Olfaction and Sharks— -Tester 
155 
TABLE 3 
Response of Sharks at Eniwetok Marine Biological Laboratory to Human Blood 
RESPONSE* 
YEAR 
MATERIAL AND SHARKS 
RR 
R-R? 
o-s 
A-A? 
AA 
Total 
1959 
Fresh or aged blood 
Normal blacktips 
4 
4 
1 
9 
Blinded blacktips 
1 
4 
2 
2 
- 
9 
Total 
1 
8 
6 
3 
- 
18 
1960 
Aged blood (4-6 days) 
Normal blacktips 
1 
2 
1 
4 
Blinded blacktips 
- 
2 
3 
- 
- 
5 
Normal greys 
- 
- 
1 
4 
- 
5 
Total 
1 
4 
5 
4 
- 
14 
1960 
Fresh blood (1-2 days) 
Normal blacktips 
2 
2 
2 
6 
Blinded blacktips 
- 
- 
2 
2 
3 
7 
Normal greys 
- 
- 
1 
4 
- 
5 
Total 
- 
- 
5 
8 
5 1 
18 
* RR, strong repulsion; R-R?, weak or doubtful repulsion; O-S, no apparent response or sensing; A-A?, weak or doubtful 
attraction; AA, strong attraction. 
Blood 
Most authors agree that blood in the water 
excites sharks. For example, Whitely (1940) 
notes that small blacktip sharks on the Great 
Barrier Reef would follow persons who had 
scratched their legs on coral and would dog their 
footsteps through slightly bloodied water. Bige- 
low and Schroeder (1948) remark that if per- 
sons in the water are bleeding from injuries 
the danger from shark attack may be imminent 
and the results may prove fatal. Moreover, they 
state that the more voracious of the larger sharks 
are excited by blood in the water to such a 
degree that they will make ferocious attacks 
whether the object be fish, whales, or man, dead 
or alive. In contrast, based on experience with 
releasing turtle and sheep blood while fishing 
for sharks, Wright (1948) concluded on ad- 
mittedly weak evidence that blood alone, with- 
out the presence of some moving object, did 
not release the attack pattern. Steinberg ( 1961 ) 
reports that a captive lemon shark was not at- 
tracted by solution of dried beef blood. 
The results of experiments with human blood 
in 1959 are included in Table 3. The responses 
were much more variable and erratic than those 
with food extract. A sensing was at times fol- 
lowed by an attraction response and at other 
times by an apparent flight reaction and a tend- 
ency to avoid the test area. The erratic behavior 
was unlikely related to a visual stimulus as it oc- 
curred in both the blinded sharks and those 
with normal vision. Moreover the quantities 
used, even when the techniques were being de- 
veloped, were not sufficient to produce notice- 
able coloration in the water. It was suspected 
that the variability in response was related to the 
freshness of the blood. 
In I960, 32 experiments were conducted with 
human blood. The results are summarized in 
Table 3 and are given in detail in Table 7. 
Quantities ranged from 0.03 to 6.0 ml of a sus- 
pension of 5 ml of whole blood in 250 ml of 
sea water. With fresh blood tested within 1 or 
2 days after collection, 3.0 ml of the suspension 
usually produced a moderate or strong attraction 
response with the usual behavior components: 
excited circling, swirling and hunting. An attrac- 
tion response was obtained with 0.3 ml of the 
fresh suspension on several occasions and with 
as little as 0.03 ml in one test. By the use of 
dye it was estimated that the shark first encoun- 
tered the material when it had mixed with Va 
to Yi of the volume of the test compartment. 
If this dilution is assumed, it may be estimated 
