Fróðskaparrit - 01.01.1991, Page 47

STUDIES ON THE LONG-FINNED PILOT WHALE
51
and Zachariassen, 1990b). One possible ex-
planation for a variable sex-ratio through
time could be the placement of the examina-
tions in relation to the c.l20-year cycle of pi-
lot whale frequency. Miiller’s examination
was at the end of an earlier cycle near the
lowest occurrence, while the other examina-
tions were close to the top of the next cycle.
Hoydal (in print) showed a linear correlation
between the catch of squid and pilot whales
around the Faroes. A possible explanation
for varying male frequency could be that in
low catch periods with little food, more
males may die of exhaustion and starvation
in connection with intraspecific fighting.
From the Japanese small-type fishery, a
gradual decline in the male percentage over a
30-year period has been shown, and it is sug-
gested that this is due to a selective exploita-
tion of adult males (Kasuya and Marsh,
1984: 296). This is not comparable with the
Faroese findings of varying male percentage
through time, since whole schools are taken
without selection according to sex or any
other factor.
Fighting marks. 73 animals from Vestman-
na, July 17, 1984 were examined for fighting
marks. This school was not measured for
length, but the skinn values were available.
The school was divided into young and sub-
adults (0-6 skinn), and adults (7-22 skinn).
Both recent and older fighting marks were
observed on the skin, as well as some very
old marks, where the distance between the
marks had grown during the life of the
whale.
This material showed that all the adult
males, but only 57% of the adult females,
had tooth scars. Among the juveniles and
sub-ađults, 58% of the males and 50% of
the females had tooth scars. According to
Martin et al (1987: 19), tooth scars were also
commonly found on adult male whales
stranded in Great Britain.
The opinion of Sergeant (1962: 78) was
that tooth scars originated from the hunts
themselves, where scars occurred in hunts
from which the whales had escaped. This is
not in agreement with Faroese hunting
procedure, where an entire school is taken,
and wounded whales do not escape. Further-
more, fighting marks are observed on strand-
ed whales which are not the object of hunt-
ing (Martin et al, 1987). The hypothesis of
the present paper is that tooth scars derive
from intraspecific fighting between males.
But until now there has still been nothing to
suggest that the scars themselves are lethal.
Fighting marks as a possible explanation for
the biased sex ratio. A sex ratio in favour of
females can be explained in three ways:
Firstly: A majority of females could be nor-
mal in the primary sex ratio. The material
presented here, however, showing an equal
number of both sexes at birth (Table 5), sug-
gests otherwise.
Secondly: The pilot whale could have a ge-
ographical segregation as occurs for example
in porpoises (Møhl-Hansen, 1955: 378) and
sperm whales, Physeter macrocephalus (De-
gerbøl, 1940: 109). Until now, however,
schools composed of males only have not
been recorded in the strandings or whale
drives (Kock, 1956; Sergeant, 1962; Martin et
al, 1987).
In the Faroese statistics, schools com-
posed of whales of more than 12 skinn on
average would mean they are made up
almost exclusively of large males. Until now,
only 5 schools reported in the official whale