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PACIFIC SCIENCE, Vol. XVII, April 1963 
TABLE 5 
Index of Activity in Successive Rings (No. 1, Center) of a Target Area for a Hammerhead 
Shark During Successive Tests of "Tilapia Water’’ and Human Sweat in Pond 5, 
Hawaii Marine Laboratory, June 16, 1960 
RING NUMBER 
TEST 
1 
2 
3 
4 
AVERAGE 
Controls, sea water 
4.5 
5.5 
14.8 
20.7 
11.4 
Tilapia water 
27.3 
29-3 
22.0 
11.8 
22.6 
Sweat 
5.4 
8.3 
13.1 
12.3 
9.8 
Tilapia water 
28.4 
36.8 
29.4 
20.6 
28.8 
Controls, sea water 
15.0 
19.1 
16.9 
20.0 
17.7 
Tilapia water plus sweat 
15.1 
30.0 
21.2 
16.9 
20.8 
and a tendency to avoid the test area. A strong 
repellent effect (RR) included in addition a 
rapid exit from the area following sensing, 
sometimes accompanied by head shaking. When 
no noticeable response occurred it was found 
usually that this was also the case with the 
known attractant. In the one case classed as 
doubtful attraction, the first sweat test which 
was conducted, it is likely that initial sensing 
was interpreted as attraction. The quantitative 
data of Table 8, illustrated for two experiments 
in Figure 7, give convincing evidence of a de- 
pression of shark activity following the intro- 
duction of sweat. In each of the 29 tests, the 
time spent in the test areas during test condi- 
tions was less than during control conditions; 
this is in striking contrast to the results with 
standard extract where the reverse is almost 
invariably encountered. 
The apparent aversion to sweat was exhibited 
by both normal and blinded blacktips, possibly 
to a greater extent in the latter. The sweat of 
one donor (ALT) seemed to be effective at a 
roughly-calculated concentration of about 1 part 
per million. The sweat of a second donor (TAP) 
produced no obvious repellent effects in the two 
tests which were made. 
Because of the possibility that the sharks in 
1959 had become conditioned to associate sweat 
with punishment, e.g., from handling, the ex- 
periments were repeated during I960, taking 
precautions against sweat dripping accidentally 
into the water and using fresh sharks, some of 
which had not been touched by hand. The re- 
sults in I960 were similar to those in 1959 
(Tables 4, 9). With the blacktips the majority 
of the responses were classed as repulsion; in 
the one case of apparent attraction, again the 
first test of the season, the sharks had just been 
introduced and still exhibited erratic behavior. 
There was no noticeable difference in response 
between the blinded and normal blacktips. With 
the grey sharks an aversion to human sweat was 
present in the majority of the tests but it seemed 
less pronounced than with the blacktips. There 
were no obvious differences in response between 
the sweat of three donors. The sweat did not 
decrease in potency with aging at room tem- 
perature for several days; rather, its repellent 
properties seemed to increase but this could 
not be established with certainty. 
In tests conducted during the winter of 1959— 
60 on the tiger, hammerhead, and grey sharks 
at the Hawaii laboratory, larger quantities of 
sweat (10-40 ml) were used because of the 
greater volume of the ponds compared with the 
Eniwetok tanks. In most cases the results, sum- 
marized in Table 4, showed vague repellent ef- 
fects following the introduction of sweat. For 
the most part, the sharks displayed only a tend- 
ency to avoid the test area (R? ), occasionally 
with a sharp veering from the presumed loca- 
tion of the material and rapid swimming 
through or away from the test area (R). Apart 
from these latter overt responses which were 
displayed on occasion by all three species, the 
only strong repulsion concerned the tiger shark 
in one test and consisted of obvious "agitation” 
and head shaking. Repellent effects were noted 
with the sweat of all three donors ( ALT, RJ, and 
ESH) but more consistently with that of the 
first two than the last. 
