510 



H. HEUSSER 



geruchliche oder kinàsthetische Kenntnis der Topographie, Befolgen einer Haup- 

 trichtung, Kompassorientierung und Navigation nach Sonne, Mond, Sternen und 

 andern sehr weit entfernten Fixpunkten (visuell); funktionelle Analoga zu diesen 

 Orientierungstypen werden diskutiert. 



Die Orientierungsweise von Bufo bufo beim Laichplatz- und Sommerquartier- 

 Finden ist vôllig unbekannt. 



SUMMARY 



The orientation of the common Toad ( Bufo bufo bufo ) belonging to 4 breed- 

 ing places in 2 neighbouring ponds near Zurich, Switzerland, was investigated, 

 both in relation to spécifie breeding places and in relation to the summer quarters. 

 Eleven sources of errors were found, which have to be considered in displacement 

 experiments. 



By means of marking wandering individuals their belonging to a spécifie 

 breeding place was established, according to their definite migration ways. 



Toads captured on the breeding migration or in breeding places and dis- 

 placed were able to find again their own breeding places from other ponds, other 

 breeding places — even in the same pond — as well as from unknown areas up to 

 3 km. Toads do not change their breeding places spontaneously, they show 

 lifelong fidelity to the same place, even when displaced into other breeding places. 



Introduced foreign toads could not find the breeding places of our indigenous 

 populations, even in easy conditions; translocated toads of our populations did 

 not accept the breeding places of the foreign populations. 



After the breeding season, toads return to their individual summer quarters, 

 distant at most of 500-1.500 m. from the breeding place. Displaced groups and 

 individuals tested in an open arena can readily be mislead by edges of forests and 

 by gradients of brightness, because they use the same orientation as they use to 

 do at their location of capture. Later they take the correct direction towards their 

 goal. In a covered arena, standing free or indoors (up to 9 km.) toads are moving 

 sometimes towards the breeding place, sometimes in the opposite direction and 

 sometimes in other directions. 



The following hypothetical orientation mechanisms are certainly not involved 

 in an appréciable manner in the localization of the breeding places and summer 

 quarters: goal-finding by chance, visual and auditory goal-perception, hydro-, 

 hygro-, chemo- and geotaxis, topographical memory by means of visual, olfactory 

 and kinàesthetical eues, following a main direction, compass orientation and 

 navigation in relation to sun, moon, stars and other distant points; funcionnally 

 analogous hypothèses are discussed. 



The orientation mechanism in Bufo bufo to the breeding places and the 

 summer quarters remains fully unknown. 



