Feeding Behavior of Sharks — Hobson 
191 
tracted from the flesh, whereupon the flesh it- 
self was left undesirable to the sharks. Tester 
et al. (1955) expended considerable effort in 
attempts at purification, fractionation, and iden- 
tification of the attractant extracted from fish 
flesh which released a response in captive tuna. 
While the precise identity of the substance 
eluded the investigators, many of its chemical 
properties were determined and presented by 
the authors. Tester et al. (1954) suggest that 
the so-called attractant which is present in the 
body juices of fish, squid, shrimp, and other 
forms may be a substance (or substances) which 
is common to all these forms. 
FEEDING DETERRENTS 
The recent increased interest in the habits 
and behavior of sharks has stemmed largely 
from a growing awareness of the need to de- 
velop a more effective means of protecting hu- 
mans from shark attack. 
A number of tests of proposed repellents were 
conducted, including a test of the repellent now 
in general use by the armed services. The re- 
sults of some of these tests illustrate many of 
the problems involved in producing an effective 
repellent. 
Experiment XII 
This experiment tested the effectiveness of 
the standard shark repellent (copper acetate- 
nigrosine dye) in protecting both dead and 
wounded fish from attack by these sharks. 
The experiment was conducted at two loca- 
tions: (1) on the bottom at the edge of Deep 
Channel, and (2) from the raft. In the tests 
on the bottom, involving whitetips, three baits 
were tied to packages of repellent and anchored 
on the bottom, while seven baits, without re- 
pellent, were anchored nearby. In the tests from 
the raft, which involved grey sharks, all the 
baits were tied to packages of repellent and 
lowered halfway to the bottom. No attempt was 
made to attract sharks before beginning these 
tests. 
The whitetips took all of the unprotected 
baits but did not take any of those tied to the 
packages of repellent. On the other hand, al- 
though the first grey to appear during the tests 
at the raft occasionally exhibited a slight hesi- 
tation when making its approach, it was never 
long before several greys were in the area and 
the bait and repellent package were quickly 
taken together. The repellent packages were 
shortly rejected, but there was no indication of 
a subdued appetite. One grey was seen swim- 
ming away trailing a black cloud of shark re- 
pellent from its gills with no show of discom- 
fort. 
The relative effectiveness of the repellent in 
protecting the baits from the whitetips may be 
related, at least in part, to the absence of the 
group feeding effect in this species. This effect, 
which was discussed earlier, was noted to lower 
the threshold for the release of feeding patterns 
in grey sharks. 
Experiment Kill 
In this experiment the standard shark repel- 
lent was presented as a large cloud, both by it- 
self and as a protective screen for various at- 
tractants. Trials were conducted at the raft in 
which 30 gm of repellent were dissolved in 64 
gal of sea water in a plastic container. This solu- 
tion was presented alone as well as mixed with 
each of the following attractant materials: (1) 
two small macerated goatfish, (2) 500 ml fish 
extract, (3) 1,000 ml of fish extract, and (4) 
2,000 ml of fish extract. The extracts were pre- 
pared by using 50 gm of grouper flesh per 500 
ml of fresh water. 
The presentation was made by simply pour- 
ing the contents of the container into the water 
after a number of sharks had been drawn in 
about the raft and noting the results. In each 
case, a cloud approximately 6 ft deep and 12 
ft wide formed at the surface next to the raft 
and slowly drifted downstream. 
When the plain repellent cloud was intro- 
duced, the sharks rapidly converged on the cloud 
to a distance of approximately 5 yd where they 
circled slowly, following the cloud as it drifted 
downstream. After a few minutes, however, the 
sharks lost interest in the cloud and returned to 
the raft. When the repellent cloud containing 
the macerated goatfish was introduced, the fish 
fragments sank beneath the cloud where they 
were quickly taken by the sharks. The sharks, 
then excited, swam unhesitatingly up into the 
cloud where they circled vigorously. Sixteen 
