Feeding Behavior of Sharks — Hobson 
193 
8. These sharks are able to follow an olfac- 
tory stimulus quickly and directly to its source 
without benefit of other orienting stimuli when 
the olfactory material has been drawn out as a 
narrow trail by a strong current or, in standing 
water, when the source of the olfactory stimulus 
is moving. 
9. Generally, olfactory stimuli are effective 
in releasing a highly motivated pattern of ex- 
ploratory behavior in grey sharks, which is ap- 
petitive in nature. Consummation of the feeding 
act then requires a subsequent specific stimulus, 
as for example one of vision. 
10. The grey shark is often highly excited by, 
and attracted to, the source of rapid and/or er- 
ratic movement. The effect is intensified in the 
presence of certain olfactory stimuli but is not 
dependent on their presence. 
11. Despite displaying varying degrees of ini- 
tial curiosity toward many unusual stimulus situ- 
ations arising in their environment, the sharks 
exhibit caution when encountering a situation 
which is unfamiliar. This caution will steadily 
subside, however, with an increasing familiarity 
with the situation. 
12. The final phase of approach to a motion- 
less prey by the grey shark is normally directed 
by vision, even though the feeding pattern may 
have been initially released by some other sen- 
sory modality, for example, olfaction. 
13. Although vision is an important sense in 
the feeding activity of these sharks, a high de- 
gree of acuity and form discrimination is not 
demonstrated. Rather, the significant visual cues 
seem to involve the detection of movement or 
contrasting brightness, or both. 
14. These sharks may attack any object which 
they sense in a high concentration of an olfac- 
tory material. 
15. The grey shark rejects, from the mouth, 
food which does not permit acceptable gustatory 
stimulation. 
16. The standard shark repellent (copper 
acetate-nigrosine dye) now in use by the armed 
forces is ineffective in preventing the grey shark 
from swimming into a cloud of this material 
when the species is present in numbers and is 
motivated by food within and adjacent to the 
material. 
ACKNOWLEDGMENTS 
The author is indebted to Dr. Albert L. Tester 
for many helpful suggestions during the course 
of the investigation and for his constructive 
criticism of the manuscript. The study would 
not have been possible without assistance in 
the field from Dr. Tester and Mr. Francois Mau- 
tin, as well as from Mr. John Kay, Mr. Bryant 
Sather, Mr. Susumu Kato, Mr. Taylor Pryor, 
and Mr. Albert Smith, graduate students, and 
Mr. Henry Yoshihara, undergraduate student, 
all of the University of Hawaii. The facilities 
at Eniwetok were made available by Dr. Robert 
W. Hiatt, Director of the Eniwetok Biological 
Laboratory, as well as by the Atomic Energy 
Commission, the Pacific Missile Range Facility 
of the United States Navy, and by the Holmes 
and Narver Construction Company. The author 
also wishes to thank Dr. William A. Gosline 
and Dr. Ernst S. Reese of the Department of 
Zoology and Entomology, University of Hawaii, 
and Dr. Donald W. Strasburg of the Honolulu 
Biological Laboratory, United States Fish and 
Wildlife Service, for critically reviewing the 
manuscript. 
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