One of the longest San Francisco Zoo residents was euthanized Wednesday after the African Nile hippo, named Mama Cuddles, grew increasingly weak.

The hippo lived at the zoo for more than four decades, arriving in 1963 from Philadelphia Zoological Gardens at the age of 1. She was one of the zoo’s many elderly animals and was diagnosed with chronic arthritis in her hind legs in 2005.

She is the mother of 16 calves, which contributed greatly to help maintain the population.