'She is so old': One-eyed wolf in Yellowstone defies odds by having 10th litter of pups in 11 years

The alpha female of a Yellowstone gray-wolf pack has defied the odds by having a 10th litter of pups at the age of 11. 

The one-eyed wolf elder, named Wolf 907F, gave birth to her latest litter last month, the Cowboy State Daily reported. Gray wolves (Canis lupus) have an average life span of three to four years, so it's rare for them to reach 11, let alone have pups at that age. 

Wolf 907F has given birth to pups every year for a decade straight since she became sexually mature, which Kira Cassidy, a research associate at the Yellowstone Wolf Project, said is likely a record for the wolves of Yellowstone National Park. 

"Every day, I expect that she might die just because she is so elderly, but I've been thinking that for the last few years, and she keeps going," Cassidy told Live Science.

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Cassidy has calculated that only about 1 in 250 wolves in Yellowstone make it to their 11th birthday, with just six recorded examples since wolves were reintroduced to the park in 1995. The oldest of all of these great elders lived to 12.5 years, according to the National Park Service.

Wolf 907F is the oldest wolf to have lived her whole life in the park's Northern Range, where there is more prey but also more competition from other wolves. Wolves rarely die of old age in the wild, and in Yellowstone National Park, the biggest threat is other wolves.