''The study of animal pleasure is the behavioural study of positive experiences in animals. Hedonic ethology acknowledges that animals are aware and that they are sentient. It uses the same sorts of methods ethologists use but the focus is to examine rewarding experiences in its subjects.
Hedonic ethology is an ethical science that regards the animals' interests are paramount. To deem otherwise would be to undermine its premise which is that animals feel and that their lives matter to them. ... To the extent that we recognize animals as being capable of feeling pleasure and joy, and pain and suffering, we also assume some moral responsibility to treat them accordingly. It is sentience, not language, theory of mind or any other attribute seeking to distinguish between animals and humans, that crucially qualifies an individual for moral protection.
Hedonic ethology seeks to build on a growing awareness of animal sentiency and develop the idea that animals are pleasure-seekers into a more ethical science of animal behaviour. ... Boredom is one of the most serious welfare problems for captive animals. To the extent that captive studies can provide positive stimulation (foraging challenges, social engagement and opportunities for play) for animals faced with the monotony and confinement of captivity, a zoo-based branch of hedonic ethology is encouraged.
The animal kingdom is teeming with an enormous variety of breathing, sensing, feeling creatures who are not merely alive, but living life. Each one is trying to get along - to feed and shelter themselves, to reproduce, to seek what is good and avoid what is bad. There's a diversity of good things to be gotten: food, movement, water, rest, shelter, sunshine, shade, discovery, anticipation, social interaction, play and sex. And because gaining these goods is adaptive, evolution has equipped animals with the capacity to experience their rewards. Like us, they are pleasure seekers.''
Excerpts from Jonathan Balcombe's Pleasurable Kingdom
Ethologists for the Ethical Treatment of Animals