Worcestershire Record No. 26 April 2009 p. 30

FROG RANA TEMPORARIA L., 1758 SPAWNING TERRESTRIALLY

P. F. Whitehead

On 22 April 2009 I had reason to examine a bed of cultivated hellebores, Helleborus orientalis Monnet de la Marck, in a garden at Broadway, Worcestershire (VC37 SP13). The garden is enclosed. The hellebore bed extends over some 12 m2 and is backed by a high wall running north to south; the arrangement and nature of the other boundaries is such that it is more or less permanently shaded. I was amazed to find a mass of frog spawn amounting to some 140 individual eggs fixed between the horizontal lower leaves of one plant. The leaves of H. orientalis are palmate; over time they incline towards the ground and it was one of these larger leaves that had been selected by the frog as a spawn depository. The female frog was present in the plant bed, like many garden frogs being rather tame and reluctant to move from the spot.

This evidently very rare observation raises some questions. The embryos were of normal size but some were smaller than average. Presumably they had not been fertilised but that cannot be proven; in global terms some frog genera are not aquatic and do not have aquatic tadpoles. However, such discussion is largely academic because there would be no ultimate prospect of survival in this case. In a completely enclosed garden lacking aquatic habitat did the female frog have no option but to spawn in an ornamental plant bed? This seems a likely explanation but a further question surrounds the spawning site. When found on 22 April the spawn was in reasonable shape, the capsules being largely gelatinous. In the period 14-17 April rain fell each day in south Worcestershire amounting to 20mm in total. The continuous and closed canopy of hellebore foliage would have fed rainwater downwards as a continuous cascade, the lower leaves no doubt retaining water superficially. Was this the best a maternal frog could do under the circumstances?

Enshrined in this observation is much of the story of animals and man; the versatile, adaptable and enormously successful frog and the abundant niches and opportunities man has provided for it. The opportunism of the frog should not be underestimated. On 19 March 2009 an emaciated R. temporaria was found at 610 m on Cadair Idris, Merionethshire (VC48 SN71). Its spawn was found in a depression on dry ground in fully insolated montane moorland, which just a few days earlier would have been a shallow peat pool. This is a near-analogue for the Broadway situation, but one in which the outcome would have been quite different.

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