Wildsong for March

The first voice on earth?

amphibians up north
Amphibians and reptiles are cold-blooded animals - meaning they don't have an internal heating system and need external warmth to raise their bodies to an adequate operating temperature. So ... it's always surprising to find groups of Common Frogs intent on procreation, with winter snows still lingering in the district.

Last year good numbers were gathered in pools in the Harthope valley beneath Cheviot, while the hillsides were still spotted with snow patches. On 7th March there was already a fair bit of spawn, but some was in the puddles formed in wheel ruts of the valley track.

There were some records of frogspawn lower down in the area for the second half of Feb, but heavy snowfalls at the end of the month stopped play. Rain and slightly milder weather in the first week of March meant that everywhere was swimming with water and the frogs, ever opportunists, had used many of the temporary pools for breeding. But without continued rain over the next 2 to 3 months much of the spawn in the small pools wouldn't survive to produce young frogs.

This site is 275m asl and although overnight temperatures were around or below freezing, on the afternoons of the 7th and 8th March the valley warmed up, sheltered from a cold north-west breeze. The male frogs were chorusing to attract females: once one starts up, others are stimulated to join in.

calling
The males usually call with their head well out of the water, but the main part of their body submerged. Their throats are extended and the vibrating resonance is transmitted both through the air and in the water. Amphibians such as these (the first land vertebrates) were probably the first creatures on earth to evolve a voice for sound production.

This is a chorus (mp3 360k) from 20th March 2003 at nightfall in the marshy edge of a moorland loch. Overnight under clear skies the temperature went down to minus five celsius, but by 11am the next day the read-out on the car was twenty degrees - mind, that was in the sun. A single male calling (mp3 76k).

So where do they find the energy? These amazing creatures are driven to put on their finest show, only just aroused from their winter torpor, presumably having eaten nothing for a good four months, with no means of warming themselves and an ambient temperature little over freezing. In these circumstances, a slightly louder or more resonant call is true indication of a survivor - the kind of father any female would want for her offspring.

close relatives
Britain and Ireland now have only one indigenous species of frog - the Common Frog Rana temporaria; there are indications that the extinct population of Pool Frogs in Norfolk may have been indigenous. Typical frogs belong to the genus Rana. There are two broad groups in Europe: the Water or Green Frogs and the Brown Frogs. Whereas the Water Frog group have external vocal sacs at each corner of their mouths, Common Frogs (and the other Brown Frogs) show no visible external appendages, though their throats and sometimes the sides of their mouths can be seen to swell a little.

The calls of Common Frogs are not loud, though a good chorus can be heard over 100 yards away in quiet conditions. The Water Frogs are noisy in comparison, with varied calls that can be heard at a much greater distance. These are Levant Water Frogs (mp3 264k) at nightfall on a Greek island.

The only other widespread vocal amphibian in Britain is the Common Toad Bufo bufo (mp3 140k). The male's calls are higher-pitched than those of Common Frogs and are rather squeakier.

As the frogs were out a-courting under Cheviot, another creature of their community was warming itself in the welcome afternoon sunshine - an Adder. Quite an early date for the area under these conditions.