For the third Mini Questions entry (see here and here for the two previous ones), Extraordinary Animals will once again be probing into a few animal mysteries – but this time with an added Easter theme. That means eggs, chicks and, of course, Easter bunnies…
How do chicks break out of their eggs?
All young birds have an external protective calcium covering – in other words, an egg. When the time comes to emerge into the outside world, chicks need a way of breaking through the egg’s tough outer shell. The beak and claws of most birds are not fully developed yet and cannot penetrate the shell, so they need to use something else.
That ‘something’ is an egg tooth. This is a small spike on its beak, which can be seen in the image above. A chick presses this spike against the inside of the egg and, using special muscles in the back of its neck to give added strength, pushes hard until the shell cracks. The egg tooth falls off a few days after hatching.
Almost all birds use an egg tooth to break out of their eggs. The only exceptions are the megapodes, a group of large chicken-like birds from Australasia, and the kiwi, both of which kick their way out instead.
Which bird lays the largest egg?
Surely the largest bird in the world, the ostrich, would be the one responsible for laying the largest egg. And you’d be correct. Weighing about 1.5kg – the equivalent of two dozen chicken eggs or 3,000 bee hummingbird eggs – it takes about 45 minutes to hard boil one. But the ostrich egg represents a mere 1.5% of its mother’s bodyweight, making it smaller, relative to the size of the adult, than any other bird egg in the world.
In terms of relative size, the kiwi lays the biggest. The egg is so large, in fact, that it takes up almost the entirety of the female’s internal cavity. During the last few days before the egg is laid, the female kiwi cannot eat because there simply isn’t enough room in her body for stomach expansion. When it is finally laid, the egg is a quarter of its mother’s weight – that’s the equivalent of a human mother giving birth to a six-year-old child.
But the largest egg EVER was laid by the now-extinct elephant bird. This gigantic flightless bird once roamed across Madagascar, and its eggs could have a circumference of over a metre and a volume 150 times greater than a chicken egg. Bigger than a rugby ball, these eggs are the largest laid by any known animal – larger, even, than eggs laid by the colossal dinosaurs. It is thought that eggs cannot physically get any larger than this for a simple reason: the greater the volume of the egg, the thicker the shell must be to hold its contents. Birds may have a small egg tooth to help them break free of their eggs, but after a certain thickness they wouldn’t be able to hatch at all.
Sadly, it was these giant eggs that led the elephant bird to its doom. They were so big they could feed several people at once. And as soon as people developed a taste for them, the elephant bird didn’t stand a chance.
Where does the Easter Bunny come from?
Rabbits and hares have been associated with religion for a long time. Pliny the Elder believed that the hare was a hermaphrodite and could reproduce asexually, which led to a connection with the Virgin Mary. They have also been viewed as symbols of fertility due to the speed at which they can reproduce – a female can conceive a second litter of offspring while still pregnant with the first, and can get through several litters in a single year. Perhaps they also symbolize new life, particularly in relation to the resurrection of Jesus around this time.
In Saxon culture in Germany, the hare was sacred to the goddess of spring, Eostre, from where we get the name ‘Easter’. It was also in Germany that the image of the Easter Bunny started to take shape, and the animal originally judged children to evaluate whether they had been good or naughty at the start of Eastertide. By 1690, the first story about a rabbit laying eggs and hiding them in a garden was published.
The legend of the Easter Bunny was brought to the United States in the 1700s when German immigrants settled into Pennsylvania Dutch country. The tradition for making nests for the rabbits to lay their eggs in soon followed. Then the nest became decorated baskets and the colourful eggs were swapped for chocolate and candy because, you know, rabbits don’t actually lay eggs. Even Pliny the Elder knew that.
What animals live on Easter Island?
In short, not very many. Famous for its giant stone heads, or moai, that adorn the landscape, Easter Island was once a sub-tropical paradise. Various native plants and animals lived on the island and nowhere else in the world. It was also home to a group of native people called the Rapa Nui.
But the human population of Easter Island soon reached, and then surpassed, its limit. As they cut down more and more trees to create rollers to move their giant statues, so the forests gradually disappeared. By the time the last tree was cut down, the Rapa Nui had doomed themselves – now there was no longer the wood needed to build canoes to carry them away from their suddenly-barren island. They could no longer catch fish or porpoises, so they turned to seabirds for food, and then rats. When even they ran out, cannibalism was the only option. The government collapsed and most the Rapa Nui starved to death.
When Dutch navigator Jacob Roggeveen discovered the island on 5 April (Easter Sunday, hence the island’s name), 1722, the only things larger than insects that he found living there were hungry people and a few domesticated chickens. Today, almost any animal species found on Easter Island, aside from a few very small invertebrates, are non-native – they have been introduced there by humans. Its once-unique ecosystem has vanished forever.
This story acts as a warning to us all. It shows what can quickly happen to a closed ecosystem by overusing its resources. It happened to Easter Island and it could happen to our own planet Earth. It just might take a little bit longer.