https://www.theguardian.com/environment/2024/feb/28/humpback-whales-sex-photographed-homosexual-behavior

During the intimate encounter photographed in Hawaii, one of the whales was seen to be holding the other in place with its pectoral fins while penetrating it. The whale underneath appeared to be ailing, being noticeably emaciated and covered in whale lice, white-colored parasites sometimes found on cetaceans.

They have pictures.

According to the new research paper, cetaceans such as humpback whales could use the genital slit or anus for same-sex copulation, to practice reproductive behaviors or to form a social alliance or assert a sort of dominance. The study has been published in the Marine Mammal Science journal.

It can't be that animals are having sex for fun. There must be a rational explanation for why someone would have sex other than pleasure.