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In The Country

Bat chat

Tim Iverson
Seasonal Naturalist
Cunningham Falls State Park

(8/2013) Tons of people think bats are creepy. Others wonder if bats really suck blood. Could one be a caped crusader soaring through the night sky protecting the innocent? Whether you love them or hate them bats are integral and necessary parts of the ecology of any region. They exist within a small niche in the environment, and serve a purpose that most other animals cannot or do not. They provide invaluable services to humanity, but have been vilified throughout literature and film. These remarkable creatures have many adaptations that serve them well, but face many threats that are putting many species into grave danger.

There are a total of 40 different bat species in North America, and over a 1000 worldwide. They can be found on every continent, except Australia, and they account for 20% of all mammal species on the planet. Maryland is home to a total of 10 species of bats. The largest being the Hoary Bat with a wingspan of 16 inches. Our smallest bat is the Eastern Pipistrelle, with a wingspan of about 8 inches. The Philippines hold the record for the largest and smallest bats in the world. The bumblebee bat measures in with a wingspan of 6.5 inches, while the Giant Golden-Crowned Flying Fox has a wingspan of 6 feet!

Bats basically breakdown into two categories: RepubliÖ wait no thatís not right. Bats fall into two classifications Ė mega or micro (these terms do not refer to size). "Mega" bats are frugivores, meaning they eat only fruits, nectars, and pollen. Mega bats are partially responsible for the pollination of many plants, so theyíre kind of like oversized bees. One endangered species in Mexico is actually partially responsible for the pollination of agave plants, which is what tequila is made from Ė this bat is endangered so tequila could be as well. "Micro" bats are carnivores and eat mainly insects, although one vampiric species in Central and South America have given the rest of bats a bad name!

The anatomy of a bat is really quite remarkable. Wings have finger-like digits with a leathery membrane in between the fingers. Bats will spread or move these fingers to adjust speed and increase their maneuverability. Contrary to popular belief bats are not blind. "Mega" bats rely solely on vision, while "micro" do have poorly developed eyes they can still see and will use sight for long distance navigation. Some bats can even see in ultraviolet light, which helps them hunt and navigate. The ears of a bat are pointy and shaped with special folds that help pinpoint the position of insects with the use of echolocation.

Echolocation works essentially like sonar for submarines. Bats will produce high pitch frequencies, which can sometimes be heard by humans, that then bounce off objects and return to their ears. Based on the time these sounds take to return and where the sound hits in their ears they know where and how far away the object is. The intensity of the echo indicates the size of insect (high intensity means a big bug, while low intensity means a small bug). Some insects have developed defenses against echolocation though! The Tiger Moth species emits a frequency back that is the equivalent of "radar jamming". Owlet Moths can hear the frequencies emitted by bats and begin to fly erratically to perform "evasive maneuvers".

Being a bat isnít all about crime fighting and making tequila though, sometimes you have to settle down and raise a family. Bats only have one offspring at a time, making population decline difficult to combat. Depending on species they may have one to three litters in a year. Mother bats will nurse their young until they are a full grown adult, which is approximately a month, because the young canít fly and catch their own prey until their wings are fully developed. The lifespan of some bats can be up to 20 Ė 30 years.

You might also be asking yourself, "Whatís the deal with sleeping upside anyhow?" Roosting upside down provides security from most other animals, and zero competition from other flighted creatures for these locations. But itís also necessary because their wings canít produce enough lift for takeoff and their legs are underdeveloped so they get enough speed to generate lift. So bats let physics do all the work and use gravity to begin flying by simply falling into flight. Itís an adaptation in action, and hereís how it works:

1. Start by clenching your fist.

  • The muscles in your arm contract to pull tendons connected to your fingers which close your fist.

2. Bats tendons are connected to upper body, not the muscles in legs.

3. They will use the claws on their feet to grab onto a surface.

4. Then they simply relax. The weight from upper body pulls the tendons shut Ė gravity does all the work, so they exert no energy to remain hanging.

  • If a bat dies in this position it will remain hanging because of this!

5. To release its claws from the surface bats will flex their muscles which pull the tendons open and off they go.

If you happen to find a bat thatís fallen or been knocked to the ground it will need a high place to take off from. If youíre brave enough you can attempt to pick it up and help it to a higher location. Just remember that bats can carry diseases so only do so at your own risk. Wearing a pair of think gloves and long thick shirts or using a shovel to gently place them in a tree would be perfectly acceptable ways to move a grounded bat.

Bats are generally pretty adept creatures though and usually donít require much assistance from people. One recent pandemic though is giving them the fight for their lives though. A new fungus called Geomyces destructans infects bats and causes "White Nose Syndrome". This cold loving fungus was first discovered in 2006. It spreads to hibernating bats and causes erratic behavior. Affected bats will awaken during hibernation with decreased and damaged wing tissue. Flying becomes harder work which depletes energy supplies during times of the year when there is little or no food, which eventually causes starvation and then death. White Nose Syndrome has been confirmed in 19 states and 4 Canadian provinces. In some species it has a mortality rate of 95%. The Little Brown Bat, which we currently have in Maryland, is estimated to be extirpated (locally extinct) from the eastern US within 20 years! The loss of bats at these numbers is estimated to cause billions of dollars worth of damage to agri-business and farmers due to increased insect populations and heavier use of pesticides. Both of which will drive food costs up and increase the use of pesticides on produce. Research is being conducted by the US Forest Service, Fish & Wildlife, National Park Services, and other state agencies, and universities. Researchers are still seeking to understand where it came from, the mode of transmission from cave to cave and bat to bat, and more. One leading theory says that itís most likely spread from cave to cave via human transmission from clothing and shoes. Thatís has led some state and local officials to enact caving moratoriums in some places. There is no known treatment at the time.

One of the most practical ways to assist bats, no matter where you live, is to provide adequate housing in the form of bat boxes. This can make a real difference in both your community and theirs. You can find excellent plans for bat boxes, information on where to place them, and more at the MD Department of Natural Resources website or at BatCon.org. By providing housing sites you can really make a difference in stabilizing the populations of bats in your area.

These animals are extremely important to the environment. They serve as a valuable pest control service to farmers and agri-business. Some bats even help to pollinate plants, and plant trees! Seeds dropped by bats can account for up to 95% of forest regrowth on cleared land. Yet despite these things and more they still suffer from a bad PR problem, deadly fungal epidemic, and encroachment of necessary resources from man. Through understanding and basic actions we can ensure that we can all see these caped crusaders continue to venture out into the night.

Read other articles by Ranger Tim Iverson