Photo/Illutration A black-spotted pond frog stays stock still while keeping close watch on a snake. (Provided by Nozomi Nishiumi)

KYOTO--Japanese commonly describe a person frozen with fear as looking like “a frog scared stiff by a snake.”

But at least from a scientific perspective, it turns out the traditional portrayal taken from a proverb just doesn't hold up.

A team of scientists from Kyoto University tested the notion that frogs freeze in place when faced with a snake by staging experiments that pitted the arch enemies against each other.

They found that frogs intentionally stay still at the sight of snakes as a means of escape.

“The saying represents the state where someone is rooted to the spot out of fear, but it may be more apt to say frogs dare to stop moving before predators in an attempt to survive,” said Nozomi Nishiumi, a member of the team that conducted the study.

The research fellow, affiliated with the Japan Society for the Promotion of Science, took part in the study while doing his Ph.D. at Kyoto University's Graduate School of Science. He currently holds a position at the National Institute for Basic Biology.

The team placed a Japanese striped snake and a black-spotted pond frog together to study how the snake assaults its prey with its fangs and how the frog tries to flee by jumping.

Videos of the showdown revealed that it's much safer for a frog to remain still than to jump, as its lack of ability to change direction once it's airborne means it might easily be caught in the air by its predator if it starts to move first.

Snakes, luckily for frogs, have as much trouble adjusting their trajectory.

Having crossed paths with prey, a snake first shrinks and then coils to extend its body to attack.

But after a snake starts moving, it too can't change direction, making it wiser for a frog to wait and dodge the attack.

The snake also must coil again after fully stretching out, crimping its ability to pursue the frog if its first bite fails.

Based on the videos, the scientists concluded that both frogs and snakes gained an advantage by starting to move later than their enemy, leading to a standoff where both carefully monitor each other before taking action.

To verify its theory, the team redid the experiment in the wild. It confirmed that if the frog succeeds in avoiding the snake's opening strike, it can flee to nearby safe water while the snake prepares to launch its next assault.

Another key factor for a frog's survival is the distance it stays from the snake, given that it must dodge the snake's initial attack.

When the distance between them is extremely short, the frog can't respond to its enemy’s motion quickly enough to escape.

At least 5 to 10 centimeters is necessary for a successful escape.

In cases where a frog finds itself stuck with less than that, the team found that instead of waiting for the snake to move first, it took the initiative in trying to escape.

Snakes, however, also were observed attempting to gain a head start to prevent the frogs from getting away.

The team published its findings on the online edition of the scientific magazine Canadian Journal of Zoology at (https://www.doi.org/10.1139/cjz-2019-0164).

Readers can view the team's videos at (https://www.youtube.com/watch?v=MBlKQ2-31P4&feature=youtu.be).

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