Captivity supporters often argue that we cannot know what captive cetaceans are feeling because they can’t speak to us. However, there are ways we can know whether an animal is experiencing stress. Stress is a response that affects animals both behaviorally and physiologically.
Analysis of behavior can be used to assess stress in both humans and other animals. When humans encounter stress, we experience the fight or flight response. We may lash out by becoming aggressive and short-tempered, or we may become lethargic and retreat in an attempt to flee the stressful situation. When we experience chronic stress, we may even develop nervous twitches, abnormal behaviors and destructive habits as we try to cope.
Animals react to stress in the same manner. Stress induced behavior like stereotypy, is commonly observed in captive animals, especially those that are large, free-ranging and/or social such as big cats, elephants, cetaceans and primates. Stereotypy is a result of boredom, distress, and frustration related to an abnormal or unnatural environment. If the animal cannot satisfy their natural repertoire of behaviors, they may try to ease the resulting tension by forming destructive habits and behaving abnormally.
Captive cetaceans in particular have been seen to exhibit stereotypy by vomiting, head bobbing, pacing or circling, self mutilation, biting on gates and bars, chewing at the environment, exhibiting lethargic and comotose-like behavior and tongue playing. Most visitors to marine parks mistakenly interpret these behaviors as idiosyncrasies or play, rather than indicators of stress.
Behavior isn’t the only way we can determine stress levels in animals. Stress also causes a physiological response. Scientists can get an idea of how an animal is feeling based on respiration rates, blood chemistry and hormone levels, and overall health. For example: The level of eosinophils (a kind of white blood cell) in one’s blood can determine the level of stress hormone (cortisol) in the body. Fewer eosinophils means that there is an over-production of stress hormone. One study found that wild bottlenose dolphins have higher eosinophils than captive bottlenose dolphins, indicating that the captives have higher levels of stress hormone in their bodies than their wild counterparts. Cetaceans also have higher stress hormones when subjected to certain procedures and situations such as capture, transport, husbandry procedures such as blood draws, removal from the water, social instability, and having swimmers present in their pool. It may come as a surprise that captive dolphins who are in contact with humans everyday, may be more disturbed by captive swim with dolphin programs than wild dolphins who experience swimmers in the ocean.
There is scientific evidence which demonstrates that elements in a captive cetacean’s environment, as well as the nature of captivity itself, is stressful to cetaceans. We cannot know whether or not animals experience stress in exactly the same way that humans do. However, we know that they do, in fact, experience stress and react to it in similar ways that humans do.
The question is not whether or not cetaceans are stressed in captivity. The question is whether or not Is it okay to subject cetaceans to stress for entertainment purposes.