A wild lioness was photographed nursing a leopard cub in Tanzania on Tuesday, the first documented instance of such cross-species behavior.

“This is a truly unique case,” wrote Dr. Luke Hunter, Australian biologist and President and Chief Conservation Officer for Panthera, a global wild cat conservation organization, in an email.

The lioness, known as Nosikitok, is 5 years old, and the leopard cub is about 3 weeks old, said Susie Sheppard, Media and Digital Marketing Director of Panthera. The two were found in the Ngorongoro Conservation Area of Tanzania, a protected area known for its lion population according to its website.

“I know of no other example of inter-species adoption or nursing like this among big cats in the wild,” wrote Hunter.

The lioness recently gave birth to her own cubs, which means that she is “physiologically primed” to take care of baby cats, said Hunter. He added that her own cubs look very similar to the baby leopard and are of similar age.

“Even so, there has never been another case like it,” said Hunter. “Why it has occurred now is mystifying.”

However, Hunter was doubtful that the leopard cub would survive for much longer.

“Lions are very well equipped to distinguish their cubs from others,” Hunter wrote. “If the rest of the pride finds the cub, it is likely it would be killed,” he wrote.

Get our Space Newsletter. Sign up to receive the week's news in space. Please enter a valid email address. Sign Up Now Check the box if you do not wish to receive promotional offers via email from TIME. You can unsubscribe at any time. By signing up you are agreeing to our Terms of Use and Privacy Policy . This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply. Thank you! For your security, we've sent a confirmation email to the address you entered. Click the link to confirm your subscription and begin receiving our newsletters. If you don't get the confirmation within 10 minutes, please check your spam folder.

Contact us at letters@time.com.