At Canaan Valley National Wildlife Refuge, we survey vernal pools every spring to monitor wood frog and spotted salamander egg masses and larvae. My major project for my service is to lead these surveys, enter the data, and write a summary about the field season. These surveys contribute to a database maintained by the USGS Patuxent Wildlife Research Center’s Northeast Amphibian Research Monitoring Initiative (ARMI). The Northeast ARMI uses data from several different parks and refuges to monitor amphibian populations in the northeastern United States. It can be a race against time to survey the larvae of both species. If we are too late, the wood frogs, which breed earlier and develop more quickly than spotted salamanders, may have already left the vernal pools. Unfortunately, not all the vernal pools we survey are productive, and some remain dry year-round. Site visits were started two to three weeks early this spring due to the abnormally warm weather.
Egg mass surveys involve two observers walking around a vernal pool to search for and count egg masses. The observers also measure the pool’s dimensions and take conductivity, pH, and temperature readings. Each site is visited two to three times, depending on whether or not we have found egg masses from both species by the second visit. Egg masses surveys are conducted from March to May, depending on the arrival of warmer weather and wood frog emergence. Wood frog activity is easy to detect because you can hear them calling (similar to quacking ducks), and they deposit eggs in large, floating groups of egg masses. Spotted salamanders lack mating calls and deposit their elongated, clear or cloudy egg masses singly or in small clusters, typically more hidden and attached to vegetation. Last spring, I jumped on the chance to volunteer for egg mass surveys because I am fascinated by amphibians. It is intriguing to watch embryos squirm around inside their jelly-like egg masses and see tadpoles swimming around. I also learned about an alga that lives inside spotted salamander embryos, giving the eggs a greenish appearance. This is a symbiotic relationship in which the alga helps provide oxygen and sugars to the embryo via photosynthesis and the embryo provides nitrogen for the alga through its wastes, and neither survives well without the other.
Dipnetting surveys are conducted to monitor larval wood frog and spotted salamander populations. These surveys also involve two observers that swish long-handled nets (dipnets) in the bottom of the pool to search for and count larvae. The observers also take the same measurements and readings taken for egg mass surveys. These surveys are conducted in June, but we are starting them at the end of May this year because of the early start to the breeding season. I volunteered for dipnetting surveys last June and was amazed by the variety of aquatic life dwelling in the depths of these pools. The most memorable finds for me included a giant waterbug, a leech, dragonfly larvae, caddisfly cases, spring peeper tadpoles, and, of course, spotted salamander larvae. Unfortunately, we didn’t see any wood frog tadpoles that day, but we did see some green frog tadpoles. I am excited to see what I find when we dipnet this year!