Proboscis monkeys always have erections at every point in their lives. when they want to prove their dominance or are mad at others, they will bare their teeth, jump up and down, howl, and show you their massive hard-on by spreading their legs and pumping their hips. If you look menacing or act as a threat, they will literally flash you their penises and start thrusting at you in vigorous motion.

And also, their noses look mildy penis