The tiger is one of five land predators with the greatest proportions of threatened prey whose plight was highlighted by researchers.
Half of the animals it hunts in the wild are on the International Union for Conservation of Nature red list of threatened species.
The other most at-risk carnivores were the clouded leopard, with 60% of its prey threatened, the Sunda clouded leopard (50%), an Asian wild dog, the dhole (42%) and the Ethiopian wolf (40%). The scientists compiled a list of 494 prey species that provided food for 17 large carnivores including the lion, tiger, leopard, cheetah, grey wolf, Eurasian lynx and spotted hyena.
Of the prey species, a quarter were on the red list. Of these, 14% were classified as vulnerable, 9% endangered and 2% critically endangered. Large carnivores that were themselves on the red list were more likely to have threatened prey. On average, 27% of their prey was threatened compared with 19% for non-red list carnivores.
The researchers, led by Christopher Wolf from Oregon State University College of Forestry, wrote in the journal Royal Society Open Science: “Abundant terrestrial mammalian prey are required for the survival of large carnivores.
“In fact, there is a strong relationship between prey and carnivore abundance — approximately 10,000kg of prey supports about 90kg of large carnivore biomass, regardless of species.
“When sufficient prey is unavailable, large carnivore populations will decline, possibly becoming locally extinct,” he said.
Carnivores deprived of prey may come into conflict with humans as they raid farms for livestock or stray into highly populated areas, said the scientists.
Large predators were said to be “ecologically important” as a group of species. As well as keeping crop-damaging herbivores in check, they played a vital role in attracting tourists to developing countries. The scientists concluded: “These results show the importance of a holistic approach to conservation that involves protecting both large carnivores directly and the prey upon which they depend.”