114 ECOLOGY AND LIFE HISTORY OF THE COMMON FROG 



plants. It is different from anything I can attribute to a direct influence 

 upon frogs. 



In my own studies of migration in R. temporaria, I found that the 

 animals moved mainly up wind and uphill, and I had no reason to 

 doubt that wind and probably convection currents were acting 

 according to the hypothesis. But workers on other species have not 

 had the same experience. Moore (1954), working on B. bufo, found 

 that some migration took place with the wind, and was often down- 

 hill, and Chapman and Chapman (1958) came to the same conclusion 

 about B. regularis. I am, however, not at all satisfied that we yet know 

 enough about the movements of air at the places that matter, namely 

 at ground level or even below it, to consider that movement down 

 wind necessarily denotes that the animals are not guided by smell. In 

 the 1935 paper, I pointed out that Giblett (1932) had shown that when 

 wind blows over level country with obstructions, eddies are produced 

 v^th their axes in all directions and with diameters comparable with 

 the size of the obstructions. It is, after all, a common experience to be 

 buffeted by the wind as one walks along, the blows often coming from 

 unexpected directions. 



Moreover, migration often takes place over rough herbage, and I 

 do not think that the movements of air under such cover bears any 

 necessary relation to the direction of the wind as shown on a 

 weathercock perhaps fifty feet from the ground. Budgett (1933) used 

 smoke bombs to study the movements of air near the ground, and 

 found that, even in a gale, smoke often travelled in the opposite 

 direction to the wind. He was investigating the effect of weather on 

 scent in hunting, and concluded that good conditions occurred when 

 the earth was warmer than the air just above it. He showed that under 

 these conditions air currents came out of the ground, but, when the 

 temperatures were reversed, the air sank into the ground. Although 

 he did not mention the point, which was not important to him, it seems 

 necessary to assume that upward air currents must be accompanied by 

 some horizontal movement of air through the upper layers of the soil. 

 Veryard (1935) also studied hunting conditions, and did not agree 

 with Budgett, considering that the favourable conditions were low 

 adiabatic lapse rates, or even inversions, for these tended to prevent 

 the dispersal of eddies. 



Both authors, it should be noted, concerned themselves mainly 

 with air currents and not with wind. This is undoubtedly a very 



