180 
PACIFIC SCIENCE, Vol. XVII, April 1963 
Experiment III 
The purpose of this experiment was to de- 
termine if these sharks are capable of orienting 
themselves in a current and following an olfac- 
tory corridor in a direct line to its source in the 
absence of other stimuli. 
A location on the edge of Deep Channel sim- 
ilar to that used in Experiment II was chosen. 
Essentially clear, colorless fish extracts were used 
as the olfactory cues. These were prepared from 
several species of grouper but always of the 
same concentration (600 gm of fish flesh or 
skin macerated in a Waring blendor with 6 
liters of fresh water and diluted in a large plas- 
tic container with 64 liters of sea water). The 
material was introduced from the glass-bottom 
boat by siphoning from the container through a 
clear plastic 34-inch hose which ran down to the 
top of the reef. From here it continued down 
the slope through a series of holes to a small 
cave at the base of a large rock. The hose was 
thus effectively concealed for a distance of ap- 
proximately 30 yd from the cave. 
Eight tests were conducted under various ve- 
locities of tidal current over a 15 -day period 
with no more than one trial on any one day. 
Each test was preceded by a 30-min control 
period during which any unusual behavior in 
sharks sighted was noted. The duration of the 
introduction varied according to the response of 
the sharks. Observations included the species 
and general behavior of the sharks and particu- 
larly the direction and nature of approach. The 
results are given in Table 2. 
A consistent response was exhibited by both 
grey and blacktip sharks during this experiment. 
In the presence of a current they appeared from 
downstream, swimming at an accelerated rate 
directly to the mouth of the cave where, in most 
cases, they briefly stuck their snouts inside. They 
then turned in very small circles here for a short 
period of time before returning slowly, in a 
random manner, downstream. After an initial 
approach by any one shark, this same shark 
often reappeared and repeated the above de- 
scribed pattern several times. However, upon 
the third or fourth approach by the same shark, 
this shark often reversed direction 5-10 yd short 
of the hole and returned downstream without 
the characteristic circling. 
TABLE 2 
Response of Sharks to Extracts of Fish Flesh or Skin (Experiment III) 
(All Sharks Came from a Downstream Direction) 
TRIAL 
EXTRACT 
TIDAL CURRENT 
NO. AND LENGTH OF 
SHARKS RESPONDING 
TIME TO 
INITIAL 
APPEARANCE 
TOTAL 
INTRODUCTION 
TIME 
1 
frozen 
flesh 
ebb, moderate 
1 6-ft grey 
1 4-ft grey 
1 4-ft whitetip 
10 min 
1 hr 
2 
frozen 
flesh 
flood, moderate 
1 4-ft grey 
1 5 -ft grey 
2 4-ft whitetips 
12 min 
1 hr 
3 
frozen 
flesh 
ebb, moderate 
1 4-ft grey 
1 5 -ft grey 
25 min 
30 min 
4 
frozen 
flesh 
ebb, weak 
1 4-ft grey 
1 4-ft whitetip 
35 min 
1 hr 
5 
frozen 
flesh 
ebb, weak to 
moderate 
1 4-ft grey 
1 4-ft blacktip 
1 5 -ft whitetip 
16 min 
45 min 
6 
frozen 
flesh 
flood, moderate 
to strong 
3 4-ft greys 
1 4-ft whitetip 
9 min 
45 min 
7 
fresh 
flesh 
flood, strong 
2 6-ft greys 
1 4-ft grey 
1 4-ft whitetip 
1 5 -ft whitetip 
7 min 
30 min 
8 
fresh 
skin 
flood, moderate 
to strong 
3 6-ft greys 
1 4-ft grey 
6 min 
30 min 
