— Bertolt Brecht
Overcrowded conditions often coincide with another of Gary Polis’s cannibalism-related generalizations, namely that incidents of cannibalism increase with hunger and with a decrease in the availability of alternative forms of nutrition, a point that will become horribly clear once we begin our investigation of human cannibalism.
Carrying the banner (albeit a tiny one) for crowd-related cannibalism are the Mormon crickets (Anabrus simplex). These insects are native to the North American West and belong to the order Orthoptera, which contains grasshoppers, crickets, and locusts. The fact that A. simplex is actually a form of jumbo katydid also makes them members of an unofficial assemblage composed of misnamed animals like “flying foxes” (which aren’t foxes) and “tree shrews” (guess).9 Attaining a body length of nearly three inches, Mormon crickets are flightless, but like their winged cousins, the grasshoppers and locusts, they’re renowned for their spectacular swarming behavior and mass migrations. According to biologist and Mormon cricket expert Stephen Simpson, favorable early spring conditions like warm weather and moisture can lead to the nearly simultaneous hatching of several million individuals. Almost immediately, the nymphs begin to march, and they do so in a spectacularly well-coordinated manner.
I asked Simpson why Mormon crickets participated in such large-scale movements. He cited studies showing that individuals separated from their swarm suffered 50 to 60 percent mortality from predators. “They got eaten by birds, rodents, and spiders if separated but were safe from predation in a crowd.”
Seeking to illuminate principles of mass migration and collective behavior, Simpson and his coworkers conducted food preference tests on captive Mormon crickets. They determined that protein and salt were the limiting resources being sought by the swarming insect masses. Incidents of cannibalism began soon after these resources were depleted, since the nearest source of protein and salt becomes a neighboring cricket. According to Simpson, “Each insect chases the one in front, and in turn is chased by the cricket behind.” Stopping to eat becomes a dangerous behavior, the biologist explained, requiring individuals to fend off other members of the swarm with their powerful hind legs. “Losing a leg is fatal,” he told me. “The weak and the injured are most at risk.”
Simpson demonstrated this experimentally by gluing tiny weights to some of the crickets, thus causing them to lag behind their unencumbered swarm-mates. Almost immediately, the miniature Jacob Marleys were attacked and eaten by the hungry horde approaching from behind.
In the end, Simpson and his colleagues determined that the massive migratory bands were actually forced marches, demonstrating “coherent mass movement at the level of a huge marching band.” Here, though, band members that can’t handle the pace run a serious risk of being eaten.
While avian cannibalism might be relatively rare in the wild, all bets are off once birds are removed from their natural setting, and packed shoulder-to-shoulder (or ruffled feather to ruffled feather). When thousands of stressed-out birds have little to occupy their time, the situation can deteriorate rapidly. In these instances the real meaning of the term “pecking order” becomes gruesomely apparent as some individuals are pecked to death and eaten. Initially, cannibalism on poultry farms was thought to result from a protein deficient diet, but researchers now believe that it’s actually misdirected foraging behavior related to cramped and inadequate housing conditions.