American clam shrimp (Limnadia lenticularis)
Listed as “of special concern” by the Natural Heritage and Endangered Species Program, these rare vernal pool crustaceans (above) have been found in only three other locations in Massachusetts besides the Middlesex Fells. Named for their clam-like exterior, they average less than half an inch, and typically live on the bottom of vernal pools, where they feed on algae, bacteria, and detritus.
American toad (Bufo americanus)
Most people have seen these brown, warty amphibians (below) hopping around their yard or garden, where they feed on insects and other invertebrates. They breed in the spring in vernal pools and other wetlands.
Fairy shrimp (Eubranchipus vernalis)
Small, delicate crustaceans (above), which grow to an inch and a half as adults, can only be found in vernal pools, where they swim by means of waving their abdominal appendages. For food, they filter bacteria, phytoplankton, and protozoans.
Fingernail clam (Sphaerium species)
Less than half an inch long, they have a muscular foot they use to move around and dig into the substrate like their saltwater relatives, and siphons for respiration and feeding.
Spotted salamander (Ambystoma maculatum)
Common though seldom seen (below) because they tend to remain underground except to occasionally feed at night or migrate to vernal pools to breed in the spring. Feed on invertebrates such as worms and insects, and grow up to 8 inches long.
Spring peeper (Pseudacris crucifer)
Inch-long treefrogs are known for the high-pitched peeping call of males. They can be identified by an “X” on their brown backs.
Wood frog (Lithobates sylvaticus)
Easily recognized by the dark mask across their eyes. Seldom hang out around water, except when they visit vernal pools to breed in the spring. The males make a loud “quacking” noise when calling for mates.
SOURCES: “A Field Guide to the Animals of Vernal Pools,” by Leo P. Kenney and Matthew R. Burne; “Reptiles and Amphibians of Eastern/Central North America,” by Roger Conant and Joseph T. Collins; Natural Heritage and Endangered Species Program species fact sheets.