Assessing the big picture in animal well-being

In our last Animal Science Blog, we examined how observations can provide useful insight into animal behavior. Watching animals and recording what they are doing is a great first step in determining their welfare. However, these indicators allow us to get just one snapshot of the bigger picture. Other parts of the same picture are sometimes less evident. Consequently, animal welfare science is complex. As scientists, we try to get at that big picture by taking multi-level approaches to ensure that we are meeting all of our animals’ needs.

These multi-level approaches include aspects of psychology, biology, ethology, and even computer sciences, which offer many possibilities to assess welfare and the affective states of our animals at Zoo Atlanta. Thus, our assessments of affective states can include physiological and biological measurements, preference tests, consumer demand/motivation tests, cognitive assessments, and of course behavioral observations. These assessments are all useful to understand our animals’ needs and the start of resolving welfare questions. Let’s talk further about two of these approaches: Physiological assessments and preference tests.

Physiological assessments use indicators such as hormones (i.e., cortisol) or other parameters such as heartrate to determine welfare. Changes in hormonal levels can be useful because fluctuations can indicate an appropriate response to stimuli and can be compared to established baselines. Cortisol is a hormone that is related to arousal—either excitement or stress. Measured along with other parameters, it can help scientists understand which one an animal is experiencing. Like most welfare assessment methods, physiological parameters should not be used solely to assess welfare due to contextual contradictions. Different situations can elicit the same response of elevated heartbeat and cortisol levels, but do not necessarily mean the same thing. Cortisol can be collected via saliva, fecal samples, or blood. Because we don’t do invasive research at the Zoo, we mostly use fecal samples. To use saliva, animals have to be specially trained to voluntarily participate.

Preference tests are also another way to measure animal welfare. In this type of assessment, animals are often given the choice between two or more resources, such as choice of food or bedding. We can offer our gorilla Floyd three options of either wood wool, shredded fabric, or hay as bedding material and then adjust his bedding preference to his selection. We can also determine how strong these preferences are by using motivation tests—for example, we can test how much harder an animal will work to access a highly preferred resource. Let’s say Floyd’s favorite bedding item is wood wool, so now we put all options behind weighted doors. We’d expect that Floyd will accept these higher “costs” (which is why motivation tests are also known as consumer demand­—a theory in economics) to access his favorite resource. Like other assessments, preference tests need to be carefully designed. Preferences can change, so results from these tests shouldn’t be taken as final. Offering only two choices in tests such as these may just show that an animal chooses one over the other—but there might be other options that are more preferred. Perhaps Floyd’s preference is an unknown fourth option and he has chosen wood wool simply because it is better than the other two choices but is not truly preferential. Ideally, more than two items should be involved in a preference test for this reason.

Although each of these various approaches individually provides some relevant aspects of animal well-being, it’s when they are combined that we can start to create that big picture that we need to assess overall well-being. Researchers at Zoo Atlanta strive to see the big picture so that we can make informed decisions on the care and well-being of our animals using approaches and assessments that put our animals first.

Alexz Allen
Research Assistant