A Missouri conservation center heralded for helping repopulate endangered wolves is tending to its latest puppy season.

But this year's spring ritual has a bittersweet vibe. That's because the furry matriarch of the Endangered Wolf Center near St. Louis is gone, and staffers consider the loss noteworthy.

Anna, a Mexican gray wolf, died last month of day shy of turning 14. Her 41 puppies over four litters came to symbolize the center's quest to save North America's rarest subspecies of gray wolf.

The Mexican gray once numbered in the thousands in the Southwest before being nearly wiped out by the 1970s. The center's executive director says the 110 now said to be in the wild all have genetic ties to her nonprofit.