Studies on the Little Piked Whale fromthe Coast of Japan
By
HIDEO OMURA and HARUYUKI SAKIURA *Introduction

The little picked whale, lesser rorqual, or minke, Balaenoptera acutorostrata, is called in Japan usually as " Koiwashi-kujira" or " Minku ".
Tbe direct translation of the former is lesser sei whale and the latteris derived without doubt from the Norwegian minke. It has been
hunted in the waters around Japan from the fairly old times by theusual catcher boats, in addition to their main catch of other baleen
whales and sperm whale. However, towards the end of the nineteen
twenties, some fishermen at Ayukawa, Miyagi prefecture, inaugurated
small type whaling to take little piked whale with motor vessel equippedwith harpoon-gun, which remained until the war as a modest industry
in these localities.
After the end 'of the war, the situation of foodstuff made whalingof such type a paying industry, and consequently number of vessels
engaged had increased with a result of expanded areas of operationand increased catch of the little piked whale. The Fisheries Agencyof Japanese Government placed this whaling under its control in 1947and simultaneously the catch of the little piked whale has been confined only to those motor vessels operated by fishermen, no licence being
issued to the large type catcher boat, which hitherto caught someminkes occasionally. The yearly catch is now amounted to about 400
whales, very fewer in number when compared with that in Norway.
The little piked whale has a worldwide distribution, inhabiting bothin the Atlantic and the Pacific, ranging northward to arctic and on
the south penetrating Ross and other antarctic seas. It has been
named Balaenoptera (Jffittoros~rata Lacepede 1803-1804, however, thisname is applied only to the North Atlantic whale, since the Pacific
one has been called Balaenoptera davidsoni by Scammon in 1872. But,
as regards the difference between those two forms, only a few reports
have been suppl~ed. Cowan (1939) had studied two specimens from theeastern Pacific externally as well as internally and describes '' Should theabove differences be substantiated there would be grounds for recognizing B. davidsoni as a subspecies of B. acutorostrata" though he says
* Fisheries Agency of Japanese Government.

2

H. OMURA and H. SAKIURA

further "but in the light of present knowledge taxonomic recognitionof a Pacific species is apparently not justified ". Since then no further
study on this matter has been carried out by any author.
Recently the little piked whale from the Atlantic has been studied
extensively by Jonsgard (1951), based upon the measurements andobservations of a great number of whales. But, as regards the little
piked whale from the Pacific rather scanty reports such as those by
Fry (1935), Matsuura (1936), Cowan (1939), Clifford (1946), Scheffer andSlipp (1948), and Scattergood (1949) has been appeared since Scammon(1872). These accounts are based mainly on one or few more stranded
whales or returns from whalers.
We tried to collect as many material of the little piked whalefrom the western Pacific as we can for these several years. In thelight of the present knowledge mentioned above, we feel it is betterto publish them now, though they are still very incomplete. So thisreport should be deemed as preliminary one. Further studies will appear when more measurements or observations be carried out infuture.
Sincere thanks are due to the whalers, who assisted us greatly incollecting material as well as in our field work at their land stations.
Material

The material at disposal for the present study is as follows :1. Whaler's reports, in which particulars are given with respect
to each whale treated at land station as to the date and approximate
position of taking, the sex of the whale, its length, stomach contents
and, if it contains a fetus, the length and sex, if ascertainable, of the
fetus. From 1948 to 1954 such particulars have been reported for 2,264
whales, excluding several reports more or less incompletely filled.
Among these particulars it is probable that fetus is not always .reported correctly. Undoubtedly most of the smallest fetuses have been
overlooked. We do not, therefore, pay much attention to the negative
information that a fetus was not present. The stomach contents may
sometimes have been reported incorrectly, especially as regards krill andcopepods, both having been confused. But regarding of the otherparticulars we are confident that they have been informed in goodorder, at least on the whole.
2. The samples, such as testes, ovaries or baleen plates forwarded
to us by whalers. These samples are rather few in number. In someoccassions whalers were requested to measure the weights of testes andovaries. A few people is deemed to have weighed accurately, thoughStudies on the Little Piked Whale from the Coast of Japan3

most of whalers had reported more or less incompletely or nil.
3. Material obtained from the examination of whales treated atland stations by biologists. Body proportions and other scientific observations were carried on only for 23 little piked whales, most of themwere examined at Abashiri, a land station facing to the Okhotsk sea,by H. Sakiura, one of the present authors. We are very regret thatthe material from the examination of whales by biologist is still insufficient at present. It is hoped more material of such nature be collected in future.
External Characters

The little piked whale from the coast of Japan is similar in generalappearance and coloration to those reported by other authors for Pacificor Atlantic species, having the very distinct white band across thedorsal surface of the flippers and the yellowish-white baleen plates.
Dorsal surface of the body is uniformly black and underparts including
most of lower mandible and lower surface of flukes, white. The extension of black pigments on the sides differ individually, most remarkably being noted in the region of shoulder. In some whales pigments inthis region extend downward considerably and reaching nearly to theventro-lateral line (plate 1, upper, plate 2, lower) whereas black area
ends at a position not far down from the flippers in some whales·(plate 2, upper). The distinct white band on the outer surface of the
flipper differs also individually in its broadness. Some has broader
band (plate 2, upper) and some narrower (plate 2, lower), but it seems
that there is always a slight projection of white area anteriorly, as
seen in the whales shown in plate 2. Such projection of white area is
not observed from a little piked whale stranded on Florida (Moore andPalmer, 1955. Plate 1). Anterior border of the white band is quitedistinct, but posterior one is shading into pale color.
As regards other coloration, Cowan (1939) describes that "on theside of the body in the region touched by the tip of the flexed pectoral
there is a large area of blue-gray that extends upward on to the dorsolateral surface." This coloration occurs also in our specimen, and sometimes very remarkable. In a whale shown in plate 2 (upper), thewhite area of the belly in the region after flipper extends upward,
drawing a curve pointing backward at first and then forward, shading
into gray gradually, and finally meets with that on the other side at apoint on the dorso-lateral line. It is thought that this marking is acharacter of the little piked whale.
In addition to this marking, certain pale streaks occur about the4

H. OMURA and H. SAKIURA

head and shoulders. A similar pale streak reaching backwards fromthe ear in fin whale is occur also in the little piked whale. Similar
streaks are also observed on the both sides of the blowhole.
The color of baleen plate is yellowish-white, with a diffuse pinkish18
g:! 17
I X
area close to the gum, caused by blood[;; 16x
In fig. 1 we have plottedpigments.
~ ~~ le'the length of the largest baleen plate
"' 13
i3 12
• x •
against the body length. The relation
;l 11
- 10
between length of baleen and animal's• MAL8~ 9 x~ 8
X FE:\!ALE
total length shows no remarkable difference from that of Atlantic individuM 1:, rn 11rn19 20 2122 2:i 24 2;; 26 212~29 :io
als as reported by J onsglird (1951,.
BODY LENGTH IN i•'l'E'r figs. 2 and 3).
Fig. 1. Relation between length of
In 1953 the measurements on thebaleen (in cm) and animal's total
following body proportions were madelength (in feet).
of 23 animals.
1. Body length, tip of snout to notch of flukes.
2. Lower jaw, projection beyond tip of snout.
3. Tip of snout to blowhole (centre).
4. Tip of snout to angle of gape.
5. Tip of snout to centre of eye.
6. Tip of snout to tip of flipper.
7. Centre of eye to centre of ear.
8. Notch of flukes to posterior emargination of dorsal fin.
9. Width of flukes at insertion.
10. Notch of flukes to centre of anus.
11. Notch of flukes to umbilicus.
12. Notch of flukes to end of ventral grooves.
13. Centre of anus to centre of reproductive aperture.
14. Vertical height of dorsal fin.
15. Length of base of dorsal fin.
16. Flipper, tip to axilla.
17. Flipper, tip to anterior end of lower border.
18. Flipper, greatest width.
19. Head length, condyle to tip of snout.
20. Greatest width of skull.
21. Skull length, condyle to tip of premaxilla.
22. Skull height.
23. Tail flukes, notch to tip.
24. Length of lower jaw.
All of these measurements are listed in the appended table, in cen-Studies on the Little Piked Whale from the Coast of Japan5

timeter of actual length and for measurements 2 to 24 also expressedin percentages of the animal's total lengths.
In table I, we gave here the maximum and minimum measurements
as well as the calculated means for males and females, all expressed aspercentages. For the convenience of comparison to those in the Atlantic, we cited in table I also the corresponding figures from J onsg~rd(1951). Further, we have plotted in figs. 2-16 each percentages according to body length, as well as ranges and means of Atlantic animals
for the sake of comparison on the left side of each figure.
Judged from the above mentioned table and figures, we can safely
conclude, in the body proportions of the little piked whale from thecoast of Japan, that
1. apart from the measurement 13 (Centre of anus to centreof reproductive aperture), no essential difference is noted between
male and female, as in the other baleen whale or little piked whalefrom the Atlantic, and2. there is no measurement which separates completely or atleast considerably from that from the Atlantic, all of them being
overlapped in major parts,
3. but there are some differences, however slightly, between
the animals from the Atlantic and Pacific in the following measurements:a) Length from tip of snout to centre of eye (fig. 4). This
length is nearly the same length of tip of snout to angle of gape.
The little piked whale from the coast of Japan has a shorter mouth,
though head length itself shows no significant difference (fig. 15).
b) Tip of snout to tip of flipper (fig. 5). All the measurements
for Pacific animals distribute within the range of those for Atlantic,
but the means are somewhat shorter for both sexes.
c) Notch of flukes to posterior emargination of dorsal fin (fig. 7).
The Pacific animal has a more posteriorly situated dorsal fin. No
measurement does not exceed the mean for the Atlantic.
d) Centre of anus to centre of reproductive aperture (fig. 11).
The Pacific animal shows a shorter distance, especially in female.
e) Vertical height of dorsal fin (fig. 12). The Pacific animal has
a higher dorsal fin.
f) Flipper, tip to axilla (fig. 13). The Pacific animal has a shorter flipper, though in it's width no difference is observed (fig. 14).
g) Tail flukes, notch to tip (fig. 16). Somewhat higher value isnoted in whales from the Pacific.
In other words, the little piked whale from the coast of Japan has

H. OMURA and H. SAKIURA

6

Table I. Body proportions of(Expressed as percentages
Males
Pacific

Measurements
No.

Range

Mean

1.

Body length in cm.

8582-799725

2.

Lower jaw, projection beyond tip of snout.

5

0.89- 2.51

1. 78

3.

Tip of snout to blow hole (centre).

811.68-13.66

12.79

4.

Tip of snout to angle of gape.

4

13.57-19.04

16.10

5.

Tip of snout to centre of eye.

8

14.21-18.40

15.89

6. Tip of snout to tip of flipper.

6

37.46-42.20

39.81

7.

Centre of eye 'to centre of ear.

74.64- 6.20

5.18

8.

Notch of flukes to posterior emargination of dorsal
fin.

7

24.27-29.11

26.97

9.

Width of flukes at insertion.

6

6.09- 7.41

6.90

10.

Notch of flukes to centre of anus.

625.43-27.88

26.68

5

47.42-49.27

48.04

11. Notch of flukes to umbilicus.
12.

Notch of flukes to end of ventral grooves.

6

46.04-56.97

54.63

13.

Centre of anus to centre of reproductive aperture.

7

5.68- 7.68

6.77

14.

Vertical height of dorsal fin.

53.00- 4.81

4.13

15.

Length of base of dorsal fin.

66.05-10.14

8.42

16.

Flipper, tip to axilla.

38.06-10.03

9.12

17.

Flipper, tip to anterior end of lower border.

5

11.84-19.65

14.50

18.

Flipper, greatest width.

43.44- 3. 74

3.54

19.

Head length, Condyle to tip of snout.

2

22.28-22.68

22.48

20.

Greatest width of skull.

2

10.72-12.71

11. 7221.

Skull length, Condyle to tip of premaxilla.

22.

Skull height.

23.

Tail flukes, notch to tip.

5

13.37-15.86

14.33

24.

Length of lower jaw.

3

21.13-23.021

21.91

1) Taken from Jonsgard (1951).
2) Tip of snout to the anterior end of the blow hole.
3) Notch of flukes to the nearest -part of the anterior margin of the flukes.

7Studies on the Little Piked Whale from the Coast of Japan

Balaenoptera acutorostrata
against body length).
Females----------------- - - - - - - - - - - - , - - - - - - - - - - - - ,~Pacific
Atlantic 1 )Atlantic1)
i
1

No.

Ra-n-ge---M-ea_n_ [l-N-o.---,----R-a-ng-e----,--i-M_e_a_n_ No.

Range

I!

\

Mean

658 I!

15461-857I

723 i 75735

13 I 1.15- 2.45

1.841

11

0.76- 2.51

i

1.54

21

1.56

I 11.86-14.102)
I

13.01 \!

15

11.71-14.90

13.27

52

13.18

11

10

13.32-18.69

16.06

24

20

488-828

I

1

11,

24

17.05-20.00

18.33 n 15

13.32-18.59

15.84

24

36.87-46.50

43.57

14

39.48-44.50

24

4. 91- 6.19

5.55 i1424

27. 76-33.29

29.97

24

6.46- 8.103)

24

41.69

75 115. 73-19.33
I
73 i 36. 76-46.47

43.43

4.66- 5.93

5.37

74

4.64- 6.19

5.50

15

23.48-28.86

27.30

73

26.35-32.13

29.29

7.03

13

7 .05- 8.32

7.45

75

5. 81- 7 .493)

6. 77

24.75-28.46

26.23

15

23.92-29.28

26.52

75

18.67-30.13

25.99

23

43.31-50.08

46.79

15

42.26-48.37

46.17

74

37.33-52.01

46.00

24

47.73-56.48

52.19

15

45.60-60.47

53.75

74

43.48-58.67

51.54

24

6.00- 8.48

7.27

15

2.11- 3.40

2.74

75

2.71- 4.08

3.41

24

3.33- 4.58

10

3.15- 4.96

4.22

72

2.93- 4.44

3.60

11

5.86- 8.75

7.36

14

7 .29-11.42

8.92

75

8.78-12.38

9.99

14

9.41-15.75

12.06

12

3.54- 3.97

3.83

75

3.20- 3.94

3.65

4

21.78-22.86

22.52

51

20.54-25.81

22.50

4

10.88-12.77

11.69

74

12.00-15.38

13.90

18.05

Ii

23

9.00-14.40

24 ! 3.40- 4.18

Ii
3.94 Ii

10.19

3.70
1:

20

i.

20.77-24.80

23.25

1

20.39

1

6.29

i

24 II 13.17-15.36

14.05

13

13.83-16.93

15.30

8

20.92-22.59

21.63

8

H. OMURA and H. SAKIURA

•MALE

10

x FE)!ALE
x

14.00

13.00
i'

2.00

LOO

lIi•

..

• ,!ALE• FD!ALE '

x x

J

12.00

11.

x

j

\•x

11.00

II

II

500

600

700

Soo

600

500

BODY LENGTH IN CM.

Fig. 2.

Lower jaw, projection beyond tipof snout.
e Malex Female
Range and mean of Atlantic maleII""
female700
800
BODY LENGTH IN CM

Fig. 3.

Tip of snout to blow hole (centre).
Malex Female
Range and mean of Atlantic maleII
female•"%"·•MALEX1FEMALE

46.6
45.00·
44.0

11....

x

.J3.0

20.00
19.00

h

•MALE
x FEMALE

x,

x

42.00

%

x
Xx

41,00

"

40.00

1·1

•39.'0iJ

18.00
17.00 I

x x

38.00

)6.00
15.00

37.00

II

l II
36.QO.

14.00
500

600

600

700
800
BODY LENGTH IN CM ..

Fig. 4. Tip of snout to centre of eye.
e Malex Female
Range and mean of Atlantic maleII/t"female700. 800
BODY LENGTH IN CM.

Fig. 5. Tip of snout to tip of flipper.
Male
x Female
Range and mean of Atlantic maleII
female•""Studies on the Little Piked Whale from the Coast of Japan
%

9

•MALE

.'!3.00i<

FEMALE

500

600

32:00
31.00
;J0.0028.00

s.oo,H

'j

27.00

..

!I

5.00

1·

29.00

•MALE
"FEMALE.]

26.00 - ii
25.00

II

2<1.00

500

BOO

700
800
BODY LENGTH IN CM.

Fig. 6. Centre of eye to centre of ear.
Malex Female
I Range and mean of Atlantic male11
11
femaleII

760
800
BODY LENGTH IN CM.

Fig. 7. Notch of flukes to posterior
emargination of dorsal fin .
e Malex Female
I Range and mean of Atlantic maleII
11"
female•%52.00• ~!ALEx FE;\1ALE·51.00
50.QO
49.00

%

•MALE
;, FEMALE

30.00

48.00

29.00

~

46.00

2&00
27.00
26.00
25.00

47.00

,x

1!

t

1..

x

...

"

x

x

45 00
44.00
x
'I<

·13.00

24.00

42 00

23.00

41.00

22.00

40 00

21.0

38.00

20.0

~8.00

19.(1

37 00

l

1
Jl

II
500

Fig. 8.

I

700
800
BODY LENGTH IN 01.

Notch of flukes to centre of anus.
Malex Female
I Range and mean of Atlantic maleII/1
11
female

e

j

600

500

·ooO

7UO ·
800
BODY LENGTH IN Cllt,

Fig. 9. Notch of flukes to umbilicus.
Malex Female
I Range and mean of Atlantic male,,
femaleII•"

H. OMURA and H. SAKIURA

10

9Q

'1G1

•'-!ALF:><FE.WALE

60.00

8.00
7.00

59.00

6.00

58.00

• ,!ALEr.

x FEMALf;l

5.00·57..00
56.00

4.00

T

3.00

l

A

x •

II

"

x

2.00

55.00
54.00

~00

E3.00

600

700
800
·BODY LENGTH IN CM.

Fig. 11. Centre of anus to centre of
reproductive aperture.
•Malex Female
Range and mean of Atlantic maleII
11
11
female,;z.oo
51.00
50.00
49.00
48.00
47.00

qr,

45.00
45.00

4.00
44.00
II

43.00

3.00

Ii

l·l
I

II

5 0

Fig. 10.

e

600

•MALE
x FEMALf;

700
800
BODY LENGTH IN CM.

500

Notch of flukes to end ofventral grooves.

800

BODY LENGTH IN CM.

Fig. 12. Vertical height of dorsal fin.
e Malex Female
Range and mean of Atlantic maleII
II
II
femaleMale
FemaleI Range and mean of Atlantic maleII
11
11
female

x

%

700

600

•MALE

x FEMALE

14.00
13.00
12.00
11.00
10.00
9.00

J11
I Il

%

l.OC

x

'

8.00

'

7.00

soo

600

x

x

700
800
BODY LENGTH (N CM.

Fig. 13. Flipper, tip to axilla.
Malex Female
I Range and mean of Atlantic male11
11
femaleII••MALE><FEMALE

' x

3.00

....h

'x

' •'

H

'i.,x

>

'•

II

500

600

700
800
BODY. LENGTH IN CM.

Fig. 14. Flipper, greatest width.
•Malex Female
I Range and mean of Atlantic maleII,,/1femaleStudies on the Little Piked Whale from the Coast of Japan

%

•MALE
X FEMALE::: !)

14 00::.·:: Ji·

13.00

.x

21.00

I

•MALE,"FEMALE

16.00
15 00

11

H

'

ij

12.00

II

I!

500

Fig. 15.

e

700
800
BODY LENGTH IN CM.

600

'o00

Head length, condyle totip of snout

Fig. 16.

Male
FemaleRange and mean of Atlantic male
female
II

x

"

"

600

700
800
BODY LENGTH IN CM.

Tail flukes, notch to tip.

e

Male
FemaleRange and mean of Atlantic male11
11
femaleIIxa shorter mouth, a more posteriorly situated, but higher dorsal fin,more shorter :flippers, more broader (or longer) tail flukes, and a moreposteriorly situated genital aperture. We can not conclude at present
whether or not such differences are significant. More material and their
Table II.

Body proportions of Balaenoptera acutorostrata from
Pacific ocean measured by different authors.
(Expressed as percentages against body length)-------

Measurements

Japan

ISnohomish
I Puget
river
sound

Los
Angeles(Fry,(Scatter- I (Scatterlgood, 1949)igood, 1949) 1935)
1

I Sooke,B.C.

i(Cowan,
1939)

Puget
sound
(Scammon) 1 )Body length in cm I

461-857

478

399

318

457

823

Tip of snout to blowhole (centre)
Tip of snout to angleof gape.
Tip of snout tocentre of eye.
Notch of flukes toposterior emargination of dorsal fin.
Notch of flukes tocentre of anus.
Vertical height of
dorsal fin.
Length of base of
dorsal fin.
Flipper,greatest
width

11.68-14.90

12.50

12.42

12.8

11.11
--

13.58

13.32-19.04

15.96

16.56

16.6

-

-

17.6

16.67

-

--

30.0

2)
20.00
--

22.93

28.7

26.11

30.86
-

4.14

-

4.44

3.09

6.37

-

-

-

--

-

3.61

4.01
-

1)
2)

I
I
I

I
13.32-18.59

16.76

17.20

23.48-29.11

26.86

27.37

23.92-29.52-

3.00- 4.96

3.72

5.86-10.14

6.12

3.44- 3.97-

Quoted from Cowan (1939).
Notch of flukes to dorsal.

--

33.332 )--12

H. OMURA and H. SAKIURA

statistical treatment are needed in future in order to get to the final
conclusion.
We do not think, however, such differences are due to the difference
in body length or age. Average body lengths of 24 males and 75
females measured by Jonsgard are 658 and 735 centimeters respectively.
The corresponding figures for our specimens are 725 and 723 centimeters.
In table II the measurements of the little piked whales in the
Pacific by different authors are given, shown as percentages to thetotal length. In summarizing in this table, we have converted feet andinches of other authors into centimeters and calculated the percentagesof each measurement to the total body length, because they give only
actual measurements in feet and inches with a exception of Fry (1935),
who shows also percentages in addition to feet and inches in his paper.
Scattergood (1949) describes that Clifford (1946)* has also reported body
proportion of the little piked whale from the Pacific coast, but we could
not able to quote it in this table, because of lacking of his paper. As
regards our measurements, we give here only the maximum and minimum values of males and females.
The underlined figures in table II show that these measurements
do not fall within the range of our material. Although there are someoccasions of such case, all of them show any remarkable difference, except those measurements by Cowan (1939) and Scammon (quoted from
Cowan) in the line "Notch of flukes to posterior emargination of dorsal
fin." It is quite natural that such difference may occur, since theymeasured "Notch of flukes to dorsal" instead of "Notch to posterior
emargination of dorsal fin". We do not think that there is any significant difference between Scammon's whale and ours, regarding of theposition of dorsal fin. But even taking account of the different position measured, Cowan's figure of 20.00 per cent is quite unique, compared with others. Cowan presents photograph of his whale, standingon the head perpendicularly, the tail being hanged upward by wire.
Scheff er and Slipp (1948) give also similar photograph of the whale
measured by Scattergood. Comparing these two photographs, we caneasily conclude that the Cowan's whale is a exceptional one whose dorsal fin situated more posteriorly rather at an unusual position.
Cowan (1939) says that '' There is a suggestion that Pacific individuals
may be found to differ from Atlantic individuals in the slightly moreposteriorly position of the dorsal fin, narrower flukes, and in proportional differences in form of the scapula and sternum. Pacific individuals may have fewer baleen plates, on the other hand the observed dif* Carl, G. Clifford, 1946: Sharp-headed Finner Whale stranded at Sydney, Vancouver
Island, British Columbia. Murrelet. vol. 27, no. 3.

Studies on the Little Piked Whale from the Coast of Japan13

ference may merely be the result of individual or age variation. Should
the above differences be substantiated there would be grounds forrecognizing Balaenoptera davidsoni as a subspecies of Balaenoptera
acutorostrata Lac?pede, but in the light of present knowledge taxonomic
recognition of a Pacific species is apparently not justified ''.
It may true, as already stated, that the dorsal fin situated moreposteriorly in the little piked whale from the Pacific coast than Atlantic
individual, but it may also without doubt that this difference in position
is not so great as supposed by Cowan. Judged from our measurement
No. 23 (Tail flukes, notch to tip), though we did not measured total
spread of tail flukes, it is not probable that Pacific individual havenarrower flukes.
As regards the number of baleen plates, also Scattergood (1949)
reports that " The number of baleen plates on each side of the jaw in
the Pacific specimens has been reported as 270 (Scammon, Tomilin), 231(Cowan 1939), and 285 (Carl 1946). My two specimens had 256 and 272
plates. It would appear that the Pacific whales have slightly fewer
baleen plates than those of the Atlantic." We have only scanty materialon this matter at present, 6 whales having been observed. They are
266, 275, 277, 282, 285, and 295, never exceeding 300. According to
Jonsgard (1951), the baleens of the Atlantic minke whale number 270
to 348 (mean: 304) on each side. It is probable, therefore, that the
Scattergood's suggestion that the Pacific whales have slightly fewer
baleen plates than those of the Atlantic may true. And we think thisfact is linked with the more shorter length of the mouth in the Pacificanimals. But these numbers of baleen plates are again overlappingfrom each other, as other differing characters do.
It is highly probable, therefore, that there would not be grounds
for recognizing Balaenoptera davidsoni as a subspecies of B. acutorostrata,
on the contrary to the suggestion by Cowan (1939), though there remains
still some doubt in skeletal characters. These differences in external
characters should be deemed as differences according to different stocks
or racial nature.
Occurrence and Migration

The catch reports from the whalers from 1948 to 1954 are tabulated in table III, which should not taken as a complete catch statistics,
because such roports on which sex or body length are filled more orless incompletely have been omitted. But such instances are few and
we are confident that this table gives an idea concerning the occurrence
and abundance of the little piked whale in the waters adjacent toJapan. As seen in fig. 17, which shows actual catch position of each

14

H. OMURA and H. SAKIURA

whale taken in the years 1953 and 1954, we have divided the grounds
in the coastal waters of Japan into 6 major areas. The catch of thelittle piked whale in each area is not spread out to a wide ground, butmore or less concentrating, usually having one concentration in eacharea. The little piked whale comes very near to the coast, and nevertaken in off shore seas over 100 nautical miles. In the Area II thecatch is almost exclusively limitted within comparatively narrow bay,
called Wakasawan. Also in Area I the catch has been carried on
Table III.

Catch records of Little Piked Whale fromthe Coast of Japan. (1948-1954).
Areas

Y<!ars

Sex

v

II

III

IV

-

-

27 I
53 I
80

VI

Total

Sex
ratio

----------

1948

1949

Male
FemaleTotal
Male
Female
Total

56
38
94

I
II

I

19
30
49

-

'

58
31
89

- - - - - - -I- - - -

-

-

11

31
42

-

1)

-

143
122
265

-~--~

61
31
92

-

53.96
46.04

---

-

-

91
92
183

49.73
50.27

141
93
234

60.26
39.74

179
155
334

53.59
46.41

----

Male
Female
Total

8
9
17

2
3 I
5

13
0
13

15
34
49

59
27
86

42
19
61

2)

1950

9
13
22

54
27
81

6
2
8

14
70
84

87
41
128

8
2
10

4)

1951

Male
Female
Total

1952

Male
Female
Total

25
19
44

122
22
144

8
0
8

19
96
115

89
81
170

1
2
3

264
220
484

54.55
45.45

1953

Male
Female
Total

35
17
52

55
30
85

36
4
40

27
55
82

75
57
132

9
4
13

237
167
404

58.66
41.34

Male
Female
Total

22
16
38

13

1954

57
123
180

22
22
44

25
12
37

5)

171
189
360

47.50
52.50

24

32
4
36

Male
Female
Total

174
142
316

246
93
339

95
10
105

170
462
632

451
290
741

85
39
124

7)1,038

Sex ratio
Male
Female

55.06
44.94

72.57
27.43

90.48
9.52

26.90
73.10

60.86
39.14

68.55
31.45

54.15
45.85

3)

----

----

11

I

6

----

)1, 226
2,264

Total

-

1) Includes 2 little piked whales taken in other area (south side of Honshu & Shikoku)
ff
ff
ff
ff
2
2)
ff
ff
ff
ff
3)
1
H
ff
ff
ff
1
4)
ff
u
ff
ff
5)
1
ff
ff
ff
ff
6)
5
ff
ff
ff
2
7)

"

15

Studies on the Little Piked Whale from the Coast of Japan

within the narrow waters along the coast, most of them having beentaken within 3 nautical miles from the shore.
As seen from table III, the highest catch was attained in Area V(North-east coast of Honshu) during these 7 years, and next to it in
Area IV (Okhotsk Sea). Regarding of other areas the catches are theorder of Areas II, I, VI, III, but the catches in these areas are very
fewer than in other two areas. Before the war some little piked
whales were taken also in the Yellow Sea, coast of Korea, and Kuril
Island's waters, as reported by Matsuura (1936), and especially in thesouth-east coast of Korea motor-vessels equipped with harpoon gun had
been operating until the end of the war with successful results. Of

JAPAN

Il

.'

SEA

..

~

•

f;
<;

~?~

v

"?>-0

I

•

Catch position of eoch whale

during the years 1953-54.
"' Location of land s1otion.
~ Main ground in Korea before~the War
J35'

Fig. 17.

14{)'

Whaling Ground for the Little Piked whale around Japan.

I

145°

16

H. OMURA and H. SAKIURA

such whaling we have no information now.
In the south coast of Honshu and Shikoku a very few whales aretaken, total catch in these seven years being amounted only 7 whales.
Several small type catcher boats
40
have been operating in these20
waters too, for the purpose of
taking small sized toothed
180
whales, accordingly we think
160 only few little piked whales will140,.
travel in these regions of the120
sea. A little piked whale wascaught by a fish trap net in
Suruga bay towards the end of
November 1955 and was kept
in captivity over one month. A
note on this whale is publishedby Messrs. Nemoto and Kimura
elsewhere in the present issue.
The sex ratio of the little120
l\'piked whale taken in the waters
100
adjacent to Japan is shown in
80
table III. A slightly more males
60
are taken as a whole than40
f emals, percentages for males
20
and females being about 54
and 46 per cent respectively. In
40
Area IV, the northernmost
ground, this ratio of sex is quite
20
striking, about 27 per cent males
and73 per cent females. In
80other areas, on the contrary,60
males occupy a preponderant
40
part of the catch over females,
20
especially in Areas II, III, V,
and VI. This fact will suggeststhat the little piked whale
migrate in segregated groups,
such as males and females.
1 ll 111 lV V \'I VI VI IX X
I II Ill IV V VI VII '1111 lX X
In fig. 18 the monthly catchof the little piked whale isshown according to each area
Fig. 18. Monthly catch of little picked
and sex in actual numbers ofwhale in each area. (1948-54)
j(IU

1IO~Tl!S~!ALE

Studies on the Little Piked Whale from the Coast of Japan17

whales taken. This figure does not show the true status on the occurrence of the little piked whale in the waters around Japan, because thecatch of this species of whale has been restricted within 6 months of
February to the end of July since 1952, though there was no restrictionof season in the previous years. In strict speaking, therefore, the catch
reports should be treated here dividing into two groups, one prior to 1952
and the other later years, but because the catch itself has not been sogreat as in Norway we treated those reports as a whole, from which
we believe, still a general conception regarding of the occurrence or
movement be gained. We give the actual number of whales taken inthis figure, instead of percentages, in order to show the abundance ofwhales too, but separately according to both sexes in each area.
As shown in fig. 18 the main catch of the little piked whale isattained as a whole in a period from April to July. Some whales arealso taken in August and September. These whales were taken in theseasons prior 1952. The main seasons for respective areas are March
to May (Areas I and II), April to July (Areas III and IV), April toJune (Area V). and July to Septemper (Area VI).
We are confident that the histograms in fig. 18 reflect the occurrence of the little piked whale in the waters around Japan with some
exceptions. There are some possibilities in Areas IV and VI that somemore whales are taken in the months August, September, and October,
if the catch is permitted also in these months. On the other hand we
think that such catch may never be so great as to exceed the peaks
shown in these histograms.
We conclude, therefore, that the little piked whales migrate into thewaters around Japan early in the spring from the south, most frequently
staying in the spring (in southern grounds) and summer (in northern
grounds), and leave in the autumn to the south. We conclude further
that there are two different stocks in the waters around Japan, the one
in the waters west of Honshu (Japan sea) and the other in the east coastof Honshu. The former migrates to the north in the spring in the orderof Areas I, II, III, and finally enters into Area IV (Okhotsk sea), wherein staying during the summer, and then travels back to the south following the similar route, but in the offing in the autumn. The latter stock
immigrates in Area V early in the spring, staying there during thespring, and going north into Area VI. It is probable' that this stock ofeast side goes father north along the coast of Kuril Islands until east
coast of Kamchatka (Bering sea), because the fact that also in thesewaters the little piked whale occur has been established by ·otherauthors (see Scattergood, 1949).
In table IV the body length of the little piked whales taken in the

18

H. OMURA and H. SAlOURA
Table IV. Body Length Frequency of Little Piked Whalefrom the Coast of Japan (1948-54) .
Per cent

Actual number
Body Length in Feet
Male

I

Female

I

Total

.
I

12
13
14
15

2
4
14
37

5
9
16
46

30
83

'

16
17
18
19
20

41
56
81
62
78

43
43
79
48
87 I

I

I

84
99
160
110
165

21
22
23
24
25

70
63
115
178
207

72 II
45 I
54
64
87

142
108
169
242
294

26
27
28
29
30

135
64
14
5
0

136
114
65
23
2

Total

1,226

1,038

Average length

22.31

22.35

I

7
13

I

I

I
I
I

II
I
!

Male

Female

Total

0.16
0.32
1.14
3.01

0.48
0.86
1.54
4.43

0.31
0.57
1.33
3.67

3.34
4.56
6.60
5.05
6.36 I

4.14
4.14 I
7.61 I
4.63
8.38 II

3.71
4.37
7.07
4.86
7.29

I

6.93 i
4.33
5.20 I
6.16 I
8.38

6.27
4.77
7.46
10.69
12.99

13.10
10.98
6.26
2.21 I
0.19

11.97
7.86
3.49
1.24
0.09

I
I

I

5.70
5.13
9.38
14.51
16.88

I

I

I

15.0

JO.a

5 ..0

J
~•~I

I_

2 B ; 15 6 7 8 9 20 l 2 3 4 2;; 6 7 8 9 so
BODY LENGTH IN FEET

Fig. 19. Body length frequency oflittle piked whale from the coast ofJapan (1948-54).

I

I

I

271
178
79
28
2

I

2,264

11.01
5.22
1.14
0.40
0

I

I

I

I

22.33

I

I

I

I

I

I

I

I

I

I

consecutive seven years ending
1954 are shown in actual numbers as well as in percentages.
Fig. 19 shows the body length
frequencies based on table IV.
As seen from the table andfigure the smallest and biggest
animals taken are 12 (male andfemale) and 30 (female) feet
respectively.
AccordingtoHarmer (1927), Fraser (1934),
and Stephenson (1951) the biggest animal from the Atlantic
ocean attains a body length ofover 30 feet. However, of theStudies on the Little Piked Whale from the Coast of Japan19

99 whales examined by Jonsg£rd (1951) the largest is a female of 914 cm(29 feet 11 inches). Accordingly we suppose that there may occur
no substantial difference in length between the animals from the twooceans, if the body length is measured correctly, in a straight line
parallel with the whale's body from the tip of the snout to the notch
between the tail flukes. No whale of exceeding 30 feet m length has
been reported from the Pacific.
As shown in fig. 19 the body length frequencies in males andfemales draw bimodal curves, having their maxima at 18 and 25 feet inmales, and at 20 and 26 feet in females. The lower maxima in both
sexes denote apparently immature groups and the higher mature. Thesemaxima are higher in females by 1-2 feet than males. The biggest
female is 30 feet, whereas 29 feet in male. Thus, in the little piked
whale female is bigger than male by one or two feet.
%
25
20
JS
JO

5
JO

5
20
15
10

5

:nr

5
5
JO

5
30

JS

30

BODY LENGTH IN FEET

Fig. 20.

Body length frequencies shown as percentages of total
catch in each area (1948-54).

In fig. 20 the frequency-curves of body length in different areas
are shown. At a glance we see that these curves resemble to thosegiven by Jonsg~rd (1951, fig. 7) for Norwegian minkes. In the waters
around Japan too, there are certain characteristic differences with regard
to the size of the animals according to the areas. In Area I the catches
were dominated by immature animals of about 20 feet or more shorter,
having their peaks at 15 and 18 feet, both in males and females. In
Area II the catch was consisted chiefly by mature animals of 24 and 25
feet in males, whereas in females there noted two peaks, one at about

20

H. OMURA and H. SAKIURA

20 feet (adolescent) and the other at 25-27 feet (full grown). In Area
III the curve for males resemble to those in Area II. We can not draw
any curve for females in this area, because the catch of females in theseseven years account only ten whales. The catches in Area IV werestrongly dominated by mature animals both in males and females, having
their maxima at 24-25 feet in males and at 26 feet in females. How. ever, there are also second maxima at 21-22 feet (adolescent) both inmales and females.
In Area V the catches were consisted of both immature and mature
animals, but more immature whales were contained in the catch offemales. These frequency-curves in Area VI are similar to those in
Area II, both in males and females.
The immature whales of about 15 feet in length, which dominate
the catch in Area I, are deemed without doubt to those who have been
weaned quite recently. As already stated elsewhere in this report, weare confident that there are two stocks of the little piked whales in thewaters around Japan, one in the west coast of Honshu and the otherin the east. Since there is no group of small immature animals of about
15 feet in the catch of Area V, we think that such whales remain more
southern waters in the eastern stock. And since there is no such grounds
for the eastern stock which correspond to Areas III and IV, where thecatches are strongly dominated by mature males and females, it is highly
probable that mature animals, more females than males, travel farther
north, beyond Area VI, to the seas of high latitude and probably along
the coast of Kuril Islands and Kamchatka.
We conclude, therefore, that the little piked whales immigrate to
the waters around Japan in segregated groups, such as immature animals,
mature males and mature females, and that the immature animals,
especially males, remain in the southern waters and only mature animals
and a part of adolescent whales travel to the northern feeding grounds.
With regards to the whaling in Korea nothing has been reported
since the termination of the war. However, a considerable number ofthe little piked whales were taken before the war in the ground on thesouth-east coast, which is shown in fig. 17. It is suggested, in thelight of the present knowledge, that the catch in this ground also be
dominated by immature animals. Matsuura (1936) reports size distribution of the little piked whale in Yellow sea, in which no whale below
20 feet is contained. We think, however, the figures in his report are
not the true reflection of the stock there, because these whales weretaken by usual whaling catchers for larger species. It is quite naturalfor such catchers to avoid the taking of small whales of less than 20
feet.

Studies on the Little Piked Whale from the Coast of Japan21

As regards the southern limit of migration, we have no scientificevidence at present. Some whalers say that the little piked whale has
been observed rather frequently in the waters near Okinawa. This
information may throw some light to this problem.
Food

As to the food of the little piked whale from the Atlantic ocean
Stephenson (1951) states that" off the English coast, the captured whales
had been feeding on herring and mackerel." Jonsg£rd (1951) also describes that "in Nowegian coastal waters different species of fish playa greater role as food for the minke whale." Thus it seems that fish
is the most favorable food for the little piked whale. However, Jonsg£rd continues further "we think it may be safely concluded that theminke whale in high Arctic waters feeds mainly on krill, in this case
Thysanoessa inermis. Even in the cases where a mixed diet was found,krill formed the major part of the content, which seems to suggestthat the herring, capelin, or small cod found together with the krill
have been feeding on the same krill swarms as the whale and havebeen taken, therefore, more or less, accidentally."
In the coastal waters of Japan krill plays more or less a greaterrole as food for the little piked whale, especially in Area IV, thenorthernmost ground in the Okhotsk sea.
In table V the reports from the whalers for 1953 and 1954 as tothe food of the little piked whale are tabulated. There may be somecases where the kind of food has been miss-identified. However, we
think that such cases may occur rather in few occasions where the foodconcerns not with commercial fish.
As seen from this table the instances where krill is eaten are mostnumerous. However, we are not confident as to the "krill" (in JapaneseAmi) reported by whalers means always euphausiids. Since there is noJapanese word corresponding to Norwegian "rcpdaaten," copepods areoften reported as Ami (krill). Of the 17 whales, investigated by us of
their stomach contents at Abashiri (Area IV) in 1953, 3 were empty, 5were with krill (mostly in rich), 2 were with krill and some fish bones,
2 were with copepods, 2 were with mixed diet of krill and copepods,
and rest 3 with fish. Of the 3 whales which had fish in their stomach,each one instance of Alaska pollack (Theragra chalcogramma) and sandlance (Ammodytes personatus) have been observed. The rest was themixed diet of the both species.
Also in Area I, southernmost ground, the little piked whale feeds
in some extent on krill. In spring krill swarms in these waters andH. OMURA and H. SAKIURA

22
Tableh V.

Stomach contents of Little Piked Whalefrom the Coast of Japan.
Kind of Food

Area

I

1953

·I

1954

:~

6
15

Krill (or Copepods)

62

12

Fish, Sand lance
Fish, Iwashil)

9
3

3
2

Krill (or Copepods)+Fish, Sand lance

2

1

Krill (or Copepods)
Fish, Sand Janee (Ammodytes personatus)
Fish, Iwashil)

5

I
Other fishes---1------------1---i---

II

Squid
1
I
-----1----------------------1----------2
Krill (or Copepods)
2
Fish, Iwashi 1 )2III30
Fish, Hokke (Pleurogrammus azonus)
34

I
1

Squid

1

-----1------- --------------------- ----------1

Krill (or Copepods)
Fish, Sand lance
Fish, Iwashil)Fish, Alaska pollack (Theragra chalcogramma)IV

Fish, Cod (Gadus macrocephalus)
Small fish, not identified
Krill (or Copepods)+Fish, Sand lance
Krill (or Copepods)+Fish, Alaska pollack
Krill _(or Copepods)+Fish, HerringFish, Sand lance+Fish, Iwashi 1 )

44
13
1
12
1

13
2

1
1
1
1
79
27
12

Fish, Mackerel
Small fish, not identified

-

i

I

10

.1'

23
3

:
3

2

I

~--i---~-4--________________ \___

Fish, Iwashi1 )
VI

5
12

4

Fish, Sand lance
Fish, Iwashi 1)c~~~;-od-s)

163

Krill (or Copepods)_ _ _ _ _ ,--:-:u-i:l-d(-o-r119

2Fish, Sand lance+ Fish, Alaska pollack
Fish, Saury pike (Cololabis saira)+Squidv

I

Fish, Alaska pollack
Fish, Cod

!
-

•

9
4

16

II

1
.
i
1) Collective name of sardine (Sardinops melanosticta), anchovy (Engraulis japonica), and round herring (Etrumeus micropus). But mostly anchovy in these cases.

are taken by fishermen by nets of fine meshes for human consumption.
The Tsu1rndani, a kind of conserved food cooked with sugar and soy

Studies on the Little Piked Whale from the Coast of Japan

23

beans souse, of krill is a traditional food in Japan. According to whalers
in the year more krill abundant, more whales come to these waters.
Among fishes found in the stomach of the little piked whales, sandlance plays a greater role, particularly in Area V. Large fish of thisspecies of about 15 cm or more in length are present in good quantity inthe stomach. The little piked whale in this area comes very near toshore pursueing this fish, and it is not very seledom that the whale betaken by fish trap net.
Most of the fish reported as Iwashi are thought to belong to anchovy(Englaulis japonica), though there are few records of Oba-Iwashi, whichmeans full-grown sardine (Sardinops melanosticta). It is noted that
Hokke (Pleurogrammus azonus) is reported only from Area III, but thisfact coincides well with the abundance of this fish in these waters.
In Areas IV and VI also AlaLka pollack (Theragra chalcogramma),
cod (Gadus macrocephalus), or herring (Clupea pallasi) have been recorded
besides above mentioned kinds of fish. Squids too are eaten, though in
few occasions, by the little piked whales.
Reproduction and Growth

Of the 13 whales examined by us of their ovaries, 5 were immatureand 8 were registered as mature, having one or more corpora lutea ofpregnancy or ovulation in their ovaries. The largest immature whalewas 709 cm (23'3") in length and had a ripening follicle of 8 mm diameter in its ovaries. Among the whales examined by us the greatest
diameter of Graafian follicle was recorded as 15 mm in the little piked
whale. The smallest mature whale was 788 cm (25'10") in length, but
this whale contained one functional corpus luteum (fetus not present)
and 12 corpora albicantia in its ovaries. In fig. 21 the relation between
body length and number of corpora lutea are shown, and from thisfigure it is clear that females of 26 feet in length or more larger are
all mature. But we can not conclude at what body length the female
little piked whale reaches sexual maturity in average from this figurealone, because we have no data concerning 24 or 25 feet. We haveinvestigated, therefore, the records of 111 fetuses obtained during theyears 1948 to 1954. Instances of pregnancy according to their respective
body lengths are as follows :Body length
23 feet
24 II
25 II
26 II
27 II
28

29
30

Instances of pregnancy
2

2
7

44
28

II

20

II

6

II

2

H. OMURA and H. SAKIURA

24

As seen from the above the smallest pregnant female is 23 feet.
Matsuura (1936) reports 8 records of pregnant females from the waters
adjacent to Japan, and amongst them the whales of 23 Shaku (1 Shaku=
0.99421 foot) are the smallest. But such instances are deemed rather
few, though we have no negative evidence, except one examined by us
as already mentioned. Jonsgard (1951) describes that sexual maturity

2 35
63

1400

:;i·

30

l'J

~

:<!

~

c;

25

..

:] 1000

C"l

g

1200

z 800

20

>o

'

c;'l

0

~

,...

;j
~

10

(fJ

0

----------------'•• ••15 16 1718 19 20 2122 28 24 25 26 27 28 29 30

BODY LENGTH IN FEET

Fig. 21. Relation between numberof corpora lutea and the length offemale little piked whale.

:

~

••

h

- :, 1 •1;'.
s:: 600
s::'1•

15:; ~ i;- ·~.

-

400

:t .

200
I

.,

!. :

•• f

t:

1516 17 18 19 20 21 22 23 2-! 25 26 27 28 29 30. BODY LENGTH IN FEET

Fig. 22. Relation between weightof testis and the length of male little
piked whale.

is attained at length of about 24 feet in the female for the whale fromthe Norwegian waters. We may conclude that the average body length
at which sexual maturity is attained is about 24 feet in the female little
piked whale from the coast of Japan, not differing from the figure
established for the whale from the Atlantic ocean.
We have plotted the weights of testes against the corresponding
body lengths in fig. 22. There are two groups roughly, the one being
less than 200 grams and the other heavier than 300 grams. Evidently theformer represents immature group, and the latter mature. The smallest
mature male is 19 feet long, and the largest immature may 24 feet.
Males of 23 feet long and over are evidently mature. Jonsgard (1951)
reports that one pair of testes weighing more than 225 gr. seem to bemature. Since weight of each testis is plotted in fig. 22, our weight
shuld be doubled in order to compare roughly to that given by Jonsgard.
Individual weight less than 200 gr. in fig. 22 seem to be slightly heavier
than those reported by Jonsgard. We are not confident that our measurements are always correct in critical point, because these data havebeen supplied mainly from the whalers, not having measured by us.
Jonsgard states that the male attain sexual maturity at a length ofabout 22 feet, 2 feet smaller than the female. There are 4 whales in25Studies on the Little Piked Whale from the Coast of Japan

fig. 22 which registered at 22 feet (each dot denotes the weight of eachtestis instead of one pair of testes). One is obviously mature, two areapparently immature, and the rest one is very doubtful whether or not
mature. We think that the average body length at which sexual maturity is attained in male is 22 or 23 feet for the little piked whalefrom the coast of Japan.
In fig. 23 body lengths of fetuses are plotted according to their- - - - - - - -~~---- B - - - - 7 - - - - -"' 280••areas I and II
area IV
X areas V and VI

§
~

2~0

t""'

i
0

....,

/
/

200

/

/

/

I
I

/

"' 160

z

A••

X

/

.

//

//

A.

......
IX_ _....-..........
X

Xl

XII

/

/

/
-10

/

/

/

//
/

80

I

/

/

~ 120

A

/

.1

//
,(

_,..../ .........._ . ·::•••;x..

..
• •

·,:.

.,xf'

">'

X

:·

... /(.
X

XI

XII

I

MONTHS

Fig. 23. Length of fetuses and months of their occurrence inwaters around Japan, showing the approximate rate of growth.
•areas I and II• area IV
x areas V and VI

respective dates. This material has been obtained during the period
from 1948 to 1954. The records of fetuses thus obtained are confinedalmostly within 5 months from March to July, because of the restrictionof the period of taking imposed on whaling. We added he:re, therefore,
the records reported by Matsuura (1936), in the days of no such restriction.
As seen from fig. 23 there are roughly two groups of fetuses evenin the same period, the one is smaller and the other bigger. The line
A is a supposed growth curve for the smaller group of the fetuses. The
body length at which the birth takes place is supposed at 280 cm.
We think this supposition may correct in the light of the present knowledge. According to the line A most of pairing take place at the endof February or beginning of March, and most whales give birth to theircalves at the end of December or beginning of January, having theperiod of conception of about 10 months. This curve coincide fairly
well with the growth curve of fetuses given by Stephenson (1951) forthe little piked whale from the Atlantic ocean, if we shift the line A amonth earlier.
But, as seen in this figure there present another group of f etuses,

26

H. OMURA and H. SAKIURA

the bigger, far apart from the line A. The occurrence of such fetuses
from the coast of Japan has already been shown by Matsuura (1936,
fig. 4) and Stephenson (1951, fig. 14), though no details are discussed
in their reports. We have examined 8 mature females at Abashiri (AreaIV) from 13th to 16th June 1953, in which 6 were pregnant. The othertwo had contained functional corpus luteum in their ovaries, but nofetus was present. It was ascertained after careful observation, cutting
open through their uterine cornua. No resting whale was observed.
The biggest fetus has been recorded as 279 cm (9'2") and was deemedas just before parturition. The smallest one was at the early stage ofpregnancy and the sex of the fetus could not determined. It is apparent
that the 2 whales which contained no fetus were just after ovulation,and may be at a very early stage of pregnancy or in pairing. Thus,
we have observed a biggest fetus of just before parturition, a verysmall one, and two cases of very early stage of pregnancy or in pairing
within a very short period of five days, even in the northernmost ground.
The line B is drawn parallel to the line A with an interval of six
months. Hatched lines were drawn also parallel to those solid lines,
but with an interval of three months. Apparently the line B denotethe average growth curve for the fetuses of another group, the bigger.
Pairing and parturition, in this case, take place at about Aug.-Sept.
and June-July respectively.
It is apparent that the period of pairing is of long duration in bothcases. Jonsgard (1951) reports for the little piked whale from theAtlantic that the pairing-season must be of rather long duration fromabout January to the end of May. Since the little piked whale fromthe coast of Japan has two seasons of pairing within 12 months andeach one lasts for long period, pairing may occur actually throughout
the whole year. Stephenson (1951) describes as to the little piked whalefrom the Atlantic that the sizes of young stranded whales suggest thatbirth can occur at any season of a year. His opinion has not been
justified by Jonsgard, but our material suggests that it may be applied
to the whales from the coast of Japan.
It is clear, as stated above, that the little piked whale from thecoast of Japan has two seasons of pairing, but it is hardly thought thatthese fact is based upon different habit of breeding between the twostocks, namely eastern and western stocks of Honshu. We have plottedwith different symbols in fig. 23 the fetuses from different areas. Samesymbols are seen in both groups A and B, presenting a negative evidence.
We conclude, therefore, that the ovulation takes place at least twicea year in the little piked whale from the coast of Japan, the first ovulation mostly in. Feb.-Mar. and the second mostly in Aug.-Sept. with

Studies on the Little Piked Whale from the Coast of Japan27

an interval of six months, and impregnation may occur in both cases.
We have calculated the numbers of individuals belonging to bothgroups with a result that the ratio of A-group to B is roughly 2 to 1.
But, we should remind here the fact that a great number of small
fetuses, which belong to A-group in the period of whaling permitted,
may have been overlooked. Accordingly we conclude further that females
get impregnated mostly at the first ovulation, having its peak in February and March, and those females who had not been impregnated at
the first ovulation may have fetuses at the second ovulation, 6 months
later from the first.
In any case, it may probable that mature female gives birth a young
within more shorter time than 24 months, which is thought generally
be applied to other baleen whales. This is suggested by our examinationof ovaries, however few in number. Of the 8 mature females, no resting whale was observed. Jonsgard (1951) states that paucity of restingfemales in the material leads to the conclusion that the majority ofmature females bring forth a young one once a year for the little piked
whale in the Norwegian waters. His conclusion may be applied also
for the whale from the coast of Japan, but slightly changed. Namely,in the little piked whale from the coast of Japan mature females mostly
bring forth a calf once a year, but there are some cases where they givebirth to their young after an interval of 18 months from the previous
parturition.
The material at our disposal can yield only a small amount of information about the growth after birth. It is seen from fig. 20 that there
are peaks in the body length frequency curves in respective areas roughlyat 15, 18, 20-21, 23, and 24-25 (male) or 25-26 (female) feet. The
small whales of about 15 feet in length are probable to have weaned
recently. These constitute the 0-year class, or about half a year old.
From 15 feet upwards the intervals of successive peaks are 2-3 feet.
Two or there feet growth is hardly taken as an annual growth for the
little piked whale, comparing with more rapid growth, about 6 feetwithin 6 months, in the period prior half a year old is attained, and in
the light of the present knowledge that birth may occur also in summer.
We may ascribe, therefore the second group of about 18 feet long to
the I-year, class, or a year old, and the third group of about 20-21
feet in length also to the I-year class, but actually one and a half year
old. In this way, the fourth group of about 23 feet may be deemedas II-year class of about 2 year old. The groups of 24-25 feet in males
and 25-26 feet in females are apparently consisted of mature animals,
and may be of different ages, older than 2 years old. Sexual maturity
may be attained at an age of 2 years. This assumption coincides well

28

H. OMURA and H. SAKIURA

to that of Jonsgard (1951) for the little piked whale from the Atlantic
ocean. There may be no remarkable difference in growth or age between
the animals from the different two oceans. But of course, more evidenceis needed before this can be regarded as firmly established.
Summary

1. The little piked whale from the coast of Japan has been studied
using material obtained from the biological examinations of whales treatedat land station as well as the information supplied by the whalers during
the years 1948 to 1954.
2. The little piked whale from the coast of Japan has a shorter
mouth, a more posteriorly situated, but higher dorsal fin, more shorter
flippers, more broader tail flukes, and a more posteriorly situated genital
aperture than the whale from the Atlantic ocean. The Pacific whale
has slightly fewer baleen plates than that from the Atlantic. We think,however, that these differences in external characters should be deemed
as differences according to different stocks or racial nature, becausesuch measurements from both oceans are overlapping in major parts.
The grounds for recognizing Balaenoptera davidsoni as a subspecies ofB. acutorostrata have not been justified from the external characters.
3. It is thought that there are two different stocks of the little
piked whale in the waters around Japan, the one to the waters westof Honshu (Japan sea) and the other in the east coast of Honshu. Bothstocks migrate into the waters around Japan early in the spring fromth.e south, most frequently staying in the spring (in southern grounds)
and summer (in northern grounds), and leave in the autumn to thesouth.
4. The little piked whale immigrates to the waters around Japanin segregated groups, such as immature animals, mature males andmature females. The immature animals, expecially males, remain in
the southern waters. Only mature animals, dominated by females, anda part of adolescent whales travel to the northern feeding grounds ofhigh latitude.
5. The little piked whale from the coast of Japan feeds on krill
or cope pods as well as various kinds of fish. Among fish sand lance(Ammodytes personatus) and anchovy (Engraulis japonica) play a greaterrole.
6. The sexual maturity is thought to be attained at a body lengthof 24 feet in female and 22-23 feet in male, and at an age of 2 years
in both sexes.
7. The ovulation takes place at least twice a year in the little

Studies on the Little Piked Whale from the Coast of Japan29

piked whale from the coast of Japan, the first ovulation mostly in Feb.Mar. and the second mostly in Aug.-Sept. with an interval of six months.
Most mature females get impregnated at the first ovulation and those
females who had not been impregnated at the first ovulation may havefetuses at the second ovulation.
8. The period of pairing is of long duration and may occur throughout the whole year. The gestation is supposed to last about 10 months.
Most of the mature females may bring forth a calf once a year,
but there are some cases where they give birth to their young after aninterval of 18 months from the previous parturition.
Literature Cited
Cowan, I. McT., 1939: The Sharp-headed Finner Whale of the Eastern Pacific. Jour.
Mamm., Vol. 20, No. 2.
2. Fraser, F. C., 1934: Report on Cetacea stranded on the British Coasts from 1927 to
1932. Brit. Mus. Nat. Hist., No. 11.
3. Fry, D. H., 1935: Sharp-headed Finner Whale taken at Los Angeles Harbor. Jour.
Mamm., Vol. 16, No. 3.
4. Harmer, S. F., 1929: Report on Cetacea stranded on the British Coasts from 1913 to1926. Brit. Mus. Nat. Hist., No. 10.
5. Jonsgard, A., 1951: Studies on the Little Piked Whale or Minke Whale (Balaenoptera
acuto-rostrata). The Norwegian Whaling Gazette, No. 5.
6. Matsuura, Y., 1936: On the Lessor Rorqual found in the Adjacent Waters of Japan.
Bull. Jap. Soc. Fish., Vol. 4.
7. Moore, J.C. & Palmer, R. S., 1955: More Piked Whales from Southern North Atlan·
tic. Jour. Mamm., Vol. 36, No. 3.
8. Scattergood, L. W., 1949: Notes on the Little Piked Whale (with Bibliography).
Murrelet, Vol. 30., No. 1.
9. Scheffer, V. B. & Slipp, J. W., 1949: The Whales and Dolphins of Washington State
with a Key to the Cetaceans of the West Coast of North America. The American
Midland Naturalist, Vol. 39, No. 2.
10. Stephenson, W., 1951: The Lesser Rorqual in British Waters. Dove Marine Laboratory Report. Third Series No. 12.
1.

Studies on the Little Piked Whale from the Coast of Japan

Appendix Table
Measurements of Body Proportions.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.

Total length.
Lower jaw, projection beyond tip of snout.
Tip of snout to blowhole (centre).
Tip of snout to angle of gape.
Tip of snout to centre of eye.
Tip of snout to tip of flipper.
Centre of eye to centre of ear.
Notch of flukes to posterior emargination of dorsal fin.
Width of flukes at insertion.
Noch of flukes to centre of anus.
Notch of flukes to umbilicus.
Notch of flukes to end of ventral grooves.
Centre of anus to centre of reproductive aperture.
Vertical height of dorsal fin.
_Length of base of dorsal fin.
Flipper, tip to axilla.
Flipper, tip to anterior end of lower border.
Flipper, greatest width.
Head length, condyle to tip of snout.
Greatest width of skull.
Skull length, condyle to tip of premaxilla.
Skull height.
Tail flukes, notch to tip.
Length of lower jaw.

31

H. OMURA and H. SAKIURA

32

Body Proportions of Little Piked
upper figures:lower figures:

I Date,No. I killed

MeasureLai:d i Sex
stat10n .
. 1

2 I 3 l 4 I 5 I 6 I 7 I 8 I 9 j 10 :1
1 I 12 Jun. Abashiri M i 5821
61
68!
791
851 2181
271
167i
42!
1481
i
1953
I 1.03 ll.68113.57114.60j 37.46j 4.641 28.69[ 7.22125.431
16881 14194!
1311
1121 2671
361
167
511
179
Kushiro I "2 / 24 Jui.
1953
I 2.03 13.66! 19.o4! 16.281 38.81. 5.231. 24.21 7 .41! 26.02
6951 911-'
119! 2301 371
180!
_
1901
3 ! 21 Jui.
Abashiri ' ff!
1953I-! 13.091 --! 17.12i 40.29i 5.32! 25.901 _i 27.34
I
ff
I
ff
4113 Jun.
I 718i
181
95j
128!
1091 303[ 361 209
481
191
!
! 2.511 13.37l 17.83l 15.l8i 42.20! 5.01 29.11! 6.691 26.601
1953
1
I
ff
5 1 15 Jun.
' 739i 18i
941 103i 1151 3osl 371 2001
52i 206i
1
1953
I 2.44j 12.72! 13.94! 15.561 41.41 5.01! 27.06 7.04/ 27.881
1
7!
1021
-I 1121. -;43i:. 788!
6 16 Jun.
I
I/
1953
i
I
i o.89112.94!
- 14.21:
6.o9!
- 1
,
1
7 22 Jun. Ayukawa I " i 794!
-97l
_I 125j 307!
2zil
55i
2131
1953
I
,
I -! 12 .22,
- 15. 74. 38.67; 6.201 27 .831 6 931 26 .83
101[' 147' _' 39j 207: .
.
8 18 Jui. 1 Kushiro I " i 7991 _j
I_I 12.64:' 18.40[_I 4.88\ 25.91:
I•1953 '
1
9 23 Jun. Ayukawa F
461j _:
541
66
182i -:
132! 33f
1351
i-i. 11.71[
14.32 39.48]-: 28.63! 7.161 29.28!.
1953
I
I
I
I
'
I
i
.
I
10 24 Jui. Kushiro , II
554: -I
70 1
84
233!
311
1361
451
152
i
- : 12.64i- V5.16j 42.06j S.59[ 24.541 8.12i 27.44
1953I
11 12 Jun. Abashiri / ff
5641
81
76l
791
91]
2301
301·
1611 42!
152:
1953
j l.42i 13.48! 14.01116.13140.781 5.32, 28.55j 7.451 26.95i
1,,
I ,, i 5971 15!
12 10 Jun.
821
94
111
2391
301
164~ 431 155[
1953
i
I 2.5li 13.74 15.75 18.59 1 40.03I 5.03, 27.471 7.20 25.961
1
Kushiro13 24 Jul.
i 6581 12\ 881 123 112 2731 391 1731 _\ 1701
1953
[ 1.82113.37 18.69 17.02 41.491 5.93[ 26.291-: 25.83j
14 14 Jun. Abashiri
"
709j
10
881 J~81203001
35j 203 1 591
194!
1953
! 1.41! 12.41 16.64116.93 42.31 4.941 28.631 8.32[ 27.361
15 13 Jun.
"
788j
151
1001
1331 133j
3361
431
18511 63; 2151"
1953
! 1. 901 12 . 69! 16. 88 16. 88j 44. 041 5 .461 23 .48'1 7. 99[ 27. 281
ff
16 16 Jun.
"
7911
100!
-:
1301
-·1 431
221
57'
1971
1953
- 5.44j 27.941 7.21'· 24.9lj.
11.641. 12.64!
-: 16.431.
ff
17 14 Jun.
II
794;
6
1151
121[
12111 327! 37! 2271
56!
197!
1953
: 0.76,1 14.48! 15.24\ 15.241 41.18! 4.66i 28.59i 7.051 24.81J
If
18 16 Jun.
I/
I 7971131 1001 -: 1211 326[ 43j 2301 57' 230i
1953
1 1.63: 12.551-; 15.18j 40.90j 5.40j 28.861 7 .15, 28.861
19 16 Jun.
II
8031 _!
106j
150[ 1271
330!
431 224
611
2061
"
!
13.201 18 681 15.821 41.10! 5.351 27.90! 7.60! 25.651
1953
ff
"
8d
15
103!
. 115i 3271
46i
224 1
224
20 15 Jun.
1953
i 1.85 12.681
14.16! 40.27] 5.67j 27.59:-: 27.59;
If
21 14 Jun.
If
8181
7,
115j 109109i 364: 45
209j
60!
2151
1953
j o.86, 14.06! 13.321 13.32! 44.501 5.5ol 25.55\ 7.33\ 26.28jff
22 15 Jun.
11
836j
ll 7j
130i
1361 351\ 46j 236! 60!
200:
1953
I -1 14.90, 15.51! 16.271 41.99 5.501 28.23 7.18 23.92
I
I
I
!
I
1
ff
23 13 Jun.
" I 8571 101 1241 136! 1391 373! 461 2331 611 2301
1953
i
1.17114.47! 15.87\ 16.22[ 43.52j 5.37f 27.19] 7.12\ 25.67j

--1

I

I

1

I

,,

I ,,

d

·1

1

d

1

I

-i

I

i

1

I

I

33

Studies on the Little Piked Whale from the Coast of Japan
Whale from the Coast of Japan.
length in centimeters.
percentage against body length.
ments
11

1

12

I 13 I 14 I 15

1

276
327
47.42 56.19
391
339
49.27 56.83
320
46.04
342
400
47.63 55.71
351
421
47.50 56.97

37l
6.361

48
2si
4.811 s.251

48i

=1

6.981
51:

16

I 17 I 18 i 19 I 20 I 21 I

' 132I 741
54!
771
201
I 9.2s!
13.231 3 .44 22 .6sj 12. 711

I

I

i

=1

30

66\
1061
9. 50!
15. 251571
72,
90.
7. 94·110. 0311 12. 531
64
-,
341
4.6o 8.661::i; ::i;r
1

421

5.~

1

-i

I

1

1

-

-1

-

1601

77

I

;1 =I-1 = =!
1

3.741
251

1

-i

3.~122.~110·~1

-j -1

_11

-

sol
123
-: 13. 75! 21.13-1 92: -113.371
160-1 23.02
'
I
-I
98'
155
--[ 13.651 21.59_i 111i
15.021-I -!-I-384
445
48.36 56.05

260
223
48.37 56.40 1

61
48
64
94
7 .68
6 .05 8.06 11.84
53
241 10.141
81
-,
157
6.63 3.00- 19.65
10
271
411
67j
2.171

;;1=1 =1::I =::I ::=1

3.50_,

3J~1 4 28! 43,ri1 : 46,~ :: ;;i651 3.97221 128-

264
3121
47.67156.32
264
3061
15
46.81, 54.261 2.661
1182671 361 1
44. 72 60.47. 3.01
303!
3451
21
46.051' 52.431 3.19
339
409
15
47.81' 57.68 2.11
470
333
201
42.26 59.64
2.541
24
369
415
46.65 52.471 3.03
361
385
271
45.47 48.491 3.40
363
373
19
45.55 46.80 2.38
181
373
4331
46.45 53.92: 2.24:
388! 443!
24[
2.96\
47. 78!1' 55
19:
379
373
46.33[ 45.60 2.32!
3641
445!
24
43.54: 53.23 2.87i
403; 458,25'
47. 02; 53.44 2. 92

.17:

ii :

4.961
27
4. 521
281
4.261
29
4.09/

-1
-1

301
3.79
251
3.151

33
4.11
38!
4.68

1

1

1

-iI

22

72
7.62i, 8.16, 11.521 3. 90, 22. 701 12. 77
451
581
711
22[
1301
72
7. 54! 7. 921· 11.891 3. 691 21. 781' 12. 06
451
48,
701
25·
-1 - i
6 .841 7 .291· 10 .64, 3.791
I
27,
-1
-1I
49
56
681
3.811
1
,
6.911 7.901 9.59
311
I
85,
921
10. 79 11.671 3.931

1

1

-i

I

55
67
941
6.95, 8.47 11.881
481
601
88
6.051 7.56111.081.
-1
91
1021
-111.42 12.80:
671
701
99'
8.34 8.72i 12.33i
55,
8.00i,-i1 -,
62
77i
7.58 9.41 1
'
92
123!
11.00 14.71
75
94,
1351
8. 75. 10. 97 15. 75j

2s[

3.~,

=I

- 1

-,
-i

311
3.89,
31:
3.86!

I

]

'

=i

-1
I

I

-1

-1

-1

;11

1

1

-i

~:

I

-j

I

I

=I-! _I-1

1201 155-, 16.93 21.86
120
178- 15.23122.59_I
123- 15.55
I_I
1231- 15.491

-11
-

-

1161
14.55
120
14.94i

-I-1

32
187!
89:
3.91! 22.86j 10.881
31'
3.711
-1
-1
1
34
195j
-3.97 22.751

-1

-:

l;

6.29 14.10 21.69_I 90 -116.25
-:
78
118
_: 13.83 20.92
_i
86
125
-114.41 20.94-1 --1-1

132'.
3. 73,

51
94
11.06 20.39

1251
15.86

-·
-

-

1331 182-1. 16.26122.25
-:
128
177
- 15.31 21.17
I-11371 185- 15.991 21.59

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36

H. OMURA and H. SAKIURA

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Photo by Sakiura)
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eI
t
a
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