Big Night!
A magical migration awaits all who take note of the first rainy spring day (in the 40’s) when the rain continues into the night. Last night these conditions resulted in what herpetologists refer to as “Big Night.” While snow still covers parts of the forest, there is ample bare ground that has warmed up enough to waken hibernating frogs and salamanders at this time of year. As if silently communicating with each other, thousands and thousands of these amphibians emerge from their subterranean hibernacula on the very same night and migrate en masse to their ancestral breeding pools, known as vernal pools. They avoid the lethal sun by travelling at night, in the rain. Unfortunately, many die, as they often must cross hazardous roads in order to reach the pool where they breed every year. If you are driving in these conditions, please keep an eye out for these jaywalkers and try to avoid them. Roads can quickly become slick with their squashed bodies.
How many Spring Peepers, Wood Frogs and Spotted Salamanders can you find in this photograph taken on Big Night? (There are six.) Thanks to the unbelievable generosity of Naturally Curious readers, this photograph was taken with my new camera and lens. I cannot tell you how deeply touched I am by your kindness and generosity.
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Amphibians Migrating
Vermonters were witness to a record-breaking (early) amphibian migration in the Champlain Valley last week on March 1st, when night temperatures were in the low 50’s. Not only did it occur a week earlier than any other previous major migration, but records show that migration for the earliest amphibians in Vermont is now approximately two to three weeks earlier than it has been during the last decade. (as reported by Jim Andrews, www.VtHerpAtlas.org).
Spotted Salamanders, Four-toed Salamanders, Eastern Red-backed Salamanders, Blue-spotted Salamanders, Jefferson Salamanders, Spring Peepers, Wood Frogs and even an American Toad were on the move. According to Andrews, “this is a concern if the weather turns really cold and the ground and ponds refreeze. If that happens, many of the early migrants (that are not freeze tolerant) could freeze and die. If the weather stays relatively mild, with only short cold snaps, they should be fine.” Weather since these sightings has been unseasonably cold, and one can only hope they survived. (Photo: Spotted Salamander, Ambystoma maculatum)
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Fall Amphibian Migration
The migration of amphibians from the woodlands where they overwinter to their breeding pools in March is a familiar spring phenomenon to most. However, some of these amphibians engage in a fall migration as well. Amphibians (and reptiles) need to find a good overwintering spot, where they won’t freeze. In some cases, that might be a few feet upstream or into a seepage area, and in others it is a few hundred yards uphill. The extent of the migration and the species participating vary in different parts of the state.
In western Vermont, Jim Andrews, Director of the Vermont Reptile and Amphibian Atlas(http://vtherpatlas.org), has observed Blue-spotted and Four-toed Salamanders moving down into wetlands in the spring, staying close to the wetland for moisture and feeding during the summer, and then moving uphill back to wintering areas in the fall. On the other hand, he has found that most Spotted and Jefferson Salamanders, as well as Wood Frogs, move down in the spring to breed, and then head back uphill in stages soon after they are done breeding.
Eastern Red-backed Salamanders (pictured) migrate as needed during the summer to maintain their body moisture, and in the fall, search for an animal burrow or crevice to hibernate in. Migration often occurs at night, while it’s raining, so as to prevent their skin from drying out. (Amphibians need to have moist skin because a large portion of the frog’s “breathing” occurs via oxygen diffusing through the skin. Oxygen will not diffuse through a dry membrane.) After the very dry summer we’ve had, a large number of amphibians were observed taking advantage of the recent rain and migrating.
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