Book T of C
Chap T of C
This is the 2007 version. Click here for the 2017 chapter 08 table of contents.
Animals commonly stake out a territory and defend it. Studies of nest spacing and population control are related to territoriality. Some birds will nest differently depending on available space and population density. Rodents will reproduce in different numbers depending on available resources.
How common is competition for territory, in nature?
Even ants have territorial battles. One species in the Southwest United States has "tournaments" during which different ant colonies meet at the boundaries of their territories. They engage in mock combat, drumming on each other's abdomens with their antennae. After 10 to 30 seconds, one or the other ant yields ground and the encounter ends. In this way, territorial boundaries are re-established with a minimum of actual fighting (Rossiter, 1976).
How do struggles for dominance relate to the male hormone testosterone, in primates?
Group-living animals commonly joust for dominance. Different animals test each other to see who is "really boss." The outcome has important implications for each animal's genetic success. Dominant animals usually reproduce more than non-dominant animals. Aggression in primates is related to the male hormone testosterone . The more testosterone a male primate has, the more aggressive it tends to be. Defeated males lose testosterone.
Similar phenomena occur in other mammals. A dominant ram mates repeatedly with his pick of the ewes. The male that loses a head-butting contest might not reproduce at all.
What does Pryor say about the nature of porpoises?
Karen Pryor is the famous porpoise researcher whose differential reinforcement of creative behavior in the porpoise was described in Chapter 5. She noted that people think dolphins (which researcher prefer to call porpoises, the technically correct name) are "cute, playful, friendly, harmless and affectionate to each other and to man." The truth is that they engage in constant struggles for dominance.
The novice trainer quickly learns that porpoises can be very aggressive. They are highly social animals, to which rank order is a matter of considerable importance. Aggressive interactions between porpoises, usually during dominance disputes, include striking, raking with the teeth, and ramming with the beak or rostrum, sometimes with serious consequences, such as broken ribs or vertebrae, or punctured lungs, in the rammed animal. A dolphin that has become accustomed to humans shows no hesitance in challenging the human for dominance, by means of threat displays and blows; a person who is in the water with an aggressive porpoise is at a dangerous disadvantage. The sentimental view that these animals are harmless stems at least in part from the fact that they are usually in the water and we are usually on boats or dry land; they can't get at us. (Pryor, 1981)
How do chimpanzees "test" human lab assistants?
Sarah Boysen, a chimpanzee expert, made a similar point. She said chimpanzees "test" human lab assistants with dominance displays such as roughhousing and hair pulling. Chimps also seem to be sensitive to gender differences in humans. Boysen noticed that the chimpanzees seldom bother male lab assistants who are physically large, especially if they have facial hair such as beards. But the chimpanzees challenge female lab assistants "constantly, every day." (Boysen, personal communication).
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Copyright © 2007-2011 Russ Dewey