Think about the term, “animal welfare”, and what it means to you. When you encounter an animal – in any setting, be it a zoo, a friend’s house or even your own living room – are there certain cues that help you decide if you feel the animal is having a good or a bad time – or experiencing positive or negative welfare? It may be the animal’s appearance, behaviors, what the space looks like where they live, or perhaps it’s based on your knowledge about that species.

In some cases, it’s relatively easy to determine that an animal is in a poor welfare state. If they’re living in dirty and cramped conditions, don’t have access to social partners – or perhaps too many – or if they have obvious signs of injuries or illness without any indication they’re under veterinary care, it’s likely the animal is not experiencing good welfare. But when you look at other, less obvious factors, such as if the animal is quietly resting in a spacious habitat, or if the animal is moving back and forth in one area of their space, the answers are less clear.

The concept of animal welfare refers to an animal’s physical, mental and emotional states over a period of time. It is based on the individual’s experience, which can be different from one species to another, and from one animal to another. It is not about what is provided to an animal, such as food and water – this doesn’t automatically ensure good welfare. Although having access to these resources is critical to creating conditions that may lead to good welfare, it is actually how the animal perceives those conditions that determines their welfare. We can’t simply measure welfare in terms of square footage, gallons of water or the nutritional content of food items. We must use indicators from the animals themselves, such as behavior, physical condition and even emotional responses.

These indicators represent the three different concepts of welfare. The first has to do with an animal’s ability to engage in natural behaviors, or live in a way it has evolved to. The second involves biological functioning and prioritizes an animal’s physical health. The last focuses on the animal’s feelings and emotional states, with an emphasis on minimizing negative emotions and promoting positive ones. Should we favor one concept over another, it is possible we would miss something important to an individual animal.

If two people were to assess an animal using two different concepts, they could come to conflicting conclusions about that animal’s welfare state. This is why we incorporate aspects of all three of these concepts when evaluating animal welfare. This allows us to gain a much more holistic picture of the animal’s experience and to consider all of the factors that impact their well-being.

– Dr. Stephanie Allard is the director of animal welfare for the Detroit Zoological Society and oversees the Center for Zoo and Aquarium Animal Welfare and Ethics.