Seymour Simon has written over 200 award-winning science books about animals, anatomy, astronomy, earth science, and vehicles! Learn about man's closest genetic relatives! Did you know that... Just like humans, gorillas can shriek, chuckle, hiccup, and even belch. Families of gorillas can have as few as two members or as many as thirty-five. Unlike in the movies, gorillas aren't mean or dangerous-they're actually quite shy. Gorillas weigh four to five pounds when they're born; fully grown, they can weigh more than four hundred pounds.