He hasn't been a European Gorilla for many years but the ex-Howletts male Mumbah, who was sent to Columbus Zoo in the USA, has died there aged 47. Mumbah arrived at Howletts as a small baby and when I first saw him he was the youngest in their early group, and stayed as the 'baby' for sometime before other youngsters such as Bitam, Etoumbi, Founa, Mushie and Djoum arrived. He was later moved to Columbus as an adult male as he was 'surplus' at Howletts who had several other males. I remember seeing him advertised in the Inter Zoo News as a 'breeding male' though I had my doubts even then.
Though a 'quiet ' male he is supposed(?) to have sired one infant at Howletts- but he certainly never did at Columbus and he later acted there as the patriarch of the 'surrogacy' group. That indicates a very laid back/tolerant attitude to baby Gorillas not his own offspring.