Husbandry of Zoo Animals
Exhibits should approximate the animal's natural environment and enhance the visual experience for zoo visitors. Naturalistic enclosures with soil and vegetation are appealing to the public and are more stimulating for the animals; however, they present challenges for both sanitation and parasite control programs and may complicate restraint procedures. Mixed species exhibits may increase risk of disease transmission between species and can result in interspecific aggression if species are not chosen appropriately. 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. Ensuring that each animal has access to a protected environment and that one dominant individual does not exclude others from shelter, food, or water is essential.
Feeders should be easy to clean, with designs that avoid fecal contamination and make thorough cleaning possible. Feeder design should also consider the species in the exhibit and be adequate in number for the exhibit's population. Domestic animal nutrition guidelines may help, especially for hoofstock, when determining the need for additional feeders, with models based on animal size and feeder bunk space.
The timing of feedings should also be considered. Feeding throughout the day may stimulate activity; however, considerations for a species' natural feeding habits may provide additional enrichment (eg, whole carcass feeding or fast days in carnivorous animals). Browsing animals generally eat continually, and the inability to replicate both their diet and an environment that supports this capability may lead to health issues. Food as an enrichment activity should always be part of a well-balanced nutritional plan with food items that closely resemble those in the natural diet of a species.
Reproductive Management of Zoo Animals
The biology and social behavior of animals must be understood to promote or control reproduction. Species should be maintained according to their established social systems, with an understanding of the effects of separation or contraception. Reproductive planning for an individual and population are important parts of zoo animal management. Breeding and rearing of offspring remain important natural behaviors that allow for zoo animals to thrive in a captive setting. Contraception—including pharmaceutical, surgical, and physical methods—may impact animal behavior, health, and overall welfare. Proactively determining an animal's reproductive life plan, based on genetics, reproductive capacity, species status, and other factors; allows for a more robust reproductive plan that considers risks of contraception and managed breeding.
Contraceptive efforts in zoos are multifaceted and include permanent or semipermanent techniques (ie, surgical castration, vasectomy, ovariohysterectomy, tubal ligation) as well as reversible means such as separation of the sexes, hormonal contraceptives (oral combination or progestin-only contraceptives, progestin implants, GnRH agonist implants, injections, or vaccines); and immunocontraception via porcine zona pellucida. Depending on the species and the deployment, contraceptive reversibility can be variable. As one example, at the St. Louis Zoo, recommendations are often based on species and reproductive plan for the individual animal (see Reproductive Management Center at the St Louis Zoo ) .
Many institutions participate in multi-institution breeding programs, such as the Association of Zoos and Aquariums Species Survival Programs, which seek to plan breeding based on kinship and other factors across captive managed populations. Management is aimed at ensuring genetic diversity of the species into the future.
Reproductive monitoring is possible for some species using a variety of techniques, including hormone level monitoring via sampling of urine or feces. This noninvasive monitoring can help determine timing for introduction of males or for intervention in reproduction. 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. Much investment is required to bring these efforts to fruition, including elucidating the basic reproductive parameters in each species and the response to artificial (ie, pharmacologic) manipulation of reproductive cycles.. These efforts remain an important mechanism for allowing breeding in species in which transport or natural breeding are challenging, and they offer hope for functionally extinct species or subspecies, such as the northern white rhinoceros.