The lions and leopards of Gir National Park, in Gujarat, India, normally do not get along.

“They compete with each other” for space and food, said Stotra Chakrabarti, a postdoctoral researcher at the University of Minnesota who studies animal behavior. “They are at perpetual odds.”

But about a year ago, a young lioness in the park put this enmity aside. She adopted a baby leopard.

The 2-month-old cub — all fuzzy ears and blue eyes — was adorable, and the lioness spent weeks nursing, feeding and caring for him until he died. She treated him as if one of her own two sons, who were about the same age. This was a rare case of cross-species adoption in the wild, and the only documented example involving animals that are normally strong competitors, Dr. Chakrabarti said. He and others detailed the case last week in the ecology journal Ecosphere.

The paper’s authors, who also included a conservation officer and a park ranger, first spotted the motley crew in late December 2018, hanging out near a freshly killed nilgai antelope.