Vernal Pool Monitoring

The SVT Vernal Pool monitoring program is a citizen research effort to study vernal pools in the watershed. Since 2005, twenty volunteers have been “getting to know” vernal pools in their community, counting salamander and wood frog egg masses, assessing vegetation, and determining how the pool water level changes over the course of the year. 
Vernal pools are critical breeding areas for a variety of organisms. Mole salamanders (including spotted salamanders and blue-spotted salamanders) and wood frogs live in upland forests for most of the year, but in the spring they move to nearby water to reproduce.  Many researchers and others eagerly anticipate this spring migration, which sometimes manifests as a spectacular “Big Night,” with hundreds of animals moving on the first warmer, rainy night of the year. Shortly thereafter egg masses can be found in the vernal pools. 
Vernal pools can be quite variable. The pools we’ve explored are large and small, deep and shallow, secluded and abutting nearby homes. All have spotted salamander and wood frogs, and some have the state-listed blue-spotted salamanders. Although many vernal pools completely dry out in summer, only one of the five that we have monitored really gets dry. Below is a brief description of the pools.
  • Cowassock Woods, Framingham.  This pool is part of a larger wetland area, and it is the one monitored pool that typically dries up. Monitors have found wood frog and spotted salamander eggs here. Fingernail clams and caddisfly larvae are also found.
  • Gowings Swamp, Concord. Monitors have surveyed this large swamp area and found wood frog and spotted salamander eggs. Fish fry have also been seen, which means that this pool doesn’t technically qualify as a vernal pool. We’ve also found evidence of the many mammal species using the area, including fisher, fox and coyote. Unfortunately, invasive knotweed is also abundant here.
  • Memorial Forest, Sudbury. Wood frog, spotted salamander, and blue-spotted salamander eggs are found in Memorial Forest. The pool is located in a forested area that keeps it mostly shaded, and it is usually the latest to get amphibian eggs. The pool is deep and cold, and has never dried out. 
  • Mineway Brook, Sudbury. This pool has woods on one side and houses on the other. A variety of invasive species, including buckthorn, multiflora rose and bittersweet are found here, along with native species. Despite the various threats the area faces, good numbers of all three amphibian species have been found here.
  • Ralph Hill, Billerica. We have only monitored this pool for three of the five years, and we have found wood frog and spotted salamander eggs.
The charts below show some of the results of our monitoring efforts.  Each year volunteers count eggs in the pools. Most amphibians lay eggs in clusters called masses.  Some species, notably wood frogs, also lay their egg clusters in the same area, resulting in huge masses of eggs. In fact, the numbers for wood frogs in our graphs are misleading in some cases, because in two pools (Memorial Forest and Mineway Brook) it was often difficult to determine how many masses the large clump contained. Notice that in all of the graphs there were relatively few egg masses found the first year; this is certainly a matter of volunteers learning about the eggs and developing good search images. Secondly, it’s notable that there is high year-to-year variation. Variation is expected due to sampling (exact date of sampling, weather when counts are done, etc.), and due to differences in the numbers of salamanders and frogs reproducing (fewer after hard winters with high die off, more synchronicity in some years, etc). Variation among pools is also obvious. For example, many more egg masses are usually found in Memorial Forest than in the other pools, and Ralph Hill and Cowassock have relatively fewer masses. Finally, it’s evident that different species use different pools; Memorial Forest and Mineway Brook are the only pools where blue-spotted salamander eggs have been found. 
For more information about vernal pools, here are some great on-line resources:
The Vernal Pool Association is a good place to start.
For information about the state-listed blue-spotted salamander, see Massachusetts' Natural Heritage and Endangered Species Program's page. 
If you’d like to join the SVT monitoring team, please contact Laura Mattei, Stewardship Director for SVT, or Marta Hersek, who’s a volunteer monitor.
Cowassock Woods, Framingham. This pool is part of a larger wetland area, and it is the one monitored pool that typically dries up. Monitors have found wood frog and spotted salamander eggs here. Fingernail clams and caddisfly larvae are also found.Gowings Swamp, Concord. Monitors have surveyed this large swamp area and found wood frog and spotted salamander eggs. Fish fry have also been seen, which means that this pool doesn’t technically qualify as a vernal pool.Memorial Forest, Sudbury. Wood frog, spotted salamander, and blue-spotted salamander eggs are found in Memorial Forest. The pool is located in a forested area that keeps it mostly shaded, and it is usually the latest to get amphibian eggs.Mineway Brook, Sudbury. This pool has woods on one side and houses on the other. A variety of invasive species, including buckthorn, multiflora rose and bittersweet are found here, along with native species.Ralph Hill, Billerica. We have only monitored this pool for three of the five years, and we have found wood frog and spotted salamander eggs.