While singing birds and budding trees are what many people think of when they list the signs of spring, it may be the amphibians that give us the best glimpse of the life that is about to burst upon the landscape. As snow melts with warming temperatures and spring rains soak into the ground, amphibians emerge after a long winter holed up beneath the ground. For many species it is time to breed, and early-breeding amphibian species feature some explosive breeding congregations.
These can be found in ponds, puddles, and the protected margins and edges of bogs, lakes, and marshes. Many of these species also utilize vernal pools – ephemeral pools of water that fill with snowmelt and spring rains. Since they aren't permanent, such pools offer protection to eggs and larvae since fish, which could eat the eggs and young, can't survive in the pools after the water dries up as the summer progresses. However, this fact places an enormous amount of importance on breeding as soon as the weather begins to warm – that way the eggs and tadpoles have enough time to develop before the pools dry up.
Therefore, many species of amphibians emerge very early in the season, and it is not uncommon to find a congregation of wood frogs or other early species breeding in one end of a pool or pond while the other end is still trapped under a layer of winter ice! Since spring temperatures can be so variable – just look at last week's cold, snowy weather – these individuals do take a certain risk in exposing themselves to the elements which can change so unpredictably. As a result many of them are somewhat freeze tolerant for short periods of time, and some species can even circulate metabolic chemicals through their bodies as a sort-of antifreeze.
Spring peepers are soon to follow the wood frogs. The diminutive peepers are well-known for their shrill, high-pitched toots which can be absolutely deafening if listened to up-close. Peepers can be hard to find due to their small size, but if you ever do see one, look for the small "X" or cross on their back, from which they get their Latin species name, crucifer.
Northern leopard frogs too join the festivities as we heard them while birding in the Champlain Valley on an unseasonably warm late in March day. Spotted salamanders also join the throng, coming out from underground and under logs and rocks at night to follow the flow of water under the leaf litter to their breeding pools. They are large (often longer than a man's hand), dark salamanders with big yellow spots, thick limbs, and a slow pace.
It is easiest to observe the movements of these animals and listen to their choruses at night near their pools, when hundreds and hundreds of individuals can congregate. During the migration to water bodies, roads can become a major impediment to the slow moving amphibians which are hit by cars as a result. In some places, volunteers assemble not only to witness the migration, but to help move animals across the roads to avoid having them get hit. Amphibians are not designed for the high speed of traffic. In fact, not quite two weeks ago when we were out looking for saw-whet owls (see my blog for 4/24/12), my friend Sean and I found many fat American toads (the large ones tend to be females) crossing Blue Mountain Road north of Paul Smith's. We safely moved them from the road.
These American toads arrive in the pools and ponds a little later than the other species, but they started emerging a couple weeks ago, laying their long black strings of eggs in the water. After last week's cold weather and snow put a chill on the progression of the breeding season, this week promises to offer a renewed frenzy in the pools and nighttime choruses. And the trills of American toads will soon be the most prominent voice in the choir. It should be a fun week to stop by some local wetlands and take a look and listen at night.
