“No, no, no,” I said to myself as I turned over rock after rock. Part of my role in this class was to help create a species inventory of wildlife in the Grande Ronde basin, and part of that entailed performing a timed search for “Herps” (amphibians and reptiles) at each site. Part of that process involves flipping over large, looming rocks that may serve as the perfect place for a snake, frog, or toad to hide. My next rock of choice was a large ominous rock, well embedded into the channel’s gravel bed.
With a little leverage the rock came loose and I was met, once again, with a frog-less, snake-less, and toad-less swirling mass of sediment. It was then that I noticed a small orange chunk stuck to my hand that I used to free the rock. I was holding a small orange crayfish pincher. The pincher’s owner emerged in the settling dirt, sadly crawling along the rocky substrate, slightly off-balance due to its missing pincher.
It was then that I recalled a great lecture that I had last quarter in my Behavioral Neurobiology class about crayfish escape behavior. It was then apparent to me that I had found something much better than a Herp; I had found an experiment! The behavior is reliable, quick, and once it is triggered it cannot be stopped. Years of evolution have made it an effective tool against predation, but not against curious folks like myself. I had never witnessed this escape behavior, and had only seen crayfish lumbering along the bottom of streams at a snail’s pace, so I wanted to see just how effective their escape behavior really is.
The neat thing about the behavior is that there are multiple neuronal pathways that the crayfish can use to escape depending on what direction the stimulus is coming from. Surely enough, a sharp tap to the head caused the crayfish to rapidly shoot backwards by flexing its tail’s most caudal muscles. The next order of business was a tap to the tail, which resulted in a rapid flexion of the whole tail that resulted in the crayfish being shot forward and up. Not only was the behavior incredibly fast, I was also very impressed in that it was still executed perfectly even though the crayfish was undoubtedly off balance due to its missing pincher.
The escape behavior is so powerful, that once it is triggered all other behavior is shut off, and all of the individual’s energy goes into executing the rapid tail flip. However, if the crayfish is engaged in important behavior, such as feeding, the threshold for triggering the behavior goes way up to prevent unnecessary flighty behavior. So naturally, I left the crayfish in peace and followed it along its lumbering course. After a few minutes it finally came to something worth eating and gave me an opportunity for me to bother it once again. I tapped the crayfish on the tail in the same manner I had before and it didn’t even flinch. The crayfish must have been on to me!
Frustrated, I have the crayfish a sharper tap on the tail. In the blink of an eye, the crayfish shot up into the water column and was carried away from he current faster than I could comprehend what to do next. As I looked at the empty water in front of me I felt a little embarrassed that a handicapped crayfish was able to evade me. However, any embarrassment was trumped by my feelings of appreciation for the crayfish’s impressive behavior that has proved to be successful in not only escaping predators, but also curious college students like myself.