These baby animals are swallowed by their fathers and ‘vomited’ out when they’re fully formed

Deep within the rainforests of southern Chile and Argentina is a tiny frog with an extraordinary parenting strategy.

Measuring just 1–3 centimetres in length, the diminutive southern Darwin’s frog has a pointed snout and camouflaged skin, which allows it to hide on the forest floor.

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These aren’t the only unusual features about it, however. After the female frogs lay their eggs on the floor, the male frogs watch out for movement. When the embryos twitch, the males scoop them up in their mouths.

But despite appearances, the tadpoles aren’t swallowed alive. Instead, they are stored inside the vocal sacs (which run down the front of a frog’s throat) of their fathers for days and are ‘vomited’ back up through their mouths when they are tiny, fully formed froglets.

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This astonishing behaviour was featured on David Attenborough’s landmark 1979 nature documentary Life on Earth. One of the camera crew, Rodger Jackman, was tasked with filming this phenomenon in controlled conditions. As the production used film stock, the camera couldn’t be left rolling, and the filmmaker had to wait and watch for the moment the froglets leapt out.

However, he missed his opportunity while taking a break – and had to start the process again.

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• “Faced with a rugby scrum of suitors, females have little choice over who to mate with.”

The future of the southern Darwin’s frog

As the name suggests, the species was discovered by Charles Darwin in 1834, during his global voyage on the HMS Beagle.

While southern Darwin’s frogs were once widespread across Chile and Argentina, they are now confined to small populations and are classified as Endangered on the IUCN Red List. They’re particularly susceptible to chytrid fungus infection (an often-fatal disease which disrupts the frogs’ ability to breathe through their skin), as well as habitat loss.

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The only other frog to demonstrate this unusual behaviour is the northern Darwin’s frog, which has been presumed extinct since 1981.

Top image: a screenshot of a video of a southern Darwin's frog and one of its offspring in the Huilo-Huilo Biological Reserve, Patagonia. Credit: BBC Natural History/Getty Images