A Rusty Bully
The Great Outdoors | July 1, 2017
By Jackie Scharfenberg, Wisconsin Department of Natural Resources
Ah, a new lake to invade thanks to a kid who dumped me out of his bait bucket…or, was that an aquarium from a school science project?
This lake makes a great habitat for us rusty crayfish (Orconectes rusticus). We love to use the rocks, logs, and other debris for cover. Now, I just need to kick out the natives, which will be easy since I possess larger claws and greater length. So long chumps!
Don’t Get Me Confused…
Check out my dark reddish-brown carapace with the rusty spots on my sides (these rusty patches may be absent on some of my friends). My robust grayish-green to reddish-brown smooth claws sport black tips. Don’t confuse me with those wimpy Wisconsin native crayfish. My ancestors came from the Ohio River basin in the states of Ohio, Kentucky, Tennessee, Indiana, and Illinois.
My Diet
With my high metabolic rate, I need to eat…and eat A LOT. I use my claws to clip off underwater plants right at the lake bottom. Sometimes, I’ll clean out an entire bed of plants. For the main course, I munch aquatic invertebrates (critters without backbones) like snails, clams, leeches, adult and young insects, and other crayfish. For a special treat, I gobble down fish eggs and, sometimes even a small fish.
I forage mostly at night, but will snack during the day. All of this eating can lead to changes in the lake’s ecology, especially regarding damaging the habitats for aquatic invertebrates and fish and their populations.
Our Young
Males and females mate in late summer, early fall, or early spring, but the females do not lay their eggs until the water warms in spring. Just before she lays her 80 to 575 eggs, patches of mucus-like substances (called glair) form underneath her abdomen. The eggs attach to these patches and take three to six weeks to hatch depending on the water temperature. After hatching, the young stick to mom until they molt their exoskeleton three to four times. Then, they will remain with her for several more weeks. They molt another eight to ten times before becoming adults – usually the following year.
Don’t Invade My Space…
If another rusty trespasses into my territory, I first raise the upper portion of my body and show off my claws (the meral spread). If that doesn’t work to ward off the invader, I’ll wrestle without using my claws. As a last resort, I’ll fight unrestrained with my claws until one of us retreats.
PREVENTION
Once we settle into a lake, pond, or stream, humans can’t get rid of us. Curb a rusty invasion by not dumping bait or science projects.
PHOTO CREDIT: Peter Pearsall/U.S. Fish and Wildlife Service
