Fróðskaparrit - 01.01.1992, Side 32

36
ANOTEABOUT. ..
nematode Anisakis simplex and cysts of the
trematode Pholeter gastrophilus. However,
comparison of the population structure of
Anisakis simplex between the Tórshavn and
the Vestmanna samples showed, on the
basis of the differences observed, that the
male-only group did not have the same
infection history that the Vestmanna school
and could, therefore, not have been a part of
this school (Fig 1).
Discussion
The male-only pod landed in Tórshavn was
mainly composed of young mature males, 6
out of 8 males of which 4 were not yet
socially mature (Desportes et al., in press).
The existence of this pod clearly shows that
young mature males of the long-finned
pilot whale can segregate at least temporal-
ly to form independent bachelor schools.
The results of the genetic comparisons
between the three schools mentioned are
still lacking. On the basis of the parasito-
logical examination, it can be assumed
already that the male-only pod landed in
Tórshavn was not part of the school landed
in Vestmanna. Even if the male-only group
was part of the school landed the day before
or the same day, the fact that this group was
spotted far from the places where the two
other schools had been first observed
shows in any case that long-finned pilot
whales segregate at times.
Sergeant (1962) reached also the conclu-
sion that mature males of long-finned pilot
whale can segregate at least in late summer,
perhaps temporarily, off Newfoundland.
Among the 85 schools he examined, some
contained an excess of adult males over
adult females, and one was composed of
ten males, of which nine were mature, and
four females probably sexually senile. He
observed also two groups of mature males
segregating from other individuals, one at
sea and the other during a drive.
Schools consisting largely of males, if
not only of males, have also been some-
times caught in the Faroese drive fishery
(Bloch, 1992).
Until now the prevailing opinion has been
that there was no clear evidence for segre-
gation of pilot whales, and the sex ratio
strongly biased towards females among
mature animals was only attributed to the
lower survival rate of adult males (Martin
et al., 1987). The matter may, however,
have to be reexamined in the light of the
evidence for the existence of at least tem-
porally segregation of male long-finned
pilot whales given by this note.
Acknowledgements
Thanks to S. Skaaning for organizing the recuperation
of the samples from the Hvannasund school.
References
Bloch, D. 1992. Studies on the long-finned pilot whale
in the Faroe Islands, 1976-86. Fróðskaparrit 38-39:
35-61.
Bloch, D., Desportes, G., Mouritsen, R., Skaaning S.
and Steffanson, E. In press, a. An introduction to
studies of the ecology and status of the long-finned
pilot whale (Globicephala melas) off the Faroe
Islands in 1986-1988. Rep. int. Whal. Commn
(Special Issue 14).
Bloch, D, and Lockyer, C. 1992. Direct fisheries for