310 



o 



CO 



NJ 



18 



I 6 



14 



12 



10 - 



8 - 



CHEMICAL SENSES 



Quadrant 2 



Quadrant I 



Quadrant 4 



> Qu 



adrant 3 



Site of Chemical Stimulation 



Figure 28 Regressions of the statistic. Conditions were as in Fig. 26, but the 

 water was stagnant. From Kleerekoper et al. (1975). 



The shark's ability to pinpoint the source of stimulation is drastically 

 affected by flow conditions, as time series of plots of its locomotor tracks 

 demonstrate (Figure 30). The localization is precise in the slowly flowing 

 water and requires only a few seconds to 3 or 4 min, depending on the 

 position of the animal at the start of the release of the stimulus. The shark 

 may remain exactly over the releasing needle for long periods, which are 

 interrupted occasionally by short excursions in other areas, mostly near the 

 stimulus source. Whether these excursions are movements in "search" of 

 additional mechanical or visual information can only be speculated at this 

 time. It is notable, however, that they are rare and of very short duration. 

 Occasionally, snapping at the needle site has been observed. 



