86 ECOLOGY AND LIFE HISTORY OF THE COMMON FROG 



became enters the water to breed. If the same sort of comparisons are 

 made with mice, and we suppose that we have a pair of mice and a pair 

 of frogs, and no deaths occur, we arrive, on a conservative figure, at a 

 population of mice of about half a million, to compare with 1,500 frogs. 



It is difficult to say how the idea that frogs have an exceptionally high 

 death rate came into the literature. It has been there for a long time, 

 for Roesel (1758) and Smith (195 1) both have it. It probably happened 

 because when a frog does die, it often does so in a conspicuous manner, 

 by being eaten at the time of the year when large numbers of them 

 congregate for breeding in the ponds. It does seem, however, that 

 the many writers who have perpetuated this myth have been un- 

 critical, for a slowly maturing animal that only lays 1,500 eggs per 

 pair per year cannot have a high death rate. It is, however, only fair 

 to point out that the high death rate in birds, which I have used for 

 comparison, was greeted with incredulity by Lack's first audiences on 

 this subject, and that the high death rate in tadpoles, which accounts 

 for so many deaths in R. temporaria, was not pubhshed until 1952. 



In the hope of getting rid of the idea, the following short summary 

 might serve as a model for future authors: "The reproductive rate 

 and the death rate of frogs is lower than that of many other small 

 animals, in spite of the fact that birds and mammals protect their young. 

 Most of the deaths take place in the tadpole stage. Frogs hve a safer 

 Ufe than most other small land vertebrates." 



The safety of the life of R. temporaria is, however, greatly surpassed 

 by that of another Anuran which lives in small ponds not unlike those 

 that are used by the frog. Bombina variegata lays only about 80 eggs 

 in a season. It does so, however, in the summer, laying at intervals of 

 some weeks, and choosing different portions of weed to which the 

 female attaches the eggs a few at a time. A catastrophe to one lot of 

 eggs does not imply that this female will leave no progeny in that 

 season. Moreover, the adult has warning coloration which it displays 

 when attacked. Even so, this is a remarkably low reproductive rate 

 for an animal that does not look after its young. Anuran life must be 

 a placid affair compared with that of those unfortunate birds and 

 mammals. 



Predators of Adult Frogs 



I remarked earlier in this book that any natural event in the life of 

 an animal that is certainly seen by even one observer is probably part 



