Springtime Brings Vernal Pools and Salamanders
March is a good time to look for salamanders during moist spring weather as they move out of dormancy to breed in vernal pools. What appears as a mud puddle to an untrained eye is actually a small natural phenomenon - and an important ecosystem in the delicate balance of life for frogs, turtles and salamanders.
Vernal Pool Activity
Vernal pools are shallow depressions that contain water only part of the year, usually in the spring. In fact, the word "vernal" comes from the Latin "vernus" — which means "belonging to spring" — an appropriate name because the shallow pools usually dry up and disappear before summer. Yet in their finite existence, vernal pools play a dramatic role in the life cycle of salamanders.
Mole salamanders live 99% of their life underground, but for a very brief time each spring, the amphibians emerge to journey up to a half-mile away to the very same vernal pool where they originally hatched from eggs. There, on a warm wet night, they will mate and lay eggs before returning underground for the rest of the year. Some salamanders will wait several years for ideal conditions.
Vernal Pool Characteristics
One reason salamanders depend on vernal pools is safety. Vernal pools are unique in that they are fishless. Because of their ephemeral nature, these small water bodies do not exist long enough to support fish. Being free of fish makes a vernal pool a safe haven for a variety of vulnerable young amphibians. However, fish aren't the only predators. Wading birds also pose a threat. In drought-stricken Georgia, for example, insufficient rainfall filled vernal pools so briefly that many dried up too soon. This left salamander larvae in the mud, where they became easy food for birds.
Trees play a key role in the vernal pool habitat. During summer when trees have green leaves, they soak up groundwater for transpiration. In winter, trees with no leaves are dormant. Since dormant trees don't need the excess groundwater, the water stays at the surface and accumulates in pools. Fallen leaves, or leaf litter, provide salamanders with insects for food and additional hiding spots from predators.
Another unique characteristic of vernal pools is that they are not connected to or fed by any other body of water. They are filled by rain water and groundwater from high water tables.
The Life Cycle of Salamanders
Among the most common salamanders in Virginia are the spotted and the marbled. The spotted salamander produces a thick egg mass in the water. It contains up to 200 eggs. The female marbled salamander digs a small hole and lays about 120 eggs in vegetation adapted for inundation. The female then stays to guard the eggs until water appears and the pool fills. Once water covers the eggs, they usually hatch within about 48 hours. Most larvae then spend about 60 to 100 days in the water before reaching maturation. They feed on zooplankton and small insect larvae in the water. Metamorphosis can be faster or slower, depending upon conditions such as water and weather.
Once the larvae begin to mature, they lose their gills and metamorphose into a juvenile stage, at which point they leave the water for terrestrial habitat. Marbled salamanders will develop their adult pattern in another one to three months, and they become sexually mature in one to three years. Adult salamanders measure 4.4 to 7.8 inches long. They feed on earthworms, spiders, insects and even other salamanders. An adult spotted salamander can live up to 20 years!
Conserving Vernal Pools
If weather conditions and predators don't pose enough of a challenge for salamanders, people do. Wooded land throughout the state is rapidly being cleared and developed, and vernal pools are being filled in. A study in California determined that 90% of the state's vernal pools no longer exist. In some states, the Natural Resources Protection Act legally protects vernal pools. Currently there is no protection for vernal pools in Virginia.
What you can do to help protect vernal pond habitat:
- Be aware. As a developer or landowner, you can resist the urge to fill in a "pocket wetland" or vernal pool, and let the area remain natural. Since pools dry up before summer, mosquitoes shouldn't be a concern.
- Allow space. A 100-foot natural buffer around a vernal pool is important to water quality. A 1,000-foot radius is ideal for the habitat and food supply of amphibians.
- Leave trees in place. Trees and leaf litter are an important part of the vernal pool ecosystem. Leaf litter is important for food and protection. Brush, logs and dead trees are important as well, since some salamanders live beneath dead trees and logs.
- Do not disturb. Never dump debris in the pool or in a dry depression. Do not dig in the bottom of a pool, even if it is dry, or you will impact the area's ability to hold water. Dormant salamanders living under the ground will also be affected.