Birds are not the only animals that lay eggs. Amphibians, snakes, and fish lay eggs, plus the reptiles, which includes lizards, turtles, crocodiles etc. But only two mammals lay eggs: the platypus and the echidna. (As an aside - before anyone jumps down my throat, fish ARE animals – they are aquatic animals that were among the first vertebrates - animals with a backbone - to evolve on earth.)

The mammals that lay eggs have the strange name of Monotremes (/ˈmɒnətriːmz/, that lay eggs rather than bearing live young.

Good or bad parents

Sea turtles are probably the most well-known for burying their eggs and pushing off to leave them to their own devices – no parenting skills required, and produce hundreds of hatchlings to make up for the natural bait they become before they have hardly even hit the waves. Snakes, in general, do not win any parenting awards either. The eggs are usually plopped in a hole, covered with dirt, then mum slithers off hoping for the best. Most of the 30 percent or so of snake species that give live birth don't give much thought to their offspring, either.

Good parents are the Emperor penguins from Antarctica, where males will keep a single egg warm snug in their brood pouch for up to 67 days, starving hungry and likely freezing in a blizzard, while the females return to the seas to hunt fish. Emperors are the biggest of the 18 species of penguin found today, and one of the largest of all birds. I wondered why they are classed as birds as they can’t fly, but to be classified as a bird, the animal must have feathers, a beak, and lay eggs, so I guess they fit the ‘bill’ so to speak, by meeting all of these requirements. Their swimming ability could be considered flying - in their comfort zone beneath the water, they are lithe and fast, with the fastest penguins clock up speeds of up to 36 km/h.

Credits: PA;

But getting back to the monotremes…

The platypus and the echidna. Despite their egg-laying reproductive strategy, monotremes still produce milk to feed their young. They lack nipples, however, and instead secrete milk from glands on their skin. The mothers care for their young in a pouch or burrow, who hatch from their eggs in a very underdeveloped state.

The platypus mum in particular is a nurturing mother – she typically produces one or two eggs and keeps them warm by holding them between her body and her tail. The eggs hatch in about ten days, but platypus infants are the size of lima beans and totally helpless. Females nurse their young for three to four months until the babies can swim on their own.

Echidna mums lay one single soft-shelled egg, and she too, looks after it, her little ‘puggle’ stays in her den for up to a year before going it alone, leaving the pouch when it grows spines, at about three months old. Young stay and suckle from the mother until they're weaned at about six months of age.

Humans have eggs too

Get ready to learn some surprising facts about human female eggs! Females are born with between one and two million eggs. The number decreases until a woman stops ovulating and reaches menopause, at which point fewer than 1,000 remain. During the course of her lifetime, she only releases about 500 eggs, and the rest of the eggs that are chosen as contenders for ovulation, but don’t end up being released. But can you imagine 500 being successfully born? The shoes! The clothes! And worse, the toys!

Author

Marilyn writes regularly for The Portugal News, and has lived in the Algarve for some years. A dog-lover, she has lived in Ireland, UK, Bermuda and the Isle of Man. 

Marilyn Sheridan