Vernal Pools

By Jennifer Correa-Kruegel, NJSOC Environmental Educator

At first glance, vernal pools do not appear to be a valuable part of our ecosystems. They look like boggy waste places that house mosquito larvae and need to be drained. Here at the School of Conservation however, we are very protective of our vernal pools and use any opportunity we can to educate the students that come here on their field trips, on the importance of these wetlands.

A vernal pool is an indentation in the ground that fills up with water for only a couple of months out of the year and then dries up completely or remains very shallow. This unique feature does not allow fish to inhabit the pools. Many amphibians, reptiles, plants, insect sand other wildlife species will take advantage of these wetlands. In particular, some amphibian species, whose eggs deposited in these waters would normally be eaten by fish, have one less predator to worry about. Several amphibian species in New Jersey, two of which are endangered, have evolved to become dependent on vernal pools for breeding habitats. When that happens, the species is considered to be an obligate vernal pool breeder.

Amphibians are animals that generally go through a developmental change in form or structure occurring subsequent to birth or hatching (metamorphosis). The word amphibian actually comes from the Greek word “amphibious” which means “living a double life.” Members of this class are frogs and salamanders. Since their skin is moist and glandular they are more susceptible to the negative impacts from pollution to their aquatic environments. This makes them an important environmental indicator species that can tell us if there is something wrong with our environment. Many of these amphibians also have the added hazard of having to cross roadways on the first warm rainy night in spring to get to their vernal pool breeding habitats that they have become so dependent on.

Earlier this spring, during a brief period of warm weather, we came across evidence of two obligate vernal pool species, wood frogs and spotted salamanders here at the School of Conservation. The wood frog (Rana sylvatica)is one of our medium sized frogs with a dark ‘mask’ on its face. The males are a bit darker in coloration and make their way to the vernal pools first. The females are a little lighter in coloration, camouflaging nicely with the leaf litter on the forest floor as they make their way to meet up with the male wood frogs. The males attract the females by making a loud “quacking” sound that can only be heard for a few days before the rush of mating and laying eggs dies down.

The spotted salamanders (Ambystoma maculatum) are a bit more evasive. They are one of a group of large salamanders – sometimes referred to as ‘mole salamanders’ – in the Ambystomagenus. They are have a very striking appearance: several inches long with black with yellow spots.

While we did not find any actual spotted salamanders on this particular trip we did find some spermatophores. Spermatophores are packets of sperm that are laid by the males on leaves or sticks in vernal pools.

After a courtship dance between the male and female spotted salamanders, the female picks up the spermatophore with her cloaca. The cloaca is an ‘all purpose’ body part that is used for reproduction and excretion. After insemination, she lays nearly 100 eggs that are protected in a white gelatinous mass underwater before leaving the pool to take refuge under logs or leaves to keep their permeable skin moist.

Through the efforts of various environmental organizations and volunteers, new legislation has been adopted to protect our vernal pools in NJ. Many vernal pools are small and (until recently) the NJ Freshwater Wetlands Protection act did not cover areas that measured less than an acre. Vernal pools can be protected and certified if they meet the following criteria according to the NJ Department of Environmental Protection:


  • occurs in a confined basin depression without a permanently flowing outlet.
  • provides documented habitat for obligate or facultative vernal habitat species.
  • maintains ponded water for at least two continuous months between March andSeptember of a normal rainfall year.
  • free of fish populations throughout the year, or dries up at some time during a normal rainfall year.


The Department of Environmental Protection depends on volunteers to assist in locating and documenting these vernal pools. The certifications that result from identifying them with the above criteria, has Land Use Regulation Program staff cross-referencing permit applications with maps of vernal pools. If a vernal pool is on a property where a project is being proposed then the permit may be redirected or denied altogether.

While all wildlife holds value in our ecosystems, amphibians in particular are a sensitive species. Since many amphibians breathe through a combination of gills, lungs and skin they are very susceptible to changes in the environment, particularly our aquatic environment. This makes them an excellent indicator species: a species that tell us if something is wrong with the environment. Taking measures to protect their habitat is something everyone can benefit from in the long run.