It’s time! April not only brought showers to Scotland, but also lured our charismatic natterjack toads (Epidalea calamita) out of their winter burrows. Natterjacks will happily dig into the earth, unlike common toads, and have different burrows depending on the season. In winter, the toads may be buried into the sand dunes here at Mersehead.
Males move first, so in late March and early April, these prospective homemovers were probably peering out of their winter hibernacula, considering two things: females and food.
Once they’re snug in their new poolside homes, they start to become more active at night. The males give away their whereabouts quickly because they call loudly from the pools to attract mates. Their calls give a female an impression of their size and, therefore, the suitability of their genes for her offspring. Presumably, ‘bigger is better’ in the world of natterjacks.
Each male wants to be heard, so one call prompts another, and another, and so on. This vocal jostling forms an immersive chorus that carries far and wide. In fact, they’re the loudest amphibian in Europe. At Mersehead, all I have to do is pop my head out of the window to know what they’re up to.
Here’s a clip of our very own amphibious choir. See if you can pick out any individual voices (and the winnowing snipe!). Credit Roseanne Watt.
As with birds, each frog and toad species has its own identifiable call. Typical mating calls are generally produced simply by pushing air back and forth between their lungs and their expandable air sac. The air runs over their vocal chords, creating the sound, and the air sac amplifies it. Natterjacks have just one sac below their mouths, but some frogs have one on each side of their head or none at all.
Here’s the big news: Mersehead’s natterjacks are out and about! On the night of Saturday 9th, one optimistic male soloist was heard, but on Thursday 14th, we saw and heard about 30. The chorus isn’t in full swing just yet because the night-time temperatures are a bit low, but it’s a positive sign for this year’s surveys. Each night, we use the chorus to pinpoint where the toads are, so I’m looking forward to seeing some soon.