It's a big day at the San Francisco Zoo! The zoo is celebrating the 45th birthday of Elly, who has officially become the oldest black rhinoceros in North America.

While the exact date of Elly's birthday isn't known (she was born in the wild), she has lived at the SF Zoo since April 1974. The average life span for a black rhino in the wild is about 16 to 20 years, which makes Elly REALLY old. 

On the momentous day, Elly, who weighs an impressive 2,000 pounds, was treated to a special cake of rolled oats and molasses as well as a feast of corn, beets and bananas — some of her favorites. 

Over her long life, she has given birth to 14 calves, helping raise numbers for her critically endangered species.

The second-oldest black rhino in North America is about 38 years old and lives in Miami. There are only about 60 black rhinos in North America zoos.