My buddy did this at a zoo once, when he was separated by the unbreakable glass of the gorilla enclosure. He is an idiot. He was probably 37 years old at the time. He started hopping up and down and pounding his chest. A gorilla quickly closed the distance between him and the glass and pounded his giant ape fist to the glass, creating a loud and echoing sound. Then the gorilla just stood there and stared him down. The glass didn't crack or break, but my friend said he had never been more scared in his life. He quickly walked away with his figurative tail between his legs while trying to catch his breath, wondering how he could have been so stupid.

cc' Conrad Chestnut
Owner at Fire Suppression Company

Awaoyelmoni:
My buddy did this at a zoo once, when he was separated by the unbreakable glass of the gorilla enclosure. He is an idiot. He was probably 37 years old at the time. He started hopping up and down and pounding his chest. A gorilla quickly closed the distance between him and the glass and pounded his giant ape fist to the glass, creating a loud and echoing sound. Then the gorilla just stood there and stared him down. The glass didn't crack or break, but my friend said he had never been more scared in his life. He quickly walked away with his figurative tail between his legs while trying to catch his breath, wondering how he could have been so stupid.

cc' Conrad Chestnut
Owner at Fire Suppression Company

Why was your friend scared? Is he not a man?

It's a challenge which means he's dominant. No self respecting silver back will tolerate that. In the wild, your friend would have been trashed to shreds with broken bones or even death.
Alpha Males!