A three-year review of data published in the scientific journal PeerJ this week challenges the conventional assumption that the iconic and famously elusive spotted cats are thriving in the wild.
It finds leopards have almost disappeared from vast ranges in China, Southeast Asia and the Arabian peninsula while African leopards confront mounting challenges in the north and west.
The big cats are threatened by spreading farmlands, declining prey, conflict with livestock owners, trophy hunting and illegal trade in their skins and teeth.
Their rangelands have shrunk from 35 million square kilometers (13.5 million square miles) in 1750 before the colonization of Africa and the spread of firearms to about 8.5 million square kilometers (3.3 million square miles), the study estimates.
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It will be used to update the endangered species list curated by the International Union for the Conservation of Nature, among several groups that conducted the study.
Others include the National Geographic Society's Big Cats Initiative, the wild cat conservation organization Panthera and the Zoological Society of London.
Its findings are "a shock as leopards were often believed to be more adaptable to human impacts ... Than other species such as tigers and lions.