Monday, April 28, 2014

Adirondack Wildlife: Emerging From Dormancy

vernal pool at Huntington Wildlife ForestThe unseasonably cool and overcast weather pattern that has prevailed over the Adirondacks for the past several months has impacted many forms of wildlife, especially the cold-blooded creatures that are early to awaken from their winter dormancy. Among the organisms that return to an active state as soon as the surroundings thaw are two common and highly vocal amphibians that spend winter embedded in the upper layer of soil, or beneath a pile of rotting, organic debris on the forest floor.

Within a few days of the frost melting from the ground around them, both the wood frog and spring peeper experience biochemical changes throughout their body that reactivate the tissues and organs that became dormant for winter. As soon as their muscles are functioning again, these small vertebrates pull themselves from the covering that engulfed them since last autumn and begin their journey to the vernal pools and shallow woody wetlands that serve as their breeding grounds.

In order to cope with low temperatures, these forest dwelling amphibians significantly alter the chemical make-up of their body to depress the freezing point of the water that remains in their tissues. Additionally, with the aid of the changes that occur in its systems, the wood frog is known to be able to tolerate the formation of ice crystals throughout its body without suffering any adverse affects. While these physiological changes allow both amphibians to remain alive in a thermally hostile environment, their muscles are prevented from functioning during this period of suspended animation. In order for them to emerge from their winter shelter, the temperature of the material around them must rise above freezing. This causes the concentration of glucose, glycerol and other substances that have developed in their system, and which act as natural antifreeze, to gradually return to normal levels. Once a proper biochemical balance is achieved, the creature can then use its legs and work its way to the surface.

It typically takes only a day or two after the soil thaws for these forest dwellers to awaken and emerge from their winter retreat. It has been determined by researchers that terrestrial amphibians that have recently returned to an active state have nearly the same physical abilities as they possess in summer. If such a small forest dweller were to be too sluggish for the first few days after it emerged on the surface of the ground, it would quickly become the target of numerous predators eager to indulge in a meal of meaty amphibian flesh.

Should a cold snap occur after these creatures emerge, their body quickly redevelops the chemical balance necessary to cope with freezing temperatures. This change, however, causes these animals to enter into another period of total inactivity. Just prior to lapsing into a dormant state, the individual buries itself beneath some leaf litter, or other material, on the ground, and waits until the weather warms again. When conditions improve, the creature gradually exits this temporary inactive phase; however, it may take a few days for its body to return to normal.

This year, the distinct clacking noise of the wood frog, along with the chorus of the peepers has been virtually absent, so far, from the various wetlands that I have visited during the evening, nor have I seen any clusters of wood frog eggs along the edges of those vernal pools and wooded wetlands in which these creatures traditionally breed. Although most of the snow has finally disappeared from my section of the Park, I recently noted that there was still ice under several fallen logs that I rolled over, and beneath a pile of rotting bark that I disturbed on the forest floor. Probably, any wood frogs or peepers that passed the winter in a sunny, south-facing hillside emerged from their dormant state, only to be confronted with freezing temperatures that sent them back into a period of inactivity.

Once a peeper, or wood frog, is successful in making the trip to a breeding pond, it usually is not as adversely impacted by a cold spell of weather, as the water serves to moderate the temperature around it and help prevent freezing. The microclimate that exists just above the surface of a body of water can be a half dozen degrees, or more, warmer than that of the air in the surrounding settings. This is why peepers, or wood frogs, may be heard calling on nights when a thermometer several hundred yards away from the water is reading in the mid to upper 20’s.

Over the course of the next week or two, a mass migration of these amphibians will occur, especially during rainy periods when the temperature remains in the 50’s. Their presence can be noted at night as they cross roads in their attempt to reach a shallow body of water that is suitable for breeding. While the chorus of peepers can already be heard in many areas of the State, the spring serenade presented by these tiny creatures is probably now only a few days away here in the Adirondacks.

Photo: A vernal pool at the Huntington Wildlife Forest in Newcomb.

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Tom Kalinowski is an avid outdoor enthusiast who taught field biology and ecology at Saranac Lake High School for 33 years. He has written numerous articles on natural history for Adirondack Life, The Conservationist, and Adirondack Explorer magazines and a weekly nature column for the Lake Placid News. In addition, Tom’s books, An Adirondack Almanac, and his most recent work entitled Adirondack Nature Notes, focuses on various events that occur among the region’s flora and fauna during very specific times of the calendar year. He also spends time photographing wildlife. Tom’s pictures have appeared in various publications across the New York State.

2 Responses

  1. Jim Fox says:

    The singing of spring peepers is one of my favorite pieces of music.

  2. Harold says:

    Another very interesting essay Tom, I look forward to each installment.

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