Definitions

A zoo or zoological garden has been defined as “an establishment where wild animals are kept for exhibition (other than a circus or pet shop) to which members of the public have access, with or without charge for admission” (UK Government 1981). While this technical definition may apply to any number of institutions exhibiting wild animals, each of the multitudes of “zoos” has different management practices, falls under different regulatory oversight, and applies a wide range of standards. Thus, each institution may be very different in practice. The American Association of Zoos and Aquariums defines a zoological park or aquarium as:

a permanent institution which owns and maintains wildlife, under the direction of a professional staff, provides its animals with appropriate care and exhibits them in an aesthetic manner to the public on a regularly scheduled, predictable basis. The institution … shall further be defined as having as a core mission the exhibition, conservation, and preservation of the earth’s fauna in an educational and scientific manner.

(AZA 2022)

Similarly, the European Association of Zoos and Aquaria requires that zoos in the European Union participate in conservation research and training and promote public awareness on conservation (EAZA 2013). The goals of promoting conservation, education, and animal care unite modern zoos. Some smaller, privately owned facilities, which best fall under the description of “menagerie,” also characterize themselves as zoos, even with a limited focus on education and conservation. Other institutions that maintain captive wildlife include sanctuaries, which may keep retired or unwanted exotic animals from zoos, circuses, or private individuals.

Stakeholders

As with any animal industry, there are competing interests in the operation of zoological institutions or aquaria. In companion animal practice, the veterinarian serves both the client and the animal: in the zoo industry there is the added layer of meeting the organization’s missions, the broader needs of the populations, and the needs of species conservation. In some cases, care may be prioritized for animals that are more genetically valuable or for individuals that have higher reproductive potential. Each of the stakeholders (except the animals) has input into the management and care of an individual animal.

Ethical Considerations for Keeping Animals in Zoos

Zoos are focused on conservation, education, sustainability, and entertainment. The broader question is whether these reasons justify captivity of wild animals. Before discussing how zoos should best care for their animals, the question should be asked if zoos should have them in the first place. This discussion is expanded when we consider the differing needs of certain species. Taylor contends that “if significant benefits can be shown, then captivity for at least some animals might be defensible, [but] it would appear that the burden of proof rests most heavily on the zoo to demonstrate that the benefits of captivity to the continued preservation of the species outweigh the costs incurred to the freedom of the individuals” (2014).

Zoos often balance the interests of multiple stakeholders with animal welfare (Hosey et al. 2013). Animals in a zoo collection are typically considered to serve a specific purpose, such as exhibit, breeding, conservation, or education. Animals that no longer serve these purposes may include animals that are off public display for health reasons or collection plans resulting in surplus animals maintained in off-exhibit holding areas in perpetuity. The ethics of caring for these animals in the numbers needed is a balance between maintaining a viable genetic pool of animals and the space, staffing, and husbandry resources needed to provide for those animals. An ongoing ethical concern is whether zoos should be responsible for the lifelong care of animals that were previously useful but now no longer serve the zoo’s mission. If such animals are to be removed from the zoo, who is responsible for identifying an ethical means of disposition, and how?

Animal Welfare Considerations for Keeping Wild Animals in Captivity

While it may be possible to ethically keep certain species in manmade enclosures, it may be challenging or impossible to house other species in an exhibit that meets the animals’ physical and psychological needs. Fraser (2009) argues that focus should be placed on meeting the needs of basic health and function, natural living, and affective behaviors.

Prioritization of Care and Conservation

Zoos and aquaria face the challenges of limited resources when advancing their missions. Finite cost concerns, space, staffing, and time necessarily dictate which species and which individuals can be kept, displayed, cared for, and conserved. Powell et al. (2019) argue that certain species need to be prioritized for ex situ conservation based not only on their proximity to extinction, but also on the likelihood of maintaining a healthy sustainable population. Some species may be so far depleted that extraordinary measures to save the last one or two individuals may do nothing for saving the species. Conversely, some species that are threatened, but not yet in dire straits, may benefit most from focused conservation efforts to prevent further decline. In a zoo, this may affect allocation of resources to certain species and even certain individuals, and can directly affect the ability of a veterinarian to care for a patient. A fractured leg in a common species may entail a different outcome than one in a high-priority conservation species. While attention to individual welfare is consistent between the cases with provision of analgesia, the more common animal may be euthanized while more extensive measures are taken for the endangered animal. This is similar to working with a private owner who determines the financial extent of care that their animal receives: a zoo might have to do the same based on the assigned value of the individual.

These limitations are not only financial, but also affect space allocation. With a limited amount of space and housing available, a zoo must determine how much is allocated to exhibit animals and to off-exhibit captive propagation, including so-called assurance colonies. The off-exhibit holding and breeding spaces do not generate revenue for the zoo but are essential to maintaining a genetic store house. With these limitations on exhibit, holding, and breeding spaces, nonreproductive animals, especially some male animals, have been subjected to population management euthanasia (culling) (Powell and Ardaiolo 2016; Powell et al. 2018).

Ethical Considerations for the Veterinarian

As with any animal industry, a zoo veterinarian faces the daily challenge of making decisions in the best interest of an individual animal’s welfare while balancing the desires of the keepers who maintain a close personal attachment to the animal and the mission of the institution. Similar to private practice, there are financial limitations placed by the fixed resources of nonprofit institutions and the need to balance the cost of care for thousands of animals.

The competing interests of species conservation, individual animal welfare, public perception and enjoyment, and financial solvency raise multiple ethical challenges for the zoo or aquarium veterinarian. In some cases, especially when the veterinarian is part of an outside contract service, the veterinarian may not be party to the management decision-making process and instead may only be included after critical decisions have been enacted. For example, a veterinarian may not be included in the decision-making process on sourcing new animals from the wild. This is still a fairly common practice, especially with reptiles, amphibians, and fishes, and a decision may be made either to improve genetic diversity or to acquire a species that is not available from captive propagation. While not involved with the decision to source the animals from the wild, the veterinarian is charged with treating medical conditions that result from that decision. In some cases, wild-caught animals may carry foreign parasites, may not be acclimated to the captive diet causing gastrointestinal symptoms, and may have prolonged periods of maladjustment to captivity resulting in stereotypical behaviors such as pacing, head-bobbing, or feather destruction. These are repetitive behaviors with no obvious goal and function that are assumed to be associated with poor welfare.

Collection of animals from the wild can create other ethical challenges for the veterinarian and the institution. In addition to the medical and husbandry challenges and the acclimation stress of bringing a wild animal into captivity, there are ethical questions associated with the potential stress and trauma of removing animals from the wild and the potential damage to fragile wild populations and ecosystems. Loss of genetic diversity inherent with captive breeding from a small founder population can cause inbreeding depression and reduce individual animal fitness. This genetic limitation is self-perpetuating with increasing infertility and reproductive abnormalities in inbred populations. Wild collection and importation of new founder animals allows for diversification of the genetic pool but can be a stressor on both the individual animal and the source population. Aquaria still rely heavily on wild collection of fishes and there is little information about the sustainability of these practices. This places the veterinarian in the challenging situation of treating both hereditary diseases made worse by inbreeding and conditions associated with the transition to captivity.

Similarly, a veterinarian may not have input into the design of a habitat but be expected to treat medical conditions that arise from exposure to inappropriate temperatures, humidity, or ambient light. Exhibiting animals with extensive housing and husbandry needs is challenging, as “natural” conditions may be impossible to replicate in a zoo or aquarium resulting in poor welfare. Many “captivity-related” medical conditions are the result of housing animals in an environment that is very different from what centuries of evolution have prepared them for. A North American zoo will have a different temperature, humidity, and diversity of available natural forage materials than an animal’s range habitat in sub-Saharan Africa. While accommodations are made to replicate the native environment, a veterinarian must be prepared to treat conditions related to inappropriate or inadequate husbandry. They should be comfortable raising ethical concerns related to captive husbandry and be appropriately positioned in the institutional hierarchy to have those concerns addressed.

Some social species (naked mole rats, African painted dogs, some primates, many fishes, and invertebrates) naturally live in groups with intense competition with conspecific injury, aggression, and even death being commonplace. In a captive setting there is the simultaneous desire to prevent injury and death while still providing for natural living. In many cases these may be mutually exclusive. Natural living as a multifaceted concept includes both positive and negative impacts on an individual animal’s health and welfare. Humans working with captive wildlife must make the decision about which natural behaviors to allow and which to restrict. The veterinarian, in conjunction with animal managers, must make decisions on the extent of medical intervention and the effect that will have on an animal’s social standing. As stated by Learmonth (2019), “Not all natural behaviors, nor natural environments, are to the benefit of animals in a captive setting, and practical application of the natural living concept has flaws. Expression of natural behaviors does not necessarily indicate positive well-being of an animal.” As a veterinarian, the option for intervention might include observation only and allowing “nature to take its course,” allowing a degree of conspecific aggression and mortality in a colony of animals. In other situations, an individual may be temporarily or permanently removed from a social grouping for its own safety, but then is forced to live alone or in a small group.

Many elective procedures performed by veterinarians on a nondomestic animal may be performed solely for the purpose of making an animal more suitable to a zoo, similar to declawing of domestic cats (see Chapter 10). Some commonly performed examples include deflighting procedures on birds, which can range from noninvasive flight-feather trimming to surgical distal wing amputation in hatchlings (pinion). Less common techniques such as tooth reduction and declawing of large felids (Panthera spp.) are typically not performed in accredited zoos and are discouraged by the AVMA. Declawing of large felids performed for any reason other than medical necessity is prohibited by the USDA for all regulated animal facilities (USDA 2006).

For many government-owned or operated zoological institutions in the United States, medical records for all animals are freely accessible by the public through the Freedom of Information Act. As such, it is exceedingly easy for any individual to obtain copies of a complete medical record and choose to distribute it to the media or public. While this unfettered access is a boon for accountability and transparency, it is possible to selectively excerpt any portion of the medical record to promote an agenda with verbiage taken out of context. As such, a veterinarian must remain vigilant to write records that are not only complete and accurate but can withstand scrutiny from the public. This can be challenging in cases of illness or injury that is partially the result of substandard husbandry conditions or human error. Conditions such as pododermatitis can occur commonly in captive birds and can be ameliorated with improving husbandry, but discussion of the etiology and the treatment in a medical record requires some admission of guilt for the poor husbandry. The veterinarian must balance the expectations of accuracy, transparency, and patient advocacy in a way that is complete and honest with a focus on improving care without laying blame.

There are many privately owned and operated exotic animal display facilities that frequently operate without the oversight of accreditation bodies. As animal exhibitors, they fall under the regulatory arm of the USDA Animal Care, but often operate with limited staff and rarely have a staff veterinarian. The veterinarian providing care for such facilities, or for private owners of wild animals, faces an ethical dilemma: by providing care to animals with compromised welfare, is the veterinarian enabling ownership and exhibit of animals in a manner the veterinarian finds substandard? While each animal may require the care of a veterinarian, the provision of that care in some cases may not remedy the suffering of animals in these facilities. Does providing immediate care for an animal that is being kept in a deficient situation enable that owner to continue “business as usual”? Does providing medical care to animals in dangerous and inhumane situations, knowing that they will continue to be kept in those settings, implicitly support the operations? These circumstances have further come to light with popular reality television programs focused on exotic animal ownership and exhibition.

Some of the most challenging ethical quandaries for a zoo veterinarian surround captive population management (Asa et al. 2014; Penfold et al. 2014). Limited space and resources require constant population control, which is often paradoxical because many zoo-housed animals are there for the purpose of reproduction, but that reproduction must be controlled in a way that allows appropriate housing, care, and disposition of animals. The goal of managing population numbers can be met by several methods, each with physiological consequences for the animal and ethical implications for the clinician. In many species, years spent not breeding, either due to contraception or being held without a mate, are associated with reproductive pathology and infertility. Multiple zoo-based reviews confirm that reproductive cycling without pregnancy negatively impacts future fertility (Hermes et al. 2004; Asa et al. 2014; Penfold et al. 2014). The clinician, the zoo, and population managers are left with the quandary of needing to keep a young animal from reproducing due to inadequate space for offspring, while knowing that the longer that the animal remains sterile, the less likely it is to conceive, essentially taking it out of the reproductive pools. Contraception and reproductive management are a huge ethical concern for zoos. In most cases, to promote conservation, responsible breeding and propagation of species are paramount, but with successful propagation, there is concern for available space and housing of nonreproductive animals. In the past few decades, the success of contraceptives has helped curb this population overgrowth, but at the same time leaves some animals reproductively inert.

Euthanasia of healthy “surplus” animals is one of the most contentious ethical dilemmas for zoo veterinarians. Regardless of the reasoning for euthanasia, culling, or humane killing, the task usually falls to the zoo veterinarian to carry out. For a clinician who is trained to treat, heal, and cure, it is antithetical to be asked to kill a healthy animal for the needs of population management. Sometimes the distaste for population management euthanasia limits discussion of the topic and may leave a veterinarian unprepared for the emotional toll of the task. Because of the effects of medical contraception on future fertility, some institutions may choose to allow animals to reproduce, knowing that there is not enough space to accommodate their offspring. In the wild, large litter sizes are often a means of countering high neonatal mortality, but with medical care in captivity those pressures do not exist, resulting in so-called surplus animals.

If surplus animals cannot be placed at other zoos, the choice may be made to cull them. Some argue that this process is the most akin to natural living. It allows a female animal to experience the natural activities of pregnancy and rearing young and allows the juvenile a short, but healthy life. If the method of euthanasia is humane, is the killing of a young healthy animal any less ethically sound than killing an old, healthy animal? Does killing negatively affect its welfare, and is this more problematic for younger animals (see Chapter 21)? Is it more ethical to house surplus animals in overpopulated enclosures or send them to institutions with lower animal welfare standards just to allow them to live, even if that longer life means added suffering? These very challenging questions get to the heart of each of the ethical dilemmas discussed earlier for the zoo veterinarian. Is the welfare and sustainability of the species population paramount, or does the final ethical judgment rest with the individual animal (Case Study 14.1 )?