Wednesday, September 3, 2014
As I may already have mentioned, I've seen fewer bats this year than in the past. It's hard to keep track of how many are in view, because they move around so erratically and so fast, but my impression has been typically 3 or 4 in the clearing, maybe half of what I saw last year. As you must know, there is an epidemic of a fungal disease that has been decimating bat populations in the region so I have been worried about it.
Last night, however, I saw lots of bats. I got 7 in a single visual field, at one point, and there must have been more because these were all below the tree tops and a couple of seconds later I saw two more at a much higher level. So maybe our local population is healthy, so far. The good news, by the way, is that the disease is endemic in Europe but the European populations are resistant to it, and doing fine. We can hope that there are resistant individuals here who will be the basis of a rebounding population.
But I got to thinking. They use a tremendous amount of energy -- they don't coast or soar, their flight depends on constant, vigorous flapping. And they are constantly turning, climbing and diving, all this to harvest tiny packages of food. It's hard to believe they manage to achieve a positive caloric budget, but obviously they do.
Which brings me to the second puzzle. Why are all those insects flying around 25 to 70 feet in the air? What can they possibly be achieving other than making themselves available as bat food? Mosquitoes and biting flies want to be down here on the ground where the meals are. Same thing with insects that feed on plants - I mean, there's just nothing up there. There are, in fact, plenty of insects near the ground but the bats don't come down to get them. What gives?