Sociobiology of Captive Breeding
During a captive-breeding program, one must take into account the species' spatial requirements, dietary specializations, environmental needs, housing requirements and medical problems.
The optimum group size for a captive species will depend upon its mating system, which could be monogamous, polygynous, polyandrous or promiscuous. The rearing strategy must also be taken into consideration. Most important are (1) the degree of contact between the mother and the young during rearing; (2) the degree to which females will rear young together and (3) the degree of participation by the male or older offspring in parental care.
In some species, the young disperse away from the parental group. To avoid aggression, this may have to be done artificially. In some species, males fight for control of several females. This ensures that the strongest males mate. However, in captive populations such fighting would cause injury and even death. Allowing only one male to mate would also reduce the amount of genetic variability within the population. When a new male takes over the harem of females, he often kills all the offspring of the old male. Under such circumstances, it is probably best to rotate the dominant male artificially every few 2-3 years.
Reduced aggression within a captive population reduces injury and death, but sometimes aggression is essential to trigger hormone levels essential for the performance of male sexual behavior. Females may also be affected. A female's estrous cycle may be irregular or depressed in the presence of a male whose urine or other glandular secretions have low androgen levels due to lack of aggressive stimuli.
Females may also affect one another via hormones or behavior. In marmosets, only one female will exhibit a normal reproductive cycle. The estrous cycle of other females is suppressed by the production of hormones by the dominant female. In wolves, a dominant female will prevent mating by a sub-dominant female through threats and attacks. If sub-dominant females do manage to produce offspring, dominant females may kill the offspring. Under such circumstances, separation of females may result in increased reproductive success.
In some species, females rearing young must be isolated from the rest of the group. In others e.g. columbine monkeys, the presence of other helper females (usually close relatives) is essential for the successful rearing of the young. Rearing animals in captivity may change their behavior and make it impossible to re-introduce them into the wild. Humans will tend to select certain behavioral genotypes, e.g. non-aggressive animals. Animals stressed by captivity will die out. Genotypes, which would not survive in nature, may survive and have many offspring in captivity. The behavior of animals may be changed greatly by hand rearing. Such animals form inadequate social behavior and may not reproduce successfully.