The hungry frogs that tap dance
There are nearly 200 species of poison dart frogs, known for their bright colours and highly toxic skin. Not only are they beautiful – they can do a kind of tapdance. The frogs have a habit of tapping the middle toes on their back feet. Scientists have never fully worked out what the frogs are trying to achieve but a recent study could have solved the puzzle.
Researchers at the University of Illinois Urbana-Champaign, in the US, filmed 22 dyeing poison dart frogs in enclosures that had soil, leaves and rocks on the ground – much like the frogs’ natural habitat. At feeding time, the hungry frogs had one of their favourite foods – fruit flies – put in front of them. The researchers found that the frogs tapped their toes an average of 389 times a minute when they had flies in their enclosure, compared to 50 times a minute when they didn’t.
The frogs changed the amount of tapping depending on the type of surface they were on. They tapped more than twice as quickly on leaves as they did on soil, glass or a type of gel.
The researchers think this behaviour could be the frogs’ way of getting the flies moving, making them easier to spot and therefore easier to gobble up. “Frogs can only really forage (search for food) when prey is alive and moving,” explained Eva Fischer, who is one of the study’s authors. Leaves carry vibrations (very small movements) better than other surfaces, so it makes sense for the frogs to tap more on leafy ground to take advantage of this.
The researchers also tried putting the flies in small dishes so the frogs could see them but not eat them. When this happened, the frogs still tried to catch the flies but only tapped at a rate of around 50 times a minute. This suggests they only tap when they think they have a realistic chance of catching their prey.