LEBENSWEISE DER ERDKRÔTE 



979 



SUMMARY 



M 



This is an analysis of the behaviour of the Common toad Bufo bufo. 

 The breeding period is short and relatively constant as to the time of the year. 

 Migration towards spawning grounds begins at spécifie periods for différent 

 : ' populations. External factors: température, rain, and twilight, act complementary 

 |to the internai factors in initiating migration. In meteorologically exceptional 

 '%ears migration can take place to a certain extent in spite of unfavourable condi- 

 tions. In such cases migration is relatively independent of température. 



When the females have spawned, their behaviour changes and they leave 

 the spawning grounds during the following night for their Summer quarters. 

 W few days later most of the maies leave the pond but a few may remain until 

 May. 



When the toads have reached their Summer quarters, their critical tempér- 

 ature of activity, 5-6° C (migration) increases to 11-12° C (search for food). 

 Should the température during the night be too low in April, the toads will bury 

 ;hemselves for 2-3 weeks and become once more léthargie. 



The toads will reappear in May only together with the young and females 

 ,vho have not spawned (most of the females do not spawn two years consecutively). 



Most of the toads have Summer quarters at 500-1500 m from the spawning 

 grounds. The spécimens from the one pond (Gattikerweiher) go about twice the 

 distance from those of the other (Waldweiher). The females of ail the populations 

 ' )n an average go farther than the maies. The surroundings of the ponds and also 

 bther areas are inoccupied in Summer. The forest is the preferred biotope. The 

 r! ireas of the Summer quarters of différent individuals are sometimes crossed, 

 : but each population has its own area. Individuals artificially deviated during 

 : >pring migration compensate both the direction and the distance. A. concludes 

 j hat there exists a problem of orientation. During the Summer months, the toads 

 1 emain in their area in which they forage for food for distances of 50-150 m. 



In August, ail toads which will go to spawn in the following Spring begin 

 ; m autumn migration. Until September, they corne closer to the pond so that those 

 ■ 'vhose Summer quarters are farthest away will have already accomplished most 

 > : ')f the migration. It is in the forest, near to the spawning grounds that the toads 

 vill become fixed from September or October. It is exceptional that a toad will 

 î jearch for water already in the Autumn. 



The autumnal migration is probably initiated by the reproductive instinct, 

 !»ut the reaction threshold is higher than in Spring and therefore copulation is 

 are in Autumn. 



During the fîrst half of October the toads dig themselves in whatever the 

 : împerature and do not émerge during warm Winter weather. 



Rev. Suisse de Zool., T. 75, 1968. 64 



