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Otto: Crayfish beat the heat in the mud

Published: Saturday, July 30, 2011 5:30 a.m. CST • Updated: Saturday, July 30, 2011 11:25 p.m. CST
Caption
(Photo provided)
A crayfish is shown.

Where do you go to beat the heat?

For most people, the answer seems to be in, as in indoors. Close the windows, crank up the air conditioning, and wait for the hot spell to pass.

For most animals, the solution is out, as in out of the sun and into the shade. This past week I saw a squirrel draped across a shady bough, its tail – so useful for warmth in the winter – drooping below the branch and waving gently in the breeze. I also saw a hummingbird perched in the shade of a willow tree. Its wings, capable of 70 wingbeats per second, were motionless as the warm air swirled around them.

Then there are those critters for which the answer is down, as in underground, where the earth’s natural coolness provides soothing relief.

Our burrowing mammals,  such as chipmunks and groundhogs, have this option available all the time. In fact, their home burrows sometimes play host to others guests too, like snakes.

(I know what you’re thinking. But those “snake holes” we see all over our natural areas actually can be traced back to burrowers like chipmunks. Snakes, limbless and lacking any sort of body armor, have a tough time punching through the soil in our area; it is way easier to take advantage of an already-dug hole than to try and create one themselves.)

When my phone rang at the height of our heat wave last week, I didn’t know what to expect. The caller was Miss Laura, one of our awesome summer camp teachers, and her daughter and co-teacher Miss Elizabeth. They had been exploring the wilds of Delnor Woods with the Nature Discoverers, intrepid young naturalists ages 3 and 4, when they’d come across a sight they had never seen in all their years of teaching: crayfish were emerging from the park’s shrinking pond, and burrowing down into the mud.

Relieved that the call wasn’t about a Discoverer who had discovered a yellowjacket nest or poison ivy or any other peril, I made plans to swing by Delnor Woods on my way home from work.

Approaching the pond later that day, it took something less than a minute to see what Laura and Elizabeth were talking about. There in the mud along the pond’s shore were crayfish – big, honking red ones – excavating their way to a more comfortable environment.

It also didn’t take long to see that, just as news travels fast among those of us in the Naturalist Department, it also gets out quickly in nature itself. All around the crayfish were signs of other animals – namely raccoons – that had come to take advantage of the crayfish bounty and snag an easy meal.

While their tracks were everywhere, no actual raccoons were at the pond when I was, making it much easier to focus on the crayfish and their activities.

What I was glad to see was that the crayfish making the exodus were native White River crayfish, Procambarus acutus, not the introduced red swamp crayfish, Procambarus clarkii, a species commonly brought to this area for eating (in restaurants) and dissecting (in classrooms). Native to the southern states, red swamps have been showing up with increasing frequency in northern Illinois, which could spell trouble for our native crayfish as well as animals like amphibians, upon which the red swamps sometimes feed.

So the crayfish weren’t red swamps, but they were still definitely signaling that something was up with the Delnor Woods pond.

Crayfish come in three basic “types:” primary burrowers, which live in burrows most of the time; secondary burrowers, which create burrows some of the time; and tertiary burrowers, which rarely if ever burrow. White River crayfish are secondary burrowers; that is, they retreat into the ground when the going gets tough – too cold, too warm or too dry.

Combine the warm temperatures we’ve been experiencing with (OK, until a few days ago) a lack of rain and Delnor Woods’ leaky dam and you end up with a pond the crayfish were finding unsuitable. So down, down underground they went.

With this week’s heavy rainfall, it could very well be that the crayfish – those that survived the raccoons’ nightly raids – are back in the Delnor Woods pond again.

But the next time it’s hot and dry, you can be sure the crayfish will be on the move again.

I’ll likely be there, too. Sitting in the shade by a pond, even one that’s shrinking, is a great way to beat the heat.

Pam Otto has been chasing after crayfish of all types for more than 40 years and beating the heat for almost 50. She’s also the manager of nature programs and interpretive services for the St. Charles Park District and can be reached at 630-513-4346 or potto@stcparks.org.

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