Colo, the oldest living gorilla in the US, is turning 60 on Thursday, 22 December at the Columbus Zoo Reuters

Colo, the oldest living gorilla in the US, is turning 60 on Thursday, 22 December, having surpassed the usual life expectancy of captive gorillas by over 20 years. The mother-of-three was reportedly the first gorilla in the world born in a zoo.

Colo, who lives in the Columbus Zoo, also her birthplace, is a grandmother of 16, great-grandmother of 12 and great-great-grandmother of three. She is reportedly five years older than the oldest known living male gorilla in the US.

The western lowland gorilla surpassed the record for the longest-lived gorilla in 2012, when she celebrated her 56th birth anniversary. She will create the new record of surpassing the median life expectancy for female gorillas in human care, which is 37.5 years, the Associated Press reported.

Doctors attribute her extended life span to the medical advances made by zoos across the country. She has reportedly undergone a recent surgery to remove a malignant tumour and her doctors said she was recovering well.

Several other elderly zoo animals too are treated for pains, aches and other age-related ailments and the medical care is extending their life span and also ensuring a healthier life for them, according to the news agency.

"Colo just epitomises the advances that zoos have made, going all the way back to her birth at Columbus," Dr Tom Meehan, vice president for veterinary services at Chicago's Brookfield Zoo and veterinary adviser to a national gorilla species survival plan, told AP.

Ozzie, who is 55 years old and lives at the Atlanta Zoo, is reportedly the oldest known living male gorilla. There are several others around his and Colo's age across the US, whom veterinarians regularly treat for heart and kidney diseases, arthritis, dental problems and even cancer.

A 13-year-old rabbit called Emma at Seattle's Woodland Park Zoo reportedly receives acupuncture, massage, laser therapy, and heat and joint supplements to stay fit. Shanthi, a 42-year-old Asian elephant at the National Zoo in Washington suffers from arthritis and receives osteoarthritis therapy.

In San Francisco, a 27-year-old giraffe, Tiki, is one of the oldest living giraffes in the country, that receives foot care, massage therapy, acupuncture and chiropractic care in addition to traditional veterinary medicine, AP noted.