608 
PACIFIC SCIENCE, Vol. XV, October 1961 
TABLE 2 
Summary of Similarities and Differences Between the Two Incidents 
FIRST INCIDENT 
SECOND INCIDENT 
Activities at time of incident 
spear fishing 
spear fishing 
Dead or injured fish present 
yes: 1 
yes: 1 
Skin diving or SCUBA 
skin diving 
skin diving 
Species of shark 
Carcharhinus menisorrab 
Carcharhinus menisorrab 
Number of sharks in area 
3-5 
1 
Size of sharks (length) 
5-7 ft. 
6 ft. 
Date 
Sep. 1, I960 
Sep. 2, I960 
Time of day 
approx, noon 
approx, noon 
Condition of sky 
clear, few clouds 
clear, few clouds 
Condition of sea 
cajm 
calm 
Location of incident 
lagoon, Eniwetok 
lagoon, Eniwetok 
Distance from shore 
200 yd. 
35 yd. 
Near deep water 
yes 
yes 
Underwater visibility 
100 ft. + 
100 ft. -!- 
Depth of water 
25 ft. 
15 ft. 
Depth at which incident occurred - 
surface 
1 5 ft., bottom 
Water temperature 
approx. 85° F. 
approx. 85° F. 
Nature of bottom 
coral reef 
coral reef 
Number of persons in water 
3 
1 
Nature of approach 
direct, fast 
direct, fast 
Area of body approached 
feet 
head 
Persistency of shark 
moderate 
considerable 
DISCUSSION 
The two incidents are summarized in Table 2. 
The authors believe that neither the coloration 
of the swimmer’s equipment, the condition of 
the water, -nor the time and nature of the day 
are significant. There are four major differences 
between the two incidents which are believed 
to be significant: (1) the number and relative 
positions of persons in the water, ( 2 ) the num- 
ber of sharks in the vicinity, ( 3 ) the site of the 
incidents, the first on the surface, the second on 
the bottom, and (4) the location of the diver 
relative to the wounded fish. There are three 
major similarities between the two incidents 
which are believed to be significant: (1) both 
occurred in the vicinity of, and subsequent to, 
the spearing of a fish; (2) both occurred near 
deep water; and (3) both involved the same 
species of shark, which attacked without hesita- 
tion. 
The last point may be explained by two facts. 
First, throughout the summer, Hobson, Mautin, 
and others noticed that C. menisorrab was a far 
more aggressive shark than the other two species 
which are common in the lagoon (C. melanop- 
terus and Triaenodon obesus) . This view is sup- 
ported by Harry (1953: 48), who reports that 
the natives of the Tuamotus fear this species and 
claim it will attack man. Second, both incidents 
occurred within approximately a mile of where 
shark behavior experiments were conducted 
throughout the summer. Hobson recognized the 
shark in the second incident as having been a 
participant in these experiments, and it is prob- 
able that the sharks Involved in the first incident 
had also had considerable experience with seeing 
human beings in the water. It is the belief of 
Hobson, Mautin, and others that the sharks be- 
came progressively bolder towards humans dur- 
ing the course of the summer. Thus it may be 
significant that both incidents occurred at the 
end of the summer. 
It appears that one can generalize to this ex- 
tent. Some species of sharks, for example C. 
menisorrab , are attracted to an area where there 
are injured fish. Apparently stimuli originating 
with the injured fish release an excited, highly 
motivated pattern of exploratory behavior In the 
shark. At such times many sharks seem to be 
particularly reactive to any unnatural distur- 
bances created by humans in the general area. 
