Platypuses (Ornithorhynchus anatinus) live in burrows in stream banks, which they excavate with their powerful front legs. There are two kinds of burrow: one for shelter and one for incubation. The incubation burrows can be up to 18m long and rise 1-7m above the waterline. As part of the courtship ritual, females carry bundles of wet leaves to their incubation chamber, at the ends of the burrow. Females then plug the tunnel with soil and lay 1-3 eggs in the incubation chamber. The eggs hatch after ten days and the young stay in the burrow, where the mothers keep them warm and suckle them. They finally emerge after four months.
Males possess spurs on their hind feet that are attached to venom glands, which produce poison strong enough to kill dogs. These are thought to be used in fighting.