In our modern society we tend to be put under stressful conditions. The origin of that stress can come from many different sources from one source at a time or several. It can be our jobs, family, the environment or many other things. These conditions can affect just one individual at a time or entire populations. In the end it really doesn't matter because as individuals or populations we all react much in the same way to stress. A key factor in that induces stress in populations is overcrowding. Examples from field biology include the lemmings. The word "lemming" or "Lemmus" comes from a Norwegian word that means destroying. This is in reference to the destruction that is visited on the Norse landscape during a lemming migration. According to several sources, lemming suicide is a myth. It is the overpopulation of the lemmings that leads to a scarcity of food and overcrowding, which in turn causes the animals to migrate in search of food. During the lemmings' single-minded quest for food they swimming lakes and rivers, cross mountain ranges and eat all vegetation that is in their path. When they reach the sea, they try to swim it as if it was a river and drown for their efforts. This mass migration does not occur very often, even though the lemming population fluctuations radically every three or four years. The lemmings are so single minded in their migration for food that nothing will stop them except death. The lemming migration could just be called a freak event in nature if something similar could not be replicated under controlled conditions in the laboratory. The effect of stress due to overcrowding on rats (Rattus norvegicus) was demonstrated by John Calhoun. He created high-density populations of rats in which aggression; pack formation (gangs), homosexuality, infanticide, and infant neglect became rampant. At the start of the study twenty pairs of rats were placed in a multi-partitioned enclosure and given unlimited food and water. After a year their population density was very high and resulted in the above negative sociological behaviors, all the while still receiving unlimited resources. It was not a shortage of resources that caused the social pathology but too much contact between animals. These findings were reported in a Scientific American article entitled "Population density and social pathology" (1962a). We all were stressed by hurricanes Ivan and Katrina in one or several ways. As we look back on those times what forms of human behavior did we see that reminded us of what the rats and lemmings do and which of our behaviors didn't? The key difference between the rats and us is that we are the only thinking animals on the planet. Their behavior is based on instinct and ours on reason.

Think Global - Act Local!