APPENDICES.
119
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PUBLIC RECORD OFFICE
Reference :-
61
MC.O. 885
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Data.
Sex and Length of Fætur.
บ
Locality and Authority.
mm.
1899, August 15...
Male
4,620
Newfoundland (True, 15 ft. 2 in. E.).
15
?
"
1
3,865
18
1+
"
Mala
2,060
(True, 12 ft. 8 in. E.). (True, 6 ft. 9 in. E.).
18
>1
>
?
3,460
1888
20
#
?
1,760 circa
1899
22
**
1913
27
"
1882
2nd balf
11
Female Female
2
2,100
2,390
**
August normally
larger fœtuses BIDaller
1903,September 4
31
:
2,800 circa 1,910-3,180 2,000--3,100
610 (or less)
3,400 circa
3,400 circa 1,195
(True, 11 ft. 4 in. E.).
Finmark (Hotf, 5-6 ft. N., in Cocks). Newfoundland (True, 6 ft. 10 in. E.).
Ireland, Belmullet (J. E. Hamilton, 7 ft. 10 in. E.). Finmark, Vardo (Guldberg).
"
(Sörensen, 6-10 ft. N., in Cocks). (Collett).
(Collett).
Newfoundland (Allen, in Collett, twins about
12 ft.)
Male Female
...
1913
4
Male
►
9
""
1911
+1
10
Male Female
2,850
... 2,750
18
Male
15
*... 2,825
1891,November 27
?
5,100
27
33
1899,December?
?
2,800 5,700
"
"
"
Ireland, Belmullet (J. E. Hamilton, 3 ft. 11 in. E.).
(J. E. Hamilton, 9 ft. 4 in.). (Burfield, 9 ft. E.) (Burfield, 9 ft. 3 in.). Norway, Christianiafjord (Collett).
BREEDING.
"
(Collett). Jaederen, new-born, stranded (Collett).
From Major Barrett-Hamilton's observations at South Georgia it would appear that the female finners of the South Atlantic become sexually mature at about the moment when they attain a length of 61 ft.; the smallest pregnant female examined measured 63-5 ft. long. The data recorded at p. 105 show that in both males and females fusion of the vertebral epiphyses is delayed until long after these whales have reached sexual maturity. In the North Atlantic, according to Professor Collett, pregnant females usually measure 60-67 ft. in length, but they have occasionally been found to be pregnant at 50 ft.
From the data relating to 22 foetal finners from the North Atlantic, Guldberg observed that, in spite of great variation in contemporaneous foetuses, their size on the whole shows a certain regularity of progress from month to month; and he thought that, while small fœtuses are found in the spring, later in the year only large fœtuses normally occur. Guldberg assumed the pairing to take place early--in and between the months of January and March; he thought the period of gestation to be about twelve months and that the young are normally born in February or the begin- ning of March. The calves follow the mothers for many months, and Guldberg thought it improbable that young are born to the dams in each year.
"}
Captain Nilsen informed Mr. Cocks (Zoologist, 1887) that on the Murman coast "he sees Common Rorquals pairing during May up to about 1st June every year, and that in the spring they have calves by their sides not more than 8 or 9 ft. long. He thinks the young whales (first calf) pair in the autumn.' Captain Sörensen of Vardö (in Cocks' Zoologist, 1889), "believes that Common Rorquals pair in December or January, and generalizes to the effect that fœtuses of this species are from 6 to 12 in. in April, and from 6 to 10 ft. in August, and are from 16 to 20 ft. long at birth." Mr. Haldane (Ann. Scott. Nat. Hist., 1906) says that the Norwegians at Shetland believe that the copulation and breeding of the finners take place at all seasons; he himself was inclined to think that most finners give birth in the latter part of the year.
Mörch (Proc. Zool. Soc., 1911, p. 666) says that:-
Impregnation is supposed to take place in January-March, and the period of gestation to be about twelve months. The length of the new-born calf is about 20 ft. Very young calves are always seen together with full- grown individuals in schools, older calves sometimes in schools by them- selves. It is supposed in the locality in question [i.e., Finmark] that among 50-60 finback cows 10-15 will have foetuses, and a lesser number will be accom- panied by calves. Some cows give birth to their young in those waters, some go westwards to other localities. It is supposed that the cows do not become pregnant every year."
**
Professor Collett states (Norges Pattedyr, p. 582) that pairing is observed " with us
about, the New Year or in the spring; but also in the summer. Parturi- tion appears to occur most often in the autumn or winter months; but it may happen also in the spring or summer, new-born young (about 20 ft. long) being often met with their mothers off the Finmark coast from April to June. During the true breeding-time the finners are, on the whole, observed but rarely under the land in the About one-fifth of the females caught at Finmark have been Norwegian seas." pregnant. Sometimes a pregnant female has been accompanied by her still sucking calf; it is probable that the period of gestation does not exceed ten-twelve months, and that individual females may sometimes reproduce in two successive years.
Mr. J. E. Hamilton and Mr. R. J. Daniel have endeavoured to calculate possible pairing dates for the fœtuses which have been observed at the Belmullet Whaling As the basis of their calcula- Station (Report, British Association, 1914, p. 20).
at
tions these gentlemen assumed the length of the finner at birth to be about 20 ft.; the period of gestation to be ten months, and the size of the fœtus to be " propor- tional to the length of gestation which has elapsed since pairing until the time when the fœtus is measured.' Their results suggest "that pairing may take place at any time between the end of December
and the beginning of July intervals of roughly two months." This would indicate that the Balaenopterids are, at any rate, polycestrous, and in season in December (February ?), April, and June. All females would not be fit for breeding actually simultaneously, but the precise time would vary for different individuals, and this would account for some pair- ings occurring at such times as the beginning of July or the beginning of May."
In my
'Preliminary Memorandum," working on the basis of similar assump- for the fœtuses tions, I endeavoured to calculate the possible
pairing dates
The 24 dates so found examined by Major Barrett-Hamilton at South Georgia. were distributed as follows:-1 in August, 11 in September, 9 in October, 2 in November, and 1 in December.
33
As stated when discussing the humpback foetuses I no longer think that the fœtus grows at an equal rate throughout the period of gestation. I have before me data relating to a large number of finner fœtuses, and I have endeavoured to find a new and more satisfactory basis upon which to calculate the possible pairing dates.
The smallest foetus of which the sex is recorded is a male 325 mm. long, seen by Professor Guldberg at Vardö on 28th May, 1883; judging from this case it would appear that the general external form, including the external genitalia, must be perfected by the time the fœtus has acquired a length of 300 mm. Such completely developed fœtuses cannot, in my opinion, be less than two months old: and they may
well be older.
After
The length of the finner at birth appears to be about 20 ft. or 6,100 mm. examining all the figures before me, I am inclined to think that the growth of the fœtus from a length of 300 mm. to 6,100 mm., or birth, occupies about nine months; and it is not improbable that the growth during this latter nine months' gestation takes place at a fairly regular and equal rate.
The age, and consequently the "pairing dates," of each foetus has been calcu- lated, therefore, as follows:-
6,100 mm.
300 mm. =5,800' mm.
5,800 mm. the observed length of the foetus minus 300 mm. : : 273 days: the days of growth subsequent to the completion of the preliminary development.
Age of fœtus=a days of subsequent growth, plus 61 days of preliminary
development.
1
120
APPENDICES.
LIST OF FINNER FŒTUBES ARRANGED IN THE ORDER OF THE POSsible Dates OF THE
PAIRING.
Length of Fætur.
Age of Fæstur.
Date of Observation.
Possible Date of Pairing.
Observed.
Equale Days Plus 61 Days Lea 300 mm, jof Subioquent Preliminary
Growth. Development.
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