Frogs and toads jump, swim, climb, and even glide. But four strange species of amphibians have evolved a decidedly unfroglike characteristic: a preference for walking. Now, scientists have discovered how they do it.
The Senegal running frog, the bumblebee toad, the red-banded rubber frog, and the tiger-legged monkey frog don’t walk like dogs or other four-legged beasts. Instead, they crawl low to the ground like a cat creeping up on prey.
To find out how, the team measured the relative size of their limbs and observed their posture and movement as they walked. Though the four species are unrelated, they all have more symmetrical limb lengths than the ordinary short front legs and large powerful back legs model of most frogs, the team reports in the Journal of Experimental Zoology Part A: Ecological and Integrative Physiology. The frogs’ front legs are a bit shorter than their hind legs, but they compensate for this by stretching their front legs out when they walk while using a slight crouching posture on their back legs.
The researchers still don’t know why they walk, but all four species live in similar grassland habitats that lack branches or foliage to latch on. So, it may be a better idea to run than jump when predators are near. Evolution hasn’t entirely ruined the essence of these species’ frogginess, though. One researcher says that the frogs can still jump and swim—they just usually don’t.