January 29, 2018

Stories to Tell - Late Night Swim

By Eric D'Aleo

Have you ever taken a late night swim? Maybe the sweltering summer heat was so bad one night that it was the only way you could cool off and get a good night’s sleep. Maybe you forgot to bring a bathing suit and went swimming in your skivvies or au naturel, grateful for the cloak of darkness. But what would you think about swimming in a New Hampshire pond on a late April night? Not enticing? Apparently it is to a black bear, because that is exactly what happened in a vernal pool on Science Center property.

The air temperature that night was 57 degrees Fahrenheit, not exactly warm, but the water must have been colder. Twelve days before the image was taken, the surface of the vernal pool was frozen, so it was probably a cold, but invigorating swim. The images show the black bear leisurely swimming around as if a cold late night bath was a routine event. I was surprised to see when I looked at the images how much the vernal pool’s depth had changed from September to April. Most vernal pools are quite shallow, ranging from several inches to a foot deep. Yet this pool was quite deep. In September the ground was completely dry. Over the winter it filled with snow and then with spring rains so that by April the pool was about four feet deep. The bear left after a few minutes, perhaps in search of food or other reasons only it knew.

Besides being a spa for bruins, vernal pools serve as important habitat for a variety of wildlife. White- tailed deer, raccoon, bobcat, red fox, grey fox, and a barred owl have been spotted by the trail camera. A number of smaller animals the camera has not seen use this vernal pool as well. Amphibians such as spotted salamanders and wood frogs breed and raise their young in these temporary water bodies each year. Invertebrates, like fairy shrimp, caddisflies, and mosquitoes also use vernal pools to live part of or their entire existence here. Each of these animals is in a race against time before the pool dries up. Amphibians need to grow and undergo metamorphosis to finish their development to survive the transition to land before the pool dries up. They will return to the same location as adults to breed each spring. The fairy shrimp operate on an even faster schedule. They complete their development in forty days, breed, lay their eggs, and die before the pool dries up. Their eggs will survive without water until the following spring, when the pool fills up, and the bruin and the shrimp share the water once more.

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