The platypus is generally a solitary animal with its own specific home range in which it feeds and lives. The platypus is shy and wary. It tends to be a nocturnal creature and generally only leaves its burrow in the early morning and evening.
The platypus sleeps in a burrow for up to 17 hours a day. The average camping burrow is 1 - 3 meters longs with the entrance hidden underwater or just above the water level. An adult platypus uses its long claws to dig through the soft river banks. It is calculated that a platypus can dig one meter of tunnel in two hours. Grooming of the fur is very important and is done in the water as well as on the land.

The male and the female platypus reach sexual maturity at two years of age. The male is unable to produce sperm and the female is unable to produce eggs until that time. The breeding season is between August and October. During the breeding season the timid male platypus becomes aggressive toward other male platypuses. It is at this time that the spurs on the hind legs become venomous and are used to fight for territory and females. This venom is not fatal to man but does cause intense pain. Mating is thought to happen in the water. It is also suspected that the spurs on the hind legs of the male may be used to hold the female. Part of the courtship involves various swimming movements including the female swimming in a tight circle as the male follows her and hangs onto her tail with his jaws.

After mating the female leaves the male and builds a nesting burrow . This burrow contains twists and turns. She blocks the burrow with earth in one or more places. She will stay in this burrow during the laying and incubation of her eggs. The female platypus lays between two and three eggs. These eggs are about the size of grapes. She holds the eggs in the middle of her coiled body during incubation causing the eggs to often stick together. The babies are about 18 millimeters at hatching and do not leave the burrow until they are about 4 to 5 months old. At that time they are fully furred and about 34 centimeters long. Milk is produced in large glands under the female's skin. These glands can be up to one-third of her body's length. The milks seeps out onto a patch of fur from where the young nurse. The milk is rich in iron. This milk contains about 60 times more iron than cow's milk. It also contains about 40% solids compared to cow's milk which contains about 12% solids.

The platypus uses its electro-sensitive bill to locate its food in the water. Once it has food in its bill, it moves the food to its cheek pouches located behind the bill. When the platypus returns to the surface, it moves the pouch contents back to its bill. Then the platypus grinds the food using its grinding pads on the upper and lower jaws. Unwanted parts of food, such as shells, mud, etc are expelled through the horny serrations located on the sides of the lower jaw.