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Viviparous or oviparous?

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The answers

Viviparous or oviparous?

Viviparous 10

  • Dolphin Right Wrong

    A marine mammal, the dolphin gives birth underwater, often tail first. The mother immediately pushes her calf to the surface so it can take its first breath.

  • Bat Right Wrong

    The only mammal capable of true flight, the bat gives birth to live young, usually a single pup a year. The pup clings to its mother's fur and feeds on her milk for several weeks.

  • Kangaroo Right Wrong

    A marsupial: the joey is born after just over a month of pregnancy, no bigger than a bean. It then crawls into its mother's pouch, where it keeps growing for several months.

  • Blue whale Right Wrong

    The largest animal that has ever lived gives birth to a calf weighing about two and a half tonnes, after almost a year of pregnancy. The calf then feeds on very rich, fatty milk.

  • Pangolin Right Wrong

    Covered in scales like a reptile, the pangolin is nevertheless a mammal: the female gives birth to a single young, which she then carries clinging to her tail.

  • Armadillo Right Wrong

    The nine-banded armadillo gives birth to identical quadruplets: all four young come from one single fertilised egg. They are born with a soft shell, which hardens within a few weeks.

  • Hippopotamus Right Wrong

    The female leaves the group to give birth, often in shallow water. The calf, which already weighs around forty kilos, learns to suckle underwater by closing its nostrils and ears.

  • Hammerhead shark Right Wrong

    Surprise: just like mammals, the female feeds her embryos through a placenta. She then gives birth to live pups, sometimes dozens at a time, which can already swim.

  • Scorpion Right Wrong

    No eggs are laid: young scorpions are born alive and immediately climb onto their mother's back. They stay there, protected, until their first moult, then go off on their own.

  • Tsetse fly Right Wrong

    A viviparous insect: the female carries a single larva at a time and feeds it with a milk-like secretion inside her uterus. She then gives birth to it, ready to turn into a pupa.

Oviparous 10

  • Platypus Right Wrong

    This Australian mammal lays eggs, then feeds its young on milk. It has no nipples: the milk seeps through patches of skin on its belly, where the young lick it up.

  • Echidna Right Wrong

    Another egg-laying mammal, a cousin of the platypus: the female places her single egg in a pouch on her belly, where it hatches after about ten days. The young then stays there for several weeks.

  • Kiwi Right Wrong

    New Zealand's national bird lays one of the largest eggs in the world relative to its size: about 20% of the female's body weight. The male then incubates it for nearly three months.

  • Emperor penguin Right Wrong

    The female lays a single egg, then heads back to sea. The male incubates it balanced on his feet for about two months of the Antarctic winter, without eating at all.

  • Leatherback turtle Right Wrong

    The largest sea turtle comes ashore at night to lay around a hundred eggs in the sand. She then returns to the sea without ever seeing her hatchlings.

  • Nile crocodile Right Wrong

    It lays its eggs in a buried nest guarded by the female. The incubation temperature decides the sex of the young, which she later carries gently in her jaws.

  • Ball python Right Wrong

    Unlike boas, which give birth to live young, pythons lay eggs. The female ball python coils tightly around her clutch to protect it until the eggs hatch, about two months later.

  • Atlantic salmon Right Wrong

    After several years at sea, the salmon swims back up the river where it was born, sometimes for hundreds of kilometres. The female digs a nest in the gravel to lay her eggs.

  • Octopus Right Wrong

    The female lays thousands of eggs in a den. She cleans them, blows oxygen-rich water over them and guards them without eating until they hatch, then dies shortly afterwards.

  • Small-spotted catshark Right Wrong

    This small European shark lays eggs protected by a tough case known as a 'mermaid's purse'. The empty cases are sometimes found washed up on beaches once the young have hatched.

Viviparous: the young develop inside their mother's body and are born alive. Oviparous: the female lays eggs, which hatch outside her body. The rule sounds simple, but the animal kingdom loves to blur the lines. Some species even surprise nature lovers, because the way an animal looks tells you nothing about the way it comes into the world. Trust biology rather than common assumptions to sort every animal before the timer runs out.

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10 cards, 20 seconds: the timer starts with your first choice.

Frequently asked questions

What is the difference between viviparous and oviparous animals?

In viviparous animals, the embryo develops inside its mother's body, which nourishes it: the young is born alive. In oviparous animals, the female lays eggs. The embryo develops outside her body, fed by the egg's reserves, until it hatches.

What about ovoviviparous animals?

Some animals keep their eggs inside their body until they hatch: they are called ovoviviparous. To avoid any ambiguity, this quiz only includes species that are clearly viviparous or clearly oviparous.

How are the young fed before they are born?

In oviparous animals, the embryo draws on the egg's reserves, especially the yolk. In viviparous animals, the mother feeds it throughout the pregnancy, most often through a placenta.

Why do some animals lay eggs and others not?

Laying eggs makes it possible to produce many young without carrying them for long; carrying them protects them better but limits their number. Both strategies have appeared several times during evolution, in very different groups of animals.

Photo credits

Dolphin : Photo NASA, public domain, Wikimedia Commons ; Bat : Photo Charles J. Sharp, CC BY-SA 4.0, Wikimedia Commons ; Kangaroo : Photo Yu Chu Chin, CC BY 4.0, Wikimedia Commons ; Blue whale : Photo NOAA Photo Library, public domain, Wikimedia Commons ; Pangolin : Photo U.S. Fish and Wildlife Service, CC BY 2.0, Wikimedia Commons ; Armadillo : Photo birdphotos.com, CC BY 3.0, Wikimedia Commons ; Hippopotamus : Photo Bernard Dupont, CC BY-SA 2.0, Wikimedia Commons ; Hammerhead shark : Photo Stevelaycock21, CC BY-SA 4.0, Wikimedia Commons ; Scorpion : Photo Mike Baird, CC BY 2.0, Wikimedia Commons ; Tsetse fly : Photo Alan R Walker, CC BY-SA 3.0, Wikimedia Commons ; Platypus : Photo Charles J. Sharp, CC BY-SA 4.0, Wikimedia Commons ; Echidna : Photo Donald Hobern, CC BY 2.0, Wikimedia Commons ; Kiwi : Photo The.Rohit, CC BY 2.0, Wikimedia Commons ; Emperor penguin : Photo Hannes Grobe/AWI, CC BY 3.0, Wikimedia Commons ; Leatherback turtle : Photo David Rabon, U.S. Fish and Wildlife Service, public domain, Wikimedia Commons ; Nile crocodile : Photo Tim Muttoo, CC BY-SA 2.0, Wikimedia Commons ; Ball python : Photo HCA, CC BY-SA 3.0, Wikimedia Commons ; Atlantic salmon : Photo William W. Hartley, public domain, Wikimedia Commons ; Octopus : Photo H. Zell, CC BY-SA 3.0, Wikimedia Commons ; Small-spotted catshark : Photo Hans Hillewaert, CC BY-SA 4.0, Wikimedia Commons