Fróðskaparrit - 01.01.1991, Blaðsíða 48

52
STUDIES ON THE LONG-FINNED PILOT WHALE
statistics may represent such male-only
schools:
1. Hvannasund in 1916: 47 animals,
2. Miðvágur in the 1930’s: 30-40 animals,
3. Hvalvík, 3. August 1938: 27 animals, an
average of 19.6 skinn.
4. Gøta, 31. August 1979: 27 animals, with
an average of 11.9 skinn.
5. Tórshavn, 18. November 1989: 8 males,
an average of 10.4 skinn.
For no. 4 some reservations have to be
made. In Fuglafjørður, October 25, 1988,
15 pilot whales were caught with an average
skinn value of 11.4. This was not a male
school, but contained an equal number of
males and females. It is not, therefore, cer-
tain that school no. 4 in the above list was a
male-only school.
But these four or five schools could not be
enough to explain a general female frequen-
cy of 58% in the schools.
The possibility also exists that males,
alone or in schools, could stay in offshore
waters where the winter areas are supposed
to be (Sergeant and Fischer, 1957; Brown,
1961), and where pilot whales are seen all
year round (Brown, 1961; Bloch, Gunn-
laugsson, Hoydal and Sigurjónsson, in
print, b; Joyce, Desportes and Bloch, in
print). This could be an explanation for the
absence of male-only schools in strandings
and drives, but this would not agree with
Mercer’s observations (1967) from one of
the winter areas in New Foundland, where
mixed schools of different sizes were ob-
served.
Thirdly: The natural mortality may be
higher in the lifespan of males, as also seems
to be shown by Sergeant (1962: 67), and was
mentioned by Martin et al (1987) and shown
by Bloch et al (in print, c).
One reasonable hypothesis for a higher
male mortality could be intraspecific male
fights within the school. Faroese fishermen
have observed fights between large males us-
ing their teeth. After shooting one of the
males from the boat for food, fishermen
described fresh, bleeding wounds located
under the dorsal fin which were made by
another male (J. Petersen, pers. comm.).
Reproduction
Sexual maturity. The age at attainment of
sexual maturity is different in males and fe-
males.
Males: In males, one testes from 43 different
animals was weighed, and both testes from
15 animals. In newborn males the testes
measured about 10 g and 8 cm growing to a
recorded maximum weight of 5.500g, with a
length of about 45 cm among the largest
males. Differences between the testes from
the same animal (range: 0.0 - 28.9%; N = 15)
□ 29 Immatufes; + 12 Matures ▲ 2 foeluses
Fig. 10. Testes weight at body length in long-finned pi-
lot whales off the Faroe Islands. N=43.