Spawning of the Common Toad


    IT is only during recent years that biologists have realized that they are far from a complete understanding of the influence of external factors on the spawning of even the commoner amphibians. The common toad (Bufo bufo bufo) is an ‘explosive breeder’, that is to say, all the sexually mature individuals in a district migrate from their diverse hibernation quarters to their breeding sites within a few days of one another, and within even large areas there is singularly little deviation from the normal of the year. There have been occasional records of isolated pairs found spawning long after the normal time, but some observations made by Mr. G. Shrub-sole, who writes from the Victoria Court Hotel, Eastbourne, made during the last two years, seem to indicate the existence in Sussex of an area which is exceptional. A series of small ponds on Beachy Head were visited at intervals for conchological work, and on July 30 and August 1, 1935, unhatched toad spawn was found in at least three of them. One pond was kept under observation and unmetamorphosed tadpoles were still found at the beginning of December. In 1936 tadpoles were first found in the same, and one other pond, at the beginning of May, but never throughout the year were they ever observed in any of the others. The development of the tadpoles was apparently very slow, for even in September the majority still had mere rudiments of hind-limbs. But whether these very late tadpoles were of the same brood as those found early in May is uncertain (the normal larval period is only 12-14 weeks), for although no fresh spawn was found, adult toads were discovered in the water in July. Their presence at a time so long after tadpoles had been observed is unusual, for the whole of the breeding operations are normally concluded within a week or so, and the adults then leave the water for the rest of the year. Their presence certainly suggests the possibility that there may have been a July spawning in 1936, as there was in 1935, and, if this proves to be a regular occurrence, a detailed investigation of the physical conditions of the district should be of importance.

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    Spawning of the Common Toad. Nature 138, 835 (1936).

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