RAUK - Archived Forum - First Frogspawn

Hi Guys,

Whilst out birding on the Lizard Penninsula, Cornwall I found several clumps of frogspawn. By far the earliest i've found it before, but then again, stuff will be earlier down here than in Shropshire!

This was on the 24th, not far from Garras.

there are definitely two spawnings on the Lizard, whether that means the adults breed twice a year, or if they are different "sub populations" (for want of a better word) i'm still unsure, both would seem plausable.

I shall endevour to find out

Hi Matt

My hunch would be that the S Wales phenomenon is, as you suggest, that normal spawning is temporarily interrupted by a cold spell.  I think this often happens with a species that breeds 'on the edge' in thermal terms.  The Cornish situation, with some frogs spawning for the first or perhaps second time in April sounds different to me, but we need more observations, I guess

Cheers

It's a long time since I read Maxwell Savage's book, but I seem to remember that he was the first person to correlate spawning dates with isotherms; if I remember rightly he argued that spawning corresponded with glycolic acid released by algae, which he reckoned frogs could smell, thereby luring them to ponds.  I'm not sure anyone has proved that frogs can smell metabolically active algae under controlled (lab ?) conditions.  Personally I reckon there's a direct link between mild and wet weather, probably with some element of daylength to prevent spawning in November (although frogs do sometimes go into amplexus in autumn)

On the subject of little interbreeding between two populations of frogs - call them early and late spawning cohorts, maybe there could be some mileage in investigating whether there is true reproductive isolation - this could lead eventually to separate species, like the common and soprano pipistrelle.  But you'd need to confirm that late spawning females and also males were not interbreeding with the early ones and vice-versa for this to be the case.  Unlikely, perhaps, but intriguing if there is a genuine April spawning.

Hi Caleb

Yes, I should have specified I meant 'increase in daylength' - a bit like some flowering plants use for determining when to flower.  I agree that a cold period is probably needed for spawning, too - although maybe not too long if Cornish frogs often spawn in late December/ early January.