Every year, on the first warm rainy night of spring (usually around 55 degrees), wood frogs, spring peepers and mole salamanders (which include several mid-sized, stout-bodied salamander species) begin a mass migration to the vernal pools where they breed. This event is commonly referred to as the "big night." It is impossible to set a calendar appointment for this event, but keep an eye on the temperature in your area and when the mercury rises from the 40s to the 50s, especially if there is a warm week prior to the first rainy warm(ish) night, be on the lookout. If possible don't drive on nights you think may be a potential "big night" to avoid hitting migrating amphibians.
How can you identify a vernal pool? They are typically small (some may be larger) ponds that fill with water for a short time during spring. Most dry up by the end of summer. In some areas, vernal pools may fill after fall rains. These small, temporary ponds may not sound very impressive, but they are critical breeding habitat for amphibians. What makes them so important to amphibian survival is the absence of predators, such as fish, during the egg and larval stages of frogs and salamanders. If you happen upon a vernal pool, look for egg masses and tadpoles as well as fairy shrimp (a tiny crustacean) and other animals that you will only find in a vernal pool in spring. If you're interested in learning more about vernal pools, you can contact local nature organizations, such as Audubon centers to find and explore vernal pools in your community. If you'd like to participate in citizen science programs for mapping and certifying vernal pools, simply do a Google search for vernal pool mapping near you or contact your state university extension office for guidance.
What are threats to vernal pools? Mainly development and adverse effects of habitat alteration. Even though there are rules and buffers in place to protect wetlands and vernal pools, impacts are inevitable. If a pool is protected but not the surrounding woods where amphibians spend the other 11 months of the year, the population will decline. Other factors contributing to vernal pool decline are pollution, water table changes and a warming climate that will dry up pool prematurely.
Vernal pools are a unique habitat and if you have an opportunity to explore one, definitely do it! Always be mindful that there may be amphibians on the move and the area surrounding the pools is also sensitive, so tread lightly!