The BBC reports that the largest species of cat, the Amur tiger, has an effective population of less than 50 animals:
They sampled nuclear DNA found within the scat samples of an estimated 95 individuals found throughout the Amur tiger’s range, likely constituting up to 20% of the remaining population.
The study sampled the amount of variation within the DNA from more tigers, across a broader geographic, than any previous research.
“Although the census population size of Amur tigers is closer to 500 individuals, the population is behaving as if it were the size of 27 to 35 individuals,” says Russello.
That’s the lowest genetic diversity ever recorded for a population of wild tigers.