Rain had washed out our first attempt at exploring vernal pools. On the rescheduled date, an
enthusiastic group gathered at Vining Lake, despite light rain. Before setting out to explore
we briefly talked about the differences between frog calls and vernal pools. Vernal pools are
important temporary pools that usually dry up by mid-summer. They are fish-free zones.
Wood frogs, salamanders and fairy shrimp meet and mate in these pools on the first warm
rainy night when it is 45 degrees or more. The egg masses they leave must develop before
the pool dries out. Because we were later in the season, the egg masses were no longer
present, however, there were tadpoles. There were also aquatic insects to observe. The fun
and fascinating thing about aquatic insects is that they live part of their lives in water (think
gills) and then become adults that live on land (terrestrial insects).
When we approached the first sampling location, as if on cue, first one, then two tree frogs
began chorusing. With the tree frogs in the background we dipped a white bucket into the
pool so we could see who was living in each spot at that moment. The aquatic insects were
gently scooped into the separate sections of an ice cube tray for a closer look. Using
identification cards we could get a sense of whom was living in each wet spot we sampled.
At the first two spots we mostly found two species: active water bugs darting about and
mosquito larva, with one in the last stage before becoming an adult (pupa stage).
On our way to the last two spots (a vernal pool and the lake) we paused to look at earthstar
fungi that have rays that make them look like idealized stars, flowering wild (vs woodland)
strawberries, scat, and lung lichens. At our third sampling spot there was a mayfly nymph and
a damselfly nymph; each have gills but located in different places. Not surprisingly, there was
one mosquito larva. Although we found nothing in our lake sampling, we did stop to examine
the tree bark closest to the water. In shaded locations near ponds and streams aquatic
damselflies and dragonflies climb on trees or vegetation to shed their aquatic exoskeleton to
become terrestrial insects that live near water. Although we did not find any, in spring and
early summer you can sometimes see the exuviae remains.
All in all it was a good experience. Although the amphibian egg masses were long gone, there
was plenty to explore and discuss.
Author – Grace Bartlett