Feeding Behavior of Sharks — Hobson 
177 
In December 1959, while fishing outside the 
seaward reef slope at Palmyra, we saw only grey 
sharks, finding these in considerable abundance. 
At the same time, only blacktips were common 
on the reef flat a hundred yards away. We saw 
comparatively few whitetips at Palmyra, these 
in shallow water over the reef. Klausewitz 
(1959) found these same species occupying 
similar habitats in the Red Sea. 
Exceptions to this general distribution pat- 
tern were noted. Large grey sharks appeared at 
poison stations in water scarcely 6 ft deep, 
while whitetips were seen swimming over open 
bottom, far from the nearest coral head or rock. 
Furthermore, Strasburg (1958) reports the 
catching of two blacktips at sea in the Mar- 
quesas. 
BEHAVIOR AND HABITAT 
The sluggish behavior noted in the whitetip 
is consistent with a life in and about the caverns 
and crevices of the coral reef. This species was 
noted as being clumsy and ineffective in at- 
tempts at taking baits which were suspended 
in midwater. However, this same shark was re- 
markably effective in tracking down and cap- 
turing prey which had taken shelter deep in one 
of the many holes or crevices typical of a coral 
reef, thus making available to it prey which 
are beyond the reach of both greys and black- 
tips. Considerable time was spent placing 
wounded fish far back into small holes in the 
reef and then watching as a whitetip appeared, 
nosed about tentatively for the correct hole, and 
then swam in and captured its prey. Large 
whitetips were seen disappearing into small 
holes from which they presently emerged, al- 
ways head first. The experiment described be- 
low involved whitetips and greys and illustrates 
the division of the food source between these 
two species. 
Experiment 1 
Three small wounded fish, each essentially 
identical, were presented simultaneously at three 
positions below the raft at the edge of Deep 
Channel, where water depth was approximately 
35 ft: (1) Suspended mid-way between surface 
and bottom; (2) on the bottom in an exposed 
position; (3) concealed in a hole beneath a 
large rock on the bottom. 
Bait 2 was lowered to the bottom at the end 
of a weighted line. Baits 1 and 3 were both 
secured to a single line which ran from the raft, 
down under one side of the rock, through the 
hole, out the other side and back up to the raft. 
By alternately hauling in one end of the line or 
the other, both baits could be simultaneously 
hauled aboard the raft or lowered into position. 
The experiment was repeated 16 times when 
both greys and whitetips were in the vicinity. 
Although the two species seemed equally adept 
at taking the exposed bait on the bottom, the 
suspended bait in all but one instance was taken 
by a grey, while the whitetips completely mo- 
nopolized the bait concealed in the hole. 
When grey sharks encountered humans in 
shallow water they often started and fled in 
much the same manner described for the black- 
tip, rather than exhibiting their usual relatively 
bold inquisitive approach. Possibly this apparent 
change in behavior was a result of their being 
out of their usual habitat. This observation 
might offer an insight into the characteristically 
timid behavior of the blacktip. Perhaps this ap- 
parent timidity is an adaption of these relatively 
large animals, which must remain in motion, to 
a shallow water habitat. The shark, unable to 
take shelter and without room to maneuver, 
may find flight the alternative. In the blacktips, 
this characteristic timidity is more apparent in 
the larger individuals. The suggestion that this 
behavior might have some survival value im- 
plies the existence of a natural predator. The 
only evidence we found of such a predator was 
the presence of an 18-inch blacktip in the 
stomach of an 80-lb grouper. 
DETECTION AND CAPTURE OF FOOD 
Sharks are well known to feed avidly on dead 
fish, meat, and many other food materials 
dumped as garbage or used as bait. It is also 
well known that they will consume living fish 
impaled on a hook or spear. These, however, are 
unnatural situations. Undoubtedly, under nat- 
ural conditions these sharks will feed on such 
prey as may have been killed or weakened by 
disease or injury. The sharks in the Eniwetok 
lagoon, as elsewhere, are highly responsive to 
stimulus situations which suggest injured 
and/or distressed, as well as dead or moribund 
