Story highlights There are only six northern white rhinos left in the world

Suni was the only male left of his kind that could mate

Now there is only one, plus two females

Mating has not happened often, but conservationist still hope for offspring

(CNN) Unique? Suni was much more than that. He was vital to the survival of his kind.

So, on Friday, after rangers found the northern white rhino lifeless in his hut on a Kenyan wildlife conservancy, a short countdown to extinction began.

Suni was one of only seven northern whites left in the world, all of which live in captivity. There are none known to be left in the wild.

More importantly, Suni was one of only two breeding males left, said the Ol Pejeta Conservancy in a statement.

Now the conservationists have but one male and two females that can breed. And that doesn't happen often. When Suni mated with female Najin in April 2012, it was her first time in ten years.

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