As It Happens

Scientists are fascinated by this itty bitty frog that's extremely bad at jumping

Richard Essner says there’s something very relatable about the pumpkin toadlet, a frog so small that every time it attempts to jump, it crashes pitifully to the ground.

‘If you didn't do particularly well in gym class, then this might be the frog for you,' says biologist

A close-up of a bright orange frog with big black eyes.
The pumpkin toadlet, native to the mountains of Brazilian rainforests, is about the size of a Tic Tac or a Skittle. (Luiz F. Ribeiro)

Story Transcript

Richard Essner says there's something very relatable about the pumpkin toadlet, a frog so small that every time it attempts to jump, it crashes pitifully to the ground.

These Tic Tac-sized amphibians launch themselves into the air, but lack the internal balancing mechanisms required to correct themselves mid-jump. So instead of landing on their feet, ready for the next leap, they spin out of control and crash onto their tiny froggy butts, backs or faces. 

Essner, a biologist at Southern Illinois University Edwardsville, has shot dozens of videos of these botched landings.

"I seem to have struck a chord with some of these videos," Essner told As It Happens guest host Tom Harrington. "I have seen people that can relate to their poor jumping ability. If you didn't do particularly well in gym class, then this might be the frog for you."

Essner and a team of researchers including biologist Marcio Pie have been studying the science behind the toadlets' inherent clumsiness. Their findings were published this month in the journal Science Advances.

Watch: A pumpkin toadlet performs an 'uncontrolled landing':

Watch this tiny frog jump and crash

1 year ago
Duration 0:20
Featured VideoA pumpkin toadlet can leap, but it can't quite land. That's because, at the size of a Skittle, it's simply too small to orient itself in mid-air.

Pumpkin toadlets are a species of miniaturized amphibian native to the mountaintops of Brazil, where they spend their days moving slowly through the leaf forest floor of the Atlantic rainforests, eating bugs. 

Most are just under a centimetre long, their arms and legs no thicker than a toothpick.

But the researchers suspect their inability to land a jump has nothing to do with their teeny tiny muscles. According to Essner, it's their exceptionally small ears that put them on their rears.

"The inner ear, the semicircular canals in particular, are used to detect angular acceleration, which is key information for the frogs as they prepare for landing," he said.

"And we believe they're not sufficiently sensitive to make use of that information because their semicircular canals have gotten so small."

A close-up of a bright orange frog with black spots on its back standing next to a pencil. The frog is shorter than the sharpened tip of the pencil, and about as thick.
A pumpkin toadlet pictured next to a pencil. The Brazilian amphibians are usually less than a centimetre long. (Luiz F. Ribeiro)

The team CT scanned more than 100 pumpkin toadlets and other related frogs, compared them to other animals, and found that miniaturized frogs have the smallest semicircular ear canals on record for adult vertebrates. 

"Without the ability to control [their] posture, these frogs end up flopping backwards and doing backflips quite often," Essner said.

He calls these falls and tumbles "uncontrolled landings." 

"They're actually the worst [at jumping] I've ever seen," he said. "I've looked at a lot of frogs jumping and, yeah, they take the prize."

Lea Randall, a Calgary Zoo and Wilder Institute ecologist who specializes in amphibians and reptiles, said the toadlets' uncontrolled landings could be the result of a combination of other factors as well.

"For example, this species has fewer toes than other species, resulting in narrower feet, and they also have short hindlimbs. Both features could make them more likely to roll and yaw mid-jump and land awkwardly," she said in an email to CBC.

"Although the authors concluded that vestibular dysfunction due to the small size of their semicircular canals was the most likely reason, they couldn't rule out the others and they may not be mutually exclusive."

Randall says she'd be curious to see whether other miniaturized vertebrates have similar mobility impairments

"Some wider implications are that vertebrates may not be able to get any smaller than this and retain certain important functions," she said.

But they're doing just fine

The most surprising part of the study, says Randall, is that despite their "ungraceful landing," the frogs appear to be doing just fine.

The study found no evidence the frogs get injured during their lopsided leaps.

"It helps to be tiny. You've probably seen animals like squirrels fall out of trees. If you're small, you can fall and really not get hurt. So that's probably not a big issue for them," Essner said.

"I think probably a bigger concern would be, you know, being vulnerable because they can't jump again to escape right away like other frogs do."

A man sits at a desk, but turned away from it, facing the camera. His hands are clasped in front of him and he's smiling. He's wearing a dark blue polo short and beige khakis. Behind him, on the desk, is a small laptop and a large computer monitor displaying an image of a bright orange frog.
Richard L. Essner is a biologist at Southern Illinois University Edwardsville. (Howard Ash)

But they have their own defence systems in place for that. Some species of pumpkin toadlets are highly poisonous, and their bright orange colours serve as a warning to predators.

There are other benefits to being small, too. Essner called it an "evolutionary trade-off."

"So maybe the cost is you can't control your landings very well. But on the other side .... because they're so small, they probably have access to tiny invertebrates as a food source that other frogs may miss or not be interested in because it's not worth their effort," Essner said.

"For a tiny frog like this, even an ant is a really large meal."

Written by Sheena Goodyear. Interview with Richard Essner produced by Arman Aghbali.

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