Article Review: Sources of Stress in Captivity, Part I

I’ve been hanging onto this review of literature for a long time, it’s about 40 pages long, so I’ve slowly gotten about half way through in my spare time. I’ve decided to break down my thoughts into two posts, not only for the length of the article, but so that I don’t have to essentially write an essay all at once.

Most of the article is written from a zoo perspective, but they do take time to review bits of literature pertaining to domestic livestock. One of my favorite things about this article so far is how they chose to define stress and stressors.

“Stress will be defined as the experience of having intrinsic or extrinsic demands that exceed an individual’s resources for responding to those demands.”

“A ‘stressor’ is anything that challenges homeostasis…in this case may be an actual physical challenge to homeostasis (such as exposure to a sudden change in temperature, physical restraint, or combat) or the threat of such a challenge (such as a direct stare from a more dominant individual, or the approach of a human with handling gloves). In either case, stressors result in a cascade of physiological events designed to prepare the body for homeostatic challenge – the so-called ‘fight or flight’ response.”

I immediately read that first definition of stress and said to myself “yes, that’s what it is”. Mostly in terms of whenever I want to define how I feel stressed. But in reality, I was much more impressed with the definition provided because “stress” is such a catch all term for essentially anything wrong with an animal or it’s environment. I remember working at the animal shelter and being told that most of the diarrhea we saw in healthy cats and dogs in the shelter was a result of “stress.” While that may have been true in many cases, the employees, myself included, used the word stress to essentially explain any question proposed by visitors regarding abnormal behavior from the animals. We gave them the assumption that we knew something they didn’t, and usually the issue was dropped. Without a clear definition of what exactly “stress” meant to those shelter animals though, we had no way of asking the important question, what is causing this animal to be stressed?

We never thought, other than taking basic care of these animals to maintain health, hygiene, and human contact; about what we should be doing to keep them mentally sound. With all the behavior and minor health issues we crossed off as stress induced, we never made an attempt to cure that. It’s not that we didn’t care, but in hindsight it’s just something that wasn’t explored or audited. When I think about it now there was probably a lot of little things that we could have been done if we had just asked the question, instead of just assuming that all stress was inevitable.

I bring this up because I’m sure that other organizations, whether they be animal shelters, veterinary clinics, small farms, or large animal production facilities might have that same oversight. Just providing yourself with a concrete, identifiable definition of stress causes you to move onto the next big one, what are the stressors?

So far in the article I’ve read the sections on abiotic stressors, which included lighting, ambient temperature, sound (ranges and pressure), odors, and tactile interaction with the environment. These are actually harder to work with in my opinion, biotic factors are easier for us to understand and study from a physiological standpoint. Figuring out the umwelt of different species is something that Temple Grandin says she does by thinking in pictures, but I think it goes beyond that. The sheer amount of Olfactory cues that we can only observe animal reactions to tell me that the sensory overload our livestock animals receive every day is beyond something as simple as changing the lighting alone. It’s like explaining the instant assailment of information that flows into your mind when you look at a classroom. Or trying to explain how (literate) people can see words on highway signs and with a single look compute the meaning of those specific shapes. How can we get into the head of a cow and understand how that whiff of estrus urine translates into information?

Anyway, some of the bigger problems noted in the article were flicker rates in florescent lighting that animals can see, extremely high sound pressure in zoo and agricultural settings from both machinery and people (that doubles what would be found in a natural setting), and problems associated with the materials used to create habitats or bedding. As a potential start to a solution, at the end of the abiotic section they make recommendations on what sort of equipment (and where to get it) should be used to measure these factors and potential stressors. Identification of what we know is the first step, so that new options and unforeseen stressors become more obvious.

I’ll have much more to say on this article in part II, but I’ll leave these preliminary thoughts for now. Look for more on this from me soon.

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