Dave McDevitt, in a pensive moment, at the Aeolus Bat Cave at the Conservancy's Dorset Bat Cave Natural Area.
By Dave McDevitt, Southern Vermont Land Steward
March 11, 2010 -- We arrived at the cave entrance after snowshoeing 1 1/2 hours through 2-3 feet of snow. It was a fairly warm day with temps in the mid 40’s and a light rain falling. Unlike the previous two winter surveys, we did not see any of the characteristic signs of WNS outside the entrance to the Aeolous, or Dorset, Cave. During the 2008 and 2009 surveys, researchers arrived to see hundreds of dead and dying bats outside the cave entrance, and the remnants of hundreds more that were consumed by scavengers on a daily basis. On this day, we observed only six bats clinging to the rocks outside the cave (all live) and just two bats were seen flying out.
Once I stepped inside the cave, I really began to see how things have changed in the three years since WNS began to lay waste to the bats of Dorset Bat Cave. Just a couple of years ago, there were thousands of live bats on the cave ceiling, now there were just a few scattered here and there.
During the surveys of 2008 and 2009, the cave floor was literally covered with tens of thousands of decomposing bat carcasses. Many live bats on the ceiling were huddled tightly with dead bats. Many more were entombed in clear ice formations along the walls and floor of the cave. Then there was the constant flow of bats leaving the cave in a last desperate attempt to survive, only to fly out into frigid temps with no insects available, and their inevitable death. If they didn’t get picked off by the hawks that were anxiously waiting for them, they would no doubt succumb to the cold March weather.
I remember standing at the mouth of the cave and happened to see a bat drop headfirst into the snow near my feet from the rocks above. Upside down in the snow and far too weak to fight any longer, I watched the little toes twitch a few times before gently relaxing and giving-in to the effects of WNS. These images will forever be burned into my memory and words cannot describe the helpless feeling that overcame me.
This year, things are very different. The cave ceiling is mostly bare with only a handful of bats here and there. The rocky floor of the cave is now covered in what seems like a thin layer of soil, with tens of thousands of toothpicks scattered about. The only problem is, this isn’t soil and these are not toothpicks. The vast majority of bats that once called this cave home are nothing more than decomposing matter on the cave floor. The horrible smell is no longer present. There are no more bats flailing about too weak to fly. Simply put, there are almost no bats remaining. We counted all the bats we could find in just a few minutes, while the remainder of our time was spent taking photographs and searching the cave floor for the little colored bands that had once been placed on these bats in previous research, years before WNS arrived.
Today, we counted a grand total of 112 bats, in a room that should have held thousands. Because of this extreme decline in bats observed, along with the lack of public reports of bats seen flying in the Manchester/Dorset area, it is now very likely that we have lost more than 90% of an estimated population of several hundred thousand hibernating bats. This is the largest known hibernacula in all of New England and the ecological implications are simply not known. Also unknown, is how this is going to affect agriculture, forestry, tourism, and our quality of life.
All of this leads me to think just how much more important our work has become. If we ever hope that bat populations could possibly recover from this, we are going to have to redouble our efforts to ensure that the summer and winter habitat requirements are conserved. This will no doubt take decades because of the low reproductive rate (one pup per year), but I am optimistic that it can be done, and that a few bats that are somehow resilient to WNS will continue to flutter around chasing insects during our summer evenings.