Platypus Reproduction & Eggs

Instructor: Julie Zundel

Julie has taught high school Zoology, Biology, Physical Science and Chem Tech. She has a Bachelor of Science in Biology and a Master of Education.

You probably know the platypus is a strange critter, but you probably have no idea how strange. This lesson will examine the world of platypus reproduction, complete with mating habits, strange facts and egg laying information.

What Is a Platypus?

The platypus is evidence that Mother Nature has a sense of humor. Imagine a duck, an otter, a beaver, a snake, and a lizard being smashed together in Frankenstein form to create a critter, and voila, you have a platypus. While the platypus does look like a bunch of other animals that were hastily stitched together, technically it's an egg-laying mammal that inhabits freshwater lakes and rivers.

An artistic representation of a platypus

It's about the size of a house cat and belongs to a group of animals known as monotremes, which are egg-laying mammals found in New Guinea and Australia. The platypus is probably the most famous monotreme, but spiny anteaters also belong to this group.

Spiny anteaters and platypuses belong to the group Monotremes

Platypus (the plural is platypuses, or simply platypus, not 'platypi') mating is another thing that makes this creature such an oddity. Let's start with the platypus battle.

Platypus Battle and Mating

Platypus mating season lasts from June through October and they reach sexual maturity at two years old. In preparation for the upcoming mating season, the testes in platypus males begin to swell. In keeping with their Frankenstein motif, male platypus have spurs on their back legs that are filled with a toxic venom. This venom can be used as a defense mechanism against predators, but it is also used against other males during these mating season fights. During these battles, one male will wrap his legs around an opponent, and stab him with the venomous spurs. The loser will be temporarily paralyzed from the venom, while the victorious platypus male can go forth and mate with the female.

Of course before mating, the male must win over the female, and he does so with some cuddling, some bill nuzzling, circling her, and placing her tail in his mouth. You might argue that these tactics aren't likely to win over anyone, but (lucky for the male) platypus females are not choosy.

The female signals she is ready by biting the male's tail. He responds by biting her tail, and then they both swim in circles. Before we get into the specifics, it should be noted that the reproductive features of the platypus are a little different than you might expect. Just like amphibians, birds and reptiles, platypus have a single body opening, called a cloaca, that is used both to remove waste and for reproduction.

When they're mating, a penis comes out of a sac near the male's cloaca. The male will bite the female's neck, hold her down and insert his penis into her cloaca. Mating usually occurs in the water with the help of some submerged object, like a piece of wood or large rock. After mating, the two will hang out together for about an hour (during which more mating may occur), and then the male will leave to find a new mate. Because they mate with multiple partners, platypus are considered polygamous.

Eggs and Hatching

Now that the deed is done, the female is left to raise her babies alone. She begins by digging a den or burrow, and will actually seal herself inside before she lays her eggs. Typically 2 to 4 soft-shelled eggs are laid around 27 days post-mating. After laying the eggs, the female will incubate them for about ten days, and then they hatch.

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