Which male mammal has a poisonous spike that sticks out of its hind leg?

The male mammal with a poisonous spike that sticks out of its hind leg is the platypus.

This spike, called a spur, is located on the inside of the hind leg, and it's only found in adult males. The spur is connected to a venom gland, and the venom can be painful and even dangerous to humans.

While the platypus is a fascinating creature, it's important to remember that their venom is a defense mechanism and should be respected.