Captivity Harms Brain Function In Elephants And Cetaceans
Animals with large brains such as elephants and cetaceans do not thrive in captivity. In nature, these animals have extensive home ranges that provide them with stimulating situations suitable for their complex cognitive abilities. Unfortunately, over 3,000 cetaceans and 17,000 elephants around the globe remain captive and are deprived of their natural environments. However, it is usually not possible (for practical and moral reasons) to study these animals’ brains in captivity, even if it means shedding light on the harms of keeping large-brained mammals in zoos and marine parks.
In this study, researchers analyzed studies of other mammals living in deprived environments to explore how captivity impacts elephants’ and cetaceans’ brains. They also attempted to understand the effects of stress on elephant and cetacean brains, as well as the neural underpinnings of “stereotypies,” or repeated behaviors often seen among animals living in captive settings. Because elephants and cetaceans tend to show similar psychological and physical reactions to other mammals in captivity, and because their brains are structurally similar to other mammals who have been studied, the researchers argue that looking at comparative research will reveal helpful insights.
In nature, elephants travel at least 8-12 kilometers a day and have home ranges as large as 10,000 square kilometers. They live in multigenerational family groups, socialize, care for their offspring, and search for a variety of foods. In captivity, however, these animals are often kept in spaces much too small for their needs, and may be restrained with ropes or chains. Captive facilities often do not provide the social groups that elephants have in the wild, while many entertainment centers require them to interact with humans on a regular basis. These conditions are likely stressful for the animals.
Similarly, captive cetaceans are held in shallow tanks that are at least 10,000 times smaller than their natural home ranges. These environments restrain cetaceans from performing their normal behaviors including swimming long distances, diving, searching for food, and forming complex social networks necessary for their cognitive stimulation.
Because the basic needs of elephants and cetaceans are not met in captivity, these intelligent animals suffer from a variety of physical, behavioral, and psychological health issues. Gastrointestinal diseases, nutrition/metabolism disorders, and skin problems are just a few examples. Depression, hyperaggression, and stereotypies are also common — in fact, up to 85% of elephants kept in zoos and 100% of elephants kept in circuses engage in stereotypical behavior.
Experimental evidence from other animals, such as rodents, demonstrates that an impoverished environment results in significant brain damage. This includes thinning of the cerebral cortex, reduction in brain blood supplies, reduced number of glial cells that support and nourish neurons, and changes in neuronal structure. In addition, marmoset monkeys housed in less complex environments for just one month showed reduced brain complexity in the part of their brain that handles executive functions, such as planning and mental flexibility. Even human brain function has been linked to environmental complexity.
Lack of exercise is a common problem in captivity. Experimental studies in other mammals have shown that general enrichments and exercise reduce anxiety, enhance memory and cognitive function, boost immunity, and ease some psychiatric problems. While zoos and aquariums provide some limited enrichment for elephants and cetaceans, the authors argue that these activities are not sufficient to protect them from neurobiological damage.
Chronic stress is another problem in impoverished environments and is associated with poorer physical and mental health. The nervous system, the endocrine system, and the immune system work together to create a normal stress response. In response to environmental stressors, these systems trigger the release of the stress hormone cortisol and similar molecules.
While cortisol is needed to prepare the body for action in response to stressors, its long-term increase results in dysfunction of cellular metabolism, inflammation, and cell death in the brain. Three brain structures, namely the prefrontal cortex, the hippocampus, and the amygdala, are particularly affected by chronic stress. The prefrontal cortex is essential in regulating the stress response. Chronic stress disrupts this mechanism and can affect important brain functions such as decision-making. It also reduces the hippocampus volume, a brain structure important for learning and memory. These changes make the amygdala, the emotional regulation structure of the brain, hyperactive to environmental stressors. In humans, these changes are associated with disorders such as depression and post-traumatic stress disorder.
Social isolation, commonly experienced by captive elephants and cetaceans, increases the brain’s response to environmental stressors. Social isolation increases normal cortisol levels, affects the brain’s neurochemicals, and results in changes in brain structure such as loss of brain volume in the prefrontal cortex.
Because both elephants and cetaceans are highly social animals by nature, putting them in isolated environments may be especially stressful and damaging to their brains and immune systems. Evidence of this may be seen in salmonellosis outbreaks among zoo elephants and candidiasis outbreaks among captive cetaceans, which are commonly observed following stressful situations. Meanwhile, elephants kept in larger enclosures and bottlenose dolphins whose enclosures offer access to ocean water flow have shown lower cortisol levels than their counterparts in less-enriched environments.
Stereotypic behaviors, observed frequently in captive animals, are also a response to chronic stress and seem to have formed as a way for animals to cope with an impoverished environment. For example, cetaceans may grind their teeth while elephants may display trunk swaying. In fact, environmental enrichment has been shown to reduce stereotypies for other animals including African lions, chimpanzees, and seals. Although it is known that stereotypies are linked to impoverished environments and social isolation, it remains unclear whether these responses are due to brain dysregulation or permanent structural damage to the brain.
In sum, experimental evidence in other mammals suggests that elephants and cetaceans in captivity experience multiple behavioral and health problems as a result of the environmental deficiencies, and stress, they face in artificial settings. When captive elephants and cetaceans cannot be rewilded, efforts should be made to relocate them into sanctuaries that can provide them with a more appropriate habitat. Reports from authentic sanctuaries show that rescued elephants display fewer or no stereotypic behaviors, are less aggressive, gain muscle mass, and make social bonds with other elephants.
In addition to supporting the shift to sanctuary housing, animal advocates can help by calling for more authentic sanctuaries around the world. There are only a few genuine elephant sanctuaries and one true cetacean sanctuary in existence. Having more of these facilities available will make it easier as advocates continue to push for the release of captive elephants and cetaceans.