Image copyright Reuters Image caption At 60, Colo outlived most captive gorillas by more than two decades

The oldest known gorilla to be born in captivity, a female named Colo, has died in the US aged 60.

Colo passed away in her sleep overnight at the Columbus Zoo and Aquarium in Ohio, less than a month after celebrating her birthday.

She was born at the zoo in December 1956 and is believed to be the first gorilla ever born in captivity.

Colo, a Western lowland gorilla, lived for more than 20 years longer than the average captive gorilla.

Despite recently having a malignant tumour removed, zookeepers said that she had been recovering well and the cause of her death had yet to be determined.

Columbus Zoo and Aquarium said in a statement that Colo was "an ambassador for gorillas" who "inspired people to learn more about the critically endangered species".

Media playback is unsupported on your device Media caption Colo the gorilla enjoys her birthday cake

"Colo touched the hearts of generations of people who came to see her and those that cared for her over her long lifetime," the statement read.

The zoo added that Colo is to be cremated, with her ashes buried on site.

In December, hundreds of people visited Columbus Zoo and Aquarium to sing Happy Birthday and watch Colo, a great-great grandmother, enjoy her cake.