There are relatively few animals that mate for pleasure. A number of animals mate for life, but that does not mean they necessarily mate for pleasure. It seems to be the case that the only animal species that mates for pleasure, aside from humans, are dolphins. Depending on how "pleasurable mating" is defined, however, the bonobo chimpanzee of Central Africa could also be included.
Definition of Pleasure
The majority of animals engage in sexual intercourse solely with regards to species propagation. That is, they mate to survive as a species. When considering which animals, other than humans, mate for pleasure, the term "pleasure" must be defined. Given the dearth of data regarding complex animal emotions with regards to sex, pleasurable intercourse is narrowly defined as intercourse without the intention of reproduction or intercourse outside of specific mating seasons.
Mating, for the vast majority of animal species, requires a great deal of time and energy. The act cannot be a frivolous one, especially given that most species experience a narrow mating season. An array of conditions must be optimal for both the males and females of a set species to begin the ritual. They may emit a particular odour or noise once they are fertile. This requires a great deal of energy that cannot be summoned on a whim. Therefore, the notion that they can mate solely for the pleasure of mating is out of the question. Only two animal species seem to mate without needing these ritual windows and indicators: dolphins and bonobo chimpanzees.
Dolphin Sexual Behavior
According to researchers, Quincy Gibson and Janey Mann, at the Department of Biology at Georgetown University, dolphins "show bisexual philopatry." They make sexual attachments to members of both sexes within a dolphin pod. These attachments are frequently engaged in and seemingly for no other reason than for simple gratification. Despite the fact that dolphins take lifelong mating partners, both sexes have been known to engage in indiscriminate sexual behaviour akin to adultery.
Bonobo Sexual Behavior
If the definition of "pleasure" is intercourse that does not coincide with fertility cycles, then the bonobos of the Congo could qualify as animals that mate solely for pleasure. Also known as pygmy chimpanzees, these mammals are known to engage in sexual contact, even when the female is not fertile. Nonfertile intercourse is typically initiated by the male and seemingly tolerated by the female. There is no evidence that females initiate indiscriminate sexual intercourse outside of their fertility cycles.