Vernal
Pools
Spring is the season to investigate vernal pools. These
small bodies of water are very important to amphibians that
lay their eggs in water, spend part of their lives with
gills, and finally develop into frogs, toads, and
salamanders. Most vernal pools dry up later in the summer,
although in a wet year they may retain some water until
snows and spring rains again fill them. Most important for
the amphibians that use them, however, they lack a
connection to a stream or river, so that fish cannot reach
them to eat the eggs and tadpoles.
Vernal
pools are protected in Massachusetts, but the amphibians
that use them also need undisturbed woodland or meadows so
they can survive on land as adults. If you find a vernal
pool, look in it in March, after a night when there has
been a warm rain, and you will probably see some egg
masses. These look like black dots surrounded by clear or
whitish jelly, and are stuck together in a floating mass
that may be attached to a branch or other growth in the
water.
Later,
when the eggs have hatched, you will see tadpoles. If the
pond has bullfrogs, their tadpoles may eat those of smaller
amphibians such as wood frogs. Some tadpoles change into
land-dwelling frogs or salamanders quickly, while bullfrogs
may take two years to change.
Vernal
pools serve as home to numerous other life forms, such as
fairy shrimp, dragon fly and damsel fly larvae, and various
diving beetles. Some in woodland may have leafy bottoms,
such as the large one on the
LPS Winthrop Dahl
Preserve.
Others that get more sunlight and different nutrients
may have sphagnum moss and grasses growing in them, such
as the one on the orange trail in the
LPS Woodward Forest.
There is also a vernal pool in the Henrich Woods where a
research site has been established for work on a Master's
Degree project on salamanders.
Photos from the
project.
The
Land Preservation Society has numerous vernal pools on its
properties and there are many others in Norton. These are
gradually being registered with the State to protect them
and the fragile species that need them for part of their
life cycle.
Frances Shirley 2005