Which Animals Lay Eggs?

mammals that lay eggs

How Two Strange Mammals Reproduce by Laying Eggs.

A major defining trait for mammals is that they reproduce by giving birth. Mammals also share other characteristics like feeding young ones through breast milk and having warm blooded bodies which basically means that they can regulate their temperature through internal processes. Humans are mammals as are lions, antelopes, tigers and even whales.

However, there exists a sub-group of mammals that refuse to be categorized with other mammals because they reproduce by laying eggs instead of giving birth. This group is called monotremes and it consists of only two animals in the whole world: the spiny anteater and the duck-billed platypus.

Why are they called monotremes?

Monotremes use a singular (mono) outlet to lay eggs and to pass waste. They also display other unusual characteristics like a lower body temperature than other mammals. This is a feature found in cold blooded reptiles like crocodiles which tend to survive in lower temperatures. Monotremes are commonly found in Australia and New Guinea but they have also been imported to western countries as zoo animals for tourists.

1. The Duck-Billed Platypus.

The duck-billed platypus is not just unique for laying eggs but it is also one of the few mammals that likes to spend most of its time in the water. Platypuses have webbed toes like those of a duck, a tail that resembles that of a beaver and the body shape of an otter which makes them look like an experiment that went wrong. Their strange appearance is only matched by their unique mating habits. The duck-billed platypus is a solitary animal that really values its privacy and it creates its own home near a river or wetland. Platypuses have been known to change up their foraging patterns to make sure they don’t run into each other. The females of their species may be slightly more accommodative and even share a nest with a few other females but the males have no interest in sharing.

During mating season which begins in spring the male platypuses will engage in dangerous fights for the right to mate. These fights include dangerous venom and the winner will then breed with the males in a particular territory. The mating takes place over ten minutes and once complete the female will usually avoid other males but the male will go looking for other females.

There can sometimes be certain courtship rituals between the male and females as they swim together, play and dive in water. The female will lay eggs close to a body of water because the platypuses are semiaquatic. The males will protect the females and their offspring and can secrete a venom that can be lethal to most animals including humans. A female will lay about two or three eggs which stay buried in the ground until it’s time to hatch.

2. The Spiny Anteater

According to Peggy Rismiller who is an anteater expert from Adelaide University, the courtship and sex process of anteaters is both careful and passionate. This is because if the female is not receptive to the advances of the male she will simply curl up into a ball and sex will be impossible. The courtship process can take several hours as several males dig a trench around the female and fight until only one male is in a position to mate. The male spiny anteater has been said to have the strangest reproductive organ in nature because it is divided into four separate parts. This baffling organ looks like a sprouting flower and despite a few theories, scientist are not 100% sure why this is the case.

Interestingly, nearly all spiny anteaters in captivity refuse to mate and this creates a huge problem for researchers. A female will lay her eggs 22 days after mating and will then deposit these eggs in her pouch. Once this is done the eggs will take 10 days to gestate and hatch. They will continue to live in their mother’s pouch for 55 days as they feed on milk and grow a spine. These puggles will then stay in their mother’s den for about one year after which they will venture into the outside world.

Spiny anteaters are very shy animals and so they will often hide or dig a hole when they feel threatened. They have a strong spine which they use for protection and their hairy bodies can help camouflage in grass.