78 ECOLOGY AND LIFE HISTORY OF THE COMMON FROG 



for 6th January for the spawn ponds is fully rehable, for it was based 

 on samples from all of them, and it is therefore clear that these ponds 

 do have high phosphate at an early date — it must be that it gets used 

 up rapidly as the season advances. It is not certain whether there is a 

 relation between phosphate and geology, for all these ponds lay 

 on only two formations, and the sample was small. These results will 

 be discussed further in Chapter 8, for they have a bearing on the 

 factors affecting the date of spawning. Detailed statistical fmdings are 

 in Chapter lo, Appendix i e. 



I do not beheve that the chemistry of the ponds has a direct action 

 on the frogs. The evidence for this lack of behef is comphcated, and I 

 cannot discuss it here. It will have attention later in Chapter 8. 



It is easy to see that an extension of the principle of avoidance that 

 I have suggested for the London Clay ponds might, if it were absolute 

 instead of relative, result in some areas being entirely without frogs, 

 even if the area was physically available to them. This does happen. 

 For example, South Haven Peninsula, Dorset, has no frogs. A part of 

 this very interesting area has been built up out of the sea during the 

 last hundred years (Diver, 1933), and is still increasing. Another part, 

 however, is ancient land, the Bagshot Beds. All the water in the area 

 is fresh, and, indeed, with one minor exception, is very poor in saline 

 constituents. B. btifo occurs, and so does the smallest British newt, 

 T. helveticus, which breeds in almost every pool, both on the old and 

 on the new land. Since the poorest traveller of all the British amphibia 

 has colonized the area, it is impossible to beheve that the area is without 

 frogs merely because they have not had time to reach it. They occur 

 on Grange Heath, only about eight nules away and with no intervening 

 obstacles (Smith, 1938). In my view, the absence of frogs is exphcable 

 on the hypothesis that the water of South Haven Peninsula is not 

 attractive to frogs. 



There are other areas without frogs. For example. West Sedgemoor, 

 all the ground above the 600 foot contour near Alnwick, Northumber- 

 land, parts of Gloucestershire have all been reported as being v^thout 

 frogs, and there are probably many such cases. In none are the frogs 

 very far away, for Taylor (1948) recorded them from every county 

 in England and Wales. On the other hand, Mr. C. Paris, writing from 

 Ireland, said that frogs were so common in his area that he could not 

 say for certain that any pond would not contain spawn. 



Geological relations have been noted by other authors in other 



