Vernal Pools are Springing Up
My original assignment for this article was to write another wildlife monitoring piece. With the weather warming up though, my mind was wandering to the greener side of things. I’ve seen some green poking through the soil, so instead I’m going to talk about a specific type of wildlife habitat, what wildlife might use it, and how to monitor.
Since we’ve been seeing the end of the maple syrup season, it’s on to the next phenomenon in our woods: vernal (or ephemeral) pools. These temporary ponds of water start to show up in our woodlands this time of year. Snow melt and early spring rains fill these depressions in the landscape, and make a unique and timely habitat area. Due to their brevity, they don’t contain fish, which makes them a wonderful breeding habitat for some reptiles, amphibians, and insects. They also attract other wildlife that use the water resource or feed on the breeding animals.
In “Counting Crawling Critters“, I wrote about doing a call survey to inventory various frogs. In this exercise you listen for various frog calls, and note their presence in your woods. Two common frogs found in vernal pools are wood frogs and spring peepers . (These links take you to YouTube videos where you can hear their calls.) In that same article, I mentioned cover board surveys to monitor salamanders. Eastern tiger salamander , spotted salamander , and blue salamanders are three types of mole salamanders (those that live most of their lives underground) that we have here in Wisconsin that depend on vernal pools for their lifecycle.
There are a variety of other wildlife that use vernal pools for which there aren’t strict inventory techniques other than encounter/observation checklists. From the reptile side, you can find common gartersnakes, water snakes, Blanding’s turtle (an endangered species), and painted turtle. Although they are most commonly associated with permanent water, you may find a snapping turtle looking for an easy spring meal. Invertebrates use vernal pools similar to amphibians as they are a safer location for breeding. Caddisflies, damselflies, and dragonflies can be seen buzzing about the pools. The caddisfly eggs can even over-winter, then hatch when the water returns in the spring. If you’ve never seen a caddisfly larva casing, do an online search of pictures; their artistry is amazing.
Since we are along the lines of identification and monitoring, there are ways you can tell whether you have a vernal pool in your woodland whether it is spring or not. These pools are only found in a forested setting, and are not connected to permanent water sources. Start by looking for depressions in the land. Vernal pools are often small in area, and may hold as little as 4 inches of water or top out at just a few feet. Surrounding trees may show water marks with the depth of the water each year, and you are not likely to find trees in the confines of the pool since the sitting water can drown roots. You may even find wetland type plants growing in dry soil.
So in the next few weeks, get out in your woods, look for vernal pools, and if you find some, listen for frogs and set up some cover boards.