(NewsNation) — Scientists captured images of humpback whales mating for the first time ever and discovered the two whales in question were both males.

The photographs, published in “Marine Mammal Science,” are unique because copulation between humpback whales has never been photographed during decades of research on the species. The animals were spotted off the coast of Hawaii by two photographers on a private boat.

Scientists confirmed the whales in the images were both male based on photographs of their tail flukes and genital regions. One whale in the encounter appeared healthy, while the other was thin, covered in lice and appeared to be suffering a jaw injury.

Animals, including whales, may engage in non-reproductive mating behavior for a variety of reasons, including enjoyment, social bonding or asserting dominance. In any number of species, including primates, penguins, dolphins and birds, mating behaviors between animals of the same sex have been observed.

While many animal species have been seen engaging in homosexual behavior, scientists don’t classify animals as gay because the word comes with social and political connotations that don’t apply to animals.

Humpback whales can measure up to 52 feet long and weigh as much as 36 tons. A male whale’s penis can be as long as ten feet, though they are rarely observed by scientists as they are usually concealed in a genital slit.

One of the whales in Hawaii could be seen holding the other whale in place with its fins while penetrating it. Prior to the act, the two whales had circled the boat, one pursuing the other. After the pair finished, the healthier whale dove off and disappeared, while the weaker whale lingered near the surface before also swimming away.

Scientists noted that the images raise more questions, including the motivation for the behavior and whether two healthy male whales would behave the same.