Kakinga was known as the gentle giant among the zoo’s gorilla population, and will be missed after passing away on Saturday at the age of 37.

The zoo’s veterinary team says he died due to a tear in his aorta that caused heart failure, which is the most common cause of death for male gorillas.

Gorillas normally live to be about 31 years old in captivity, so Kakinga was a rarity. He was born in 1978 at the Jersey Zoo in the United Kingdom and came to live in Calgary in 1984. He became the dominant male, or silverback, in 1993 and sired 13 offspring during that time. Eight of those offspring survived, with the most recent being born just this past March.

Kakinga was well-loved by zoo staff for his calm and gentle nature and was a protective and nurturing father to his offspring.

The Calgary Zoo is asking that anyone who wants to express their condolences can do so by recycling an old cell phone, as this small action will help protect wild gorilla habitats and allow the species to thrive.