In 2003, scientists described a new family of frogs – the first time such a discovery had been made among the anurans in around 70 years. Their prize was a weird one, a purple frog described as the “coelacanth of frogs”. Why? Because it stemmed from an ancient lineage that was wriggling around in the mud when dinosaurs were still alive.
With a bloated body and stubby limbs, tiny eyes, and a protruding snout, the purple frog isn’t winning any beauty contests – but if you’re a fan of “living fossils” then this is the amphibian for you. It’s thought to have emerged over 80 million years ago, but it wasn’t until 2003 that it was formally identified in the Western Ghats Mountains. Incredibly, its DNA revealed that its closest relative hailed from the Seychelles, around 3,000 kilometers (1,864 miles) south of its native India, with the two having split on the family tree sometime between 251 and 65 million years ago, during the Mesozoic era.
The Purple Frog
How utterly extraordinary it is that an animal can spend so much time underground, and so little is known about it.
Patrick Evans
Around 180 million years ago, the world looked very different. The supercontinent Gondwana was still in one piece – but over tens of millions of years it broke apart, separating these frog cousins as the power of plate tectonics transformed the Earth into the sprawling puzzle of continents we see today. The Seychelles are to the east of the African continent, while India sits firmly on the continent known as Asia, and it’s in a new series of the same name that the purple frog recently starred.
Asia, narrated by Sir David Attenborough and created by the BBC, dives into the curious wildlife that’s to be found across Earth’s largest continent, from fish that climb trees to firefly squid, and poisonous sea bunnies. But us? We really needed to know more about the purple frog, a sentiment that was shared by producer Patrick Evans who worked on the Tangled Worlds episode.
“Something struck me in particular about the purple frog,” he told IFLScience, “which is just how utterly extraordinary it is that an animal can spend so much time underground, and so little is known about it, and it just looks so bizarre. So different to most other frogs.”
Purple Frogs Live It Up Underground
Part of that bizarre appearance comes down to its history, hailing from a deep branch in the family tree of frogs that stretches back to the Mesozoic era. It was described as a “once in a century find” when the family was officially named Nasikabatrachidae, and while a new species was identified in 2017, they’ve not been the easiest creatures to study.
The frogs have apparently got this technique of passing under low branches to scrape the toads off.
Patrick Evans
Spending all your time up to 8 meters (26 feet) underground will do that, I suppose, and it’s an equally difficult obstacle for anyone trying to film them. Fortunately, they do emerge once a year to breed, but this knowledge didn’t make it any easier for the Asia team.
“It was outrageously challenging to [film],” said Evans. “We work quite closely with an Indian scientist who’s been following the frogs for quite a long time, Dr Sandeep Das, and he had spent several field seasons staking out the streams where the frogs had emerged or been known to emerge in the past, and eventually he’d be there on a night when the frogs came out.”
“He knew quite a lot about these potential spots where they would emerge, and he obviously had quite a lot of background information on timing. So, for example, he would say that if it rained for a certain number of days before the main monsoon would hit, then that would provoke quite a lot of calls. And if there was just enough rain, then you might see frogs emerge. We just had spent a lot of time in the field, waiting and hoping that would rain just enough.”
Purple frogs only have to emerge once a year to get their business done. Is this what peak performance looks like?
Purple Frog Reproduction
It took the Asia team two years to get the timing right, but eventually, they were able to capture the grueling process of purple frog reproduction. Well, grueling for the female, at least. She emerges from the mud with a belly full of eggs, and with a (much smaller) male clasped onto her back like a needy rucksack, she scales upstream to find a safe place to leave her fertilized eggs to develop. However, occasionally she picks up an unwanted tag-along.
We have no idea what their lives are like underground.
Patrick Evans
“Toads, who are – how shall we say – quite ‘up for it’ as well, they will jump on and try and mate with purple frogs heading off to breed,” said Evans, “because they just think ‘Oh well that’s something I can probably mate with’ [FYI, misdirected amplexus is famous among these animals]. So, they jump aboard, and the frogs have apparently got this technique of passing under low branches to scrape the toads off.”
A pain in the butt for a female purple frog who already has to do most of the heavy lifting during her brief breeding window, but a remarkable adaptation that shines a little light on the elusive lives of these soil-dwelling animals.
“I think this frog has got a lot more to offer,” said Evans. “We have no idea what their lives are like underground, and that’s something that’s still out there to be figured out and documented.”
“How they communicate with each other, how they find each other underground, and how they sense whatever amount of rain it is that they think is exactly the right amount and to risk emerging into the darkness. What a mystery.”
All episodes of Asia are available on BBC iPlayer now.
