Can You Use a Live Crab as a Timer?

When I was at the tidepools on Friday, I set up my little Kodak Zi8 to capture some crabs scuttling about on the rocks. I was big and the crabs were small, so they wisely hid from me, wedging themselves into various nooks and crannies in the rocks. Once the little camera was on its tripod and had started filming, I backed off about 20 yards - more than out of sight of the myopic little crustaceans.

Over time, the crabs came out of their hiding spaces to feed on the algae and weeds on the rocks.

That made me wonder if you could use a crab as a timer. Inside the crab there are chemical processes that move the crab from anxiety to relaxation. When they saw the big monster right in front of them, their bodies must have released crab adrenaline (Crabdrenaline?) which triggered their flight into the rocks. Once the threat left, it took their bodies some time to consume those chemicals to the point where they felt comfortable enough to come out and feed. Those chemical processes take a certain amount of time and could be used as a crude timer.

Smaller crabs emerged sooner than the larger ones. This indicates to me that you might be able to construct a relatively sophisticated countdown timer using a group of crabs of differing sizes.

Next time I go, I'm going to bring a ruler with me so when I video the crabs, I can have the ruler in the shot to use as a reference measure for the crabs. Since it's a chemical process and crabs are cold-blooded, the ambient temperature will matter as well - chemical processes are slower at cooler temperatures.

I wonder if I can get my daughter interested in this as a science fair experiment. Hmmmm....