Every year, right about this time, I start getting excited about the prospects of exploring vernal pools. I hope you do too.
What’s a vernal pool? These are the fairly shallow, temporary pools of water you find during the spring season, usually in forested areas. The pool returns each year, varying in size, depending on the quantity of snowmelt and rainfall. During droughts, they may not return at all — and that’s a problem.
What makes vernal pools special is that they are the breeding ground for certain species, including some that have no alternative options. These include certain types of wood frogs, salamanders, and, my favorite, fairy shrimp, to name just a few.
Why don’t these species chose to breed in permanent sites such as ponds and streams? There are some positive trade-offs to what seems like a precarious location. For example, vernal pools are safer than other bodies of water because there are no fish to eat the eggs or larvae. Also, there may be specific plants growing close by to where the pools form, providing food and cover from predators.
What shall I look for in the ponds? First, look for the sunny patch on the pond. Then see if you can spot some tiny (about 1 inch long) lobster-like creature. In some cases, they may be seen swimming on their backs, with their legs up toward the sun. You’ll want to find these guys early in the season because they cannot survive water temperatures above 70℉. Interestingly, however, their eggs can and will survive the heat. On the other hand, the eggs will survive the drying out of the pond and will hatch the next time conditions seem right.
In mid to late spring, you will find egg masses in the pond. By late spring and early summer, you may find larval salamanders and tadpole frogs. You may also discover turtles (including some rare species), snakes, interesting plants, and possibly even some birds that are specifically attracted to the area.
Can I find a vernal pond where I live? Vernal pools occur in many states, including Missouri, Minnesota, California, Arizona, New Jersey, and in all the New England states.
For more information, check with your local Department of Environmental Protection or Audobon group. They are likely to have additional details about the specifics of vernal pools in your state.
Here are two sources that are particularly good: https://mnfi.anr.msu.edu/abstracts/ecology/Vernal_Pool.pdf