Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!umich!samsung!cs.utexas.edu!asuvax!mcdphx!mcdchg!att!cbnewsd!kja From: kja@cbnewsd.ATT.COM (krista.j.anderson) Newsgroups: sci.bio Subject: Re: War and Peace and Chimpanzees Summary: encyclopedia info about animal aggression Message-ID: <12994@cbnewsd.ATT.COM> Date: 31 Jan 90 23:07:42 GMT References: <12900@cbnewsd.ATT.COM> <1283@oravax.UUCP> <31315@shemp.CS.UCLA.EDU> <19712@netnews.upenn.edu> Organization: AT&T Bell Laboratories Lines: 88 <> Well, I decided to get a little more information about animal aggression. I knew, really, that the idea that "animals never kill" is outdated. Here's some further info, from the Encyclopedia Americana (1989) and Academic American Encyclopedia (1981). Instinct is unlearned, inherited and species-common. Closed instincts cannot be modified. Open instincts can be modified. An example of a closed instinct is that certain fish and birds will respond aggressively to a red belly or chest and that behavior cannot be extinguished. An example of an open instinct is nest-building in some birds. The instinct is to pick up any material to build the nest. But as the bird learns, it ignores materials in the area that did not work well and picks up only those materials that have worked well. Aggression and territoriality are not necessarily related. Some advantages of territoriality: 1. Territorial species will have flexible dimensions of each individual's or group's territory, depending on the amount of food available each year. These species have less fluctuation in population densities than non-territorial animals. 2. Being more spread out lends protection against diseases and parasites. 3. Group defense cooperation leads to social organization. In lower animals, aggression is inherited and laboratory rats can be bred to be more docile or hostile. In higher animals, including humans, learning plays a role in aggression-looking behavior. 13 types of aggression have been identified and each is elicited by different stimuli and each is associated with different neural and endocrine bases: 1. predatory - in response to presence of prey 2. anti-predatory - in response to presence of predator 3. territorial - in response to intruders 4. dominance - in response to challenge to rank or possessions 5. maternal - in response to threat to offspring 6. weaning 7. parental discipline 8. sexual 9. sex-related 10. intermale - in response to presence of competitor 11. fear-induced - in response to being confined or cornered 12. irritable - in response to signals such as red belly 13. instrumental - change in environment making any of above more likely On the one hand, the encyclopedia says that threats of aggression and withdrawal are much more common than actual fighting. On the other hand, langurs will kill the offspring of other males. Also, male lions will go as far as to kill one another when they are fighting for possession of a pride, and if the challenger wins, he might kill the cubs sired by the deposed male. The encyclopedia points out that a certain amount of aggression can give a breeding advantage to individuals, which then passes on the level of aggression to the offspring. On the other hand, too much energy spent in aggressive behavior can be a disadvantage, for instance, in the case of birds whose time would be better spent caring for the young. Hence, a balance is maintained for each species and probably for a particular environment. Well, this is grisly stuff, as Mickey said. Personally, I think humans can do better than nature in the sense of putting justice and compassion into practice. Nature is competitive. Sorry if this is a depressing topic. Then again, how do we know that the chimps, gorillas and lions that killed did not feel unusual pressures due to the presence of humans? If lions and apes have been killing all along, why didn't someone notice it sooner? Weren't the "Born Free" people studying lions for a long time (before they got murdered)? There are certain mechanisms I've heard of that take effect under crowded conditions. Lemmings go nuts and run into the sea in their panic. Mice will have spontaneous abortions or the males may eat the offspring, I seem to recall. Guppies will eat newborns under crowded conditions, I've heard. And as Barbara said, the alligators can afford to eat the young because there are so many compared to the area available. I'm not sure where these mechanisms would fit into the 13 types of aggression above. "Instrumental", I guess. Apologies if this is too depressing or grisly. -- Krista A. HONOR Our Neighbors' Original Rights!