Saturday, March 20, 2010

Bats on the Wane

Thursday, March 18, I went to see a talk called Bats on the Wane by NYS Department of Environmental Conservation biologist Carl Herzog at SUNY New Paltz.  It was sponsored by the Shawangunk Ridge Biodiversity Partnership.  It was one of the most depressing things I've seen in a long time.

Bottom line - the species of bats that overwinter in caves and mines in the Northeast are on the verge of extinction from the fungus Geomyces destructans which causes White Nose Syndrome (WNS) disturbing the bat's hibernation and causing them to essentially starve to death.  In some bat hibernacula, the mortality rate is virtually 100%!

Geomyces destructans image from Tom Volk's Fungus of the Month

WNS was first seen in Howes Cave up in Schoharie County in the winter of 2005/2006.  Within a year it was seen in other caves in the Albany/Schoharie area and within two years throughout the Hudson Valley and into Vermont and the Adirondacks.  Then it started spreading down the Appalachians and is currently moving west toward caves in KY, MO, and IN.  There's really no stopping it.

Some statistics I jotted down during the talk.  WNS affects bats which hibernate in mines and caves over the winter - there are about 500,000 of them in NYS based on previous bat surveys by the DEC.  A surpising 75% of the bats were found in only 5 hibernacula in the State - this is really the problem since a disease will then spread rapidly.  At those sites, 85% were little brown bats (Myotis lucifugus) and 11% Indiana bats (Myotis sodalis).  The Indiana bats are an endangered species which is why the DEC had been studying them prior to WNS.

Two important bat hibernacula are near Williams Lake - an old hotel in the Town of Rosendale where I live.  These are abandoned limestone cement mines that the bats have taken over in the past 100 years.  Surveys in these mines have shown that bat populations dropped from 10,336 bats to 268 bats (97% mortality) in one and from 97,084 bats to 10,000 bats in another (90% mortality).  This is over two years!

So what is WNS?  It's basically a white fungus that grows on the bat (on areas of exposed skin like the face leading to the name "white nose").  This fungus somehow disturbs the bat's torpor during hibernation causing it to awaken multiple times over the winter and burning off it's fat reserves such that it starves to death before it can come out in spring and find insects.  That's why one of the signs of WNS in the area are bats seen flying around in February and March - they're starving to death and looking for food (last winter I found a dead bat in my yard - probably from the Williams Lake mines).

Bats with WNS (Al Hicks - NYSDEC)

Of the six species of bat which overwinter in NYS, the numbers are grim.  Here are the mortality rates:

  Little brown bat (Myotis lucifugus) - 90%+
  Northern long-eared bat (Myotis septentrionalis) - 90%+
  Tricolored or Eastern pipistrelle bat (Perimyotis subflavus) - 90%+
  Small-footed bat (Myotis leibii) - 78%
  Indiana bat (Myotis sodalis) - 57%
  Big brown bat (Eptesicus fuscus) - Relatively unaffected

Two notes - it's ironic, but for some reason the federally endangered Indiana bat is least affected (but a 50%+ mortality for an engangered species is not good news) and the big brown is relatively unaffected apparently because it doesn't hibernate in large cave colonies like the others do.  There are a few species of forest bats that live in NY over the summer but don't overwinter and they're fine.

So, what's going to happen.  We can't treat this fungus, caves apparently stay infected even after all bats die (the fungus becomes established), and 5 of the 6 species above are very likely to become extinct in NYS.  Bats can eat over 50% of their weight each night in insects (mostly moths and beetles, not mosquitos as many people think).  I used to see lots of bats on summer nights swooping around the lights.  Now I don't.  The entire night ecosystem will change.

Dead bats in a NY cave (US Fish & Wildlife)

Like I said, a depressing talk.

1 comment:

  1. Thank you for posting about this...very helpful and very sad..Iunderstand the mosquito problem now. So, obviously just putting up bat houses doesn't help. Are they trying to develop a take back immunization for this or a way to fog the caves with antifungal? What is their plan?