Fróðskaparrit - 01.01.1991, Page 49

STUDIES ON THE LONG-FINNED PILOT WHALE
53
with a mean of 7.2 t 1.8 (r=1.0) was
shown. The testes grow slowly until a body
length of about 480cm at 12 years of age and
a testes weight of about 300g, at which point
the testes begin to increase rapidly in weight
(Fig. 10). Histological examinations of the
present material display a range of
446-520cm and 12-18 years of age at the at-
tainment of sexual maturity (Desportes, per.
comm.). The males were therefore defined
as sexually mature at about the time when
their testes began to grow rapidly. This oc-
curred on average with a body length of
480cm and age of 11 years. This is in agree-
ment with the findings of Sergeant (1962:45)
from New Foundland of 490 cm and 12
years (see also Perrin and Reilly (1984:
103)), as well as the findings by Desportes et
al (in print).
Females: In the females, both ovaries from
158 animals were weighed and examined in
order to find the corpora. The females were
defined as mature when at least one corpus
(luteum or albicans) was found (Perrin,
Brownell and Myrick, 1984; Perrin and Reil-
ly, 1984: 101). But to establish the range
length for attainment of sexual maturity, fe-
males with only one corpus luteum are con-
sidered in the present study. On average it
occurred with a body length of 375 cm
(range 375-445cm, N = 58, Fig. 11) and an
age of 6 years (Fig. 3), with a range from
6-13 years. The wide range in length and age
could perhaps indicate that the attainment
of female maturity is more a question of
weight than age, as pointed out for the por-
poise (Møhl-Hansen, 1955: 380) and in con-
nection with further examination of the pi-
lot whale (Bloch et al, in print, c).
Studies in New Foundland showed that
Fig. 11. Number of ovarian corpora at body length in
long-finned pilot whales off the Faroe Islands. N=158;
r=0.57; t=4.83.
the females of the long-finned pilot whale
were mature on average at a length of 365
cm and 6 years (Sergeant 62: 42). The short-
finned pilot whale is not directly comparable
since it grows larger, so here the females
reach sexual maturity at an age of 9-9.5
years (Kasuya and Marsh, 1984; Kasuya and
Tai, 1991b).
Pregnancy: The number of pregnant fe-
males in 7 schools was recorded (Table 8).
The numbers found represent a minimum
figure because not all females were exa-
mined, and it was sometimes difficult to
find the smallest foetuses in the time availa-
ble for examination.
The length of 61 foetuses, all from July to
September, was measured (Table 3). Nearly
all the foetuses were placed in two distinct
groups, one comprised of 15 very big > 140
cm foetuses, and 30 in another group of
small foetuses up to about 100 cm.
If the gestation time is known, the expect-
ed time of birth can be calculated. The
length of gestation is said to be 10-14