The animal’s exhibit should approximate its natural environment and enhance the visual experience for zoo visitors. Many healthy mammals and birds can tolerate a fairly wide temperature range if given access to shade and water in hot weather and to a dry, draft-free shelter with a warm spot and ample food to meet increased energy requirements in cold weather. It is essential to ensure that each animal has access to the protected environment and that one dominant individual does not exclude others from shelter, food, or water; such exclusion can result in frostbite or even death due to exposure. Feed receptacles should be designed to avoid fecal contamination and be easy to clean.
With large numbers of birds or mammals, and especially in mixed species exhibits, several watering and feeding stations should be established at appropriate heights to reduce territorial conflicts that may result in injuries or deaths. The timing of feedings is important. In many species, it is best to feed small amounts throughout the day to stimulate activity; this is beneficial for the animal and results in a better display. Food can also be used to attract an animal to an area where it can be more easily and safely examined or treated.
The biology and social behavior of animals must be understood to promote reproduction. Species should be maintained alone, in pairs, or in groups, depending on their established social systems. For example, in mixed species groups of Artiodactyla, it is possible to establish species estrous cycles through a variety of techniques, including monitoring hormone levels in the urine and feces. Monitoring reproductive cycles may be used to determine when to introduce and remove breeding males, with males of other species rotated to coincide with the estrous periods of the females of each species. This may also reduce injuries from interaction between breeding males. At parturition, the males of some species should be removed for several weeks to prevent attacks on the postpartum females or their offspring. In colder climates, males should be introduced at a time that will allow births to occur during warm weather.
Artificial reproductive technologies such as artificial insemination, in vitro fertilization, and embryo transfer have been successfully used in diverse zoo species. These efforts have made a significant difference in some endangered species breeding programs (eg, black-footed ferret). However, success requires substantial investment of resources (financial, personnel, etc) to determine basic parameters of reproductive cycles and responses to pharmacologic manipulation.
An emerging management priority in maintenance of zoologic collections is the need for selective reproduction. Indiscriminate reproduction is unethical and carries the potential for overproduction that exceeds the capacity of the exhibit, the zoo, or other zoos to appropriately house the progeny. Overly successful breeding programs carry a risk of limiting resources that could compromise other captive propagation programs. Regional cooperative breeding programs such as Species Survival Plans should be followed. Management is aimed at ensuring genetic diversity of the species into the future. Contraceptive efforts in zoos are multifaceted and include permanent techniques (castration, vasectomy, ovariohysterectomy, tubal ligation), as well as reversible ones such as separation of the sexes, administration of birth control pills, hormonal implants, gonadotropin-releasing hormone agonists, and oral or injectable progestins. Reversible contraception can also be used to control timing of reproductive cycles. There is ongoing work with immunocontraception through administration of porcine zona pellucida vaccines. The Association of Zoos and Aquaria Wildlife Contraception Center (view website) is a good source of up-to-date information on contraception techniques.