Gorillas are the largest extant species of primates. How long are their penises?

Explanation

Gorillas are the largest extant species of primates. The older male gorillas, called silverbacks, are enormous and can weigh up to 200 kg. A silverback lives in a troop with 5 to 30 females that he can copulate with all year round. There is not much competition as he is strong and easily able to protect his troop against other suitors. Despite his large size, a gorilla's penis is only around 4 cm long.