Feeding Behavior in Three Species of Sharks 1 
Edmund S. Hobson 2 
This report concerns a study of the feeding 
behavior in three species of sharks: Car char - 
hinus menisorrah Muller and Henle, the grey 
shark (Fig. 1), Car char hinus melanopterus 
Quoy and Gaimard, the blacktip shark ( Fig. 2 ) , 
both of the family Carcharhinidae; and Triae- 
nodon ohesus Ruppell, the whitetip shark (Fig. 
3 ) , of the family Triakidae. The study was con- 
ducted in the lagoon at Eniwetok Atoll, Mar- 
shall Islands, during the summers of 1939 and 
I960. It was a segment of a broad program of 
investigation of shark behavior in which labora- 
tory and field work were coordinated whenever 
possible. The overall program, conducted at 
both the Eniwetok Marine Biological Labora- 
tory and the Hawaii Marine Laboratory, Coco- 
nut Island, Hawaii, was under the direction of 
Dr. Albert L. Tester, with financial support 
from the Office of Naval Research (Contract 
Nonr 2756(00), Project NR 104503). 
Observations of sharks in their natural en- 
vironment have been the basis for most of the 
shark literature which is available today and 
yet comparatively little has been offered toward 
a realistic understanding of shark behavior. 
Most of this material has been written for popu- 
lar consumption and is therefore oriented to- 
ward the sensational rather than the scientific. 
We do find scientifically oriented accounts in 
the literature (as for example, Eibl-Eibesfeldt 
and Hass, 1959; Limbaugh, 1958; and Wright, 
1948) but these observations are limited largely 
to incidental encounters. 
A critical study of shark behavior, undertaken 
with planned experiments in the sharks’ natural 
1 Prepared as partial requirement for the Master of 
Science Degree, University of Hawaii. Contribution 
No. 180, Hawaii Marine Laboratory, University of 
Hawaii, Honolulu, Hawaii. Manuscript received No- 
vember 23, 1961. 
2 Department of Zoology, University of Hawaii. 
Presently at the Department of Zoology, University of 
California, Los Angeles 24, California. 
environment — the aim of this investigation — 
has been almost completely neglected. 
In this study, a comparison is made of the 
feeding behavior of the three species. Behavior 
is further related to habitat and to distribution 
within the lagoon. Experiments designed to il- 
lustrate the roles played by the major sensory 
modalities are presented. This last portion of 
the investigation, dealing primarily with grey 
sharks, includes a consideration of the specific 
stimuli involved in releasing feeding behavior. 
Consideration is also given to food preferences 
and to factors which may possibly inhibit feed- 
ing. 
GENERAL DESCRIPTION OF STUDY AREAS 
The study was centered about two primary 
locations: (1) the lee of Engebi Island during 
1959, and (2) the lee of Bogen Island, adjacent 
to Deep Channel, during I960. The Engebi 
Island site was in 1 5 ft of water over a relatively 
shallow sand and coral rubble flat extending out 
from shore for approximately 400 yd before 
dropping suddenly into the deeper regions of 
the lagoon. Currents are weak in this area and 
the water is generally turbid, with underwater 
visibility commonly less than 20 ft. At the 
Bogen Island site strong tidal currents are pres- 
ent and underwater visibility often exceeds 100 
ft. The edge of Deep Channel at this point drops 
abruptly from a depth of approximately 10 ft 
at the rim to 110 ft at the bottom. 
At these locations, observations were made 
from the following vantage points: 
1. An underwater chamber was fitted to a 
vessel moored in the lagoon. This chamber was 
a metal cylinder, 14 ft long and 2 V 2 ft in di- 
ameter, open at the top and closed at the bot- 
tom, with viewing ports on three sides near the 
bottom. An observer in the chamber was situ- 
ated approximately 8 ft below the surface. 
171 
