For much of the past year and a half, many of us have felt captive. Confined for the most part in monotonous walls, unable to practice the full range of our natural behaviors, we suffered from stress and anxiety on a massive scale. In other words, says Bob Jacobs, a neuroscientist at Colorado College, the pandemic has given us a brief glimpse into life as experienced by many animals.
Although anthropomorphism is still suspect, Jacobs observes that “some humans were quite frustrated with all of this.” This is no surprise – we understand the tension of captivity as we experience it. But how to do do animals cope under the same circumstances? Aside from the billions of domesticated livestock in the world, some 800,000 wild and captive-born animals reside alone in accredited U.S. zoos and aquariums. Many people cherish these institutions, many hate them. Everyone wants to know: Are the creatures inside happy?
Signs of stress
Happiness is difficult to judge empirically, but scientists are trying to quantify well-being by measuring chronic stress, which can occur as a result of restricted movement, contact with humans, and many other factors. The condition is revealed by high concentrations of stress hormones in the blood of an animal. These hormones, called glucocorticoids, have been correlated with everything from hair loss in polar bears with reproductive failure in black rhinos.
Having said that, it’s hard to say what the normal level of stress is for any given animal. An obvious baseline is the wild counterpart of the captive (which surely has its own issues, from predation to starvation). But the problem, says Michael Romero, a biologist at Tufts University, “is that there just isn’t enough data.” Given the challenge of measuring stress in a wild animal – the capture required is not exactly calming – few studies of this type have been undertaken, especially in large animals.
Additionally, hormones can be an imperfect measure of an animal’s actual restlessness. âThe stress is so complicated,â Romero says. “It’s not as well characterized as people think.” So researchers can also look for its more visible side effects. Chronic stress weakens the immune system, for example, resulting in higher disease rates in many animals. Opportunistic mycoses are the leading cause of death in captive Humboldt penguins, and maybe 40 percent of African elephants in captivity suffer from obesity, which increases their risk of heart disease and arthritis.
Another sign of stress is the decline in reproduction, which is why it is often difficult to breed animals in captivity. Libido and fertility drop in cheetahs and white rhinos, to name just two. (A related phenomenon may exist in humans, Romero notes: Some research suggests that stress, anxiety and depression can reduce fertility.)
Even when breeding is successful, high infant mortality rates affect some species, and many animals that reach adulthood die much younger than they would in the wild. The trend is particularly poignant among orcas – according to a study, they only survive an average of 12 years in American zoos; males in the wild typically live 30 years and females 50.
Big brains, big needs
Our wild loads do not all suffer as much. Even in the above species, there appears to be some variability between individuals, and others seem quite comfortable in human detention. “Animals in captivity are often healthier, live longer and are more fertile”, writes Georgia Mason, behavioral biologist at the University of Ontario. “But for some species, the opposite is true.”
Romero made the same point in a paper 2019: the effect of captivity is ultimately “highly species specific”. In many ways, it depends on the complexity of the brain and the social structure of each species. A good rule of thumb is that the larger the animal, the less it will adapt to captivity. Thus the elephant and cetaceans (whales, dolphins and porpoises) have become the standard bearers of the movement to protect zoo animals.
Jacobs, who studies the brains of elephants, cetaceans and other large mammals, described the caging of these creatures as a form of “neuronal cruelty. “He admits they’re ‘not the easiest to study neurally’ – you can’t cram a pachyderm into an MRI machine. But he’s not bothered by this lack of data. In its absence. , it supports evolutionary continuity: the idea that humans share some basic characteristics, to some extent, with all living organisms. “We accept that there is a parallel between a dolphin’s fin and the human hand , or the foot of an elephant and the foot of a primate, “explains Jacobs.
Likewise, if the brain structures that control stress in humans closely resemble the same structures in zoo chimpanzees – or elephants or dolphins – then it stands to reason that the neurological response to captivity in these animals will be somewhat the same as our own. This, says Jacobs, is confirmed by half a century of research into how depleted environments alter the brain species as diverse as rats and primates.
Of course, not all forms of captivity are equally impoverished. Zookeepers often speak of âenrichmentâ. In addition to meeting the basic material needs of an animal, they strive to make its enclosure attractive, to give it the space it needs to carry out its natural routines. American zoos today are generally a big improvement over those of yesteryear. But animal advocates contend they will always fall short of the needs of large animals. “It doesn’t matter what zoos do,” says Jacobs, “they can’t provide them with a proper and nurturing natural environment.”
If there is even the slightest doubt about the welfare of a captive animal, even the untrained zoo visitor can spot what perhaps the best clues are: stereotypies. These repetitive, aimless movements and sounds are the hallmark of a stressed animal. Elephants sway from side to side, orcas grit their teeth in mush against the concrete walls. Big cats and bears come and go along the boundaries of their enclosures. Investigation found that 80 percent of giraffes and okapis exhibit at least one stereotypical behavior. âStress can be difficult to measure,â says Jacobs, âbut stereotypies are not difficult to measure. ”
Proponents are quick to point out that zoos convert people into environmentalists and sometimes reintroduce endangered species into the wild (though critics question how effective they really are on these fronts). Given their potential to strengthen the conservation movement at large, Romero suggests that an ethical calculation might be in order. âMaybe sacrificing the health of a few animals is worth it,â he says.
Wherever these moral arguments lead, Jacobs argues that “the evidence becomes overwhelming” – large mammals, or at least many of them, cannot thrive in containment. Environmental writer Emma Marris concludes the same in Wild Souls: freedom and fulfillment in the non-human world. “In many modern zoos, the animals are well cared for, healthy and probably, for many species, contained,” she writes, adding that zookeepers are not “mustache twirling baddies.” Nonetheless, by ceaselessly swaying and swaying, gnawing on bars and pulling their hair, “many animals clearly show us that they do not like captivity.”