Much progress has been made in recent years to free chimpanzees from captivity, but despite these best efforts, some chimpanzees still remain in research labs, zoos, and other forms of captivity worldwide. Chimps are very similar to us, and yet we sometimes struggle to understand what they need when it comes to welfare: we can easily misinterpret certain visual cues (for example, the chimp “fear grimace” that looks like a smile), and we also often fail to understand that chimps are not simply big people. Welfare is measured in a variety of ways, from behavioral observation to measuring blood cortisol, and though there is some debate over how well caretakers can assess the welfare of captive animals, it is one of the few tools available.

This study, based on previous study with capuchin monkeys, was conducted at a zoo in Edinburgh, Scotland, as well as Fundació Mona in Girona, Spain. In both cases, the chimps had fairly sizeable enclosures, despite still being captive. The researchers wanted to know whether “chimpanzee subjective well-being and welfare states, such as stress frequency and physical health, are related,” and also how much chimp personality is “related to a more extensive set of welfare indicators.” The researchers collected welfare ratings, subjective well-being ratings, and personality evaluations in chimps, first to see how much staff agreed in their assessments, and then to see whether there were associations and relationships between ratings on the different scales. Curiously, they found that staff familiar with captive chimps tended to agree on ratings; also, they observed that chimps that played more rated lower in welfare. Though they found that welfare ratings stayed stable over time, there were no major changes in either observed group that might affect welfare. Through their various triangulations of ratings, they found that “emotional stability and sociability are pillars of primate happiness.”

The researchers suggest that such evaluations can be used to provide enrichment more efficiently, for example, “to identify chimpanzees at low risk, so that time resources dedicated to enrichment can be effectively allocated.” That may be useful information for zoos and other captive situations, but the results could equally be useful for sanctuaries looking after chimps into their “retirements.”