The fate of our bats

As many bloggers and the very sexy and articulate Anderson Cooper have already mentioned, our planet is in peril. Ice caps are melting, forests are disappearing, coral reefs are dissolving, and polar bear cubs are drowning off Canada's northern shores.  It is a sad time to live on earth, with a diverse range of cute and cuddly species in danger of disappearing. So why, with so many other wonderful animals to have an interest in, do I care so adamantly about bats? 

Bats are an essentail component of our ecosystems. They can reportedly eat their weight in insects each night, and provide millions in ecosystem services each year. (http://www.nsf.gov/discoveries/disc_summ.jsp?cntn_id=112602  - recent NSF discoveries blog about the impact of free-tailed bats in reduction of crop pests in Texas) The loss of bats could cause drastic increases in number of insects, making crop growth more difficult for struggling farmers. Small local farms that have been able to increase profits in recent years due to the movement toward locally grown organic food, will suffer from decreased crop yields and an inability to market produce as organic due to neccessity of increase pesticide applications. Mosquitoes, the carrier of West Nile Virus, could increase with subsequent increases in insect borne diseases in humans. Effectively, bats are pretty important to human existence. 

North American bats are in trouble. Widespread deaths of hundreds of thousands of bats have been occuring all across the northeastern United States, and spread of the disease seems inevitable. White nose syndrome, is the term used to describe the series of widespread die outs spreading from a disease epicenter southwest of Albany, NY. The disease is called "white nose" due to the appearance of a white fungus around the muzzle of affected hibernating bats. The fungus can also be found on the wings, tail, ears, and even genitals. It does not seem that the fungus is directly responsible for the deaths, and some scientists have suggested that the infection may be opportunistic, or even totally unrelated. Theories are still being tested. 

Whatever the cause of the syndrome, we are losing such a high number of bats that recovery of bat populations in the near future is very unlikely.  Bats, unlike other small mammals, are K selected. Most bats have long life spans (the longest lived little brown bat was in its 40's with many living well into late 20s and 30s) and have only one pup per year. Bats are true hibernators, and in the northeast, can sleep 5 months out of the year. In colder months they migrate to mines and caves (called hibernacula) and sleep through the winter. They lower their body temperature and slow their metabolism, living off stored fat for the entire winter. Bats occasionally wake up, get a drink, urinate, and then go back to sleep. These periodic arousals can use up the same amount of fat a bat would need for 45 days in hibernation (or torpor). One of the prevailing theories regarding the cause of the bat deaths is that the fungus is causing bats to arouse more frequently, or never achieve deep torpor, which is causing bats to burn through their fat stores too quickly. Since white nose syndrome (WNS) was discovered bats have been observed streaming out of caves throughout the winter, perhaps attempting to migrate to summer feeding grounds. Many of the bats found have had very small amounts of fat, indicating that these bats have already worked through their fat stores in early winter. In addition, bats cluster tightly together, meaning that even unaffected bats could be woken up due to the activity of their neighbors, which could in general mean greater number of arousals for the entire bat population of the hibernaculum (a cascade effect). 

The fungus has been identified as a member of the Geomyces genus (published in November Science). It is a cold growing fungus that is, in at least one fungus species, associated with Arctic permafrost. On bats it seems able to degrade the tissue of the wing membrane. It seems that the bat must be in torpor  for the fungus to grow, and as the fungus often disappears (visually, although most likely not microscopically) on active bats that have raised their body temperature. If contagious, as we believe it to be, it will be very difficult to stop its spread. Every year since its discovery two years ago the fungus has been found further away from the epicenter. Given the migratory nature of bats, it could move across the northern United State in a very short span of time. The existence of our bats is in trouble.