For the past month or two I have been highlighting different science stories that I read about, listen to on a podcast, or are told about by friends that I find particularly interesting. This week's "Favorite Science Story of the Week" once again comes from a favorite new blog I read called Not Exactly Rocket Science. The article, March of the locusts - individuals start moving to avoid cannibals, highlights some recent research on the why locusts migrations occur. The researchers note that they originally studied Mormon Crickets and found the results there consistent.
The great State of Idaho has Mormon Crickets. As stated in the Wikipedia articled linked above they most often occur in low densities. A few years back we had a huge population explosion in our area. In some cases they were so thick that they caused a car crash due to them making the road slippery. The highway department actually cleared the road with a snowplow! I remember mountain biking through swarms. They would jump up, hitting your legs and bike, squishing in the trail, etc. It was all quite disgusting. But most disgusting of all is that they are cannibals. Once one is run over on the trail, the others swarm in to fight over the carcass. This of course leads to more being run over and more cannibalism.
One of my observations from the cricket explosion was that all of these crickets appeared to be walking in the same direction. At least when they weren't fighting over their dead brethren. On a 15 mile mountain bike ride, all of the crickets would be walking in one particular direction. I remember wondering at the time what this was all about.
This new research study on locusts illustrates the primary reason they all start marching - to prevent the cricket behind them from eating them. Once the density reaches a certain level, they start watching their backs and moving out of the way. In large populations this results in a migration largely in a particular direction. The researchers proved this by blocking eyesight behind the locust and disabling the nerve cells on the rear legs (how exactly do you perform nerve surgery on a locust?). With these two modifications, the locusts no longer migrated. Imagine what we would do if every other person out there was a likely predator. It would definitely have a significant impact on our cultural norms...