Vernal Pools are Teeming with Life!

That's a crayfish, and last Friday, we saw several tiny, immature crayfish in vernal pools up in Alden Township. They were so tiny that the claws were about the width of a strand of hair! The entire critter was perhaps a quarter of an inch long, looking like some random bug larva, but under a magnifying glass, it became clear that these little guys were teeny-tiny crayfish!

A project to gather information about our local vernal pools has been organized by George Johnson, formerly of Alden Township but now living in Madison Wisconsin. One of the things that George had always hoped to accomplish when he lived in McHenry County, was to raise awareness of the presence and importance of these local temporary, spring ponds.

These seasonally wet areas are uncommon in the Chicago region, in large part because they are places that are filled in by homeowners and developers who do not see the benefits of having a wet, mucky spot in the yard each spring and perhaps into the summer.

The spring ponds are fairly common in Alden Township for a couple of reasons: 1. the area is still sparsely developed, and 2. historically, much of the area was used for livestock grazing instead of row crop farming. This meant that the seasonally wet spots survived, along with a lot of critters that are not often seen in the "suburbs."

Friday April 3rd was the inaugural day of McHenry County vernal pool monitoring. During their pool sampling, volunteers saw a large number of fairy shrimp (ranging in color from pink to red to blue to yellow, and everything in between), a wide variety of midges, scuds, and other tiny aquatic life that plays an important role in the overall food chain.

It was a cold day -- 43 degrees in the sun. The water was cold too -- 45 degrees. Yet, when we gazed into our dipping nets as we pulled them from the pools, tiny little eyes looked back at us! I had no idea there was so much activity on a cold day in cold water!

Unfortunately, there were also lots of mosquito larvae. These are another link in the web of life, providing a food source for dragonflies, frogs, fish, birds and other species that feed on water organisms, but I still don't like them. The skeeter larvae spend most of their time at the surface of the water breathing through a tube in their abdomen, as shown in the picture.

The eggs from which the larvae hatched were probably laid in the damp ground last summer or fall, and remained in an embryonic form until conditions were right for them to develop into larvae. The larval stage lasts a week or two, then turns into a pupa for a couple of days -- just long enough for it to become a fully-formed adult mosquito, ready to start feeding...

Now, don't blame the vernal pool for the mosquito larvae. These guys will develop in any little wet spot, regardless of the habitat. Lawns, bird baths, potholes in the road, etc. If it holds water for even a few days, it can be a source of skeeters!

One of the beautiful things about these vernal pools is that they are literally teeming with life of all shapes and sizes. There are microscopic things being eaten by tiny critters, which in turn are eaten by somewhat larger things, etc, etc. In that chain are tadpoles, young frogs and salamanders that eat mosquito larvae.

My wish is that there will be a large number of frog and salamander babies in all of our local vernal pools to eat those larvae before they become adults!