Dressed up in bright blue and with loud croaking, they sit tens at a time in shallow pools: the moor frog makes no secret of the fact that the mating season has started.
You have to, because within a few days the whole party will be ready again. The Moor frog is an “explosive brother”, says Jelger Herder, project leader and frog expert at RAVON (Reptile Amphibians Fish Research Netherlands).
No risk to walk a blue
Their blue suits also attract the male moor frogs only for a few days. The rest of the year the frog is ‘just’ brown.
The reason for this color change isn’t quite known, Herder says. “That’s funny, you would expect them to be that color to impress the females,” he notes. “But those females don’t have much to choose from. As soon as they enter the water, they are jumped by males who were already waiting there.”
It has therefore not been established why the men do turn blue. One theory is that this makes them less noticeable to predators because their back color resembles the color of the water reflecting the blue sky.
It could also be a signal for the male frogs themselves. Herder: “So that the men don’t accidentally jump on each other.”
The moor frog is there early
When exactly the mating season starts, is temperature dependent. The moor frog moves towards the water during the first warm days of spring. Sometimes that is already in February, but usually around this period, in March. This frog species is one of the first to mate with this. A lot earlier than, for example, the brown frog or the common toad, according to Herder.
Good news for the frog fanatics among us: the blue amphibian is fairly easy to find. That’s because of its special sound, which sounds like “a bottle of air that you empty underwater”, according to Herder. “He’s terribly shy,” he adds. So you have to be lucky to spot him.
Want to see the moor frog yourself? On observations.nl you can find out where the frog has been spotted. Quite a few were seen last week at the Davidsplassen near the Dwingelderveld.