APPENDICHBS.
59
PUBLIC RECORD OFFICE
Reference :-
CO. 885
23 PUBLIC RECORD OFFICE, LONDON
ALLY WITHOUT PERMISSION OF THE COPYRIGHT PHOTOGRAPH-NOT TO BE REPRODUCED PHOTOGRAPHIC-
These particulars are followed by notes dealing principally with the inferences to be drawn from the data collected as to the sexual season and rate of propagation. Finners :-
Total number captured and examined at Leith Harbour Of these there were captured between 15th November
and 15th December
And between 16th December and 18th January Number captured between 15th November and 15th
December
Number captured between 16th December and 16th
January
Males Females
Males
Females
Average length (notch of flukes to tip of mandible) of all
(184) specimens
Average length of all (105) males
Of these 6 or 5-7% were sexually immature and their
length ranged from
The remaining 99 or 94-3% were sexually mature and
had an average length of
Smallest sexually mature male
+++
Average length of all (79) females
Largest male
Smallest female
Smallest pregnant female
Largest female
184-100
25= 13.6%
159 86-4%
25-100 14- 56% 11- 44%
159=100
91= 57.25%
68= 42-75%
68.8 feet 66.54
11
53 to 59
31
67.15 61.75 72 71.81
1
"
61 68.5
15
82 "}
Note. All the females appeared to be sexually mature; the smallest specimen (No. 79), though apparently a virgin, was surrounded by a herd of males at the time of capture, and her rather large ovaries were reddish and inflamed.
If the length of the largest male (72)=100 If length of largest female (82') = 100
That of smallest sexually That of smallest sexually mature
mature female male
= 88.3 If length of largest female = 100 That of largest male
The genitals were examined in 38 females Foetuses were found in
Foetuses must have been present in
Impregnation was recent or probable in
Pregnancy was doubtful in
=
88
No evidence or suspicion of pregnancy in (No. 79)
The organs of lactation were examined in 72 females
No milk was present in
Some milk was present in
Suckling dam
Suckling dam (?)
The foetuses fall into three groups as follows :—-
= 74.4
8=100
27= 71%
8=
21.1% 2= 5.26% 1= 2.73%
38 100.09
72=100
68= 94.5%
2- 2-78% 1= 1.39% 1= 1.39%
72 100.06
i. Seven examined between 15th November and 15th December:
4 male, 3 female; length from 1 ft. 11 in. to 6 ft. 8 in.; average length, 4 ft. 8 in.
ii. Eight examined between 18th and 27th December:
4 male, 4 female; length from 2 ft. 1 in. to 7 ft. 7 in.; average length,
4 ft. 11 in.
iii. Nine examined between 8th and 15th January:
3 male, 8 female; length from 1ft. 8 in. to 8 ft. 9 in.; average length,
6 ft. 5 in.
From the high percentage of pregnant and the low percentage of nursing femalest two inferences may be drawn, viz. :-
i. During the period between mid-November and mid-January, the finner cows frequenting South Georgian waters are those which have paired in the present season or else are about to do so.
ii. These finners usually wean their calves before being impregnated afresh and, therefore, as a rule, they cannot give birth to a calf more frequently than once in each alternate year.
The number of corpora lutea, when any were found, in connexion with the ovaries of these finners varied between one and seven; in pregnant females one corpus luteum was enlarged and was thus apparently connected with the shedding of that ovum which was subsequently impregnated. The large number of corpora lutea sometimes present points to a long polyœstrous sexual season.
In No. 50, captured on 13th December, one of the ovaries had five or six corpora lutea, "of which one was extra large, denoting recent impregnation"; the other had one small corpus luteum and several Graafian follicles. Major Barrett-Hamilton endeavoured to calculate the date of the beginning of the "season" for this female from the seven corpora lutea; if an ovum had been shed at intervals of three weeks the seven corpora lutea would represent 21 weeks and this female might have paired for the first time about 21st July; if the intervals between ovulation were four weeks the first pairing might have taken place in the first week of June. this whale grew 1 ft. a month her length when she shed her first ovum would have been "69-7 minus 7=62/
which is about right."
If
I have tried to calculate an approximate date for the beginning of the sexual season from the recorded lengths and dates of the foetuses. The considerable dif- ferences of size which exist between the maximum and minimum observed at any given date indicate, of course, that the pairings concerned took place at quite diverse times. There is, however, a steady rise in the average length of the fœtus in South Georgia from mid-November to mid-January; in the north a similar increase is seen from early to late summer months (Cocks, Collett). Such a gradual increase of the average length of the fœtus seems to be explicable only on the hypo- thesis that the sexual season has a definite beginning and that, although it continues through several months of the year. it is followed by an appreciable period of sexual rest. I have assumed that Collett's estimate of a period of gestation of ten months for northern finners is reliable and that it applies to those of South Georgia. I have further assumed that the fœtus grows at a uniform rate throughout gesta- tion and that the length at birth is 20 feet. I find on these assumptions that the pairings for the 24 foetuses examined took place at various dates between 30th August and 22nd December: these dates are distributed as follows:-1 in August, 11 in September, 9 in October, 2 in November, and 1 in December. The months of September and October would, therefore, appear to represent the principal time for pairing. Of course, if the period of gestation be really longer than ten months the precise dates of pairing would be more remote than those calculated; on the other hand, it is not unlikely that the average length at birth of the South Georgia Finner is somewhat greater than 20 feet. and that would tend to bring the dates forward. In any case, observations on the living whales at sea will probably afford the best means of testing the reliability of these estimates.
Finners are stated to be present all through the year at South Georgia, but some migrate; the general scarcity of whales which was experienced there between 15th November and 15th December. 1913, may have been connected with this migra- tion, and, if so, it would indicate that in some years at all events, assuming the esti- mates given above as to time of pairing to be substantially accurate, most of the pairing is done away from the neighbourhood of the island. In his journal, under date 27th November, Major Barrett-Hamilton says that the dearth of whales was partly due to bad weather but partly "to actual scarcity. This the whaling people explain by saying that the whales have not vet arrived and that feed is scarce, and that the water is too cold." Mr. Henriksen [or Hendriksen] told Major Barrett- Hamilton that large numbers of whales, "left South Georgia in peace in 1911," and that they have not come back since.
Not less than 92 per cent.
+ Not more than 3 per cent.
This assumption is not made in the complete report; the method of calculating the age of the fœstuses now adopted yields the following result:-4 in July, 14 in August, 1 in October. and 1 in November.