Researchers unearthed seven mummies along with the bones of 54 other leopards from a site near the city of Arar.
Mummification prevents decomposition by preserving the bodies of the deceased. Egyptian mummies are the most famous example, but this process can also occur naturally in places like glacial ice, desert sand, and swamp mud.
"It's something I've never seen before," said Juan Madurel-Malapera of the University of Florence in Italy, who was not involved in the discovery.
According to the new study published Thursday in the journal Communications Earth and Environment, researchers are unsure exactly how these leopards were mummified, but the dry conditions in the caves and the stable temperature may have played a role.
They also don't know why there are so many leopards in the caves. Perhaps they were dens where the mothers gave birth and raised their cubs.
It is unusual for large mammals to be preserved to this extent. In addition to being in a suitable environment, the carcasses must also avoid becoming a meal for hungry scavengers such as birds and hyenas.
