their environment.  They also need social interactions.  Caring for baby bats in captivity is challenging because pups must be in an enriched environment with both physical and social needs met to thrive.
Last updated: June 8, 2015