Despite decades of research into humpback whales, male genital exposure is rare. Mating had never been recorded by humans until two photographers captured the interaction of a pair of male whales off the coast of Hawaii, according to the Guardian .

The photo by Lyle Krannichfeld and Brandi Romano is the first evidence of same-sex behavior in humpback whales. Homosexual behavior is fairly common in the animal kingdom, having been previously documented in dolphins and killer whales.

Stephanie Stack, a specialist at the Pacific Whale Association and lead author of the study published on February 27 in the journal Marine Mammal Science, said the mating behavior of humpback whales has remained largely a mystery. "This discovery changes our understanding of humpback whales. While we have long recognized the complex social structures of these remarkable animals, witnessing homosexuality between two males is a unique and remarkable experience," Stack said.

Humpback whales grow up to 16 metres long and weigh 36 tonnes, the same as several buses. They spend the summer feeding in the polar seas before migrating to warmer tropics in the fall and winter. Once threatened by commercial fishing boats, humpback whale numbers have rebounded in recent years.

During mating in Hawaiian waters, one whale holds the other by its pectoral fins. The whale below appears frail, emaciated, and covered in parasitic lice. The humpback whale’s penis is often hidden in its genital opening to help it swim more efficiently. According to Stack’s research, marine mammals like humpbacks may mate to practice reproductive behavior, form social alliances, or demonstrate dominance.

An Khang (According to Guardian )