The Role of Olfaction in Shark Predation * 1 
Albert L„ Tester 2 
It IS RECOGNIZED that most if not all species 
of sharks possess a keen sense of smell which is 
used in detecting dead and wounded prey or 
other edible material during their well-known 
scavenging operations. The early experiments 
of Parker ( 1910) , Sheldon ( 1911 ) , and Parker 
and Sheldon (1913) established the role of the 
paired nasal organs as olfactory receptors. Parker 
(1914) demonstrated directional response in 
the smooth dogfish (Must elm canis) and pro- 
vided a plausible explanation of how this was 
accomplished; he postulated that the two sep- 
arated nostrils have the ability to detect small 
differences in the concentration of odorous ma- 
terials enabling the shark to orient in the direc- 
tion of equal stimulation and to head "up- 
stream” to the source. This tracking ability is 
well recognized by skin divers and fishermen 
who have involuntarily attracted sharks by re- 
taining speared fish or by discarding trash fish 
and offal from their boats. 
It seems unlikely that any shark species could 
maintain itself entirely by scavenging opera- 
tions, except perhaps in areas where man pro- 
vides forage such as bait, fish offal, or other 
forms of edible garbage. Certainly the larger 
species are recognized as active predators which 
attack uninjured living prey, including man. 
Doubtless, vision plays a predominating role in 
locating and tracking normal living prey, and 
possibly other senses such as hearing are also 
involved. In considering olfaction, attention has 
Presented at the Tenth Pacific Science Congress of 
the Pacific Science Association, held at the University 
of Hawaii, Honolulu, Hawaii, August 21 to September 
6, 1961, and sponsored by the National Academy of 
Sciences, Bernice P. Bishop Museum, and the Uni- 
versity of Hawaii. 
1 Contribution No. 179 of the Hawaii Marine Lab- 
oratory, University of Hawaii, Honolulu 14, Hawaii. 
2 Department of Zoology, University of Hawaii, 
Honolulu 14, Hawaii. Manuscript received November 
23, 1961. 
focused largely on feeding activity induced by 
the release of attractive substances such as blood 
or other body fluids from the wounds of in- 
jured prey. The possible part played by olfaction 
in the detection and tracking of uninjured liv- 
ing prey has been largely overlooked. 
In this paper I will present the results of 
experiments on the olfactory response of cap- 
tive sharks to extracts of natural foods, to hu- 
man materials, and to uninjured living fish in 
the hope of clarifying the role of olfaction in 
shark feeding activity. The results form part of 
an investigation of factors affecting the be- 
havior of sharks sponsored by the Office of 
Naval Research (Contract Nonr 2736(00), 
Project nr 104503) over the period 1959-61. 
The work was undertaken at the Eniwetok Ma- 
rine Biological Laboratory, Eniwetok Atoll, Mar- 
shall Islands, and at the Hawaii Marine Labora- 
tory, Oahu, Hawaii. I am grateful to the respec- 
tive directors, Dr. R. W. Hiatt and Dr. A. H. 
Banner, for laboratory facilities. I am indebted 
to personnel of the Atomic Energy Commission 
and the Pacific Missile Range Facility for logis- 
tic and other help. I am particularly indebted to 
those graduate students who have assisted in 
phases of the project: Edmond S. Hobson, Su- 
sumu Kato, Taylor A. Pryor, and Bori L. Olla. 
FACILITIES, MATERIALS, AND METHODS 
Eniwetok Marine Biological Station 
At Eniwetok, small (18-36 inches) blacktip 
sharks (Carcharhinus melanopterus ) and small 
(20-36 inches) grey sharks ( C . menisorrah) 
were readily caught in shallow water by hook 
and line and established in captivity. Holding 
facilities consisted of two large concrete tanks 
housed in a building and illuminated by over- 
head fluorescent lighting (Fig. 1). The tanks 
were supplied with running sea water pumped 
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