Monday, April 15, 2013

Adirondack Amphibians: Spring Peepers

Silence still prevails along the shores of marshes clad in alders, willows, dogwoods and wild raisins, but this will change shortly. The warmth forecast for the coming week should be sufficient to finally melt any remaining patches of snow and ice still on the edge of open wetlands. Additionally, the appearance of the sun and a period of mild showers should help eliminate the remnants of frost in the upper parts of the soil.

As the ground loses its winter characteristics, the spring peeper is quick to awaken from its winter dormancy, crawl from its shallow, subterranean shelter along with countless numbers of fellow peepers, and travel to a nearby marshy setting. Once it arrives at the water’s edge, this amphibian loudly announces its presence and willingness to breed.

Even though the spring peeper is the most commonly heard amphibian throughout the Park in spring, this chorus frog is very seldom seen. When full grown, a peeper averages only an inch in length and supports a smooth, grayish-olive skin able to change shades and hues under different conditions. There is a characteristic “X” marking on the peeper’s back that helps this chameleon-like vertebrate blend into a setting overgrown with weeds, grasses and small shrubs. Anyone who has attempted to see a peeper as it bellows out its love song knows well the extreme challenge of spotting such a tiny creature, especially during times of fading light. Even during a warm afternoon when a light shower, or mist, creates the opportunity for this moist-skinned organism to engage in a period of song, it is still nearly impossible to catch sight of a vocally active peeper squarely in front of you. Even predators, like the mink, otter, fox and crows, have a difficult time spotting a peeper against a dark background of dead vegetation. The easiest time to see a peeper is when this creature is crossing a road the day before the spring serenade commences at a traditional breeding spot.

It is believed that an adult peeper spends much of the summer on the ground in wooded areas. Although this animal has enlarged pads at the tips of its toes that enable it to effectively cling to twigs and small branches, the peeper does not spend much time off the forest floor. This is probably the result of the greater abundance of bugs, small worms, grubs, and other invertebrates amongst the leaf litter than several feet off the ground.

With the arrival of cold weather in mid autumn, the peeper works its way into the layer of debris on the forest floor. With enough twisting of its body and scratching of its feet, a peeper is able to burrow several inches, or more below the surface and get under some sizeable object on the ground, like a rotting log, a chunk of fallen bark, or a large rock. Such objects provide additional insulation from extreme winter cold.

Like several other amphibians, the peeper develops a high concentration of glucose in autumn that acts as internal antifreeze. Even though ice crystals regularly form within a peeper, the chemical changes that occur in its body prevent cellular damage and allow this animal to survive in a supercooled state for the entire season.

When the ice thaws around it, the peeper’s body quickly transitions into its more normal state and it reemerges on the forest floor. The reduction in the amount of glucose in its system provides for a more active existence, yet it impacts the ability of this creature to tolerate freezing temperatures. A severe cold snap after a peeper emerges from it dormant period is now dealt with by seeking refuge in water, or by retreating into a crevice on the forest floor that is thermally favorable.

Upon vacating its winter shelter, the peeper instinctively migrates toward the body of water it left late last spring. Some individual peepers have been reported to travel over a quarter mile to return to a breeding pond. Because its skin is sensitive to dry conditions, travel usually occurs at night when the air becomes saturated with moisture. Migration may also take place during the day if the sky is overcast and the relative humidity is high.

Once it arrives at a suitable waterway, the male establishes a small breeding spot and begins to announce its presence with a whistling burst of vocal energy that resembles a “peep”. Since rival males are often close by, each individual attempts to outperform those around it in an effort to win the attention of any female in the vicinity. This competition leads to a chorus of frenzied “peeps” that can be deafening to a person standing on the shore during a mild evening when the rate of activity is high.

The music of the peepers is an integral part of spring in the Adirondacks, but don’t ever count on seeing one of these tiny amphibians, unless you happen to be on a road after dusk just prior to the start of this vocal season.

Photo courtesy Wikimedia user Well Tea.

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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.

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