Monday, October 26, 2015

Batty for Bats

People generally like “all creatures great and small,” at least the ones that include puppies, kittens and butterflies. A much smaller percentage includes bats in their "creature" affection. If the mere mention of them makes you wince or hide, then perhaps learning about their good nature might ease your mind. I had a bit of bat fear myself until I attended a bat presentation by Rob Mies from the Organization for Bat Conservation at Denver Botanic Gardens a few years ago.

I volunteered as the room assistant for his show and tell program, and of course it was in October. Once everyone was seated I scanned the faces of the packed room (young to old) awaiting their reaction to Rob and his bat tales. The outcome... in a word captivated. In another word, no fear, okay that’s two words. No one not the five or fifty-year-olds seemed afraid of the dozen bats Rob wheeled out for viewing while they calmly hung upside down on a bat coat rack waiting their stage debut. The audience listened and watched with focused awe then admiration as Rob took each bat from the rack and told their story. You can guess what happened to my bat apprehension after that night.
 
It’s true, many people in the Western World equate bats to evil spirits, attic invasions, or carriers of rabies. Conversely in the Far East bats are highly regarded as signs of good luck, happiness, fertility and long life. The facts speak for themselves; bats are extremely important to humans and our worldwide natural communities for both pollination and preying on insect pests. For more than 60 million years they have co-evolved with plants they pollinate, who in turn provide many fruits and nuts we enjoy today.   

Over 300 species of fruit depend on bats. Bananas, mangos, avocados, dates, figs, and cashews rely on bats for pollination and seed dispersal. Several products were, or currently are derived from bat pollinated plants – kapok plant fibers used in surgical bandages and life preservers, sisal fibers for rope and until the 1960s, chicle latex from the sapodilla tree (Central America) for chewing gum. And next time you raise your margarita or tequila sunrise glass, thank a long-nosed bat (Genus Leptonycteris) for pollinating the white tubular flowers of century plants (Agave sp.) growing in the southwestern U.S.

Bat guano pile
Insect eating bats consume large quantities of backyard pests (mosquitoes, moths, gnats, wasps and midges). A single little brown bat can eat 1,200 mosquitoes an hour, plus consume their body weight in insects every night. 

Bats control harmful forest and agricultural pests including cucumber beetles, June bugs, leafhoppers, and stinkbugs.  Scientists from the United States Geological Survey suggest the value of bat pest control for agriculture is anywhere between $3.7 billion and $53 billion a year. 

Bat poo is valuable too. As a fertilizer, bat guano is a good source of nitrogen and phosphorous. In a tiny region of Malaysia the total black and white pepper crop (about a third of the world’s supply) is fertilized with bat guano. Organic Fertilizers 

Eighteen species of bats live in Colorado. Bats of Colorado. Sixteen of these are considered common bats (Vespertilionidae) which are insect eaters, most are cave dwellers and roost by day in rock fissures, loose tree bark or hollows and mines. The short list includes the Pallid BatBig Brown Bat, Silver-Haired Bat, Hoary Bat, Western Small Footed Bat, Western Long-Eared Bat, Little Brown Bat, Long-Legged Bat, Yuma Bat, and the Western Canyon Bat. The other family (Molossidae) are the free-tailed bats – Brazilian Free-Tailed Bat and Big-Free Tailed Bat, both insect eaters.  

Bats hibernate or migrate in the winter. Some remain in Colorado, but their habitats are not completely known. Some will fly far distances, while others like a Big Brown bat may fly from one building to another, only a short distance each fall season. They are very loyal to their hibernating and roosting sites, returning each year to the same location.   

Bats are the only mammals on earth that fly. Squirrels, Australian possums and colugos from Southeast Asia just glide, they don’t actually take flight.  And because bats are so special they have their own scientific order, called Chiroptera which in Latin means “hand-wing.” Up close a bat’s wing looks like four very elongated fingers and a thumb all connected by a membrane of skin. They come in a variety of sizes and weights, the smallest, close to bumblebee size, weighs less than a penny (hog-nosed bat of Thailand). Our own western canyon bat (formally western pipistrelle) weighs less than a nickel. Large, fruit-eating bats of the tropics may weigh up to two pounds with a wing span of six feet. All bats roost upside down and it remains a mystery to scientists why they do so.   

Bat flight agility skills are remarkable. Wings of various sizes between bat species determines if they are better at hovering (short wings) to glean insects off the ground or fly for longer distances (long narrow wings) to catch insects midair.  Fruit eating bats in the tropics use their sight and smell senses to find food, but insectivore bats use echolocation, or biological sonar to detect insects and prey.   

Basically they see with their ears, and the same is true for dolphins, some whale species and birds. As a bat flies searching for food it emits a frequency per second, and the frequency increases as it figures out what insect lays ahead along with the insects flight pattern, speed and size.  They call this high-rate vocalization their “feeding buzz.”  And it’s a good thing we can’t hear it, several bats in a chorus of echolocation cacophony might sound to us like scores of smoke detectors gone wild. The normal chattering squeaks we hear are from bats in roost, though some bats in Colorado have audible calls that we can hear as they fly. Once an insect is found bats knock them off balance with their wing tips, and then transfer it to their mouth, while other bats catch insects directly in their mouths.

Bat faces are very distinctive and often describe their common name (tunnel-eared, leaf-nosed, etc). For most of the insect eating bats their unusual facial features aid them in sending and receiving ultrasonic signals.  

Bat House, Central Denver, East Facing
Just like all mammals, bats breed and produce young, nurturing them with milk.  Mating occurs in the fall, near their time for hibernation. Females store the sperm over the winter until spring. Young are born after a 30 to 60 day gestation period, usually in the late spring in Colorado. Most females have just one “pup,” but some species have twins up to quadruplets. Females form maternity colonies with focused care on their own pup. 

Pups are nursed until they are able to fly by themselves, roughly 3-5 weeks, but will remain with their mother as they learn the ropes of night foraging. Mortality is high while pups learn to fly; many will give up on their first flights and just walk or climb back to their roost. During this development stage they are easy prey to skunks, raccoon, coyotes, hawks and domestic cats or dogs. 

A bat can live over twenty years. Six species in the United States are considered endangered, and another twenty are threatened, according to the U.S. Fish and Wildlife Service. Bat populations are declining due to habitat destruction of summer and winter roosting areas, fear of bats and disturbance by cave explorers, and chemical poisoning by pesticide use.

Bats are exceptionally beneficial animals many gardeners encourage them to live in their yards. First, they need the basics of life – food, water and shelter.  Maintain a natural landscape with live trees and dead snags (careful if they become hazards and need to be removed). Plant night-blooming plants plus flowering annuals, perennials, fragrant plants, herbs and shrubs.  The choices are many Nicotiana, Evening Primrose, French Marigolds, Four O'Clocks, Asters, Heliotrope, Butterfly Bush, Salvia, Phlox, Soapwort, Rosemary, Lavender, Lemon Balm and Honeysuckle. 

Bats like to have a water source too, so a pond, water feature or close by stream is ideal. Put up bat houses for female colonies or general roosting. Design plans are available online, or purchase from bird shops and garden centers. Your bat house should be fifteen feet off the ground or higher on the south or east side of a house or barn, or a free-standing pole works too.  

They need an open area below, and 15 – 20 feet of clearance in front of the house to give them room to come and go. The ground below the bat house will collect bat guano so site it properly for collection. Bat houses mounted on trees don’t work as well as houses, they tend to block views and aren’t as warm. Three or more houses in one area will increase the chance of attracting bats.  It may take up to two years for bats to find their new house. Once occupied expect the bats to return year after year.

Homemade Bat House

If bats are occupying an unwanted space in your home be sure to allow them time and opportunity to leave on their own (at least 45 minutes after sunset) before sealing up their entrance. This is called a humane exclusion. Provide an alternative bat house nearby if possible and construct a one-way device that won’t allow them to return, but lets them exit, more - bat exclusion. Keep in mind that new pups generally won’t be leaving the roost until sometime in the summer so exclusion is best done in the fall to early spring.  


Bat Facts and Misconceptions:

  • “All Bats carry rabies.”  All mammals can contract rabies, but less than 0.5 percent of bats ever do. The chances of coming in contact with a rabid bat are rare. Never touch any wild animal.  
  • “Bats are blind.”  Bats cannot see color, but their vision is better than ours.  Echolocation helps them see in the dark, so no worries that they’ll get tangled in your hair
  • “Bats attack people.”  They are small and gentle; we are large to them so they are afraid of us. 
  • “Bats drink human blood.”  Vampire bats live in South and Central America and southern Mexico. They prefer the blood of birds, cattle and horses. And they don’t suck blood; they lap up blood after making a slit with their sharp teeth.
  • “Bat guano is dangerous.” Histoplasmosis is a fungal disease that develops from bird or bat droppings that have sat in moist, humid conditions for a period of time. Always wear a mask to prevent inhaling fungal spores if you’re in an enclosed area with animal droppings.
  • “Bats try to attack you if caught in your house.”  If this happens, bats are simply looking for a way out. They fly in a figure eight pattern to gain clearance and make turns, so just open doors and windows and quietly sit down so the bat finds its way outdoors.  

Bat Resources:

FYI - this essay is the longer version that was published in The Denver Post in early August of 2015.



2 comments:

  1. I have never seen a bat (some 60yr.) here in Montrose, Colo .. If we have bats and I build the bat house "will they come" ?

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  2. From what I've read, bat houses are a wonderful way to attract bats to your landscape. It may take several months to possibly a year for them to find the bat house. Good luck!

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