Article Review: Sources of Stress in Captivity, Part II

Took me forever to get around to reading the rest of this article, this last term was pretty heavy. But nonetheless I haven’t forgotten about this thing, and it’s not like I have to keep an update schedule for my breathlessly waiting readers on here. So with that, let’s get back into it.

The second half of the article focused on more biotic and behavioral stressors, still mostly from a zoo perspective. This half was much more interesting, as the abiotic factors discussed in the first half were pretty simple. That’s not to say that they weren’t well explored and there wasn’t any new information presented, but I’m pretty sure it wasn’t hard for them to come to the conclusion that if we cook our captive animals on concrete on a hot day that it’ll cause stress. One of the neatest things when they were examining behavioral stress was that they always identified when a certain stressor was used as the definition of stress in other studies. Things such as separation from conspecifics and invasive handling were not only examined, but identified as the state of being “stressed” in other studies.

Both at the beginning and the end of this section they really hit the nail on the head for stress in capitivity.

“…the primary difference between such stimuli in nature and the same stimuli in captivity is in the animal’s ability to control it’s exposure to these stimuli…confinement in captivity brings with it a host of other potential stressors, largely in the form of restricted choice” (Morgan and Tromberg, 2007)

Like in The Matrix, it’s a problem of choice. Whether that’s removal of the choice to retreat from people or animals, of feeding time and meal composition, of which animals it shares space with, of mate selection, and obviously of home range/habitat selection. That’s the reason for stress in captivity as broadly defined as it can be. It makes sense, but they touch upon it again later when they discuss the roles of predictability for environment enrichment. Animals when given a choice will chose a predictable schedule over unpredictability, but there are conflicting results as to which one provides more benefits. Novelty  has been shown to be necessary for environmental enrichment: the provision of toys in stall horses greatly reduces stall vices/stereotypies such as cribbing and swaying. Stereotypies are also reduced in pigs with long pieces of straw to chew (see Grandin for perspective on this behavior). Novelty comes up in the article when discussing controlled things such as feeding and cleaning times, and uncontrolled factors like the number and behavior of visitors to zoos.

Human contact is discussed thoroughly as a stressor and enrichment. Social and domesticated species have been shown to benefit greatly from human contact, however other species display obvious detrimental effects.

“In one review of black rhinocerous breeding success in US zoos, animal mortality was positively correlated with the degree of public access to the animals.” (Morgan and Tromberg, 2007)

The only real trend is that the effect of human contact creates wildly different effects based on its nature. If the contact is social or feed associated, it can be great, but across the board, negative contact whether in treatment, handling, or painful/invasive medical procedures will make future contact with people a negative and stressful experience. The article does take a moment to clarify what they thought created a pleasant experience.

“Part of what pleasant handling appears to involve is meeting the animal on its own terms.” (Morgan and Tromberg, 2007)

Grandin talks about this a lot with how animals approach novelty with caution. They enjoy novelty because it turns on the SEEKING blue ribbon emotion, but if that novelty moves beyond what they’re ready to explore, they crank on the FEAR emotion and the novel thing becomes stressful.

So, given everything examined, how do we fix it? That depends on your goals. If you want to create a zoo/farm that keeps the animals at the same stress level as them living in the wild, you better work at Yellowstone (and even then!). It’s really not going to happen. So let’s say we set some reasonable goals, like wanting to reduce pacing stereotypies in our larger animals. So, how do we identify the stressors in those enclosures?

“Many of the stressors reviewed above produce the same or very similar effects on animals…This ambiguity makes such behavioral and physiological responses unreliable symptoms for troubleshooting a given captive situation” (Morgan and Tromberg, 2007)

All we get is that something is wrong, but have no idea what. It’s like saying a person or animal has nausea, diarrhea, and fever. Helpful, we now know it could be one of a thousand issues that all cause those symptoms, more information is needed to make an appropriate diagnosis. In all honesty, other than some simple species specific observations, it comes down to individuals. Some will do better in captivity than others, and some will respond to changes you make to minimize stress better than others. The article mentions that if your goal is a conservation effort, captivity can promote learned helplessness, which results in the loss of adaptive coping strategies. There’s a lot of issues with conservation efforts: loss of genetic diversity (cheetahs), over-success (grey wolves), and loss of natural adaptability and wild behaviors (pandas). Learned helplessness can be useful or at least non-detrimental with respect to domesticated species, but anything you intend on reintroducing to the wild may have issues.

Perhaps (unless it’s a conservation effort) we should just resign ourselves to the fact that when we put animals in a zoo, we are domesticating them. Part of the lure of the zoo is to see wildlife in a controlled setting, but there’s an oxymoron there. Wildlife is out of our control, deer that have problems giving birth die, and predators won’t discriminate between a keystone species and other food options (oh if only we could keep all the salmon to ourselves). Maybe the new direction should be not to impersonate nature, but promote behaviors that inherently make zoo life less stressful for those animals. The article briefly mentions “contrafreeloading” behavior, in which animals will choose to work for a food reward even when it is offered freely. I want to bring up circus animals and how, even though many inhumane techniques have been used to teach them the tricks they do, many of them have been selected for their willingness to do a shapeable behavior or to work with items. We could be selecting our zoo animals for their willingness to participate with handlers and items, and we could provide enrichment through allowing them to work for their rewards. This is accepted with marine mammal exhibits where wild whales, dolphins, sea lions, and anything else we can seemingly fit in a tank receives enrichment in this way (not to say that swimming stereotypies still don’t exist). You can’t argue that we’re attempting to keep their wild habitat and behaviors with three shows a day jumping through hoops. I would need to read more on the subject to provide a supported discussion, but that’s my feeling. And that’s the end of that article, I highly recommend reading through it, but be prepared for a grind, it’s a long one.

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