Luke Hunter, president and chief conservation officer of the global wild cat organisation Panthera, received an email last week from one of his group's partners in Tanzania. When he opened the attached photos, Hunter said, "My jaw just dropped."

The images show a lioness lounging on a flat, dry spot in the Serengeti. Attached to her is a nursing cub - and the cub is a tiny, spotted leopard.

A leopard cub nurses from a lioness known as Nosikitok in Tanzania's Ngorongoro Conservation Area. Credit:Courtesy of Panthera/Washington Post

This is the sort of sighting that is pretty much mind-blowing to lion experts such as Hunter. Interspecies suckling has been documented among captive animals, and on very rare occasions wild carnivores such as leopards and pumas have been known to adopt an orphaned cub of their own kind, usually one that is related. But never before has interspecies suckling among large carnivores been recorded, Hunter said (and he checked the literature).

"It's unprecedented," he said, almost gushing. "It's a once-in-a-lifetime event."