The game of life
Competing for survival
Most animals interact with other animals or plants directly because they depend on them for food. They also compete with animals of their own species, or with other animal populations, for the same food sources, especially when these are scarce.
Human populations are involved in more interactions with other species than it seems possible to count – from our domestication of animals for food and companionship, to the destruction of natural ecosystems, to the communities of bacteria in our guts that help us digest our food. Of course, human populations also interact with one another. Like all animals, we fight over territory and resources, even as we try to cooperate for the greater good.
Within all ecosystems there is competition for precious resources, such as light, water or space. When competition is between members of the same species, it is intraspecific; when it is between different species, it is interspecific.
Scientists have spent many years studying interspecific competition between crayfish species across Europe and North America. In many areas of the UK native white-clawed crayfish are being replaced by invasive North American signal crayfish, which originally escaped from British crayfish farms. The larger invaders oust the native crayfish from the limited refuges under rocks in streams and rivers and compete for food. They also carry a fungal plague, to which the UK species has no defence.
Their battle over niche is an example of the competitive exclusion principle, which states that it is impossible for two species in the same ecosystem to coexist if they are competing for the same resources.Lead image:
University of Leeds, Faculty of Biological Sciences