Thursday, September 10, 2009

White-Nose Syndrome

Little Brown Bats exhibiting WNS symptoms
photo courtesy of Nancy Heaslip, New York Department of Environmental Conservation

I'm going to switch gears now and tell you about something quite serious that is devastating bat populations in the Northeastern United States and continuing to spread. It is called White-Nose Syndrome, or WNS, and since its discovery in a cave near Albany, New York in February 2006, it has wiped out an estimated 1 million bats in 9 states - with some caves experiencing a 90-100% mortality rate! - and scientists have yet to figure out the how's and the why's.

So far, it has affected 6 different bat species, all of which are insectivorous and hibernating species - the endangered Indiana myotis (Myotis sodalis), the little brown myotis (Myotis lucifugus), the big brown bat (Eptesicus fuscus), the tri-colored bat (Perimyotis subflavus), the northern myotis (Myotis septentrionalis), and the eastern small-footed myotis (Myotis leibii).

To begin, let me provide a bit of background information concerning hibernation (because this appears to be when the bats are dying). During this state, the bats' body temperature and heart rate slow down dramatically (sometimes within 1 degree of the temperature of the cave!) and they live off of their previously stored body fat. If a bat is disturbed too many times during hibernation, it is likely to die because all of the fat reserves are used up, and the bat cannot go out in search of more food because it is the dead of winter, and there are no insects to be found.

Again, it is at some point in their hibernation that these bats are dying. The dead bats are found inside their hibernation caves or just outside of them. They are emaciated and have a never-before-seen white fungus on their noses, ears, and/or wings. However, it is not yet clear whether it is the fungus, named Geomyces destructans, that is killing the bats - there is no evidence that a fungus has ever killed a mammal - or if the fungus is an opportunistic invader, coming in after the bats have been weakened by something else. What can be said of the fungus is that it thrives in the same temperature range and dark, moist conditions in which the bats hibernate. It is not known how the fungus - which is genetically similar in all of the cave sites - was introduced. It is known, however, that the fungus is transmitted from place to place via fungal spores, which could be carried on the bat's fur, the clothes or shoes of humans, or through the air.

Now, I mentioned that the dead bats found are emaciated. What appears to be happening is that the bats are losing their body fat mid-winter, so that they either die before they are able to wake from their torpor, or they wake prematurely and fly outside in search for food and freeze. (The few bats that do survive the winter are found to have wing damage from frostbite and/or the fungus.)

Some scientists have hypothesized that the loss of body fat is due to an inadequate supply of polyunsaturated fats that are supplied by certain insects, which are dying off because of pesticides. (Pesticides that shouldn't need to be used in the first place because these bats act as nature's pest controllers by consuming these insects.) It has also been suggested that the bats perhaps rouse prematurely because of irritation due to the fungus, which reaches their dermis, or living part of the skin. The fungus could also have physiological effects on the delicate wing membrane which regulates body temperature and blood pressure, thus interrupting hibernation. The warm or variable winter weather is also a hypothesis as to why the bats are waking mid-winter.

Unfortunately, the money needed to fund WNS research is slow-coming. So far it has come mainly from Bat Conservation International, the National Speleological Society and other non-governmental sources. The scientific community is trying to obtain more funding from the federal government, but according to BCI's website, the Senate Appropriations Committee report "contains only $500,000 of the $11 million identified by the scientific community for immediate WNS funding."

Such a devastating loss in bat populations doesn't just mean that 1 million bats are dead. The loss of 1 million bats means that the organisms supported by the guano on the cave floor will die, the pest population that the bats are no longer consuming will increase, you will get more mosquito bites, the increased number of agricultural pests will damage more crops, the crops will be sprayed with more pesticide... And - if the pesticide/polyunsaturated fat hypothesis holds true - more bats will die. Of course, the greatest thing at stake here is the potential extinction of entire bat species.

Thursday, September 3, 2009

Why Bats Are So Amazing, Important & Misunderstood - part III

adult White-Winged Vampire Bats (Diaemus youngi) - photo by Daniel Riskin

So Why the Misunderstanding...
Like most misunderstandings, it comes down to people's ignorance. Through research, the myths surrounding bats have all been dispelled:
  • They're not blind.
  • They don't get tangled in your hair.
  • They don't carry rabies any more than any other wild animal.
  • They're not mice with wings.
  • They're not bloodsuckers.
  • They're not ugly.

Why Bats Are So Amazing, Important & Misunderstood - part II

Tamana Cave, Trinidad - photo by Daniel Riskin

Some Amazing Bat Trivia
click on the links to view a photo of the bat/s*
  • The world's smallest mammal is the bumblebee bat of Thailand, weighing less than a penny.
  • Giant flying foxes that live in Indonesia have wingspans of six feet.
  • The common little brown bat of North America is the world's longest-lived mammal for its size, with life spans sometimes exceeding 34 years.
  • Mexican free-tailed bats sometimes fly up to two miles high to feed or to catch tailwinds that carry them over long distances at speeds of more than 60 miles per hour.
  • The pallid bat of western North America is immune to the stings of scorpions and even the seven-inch centipedes upon which it feeds.
  • Fishing bats have echolocation so sophisticated that they can detect a minnow's fin as fine as a human hair, protruding only two millimeters above a pond's surface.
  • African heart-nosed bats can hear the footsteps of a beetle from more than six feet away.
  • Frog-eating bats distinguish between edible and poisonous frogs by listening to the male frogs' mating calls. The frogs counter by hiding and using short, difficult-to-locate calls.
  • Red bats, which live in tree foliage throughout most of North America, can withstand body temperatures as low as 23 degrees Fahrenheit during winter hibernation.
  • Tiny woolly bats of West Africa live in the large webs of colonial spiders.
  • The Honduran white bat is snow white with a yellow nose and ears. It cuts large leaves to make "tents" that protect its small colonies from jungle rains.
  • Vampire bats adopt orphans and have been known to risk their lives to share food with less fortunate roost-mates.**
  • Male epauleted bats have pouches in their shoulders that contain large, showy patches of white fur, which they flash during courtship to attract mates.
  • Mother Mexican free-tailed bats find and nurse their own young, even in huge colonies where many millions of babies cluster at up to 500 per square foot.
(taken from a BCI booklet from the 1990's "Amazing Bat Trivia")

* Note that you are linking to photos on other people's websites and these photos are/may be copyrighted by the owners.

** This is a fascinating altruistic behavior that is exhibited by vampire bats. Reciprocal Altruism (wikipedia)

Wednesday, September 2, 2009

Why Bats are So Amazing, Important & Misunderstood - part I

Lesser Short-Nose Fruit Bat (Cynopterus brachyotis)
photo by Jose Iriarte-Diaz & Arnold Song*

Some Important Bat Facts
click on the links to view a photo of the bat/s**
  • Nearly 1,000 [now 1,100] kinds of bats account for almost a quarter [now 20%] of all mammal species, and most are highly beneficial.
  • A single little brown bat can catch 1,200 mosquito-sized insects in just one hour.
  • A colony of 150 big brown bats can protect local farmers from up to 33 million or more rootworms each summer.
  • The 20 million Mexican free-tails from Bracken Cave, Texas, eat approximately 200 tons of insects nightly.
  • Tropical bats are key elements in rain forest ecosystems, which rely on them to pollinate flowers and disperse seeds for countless trees and shrubs.
  • In the wild, important agricultural plants, from bananas, breadfruit, and mangoes to cashews, dates, figs, rely on bats for pollination and seed dispersal.
  • Tequila is produced from agave plants whose seed production drops to 1/3,000th of normal without bat pollinators.
  • Desert ecosystems rely on nectar-feeding bats as primary pollinators of giant cacti, including the famous organ pipe and saguaro of Arizona.
  • Bat droppings in caves support whole ecosystems of unique organisms, including bacteria useful in detoxifying wastes, improving detergents, and producing gasohol and antibiotics.
  • An anticoagulant from vampire bat saliva may soon be used to treat human heart patients.
  • Contrary to popular misconceptions, bats are not blind, do not become entangled in human hair, and seldom transmit disease to other animals or humans.
  • All mammals can contract rabies, however, fewer than one-half of one percent of bats do, and these typically bite only in self-defense. Bats pose little threat if people simply do not handle them.
  • Bat are exceptionally vulnerable to extinction, in part because they are the slowest reproducing mammals on earth for their size. Most produce only one young a year.
  • More than half of American bat species are in severe decline or are already listed as endangered. Losses are occurring at alarming rates worldwide.
  • Loss of bats increases demand for chemical pesticides, can jeopardize whole ecosystems of other animal and plant species, and can harm human economies.
(Taken from a BCI booklet from the 1990's "Important Bat Facts". The text in brackets reflects updated information.)

* This photo was part of research done at Brown University by Kenneth Breuer and Sharon Swartz on the aerodynamics of bat flight.

** Note that you are linking to photos on other people's websites and these photos are/may be copyrighted by the owners.