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| 1 |
Many species of animals live in a group with some kind of social organization.
This organization is based on aggressiveness, intolerance, and the dominance
of one individual over another. Two opposing forces are at work. One is mutual
attraction of individuals; the other is a negative reaction against crowding,
the need for personal space. |
| 2 |
Each individual occupies a position in the group based on dominance and
submissiveness. In its simplest form, the groups include an alpha individual
dominant over all others, a beta individual dominant over others except the
alpha, and finally an omega individual subordinate to all others. Individuals
settle social rank by fighting, bluffing, and threatening at initial encounters
between any given pair of individuals or a series of such encounters. Once
individuals establish social rank, they maintain it by habitual subordination
of those in lower positions. They reinforce this relationship by threats and
occasional punishment meted out by those of higher rank. Such organization
stabilizes and formalizes competitive relationships and resolves disputes with
a minimum of fighting and wasted energy. |
| 3 |
Social dominance plays a role in population regulation when it affects
reproduction and survival in a density-dependent manner. An example is the wolf.
Wolves live in small groups of 6 to 12 or more individuals called packs. The
pack is an extended kin group consisting of a mated pair, one or more juveniles
from the previous year who do not become sexually mature until the second year,
and several related, non-breeding adults. |
| 4 |
The pack has two social hierarchies, one headed by an alpha female and
the other
headed by an alpha male, the leader of the pack, to whom all other members defer.
Below the alpha male is the beta male, closely related, often a full brother,
who has to defend his position against pressure from males below. |
| 5 |
Mating within the pack is rigidly controlled. The alpha male (occasionally
the
beta male) mates with the alpha female. She prevents lower-ranking females from
mating with the alpha and other males, while the alpha male inhibits other males
from mating with her. Therefore, each pack has one reproducing pair and one litter
of pups each year. They are reared cooperatively by all members of the pack. |
| 6 |
The size of the packs, which is heavily influenced by the availability
of food,
governs the level of the wolf population in a region. Priority for food goes
to the producing pair. At high pack density, individuals may be expelled or leave
the pack. Unless they have the opportunity to settle successfully in a new area
and form a pack, they may not survive. Thus, at high wolf densities mortality
increases and birthrates decline. When the population of wolves is low, sexually
mature males and females leave the pack, settle in unoccupied habitat, and establish
their own packs with one reproducing female in each. In this case, nearly every
sexually mature female reproduces, and the wolf population increases. At very
low densities, however, females may have difficulty in locating males with whom
to establish a pack and so fail to reproduce or even survive. (Smith, Robert
Leo and Thomas M. Smith. Elements of Ecology, 4th ed. 2000, p. 171) |
Copyright © 1995-2010 by Pearson Education, Inc., publishing as Pearson Longman.
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