Lioness nurses adorable baby leopard in 'truly unique' cross-species interaction

The unlikely pair was seen in the grassland of the Serengeti Plain in Tanzania.

— -- An incredibly rare image shows the moment an adorable baby leopard suckled a lioness in Tanzania.

A guest at the Ndutu Safari Lodge in the Ngorongoro Conservation Area snapped the shots Tuesday in the heart of the Serengeti Plain of Tanzania.

Luke Hunter, the chief conservation officer for Panthera, an organization devoted to the conservation of wild cat species, said his jaw dropped when he received the photos of the unlikely pair from the tourist.

Interspecies adoption or nursing among big cats in the wild had never been documented, Hunter said. "This is a truly unique case," he added in a post for Panthera.

ABC News has been unable to reach Hunter.

Nosikitok is a 5-year-old lioness well known locally, and the leopard cub is estimated to be 3-weeks-old.

Hunter suggested that the tender and vulnerable moment came as a result of the lioness' recently giving birth to her own cubs.

"She is physiologically primed to take care of baby cats, and the little leopard fits the bill,” Hunter said. “It is almost exactly the age of her own cubs and physically very similar to them.”

But while cross-species nursing and adoption has been seen in captivity, Hunter said the odds are very low that this relationship will continue.

"It is very unlikely that the lioness' pride will accept it," he said. "Lions have very rich, complicated social relationships in which they recognize individuals -- by sight and by roars -- and so they are very well-equipped to distinguish their cubs from others. If the rest of the pride finds the cub, it is likely it would be killed."