Species of the Month - March 2011
(Rana temporaria - Common Frog)
Every month this page will feature a species to look out for. It may be a plant, an insect, a mushroom, or something else. The chosen species will be easy to recognise, so that all can contribute.
For the first ever species of the month we're starting off with something common. This is the month when frogs get busy filling the pools and ditches with spawn.
It is easy to tell frogspawn from toadspawn. Frogspawn is laid in large shapeless masses, as in the photo above, while toadspawn is laid in neat double rows like two strings of black beads.
Frogs are becoming scarce in some parts of Britain owing to lack of suitable water for spawning, but that is not likely to be a problem in this part of the country. However the exceptionally long icy spells during the past two winters and the relatively dry Springs may have taken their toll.
Spawn is often laid in temporary pools which look as if they may dry up before the young frogs are ready to leave. The reason frogs choose these shallow water-bodies is because they tend not to contain predators such as fish. In wet years some of these pools may produce frogs in numbers, while in drier years only those from deeper pools will survive - if they escape the fish. This system has worked well for thousands of years and should not be interfered with. Moving spawn is not recommended as it can spread disease, which is a much more real danger for frogs than the loss of a few hundred tadpoles. After all, each frog only needs to replace itself once in its lifetime to keep the population stable!
This survey will help us assess how the local frog population is coping with changing climatic conditions, and may reveal variations in spawning time between different parts of the region.
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Sightings so far
John Gordon reports from Easdale that spawning in garden ponds peaked on 22-23 Feb in line with previous years.
Alan Hawkins found two recently laid clumps of spawn in a bog pool at Kilmartin on 7 Mar
I found about 15 clumps in a pool fed by a burn near Oban on 7 Mar. This looked a good choice of site as it's unlikely to dry out; however heavy rain could cause the burn to wash the spawn out of the pool. The embryo tadpoles were about 5 mm long.
Having stated above that frogs would have no difficulty finding suitable water in Argyll, I'm beginning to wonder after noticing that a large pool near my home which had a huge amount of frogspawn last year is currently completely dry and has grass growing all over it. Water levels are certainly very low at the moment so the choice is more limited than usual, but this could work to the frogs' advantage since they won't make the mistake of laying in pools that only exist in wet weather.
18 Mar - The ones I found on 7 Mar are doing well despite some heavy rain since that time. They are now a recognisable tadpole shape. I have not found any spawn elsewhere despite examining many suitable spots.
24 Mar - Sallie Jack found some fresh spawn in an old stone disused water tank at Onich.
25 Mar - Still none in my area, then to my delight I found a frog had laid some spawn in the garden pond where I live in Taynuilt. I think it was laid yesterday. One large clump.
28 Mar - Sallie found a clump of fresh spawn in a ditch at 350 m alt, below Buachaille Etive Mor.
28 Mar - Marion Moir has seen lots of spawn in Ardgour.
29 Mar - Trevor Davies reports several clumps in his garden pond at Clachan Seil, with the tadpoles about 5 mm long and some of them already free from the spawn, possibly due to disturbance by ducks.
31 Mar - I myself have still only seen spawn in two places, one of which is the garden pond outside my front door. It seems to be commoner further north in Lochaber, as are several other signs of spring at the moment.
These results show the value of garden ponds even in a place like this with so much standing water, since there are 3 sightings of spawn in garden ponds out of probably just a handful looked at, but a large number of other apparently suitable pools have been looked at and only a very small percentage had spawn.
Any further sightings as we go into April will be welcome.
9 Apr - Hundreds of good-sized tadpoles in a puddle across a track at a gate used by cattle, at Cuil Bay. The tadpoles in the Taynuilt garden pond are now free from their spawn but still very small; the Cuil Bay ones were much larger.