DISTRIBUTION AND ABUNDANCE 89 



must have been far more frogs than I have ever known in a district. 

 I cannot help w^ondering whether Fischcr-Sigwart was not witnessing 

 one of the violent fluctuations so characteristic of tliis species, of wliich 

 man is only one cause. 



Smith (1953) considers that the demands of laboratories in the 

 British Isles amounts to at least 150,000 frogs every year. This seems 

 a very large number, until one calculates some proportions. Taking 

 five frogs per acre as a fair average for the whole country, 1 50,000 frogs 

 is approximately the entire population of about fifty square miles of 

 country. This could be devastating if concentrated in one area, but this 

 is unlikely. It only represents 0-04 per cent of the total area of the 

 British Isles, and this is really the measure of the effect of taking 

 150,000 per annum. I think it is almost certain that in countries that 

 have the custom of eating frogs, the numbers taken must be much 

 larger. A dish o£ grenouilles aux fines herhes contains many frogs, and 

 there are more gourmets than laboratory workers. 



Fatio (1872) made arrangements with the peasants who brought 

 frogs of this species to the Geneva market, so that he could examine 

 variations in the colour and markings. In December, January and 

 February, 1860-1861, he examined in this way more than 12,000 

 specimens. There is no indication that he saw all that were brought 

 to market, and Geneva is only one town in Switzerland, a country 

 with an area only about half that of Scotland. It is probable that the 

 number of frogs eaten in Switzerland must have been at least as large 

 as the present demands of laboratories in the British Isles, and probably 

 far more. This trade has, we must assume, been going on for centuries, 

 but thirty years later, Fischer-Sigwart's frog-catchers were still at 

 work, and took very large numbers. 



Nothing I have said in the last paragraph should be taken as sup- 

 porting the practice of using wild animals that breed slowly and are not 

 very common for scientific purposes on this scale. Every effort should 

 be made to use animals that can be bred in captivity, so that a sudden 

 and new load is not placed on a natural population. Smith suggested 

 that something can be done to counteract the drain on the frogs by 

 dispersing clumps of spawn into different parts of the pond. I am, 

 however, doubtful if this is the right way, for the habit of mass- 

 spawning is adaptive. My own suggestion is addressed to school 

 teachers, who often ask their pupils to collect spawn for life-history 

 instruction. Usually a child brings a whole clump, far too many for 



7— (T.914) 



