SCHOOL OF BALEEN WHALES IN THE
FEEDING AREAS
TAKAHISA NEMOTO
From the ecological point of view, the school of the baleen whale is one of the mostimportant theme although it has not been fully studied. The observations on theschool of whales from the aircraft, ships and the marking cruise have been carriedout (Chittleborough, 1953: Clarke & Ruud, 1954: Brown, 1957: 1958: Nemoto,
1959: Clarke, 1962), however, these are descriptions on the constituent numberof whales in schools in general.
Andrews (1914), Slijper, (1958) and Nemoto, (1959) discuss the schools ofbaleen whales considering the socionomic sex ratio, the affection, number ofwhales and the mutual help among whales in a school. Some studies and discussions on the ecological segregations in the migrations of certain baleen whales also
have been done, (Mackintosh, 1942: Fujino, 1960: Laws, 1961: Nemoto, 1959:
1962b), but it may be generally accepted that there has been few ecologicalstudy on the school of baleen whales.
The catch data and the whale marking results of the whales in the North Pacificand the Antarctic waters give biologists many materials, and I examine here themchiefly in the feeding grounds. The number of baleen whales in a school andthe sex ratio are checked in a first step. Sexual maturity in each member of a schoolis also important for this study, however, it is impossible to examine the whales
observed in the marking cruise in the sea. The most reliable data on the sexual
conditions of the baleen whales are obtained through the investigations carried out inthe factory ships, in the whaling stations, in the North Pacific and in the Antarctic.
It should be noted that the most part of the sexual conditions are obtained in the feeding areas, not in the breeding areas in the lower latitudes. I would think theschools of baleen whales should be examined also in the breeding areas, in which
the meaning of the school of baleen whales is somewhat different from that ofschools in the feeding areas.
The whaling has been opressing whales and have the great influence on theconditions of baleen whales such as migrations, reproductions and formations ofschools. Especially the whaling in the feeding grounds break up the schools by
the catch, and this affects the data treated here too.
Several populations are considered both in the Antarctic and in the North Pacific,
and individual numbers of baleen whales effect the schooling of them. But materials
are treated here as a whole in each whaling areas, Antarctic, North Pacific, andadjacent waters to Japan. Futher consideration will be made in due course on
these points.
The term ' school' of baleen whales is also said in other ways, pod, herd andgroup. 'School' and 'herd' are commonly used in the biology of whales, andI use here the word ' school' for the baleen whales. According to Clarke, (1956)
89

T. NEMOTO

90

the old whalernen distinguished ' pods ' or 'garns ' numbering up to about twenty
whales, 'schools' or 'shoals' of some twenty to fifty, and the 'herd' or 'body ofwhales ' comprizing some fifty to serveral hundred. The term ' herd ' is usedmostly for the land mammals ungulates, ' school ' for fish, and group ' is used
for the general expression in the recent ecology.
MATERIALS

The materials. treated here consist of two parts. One is the marking data in the
North Pacific, adjacint waters to Japan and the Antarctic ocean. The anotheris the catch data in the North Pacific by the Japanese factory ships in 1955 and 1956.
The marking data base on three groups described following.
North PacificAdjacent waters to Japan andBonin Islands
Antarctic
l:fj'

t,.j'

1953 ............ 1961
1949 ............ 1955
1954............ 1961
l2J'

120'

iCJ'

12J'

--~''

Fig. 1. The whaling grounds where the observations on the schools of baleen whales
have been carried out. Lateral line--North Pacific pelagic : Straight line-Coast ofJapan: Black circle--Okinawa, Black square-Bonin Island pelagic: Obliqueline-Antarctic pelagic.

From the marking data, the number of whales in a school is discussed
as well as the formations of the school of different species of baleen whales. The

91

SCHOOL OF BALEEN WHALES

socionomic sex-ratio and sexual conditions are mostly obtained from the biological
data based on the whales caught in the North Pacific. The pair schools of cow andcalf have been obtained through the marking research, and the variation in the number of baleen whales in a school from the marking and catch results both in the North
Pacific and the Antarctic. These research areas are shown in Fig. 1.
SCHOOL OF BALEEN WHALES IN THE NORTH PACIFIC,FIN WHALES (BALAENOPTERA PHYSARUS)
Number of fin whales in a school
The number of fin whales in a school has been discussed by Clarke & Ruud ( 1954)
Nemoto (1959) and Clarke (1962). According to their reports and other descrip
tions (Chitterborough, 1953 etc), fin whales have been. mostly found four or lessin a school in the feeding areas. The schools consist of five or more whales are
TABLE 1.

June
July
Aug.
Sept.
Total

62
178
64
305

NUMBER OF FIN WHALES IN A SCHOOLIN THE NORTH PACIFIC IN 1956
Number of fin whales in a school

2

3

4

5

6

7

8

88
204
151
2
445

32
100
52

17
72
28

8
32
9

3
9
7

2
5
3

10
3

18
13

184

117

49

19

10

13

31

May
Male Female
3
5
1955
1956

TABLE 2. SEASONAL OCCURRENCES OF SINGLE
FIN WHALES IN THE NORTHERN PACIFIC
Aug.
Sept.
July
June
Male Female
Male Female
Male Female
Male Fema,le
103
33
9
81
38
41
45
13
100
36
78
28
36
26
1

---------- -----------

9

10-

Total
Male Female
173
198
173
132

TABLE 3. OCCURRENCES OF IMMATURE FIN WHALESIN THE SINGLE SWIMMING FIN WHALE
MatureImm.
MatureImm.
Preg .
..---"'-..
. 164
34
45
71(55.5%)
128
1955
110
22
141
32
62(43.9%)
1956

comparatively scarce. The number of fin whales in a school in the North Pacificin 1956 is shown in Table 1 on 1298 fin whales. The number of fin whales in aschool vary with the proceeding of the seasons, an:d the single swimming fin whale
decreases in number in the late of summer (Nemoto, 1959).
This tendency is clearly shown in the Table 1 and Fig. 2. The one of themain reasons for the fact may be the leaving of the single swimming pregnant
female to the breeding area as it has been considered (Mackintosh, 1942 : N emoto,
1959: Laws, 1961), however, July in the North Pacific must be the feeding season
for fin whales and they come to the feeding areas in July successively. The forma-

~I

92

T. NEMOTO

tion oft he school in the feeding areas also should be considered as suggestedby the prevous report (Nemoto, 1959).
Single swimming fin whale
From the observations in the catcher boats chasing fin whales are used for the examination. The seasonal occurrences of male and female in single swimming
fin whales is given in Table 2 and 3 according to the data in 1955 and 1956. Thereis no consistent tendency in the occurrence of each sex, and no clear tendency inthe occurrences of immature and pregnant whales too. It has been generally ac100

JOO

50

50

<ll

g

~
=>
u
u

0

2

I~

l~

May

June

June

July

Aug.

Juiy

Aug.

Fig. 2. Seasonal variations of the number of fin whales in a school in the North Pacific.
Left-1954: Right--1956.

cepted that there are some ecological segregations in the baleen whales according
to the sex and sexual conditions. But there is no pecurial feture in the characters of
the fin whales in the data in 1955 and 1956. The pregnant ratio is also not so highor low comparing with other fin whales caught. Five lactating fin whales arepresent out of fifteen resting whales in 1955. The occurrence of the immature fin
whale are also not so different from the total catch of the fin whale. This may
partly be affected by the size regulation in the whaling. The shorter young fin
whales may sometimes form a large school but they are saved from the catch. As
a conclusion, single swimming fin whales in the feeding areas show no pecurialfeature. But it will be re-examined by the futher accumulated data in due cource.
Pair fin whales
The catch data of the pair fin whales are not so large in number. Twenty-six
pairs of fin whales in 1955 and sixty pairs in 1956 are caught by whaling, the occurrences of each sex of which are illustrated in Table 4. The combination of maleand female is dominant among three combinations. Male and male combinations
exceeds female and female combinaions. This may due to one reason of theaffection between male and female form the school. The sexual conditions of

93

SCHOOL OF BALEEN WHALES

those pair fin whales are as follows. Although the number of cases is not so large,
the immature combination of male and female is scarce. In the pair of female fin
whales, the occurrences of the combinations of mature and immature females andimmature combination are observed. Among the pregnant females in the pair of
two female fin whales, there are two cases of the two female fin whales pregnant outof seven. Among the mature male and female pairs, four male and female combinations are pregnant out of nine in 1955. Twelve pairs out of twenty-five
have the pregnant female and others are resting in 1956. From the above facts, it
is considered that all these pairs of mature male and female fin whales are not theTABLE 4.

1955
1956
TABLE 5.

Both Mature
Female Imm.
Male Imm.
One Imm.
Both Imm.

SEXUAL COMBINATIONS OF TWO FIN WHALESIN A SCHOOL IN THE NORTH PACIFIC (%)

Female & Female4(15.4)11(18.4)

Female & Male16(61.5)33(55.0)

Male & Male6(23.1)16(26.6)

Total
26
60

SEXUAL MATURITY IN TWO FIN WHALES IN A SCHOOLIN THE NORTHERN PACIFIC IN 1955 AND 1956
F. & F. F. & M. M.&M.
F.* & F. F. & M*. M.&M.
9
3
2
3

4

6

2

2
3

2

25
5
2

12

3

* M-Males, F-Females.
TABLE 6. OCCURRENCES OF MALE AND FEMALE FIN WHALESIN ONE FIN WHALE CAUGHT FROM A SCHOOL OFTWO FIN WHALES IN THE NORTH PACIFIC
FemaleMale
Mature Imm. Total
Mature Imm. Total
95(57) 37
132
119
21
1955
140
127 (56) 43
181
170
34
215
1956
Numbers in blacket are pregnant females.

school from the breeding areas. Some of them may be formed in the feedingareas bacause these resting fem ales are sometimes considered not to migrate to
the breeding areas.
Three of female fin whales pairs are not pregnant, and other two cases havepregnant females in the pairs. Three cases of mature and immature fin whales
out of five, the adult female fin whales are pregnant.
It seems that the more common pairs of fin whales in the feeding areas iscomposed of different sex fin whales, namely the pair of male and female. The
tendency is comfirmed by the catch of one fin whale from the pair of two fin whale's
school. The number of fin whales caught as only one whale catch from the pairof two fin whale's school are shown in Table 6. The sex ratio is high in male bothin 1955 and 1956. Generally speaking, the females are larger than males in Ba-

T. NEMOTO

94

laenoptera whales, the selection may choose females better. But the contraly tothis, the male is dominant. If the ratio of male and female fin whales is the sameas it is seen in the former example in the pair of two fin whales, the probability of
male from the pair fin whales is 0.539 in 1955 and 0.542 in 1956. The sex ratio ofmale is 0.515 in 1955 and 0.558 in 1956 which fairely coincide with the calculations.
These combinaions of the pair fin whales may be consistent both in two years in 1955
and 1956. The occurrences of immature fin whales do not differ from those of thecatch of two fin whales in pair, however, the slight high maturity ratio is observed
comparing with the single swimming fin whales., The pregnant ratios are 0.60
in 1955 and 0.44 in 1956 respectively which show no pecurial tendency.
Three fin whales in a school
The observation and chasing for three fin whales school are far less than the single
and pair fin whales. There have been five cases in 1955 and only one in 1956. As
shown in Table 7, one school is composed of all males, and three cases of two males
and one female and one case of one male and two females. The three males in themale trio are sexually mature, however, one of which is just mature. Perhaps it is
not the potencial male and it may not play the active sexual behaviour considering
the weight of the testis, 2.5 and 3.0 kg, (N emoto, 1962).
TABLE 7.

SEXUAL COMBINATION IN A SCHOOL OF THREE FIN WHALESIN THE NORTH PACIFIC IN 1955 AND 1956
Sexual combination
3 males

2 males & 1 female

3

1955
1956

male & 2 females
2

TABLE 8. SEXUAL OCCURRENCES IN THE CATCH OF TWO FIN WHALESFROM THE SCHOOL OF THREE FIN WHALES IN THE NORTH PACIFIC
IN 1955 AND 1956
Sexual combination

1955
1956

Male & Male
7
14

Male & Female
17

15

Female & Female
75

One mature male and one mature but resting female and immature female makethe school in one case, and one immature male, pregnant female and resting female
make the another school of one male and two females. There are three cases of two
males and one female. The mature males and one immature female are found in
two cases, two mature males and a mature pregnant female are found in anothercase.
It is very difficult to get general tendencies about the school of three fin whales,
however, it is interesting to note that two males and one female combinations occupy
the first rank. The period of pregnancy is about a year in fin whales (Ohsumi, Nishiwaki & Hibiya, 1957: Laws, 1961), and the nursing may be about seven months.
The number of males is dominant owing to above reason in schools as usually the
cow and calf pair do not allow the joining of other male whales in the feeding areas.

SCHOOL OF BALEEN WHALES

95

There are rather many examples of the catch of two whales from the school of three
fin whales. The occurrences of each sex are given in Table 8. The combinationof male and female is dominant through the catch in 1955 and 1956, and two males'
pair stands as the second. Especially fourteen pairs of males are caught out ofthirty-four examples in 1956. As compared with the occurrences of three males
school in 1956, it is the same tendency in the catch of the two fin whales from theschools of three fin whales. In 1955, seventeen pairs of male and female are caught
TABLE 9. SEXUAL CONDITIONS IN THE CATCH OF TWO FIN WHALESFROM THE SCHOOL OF THREE FIN WHALES IN THE NORTH PACIFIC
IN 1955 AND 1956 EXCLUDING UNKNOWN PAIRS
Sexual combination
Male & Female Female & Female
Male & Male
1955
1956
1955
1956
1955
1956
Both mature
11
10
5
3
5
II
Mature & Immature2
2
Both immature
J
2
Male mature & Female immature
3
4
Female mature & Male immature
TABLE 10. SEXUAL COMBINATIONS IN THREE FIN WHALES CAUGHTFROM THE SCHOOL OF FOUR FIN WHALES IN THE NORTH PACIFIC
IN 1955 AND 1956
1956
1955
Three males
I
3
Female & Two males
Two females & One male
TABLE JI. SEXUAL OCCURRENCES IN THE CATCH OF FIN WHALESFROM THE SCHOOL OF MANY FIN WHALES MORE THAN FIVE
IN THE NORTH PACIFIC IN 1955
2/5* 3/5 2/6 3/6 4/6 2/7 3/7 2/8 2/!0 2/12 2/10-15 2/20** 2/50**
13
3
7
3
1
2
1 2
4
1
1
I
I
2\iumber
Male & Male
5
3
6
Male & Female
43Female & Female
2
Male & Two females
2
Three males
Two males & One Female
Three males & One female
Three females* The lower shows the number of fin whales in a school and he upper shows number of whales caught.
** These schools are somewhat doubtful, possibly shoals of schools.

and there are seven pairs two males and two females respectively. The sexual
conditions of those fin whales are as follows. Among the seven pairs of male andmale, five cases are both mature and one mature in two cases. This may be affected by the size regulation for the catch as stated in the formar part. In those groups,
the pairs of mature male and immature female are more than the one of immature
male and mature female in general, which is already pointed out in the case of two
fin whales' school. Eleven pairs of males are sexually mature and two pairs are

96

T. NEMOTO

composed of one mature male and another immature male in 1956. There are ten
combinaions of mature one male and another female fin whales, two combinations aresexually immature in both whales. Mature males and immature females form threecases but there is no case of immature male and mature female fin whales in 1956.
School composed of more than four
There is none of the record of the perfect catch of the school composed of morethan four, but there are considerable number of the chasing for the school ofmany fin whales more than four. Two cases in 1955 and four ones in 1956 arefound catching three fin whales from the school of four fin whales as illustrated
in Table 10. It is very interesting to note th~t the males are dominant in the catchin spite of the size selection by catcher boats.
Especially the immature males are scarecely observed in those cases. If thesize selection is effective for the catch of those fin whales, the number of female fin
whales might be dominant. It is suggested the dominant catch of males showthese school are composed of more males than females.
The example of the catch of fin whales from the schools of many fin whales isfound in 1955. The occurrences of males and females are given in Table 11. Malefin whales are found more than female in general and if the size selection affectthe catch it should be reverse to the facts. This tendency may comfirm the generalfeature of schools of fin whales in the feeding grounds. In the land mammals, thesocionomic sex ratio is high in females in their group and herd (Ito, 1959), the factof which is the reverse to the fin whales.
It is interesting that the catch of immature males and females are observed
from the comparatively large schools. Two fin whales are caught from the schoolof five fin whales in 1955, and both males are sexually immature. The body lengths
are 53 and 50 feet and other fin whales in the same school are estimated as the samelength. The catch of two fin whales from the school of five whales show those two
females are immature, the body length of which are 58 and 59 feet respectively.
These two cases show to some extent the young agers assemblage and sexual assemblege in fin whales as it is supposed up to this time.
Andrews also recognizes such assemblege in grey whales (Andrews, 1914).
There have been sometimes found the school of fin whales more then ten, however,these schools may be the congregation of many schools especially in the feedingarea to take the shoal of euphausiids. It is generally accepted the schools of
many fin whales have been observed in their migartion route to and from the feeding and breeding areas. Brown (1958) reports the greatest numbers of rorquals
observed by ships are about fifty and thirty in the north Atlantic.
BLUE WHALE (BALAENOPTERA MUSCULUS)

In the North Pacific, blue whales are ocean denizen and their main schools neverpenetrate into the Bering sea (Nemoto, 1959). The number of blue whales observed in the data is also small, and there still remains some question for the reliability of the samples.

SCHOOL OF BALEEN WHALES

97

Signle swimming blue whales are dominant among the schools in the data, and thirtysix blue whales out of thirty-eight schools in 1955. and fifty-eight blue whales outof sixty-seven schools in 1956 are observed to be single in the feeding areas. In
1955, those single swimming blue whales are of more males than females and thisis the same in 1956 too. Sexual maturity conditions are given in Table 12 but it
is difficult to get any concludion from the table because the number is rather limited.
The chasing and the catch are done for one school in 1955 and nine schools
in 1956 which consist of two blue whales in a school. Two blue whales in a school
are caught in 1955, one ofwhch is male, sexually mature, and another is also malebut it is considered it just attains sexual maturity. In 1955, two blue whales are
TABLE 12.

SEXUAL CONDITIONS OF BLUE WHALES CAUGHT
IN THE NORTH PACIFIC IN 1955 AND 1956
Number of whales in a school

1955
1956

2

3

MatureImmature

MatureMatureMale
Female227

42(2/2*)

2(2/3*)

Male
Female

28
21

2
7

3
8(1/2*)
I (1/2*)* Upper shows the catch number and the lower shows the number of whales in a school.
caught from the three blue whales' school, which are sexually mature and just matured ones. I have nine cases of the capture that only one blue whale is caught
from the two blue whales' school in 1956. All eight males are sexually mature andone sexually mature female blue whales is pregnant. It is suggested two blue
whales' schools are composed of more males than female like the cases in 1955.
But it is also considered the male sex ratio in single swiming blue whales is high,and the female blue whales swimming with calf escape the chasing by catcher
boats.
The one reason that the number of blue whales in a school is rather small, is
attributable to the relative abundance of blue whales in the North Paciffc. Comparatively large schools of blue whales had been observed in the Antarctic in
the former age of the whaling, when blue whales were dominant.
SEI WHALE (BALAENOPTERABOREALIS)

There have been considerable differences among the annual catches of sei whales.
The general tendency has not been obtained as for the school of sei whales, butthree sei whales have been found in a school both in 1955 and 1956 as the maximun
number. The school of six sei whales is reported in the previous report (Nemoto,1959), however, the most common schools are up to three sei whales in a school.
Generally speaking, the number of sei whales are comparatively small in a school
comparing with other fin and humpback whales.
In 1955, ten males and nine females are caught from single swimming sei whales.

T. NEMOTO

98

Four males and two females of them are sexually immature. But two immature sei
whales have been caught from the school of two sei whales. Although the sample
is rather scarce, it may be considered that immature sei whales sometimes swim
alone to feed more often than the sexually mature sei whales. The sei whales caught
in 1956 also show such tendency that the sexually mature whales form the schoolof two or more whales
The cases of two sei whales caught from two whales' school are observed bothin 1955 and 1956. One case in 1955 and five cases in 1955 respectively. All sei
whales are sexually mature and all females are pregnant, the compositions of which
TABLE 13. NUMBER OF SEI WHALES IN A SCHOOL CHASED BY
CATCHER BOATS IN THE NOTH PACIFIC IN 1955 AND 1956
Number of sei whales
in a school
1
19
4

1955
1956

2
II
5

3
2

TABLE 14. SEXUAL COMBINATIONS IN SEI WHALES CAUGHT IN
THE NORTH PACIFIC IN 1955 AND 1956
IN RELATION TO
NUMBER IN THE SCHOOL
M&M

2/2*
M & F

F&F

3

1 (Female )pregnant

I (Both)pregnant

1955
1956

2/3*
_________,..___
M&M M & F
1 (Female )pregnant

3 /3*M, F & F
1 (Both females)pregnant* Upper shows the number of sei whales caught from a school and the lower shows thenumber of whales in a school. M-Male, F-Female.

are given in Table 14. Although the number is rather small, the male pair is dominant among the schools, and there are one combination of male and female, andanother of both females respectively. Three sei whales are caught from three whales'school in 1955. Two pregnant females and one sexually mature male are present
in the school. There have been two cases of the catch of two sei whales from theschool of three sei whales, and one is the pair of male and female sei whales, and two
males are another.
Owing to the small number of the examples as repeated, there has been no clear
tendency in the schooling of sei whales. It is suggested only that the two males'school is more than female combination in the school of two sei whales like thecase in fin whales.
HUMPBACK WHALE (MEGAPTERA NOVAEANGLIAE)

The number of humpback whales caught in 1955 and 1956 is not so large as fin
whales. In 1956, single swimming humpback whales are observed in nineteencases and two humpback whales in a school eight cases. Three or more whales

SCHOOL OF BALEEN WHALES

99

found in a school are rather scarce, and humpback whales are observed up toseven in a school. The same tendencies are found in the data in 1955, whensingle humpback whales and schools composed of two humpback whales are dominant among them. Especially many pair humpback whales in a school are reported
m 1955 as shown in Table 15.
TABLE 15. NUMBER OF HUMPBACK WHALES IN A SCHOOLIN THE NORTH PACIFIC IN 1955 AND 1956
Number of whales in a school

1955
1956

2
31
8

27

19

3
2
1

4

6

5

7

TABLE 16. SEXUAL COMBINATIONS IN THE PAIR HUMPBACK WHALESIN THE NORTH PACIFIC IN 1955 AND 1956
Sexual combination
Male & Male

1955
1956

Male & Female
31

Female & Female

TABLE 17. SEXUAL CONDITIONS OF HUMPBACK WHALES'SCHOOLS IN THE NORTH PACIFIC IN 1955 AND 1956
1/2*

1/1*

MatureImmature(Pregnant)Total----------

8
9
(5)
17

10

1955

1956

1955
....---Female

Male
10

1956

Male

FemaleMale

FemaleMale

Female

7
2

5
5
(3)
10

7

6

1

2

7

4
(3)
10

2

3

9

* Upper shows the number of whales caught and the lower shows the number of sei whales
in a school.

TABLE 18. SEXUAL COMBINATIONS IN HUMPBACK WHALESIN THE NORTH PACIFIC IN 1955 AND 1956
Male
Female

2/3*

2/4*

3/4*

1

2

2

2/5*

1/7*

2

* Upper shows the number of catch and the lower shows the number of whales in a school.
From the biological data collected on the whaling factory ships, comparatively
many immature humpback whales have been found as the single swimming whale.
The termination of two whales in a school is done in four cases in 1955 and three
in 1956, the occurrences of each sex of which are given in Table 16. The pair ofmale and female is dominant among the schools although the school number israther small. It is interesing the sexually immature male or female humpback
whales are present in the pairs in five cases, and only two cases composed of sexuallymature whales. This tendency has not been observed in other baleen whales.
The sexual conditions of one whale from the pair are illustrated in Table 17.

T. NEMOTO

100

The catch of humpback whales from three or more party is far less comparedwith said cases. Three whales are caught from four humpback whales in a school
in 1955 which composed of one resting mature female and one mature male and immature male. The occurrences of each sex in those catches from schools composedof three or more whales are given in Table 18.
The humpback whales in the breeding area seem not to form groups of many
whales, Chittleborough (1953) describes only up to three adults in a school in the
coasts of Australia, and Brown (1957: 1958) describes that seven is the greatest
number and other observations are all of single or very small parties in the northof the equator in the Indian ocean. About twelve whales are found in the coast ofAustralia in two of the four records in his report, however, the number of the observations on humpback whales in the area is rather scarce and these observations do
not reliably sample the coastal areas of Australia as discussed by Brown. The sexual
segregation in humpback whales in migration is very tipical, and those results should
be examined by futher materials. In the breeding areas of the North Paific,
there is also very few data on the schools of humpback whales.
RIGHT WHALE (EUBALAENA GLACIALIS)The observations, marking and bilogical research on right whales have been rather
scarce both in the Antarctic and in the North Pacific. The observations on rightwhales in the North Pacific are given in Table 19. The single swimming rightwhale is dominant among the schools and four right whales is at most in a school.
Japanese investigations on right whales have caught eleven right whales in recent
years with special permssion by government. And those right whales have been
all single swimming right whales but one case, which consists of two right whales.
When the one puberty female is caught (Kasuya, 1962. personal communication),
it is said the another right whale comes back again after a little while and swims
around the captured right whale.
TABLE 19.

NUMBER OF RIGHT WHALES IN A SCHOOLIN THE NORTH PACIFIC
Number of whales in a school

1941-1957*
1961-1963

Coast of Japan
North PacificNorth Pacific

53
58
21

2
15
30
8**

3
2
4
4

4
2

* Omura (1958).

* * Including one cow and calf.
Other ten right whales consist of seven males and three females. Among sevenmales, three whales are sexually immature, and two females are also sexually
immature out of four females. Two pregnant females are caught in 1963, when
they are swimming as the single in the feeding areas in the North Pacific.

SCHOOL OF BALEEN WHALESIOIGREY WHALE (ESCHRICHTIUS GLAUCUS)
According to Gilmore (1958), grey whales are not a highly social animal, and the.
most commonly integrated social groups are the pair, and the trio. He considers
the trio is made up usually a female and two males, and is also somewhat imparmanent. Scammon (in Andrews, 1914) writes also the case of the school, composedof a female, her calf and a male will go to the northward to the feeding. The observation of schools of grey whales are also found in the papers by Andrews (1914),
Nasu (1960) and Pike (1962), which suggest the school of grey whales is sometimes
containing many whales. As a important notice, the leadership by the female inthe school of grey whales should be noted in relation to the land mammals such as<leers. But the discussion by Andrews is a preliminary one, and these ecologicalpoints should be examined on more detail characteristics.
The available observations on the school of grey whales are rather few. In
1955, Japanese marking ship found grey whales feeding in the north-west sea of St.
Lawrence Is. in Bering sea. In the descriptions, one to three groups of grey whales
are mostly found. Two grey whales, 41 feet and 37 feet long are found in a schoolat 63-34 N and 172-48 W on 2th August. Other two pairs of grey whales, 40 and
36 feet, and 37 feet, and two trio (36 and 37 feet trio) are reported in tne neigbouring
waters and the most schools are single, pairs and trios.
In recent observations, Wilke and Fiscus (1961) describe eight grey whalesin scattered pairs were seen moving toward narrow Kodiak and Ugak Is on llth
May in 1957, and two grey whales were seen from the 'John N. Cobb' feedingnear 67-40N, 167-12W on 19th Ausust in 1959, and on 20th Aug. three others
are feeding. These observations comfirm the comparatively small unit in schoolingof grey whales in the feeding areas, although they sometimes form the huge congregations in the feeding areas in the narrow place.
DISCUSSION AND RESULT BY MARKING RESEARCH
The general observations on the school of whales chased in the marking research
have been carried out in the North Pacific and the Antarctic, and the catch log on
the recaptured marked whales usually refer the behaviour of the whales including
other whales in the same school. From these materials, very interesting consideration on schools of baleen whales are deprived.
One of the most interesting example is found in the marking for the pair of cow
and calf of fin whales in the North Pacific. In 1955, two cows with calves weremarked on 18th July and 26th July. These adult females are caught in 1957, when
they are feeding in the North Pacific solitary. Further, these two whales are pregnant.
The patterns of the whales may be summerized as follows. In the summer of 1955,
these two mother whales were feeding with their calves, and their calves were within
two years after the birth, perhaps yearing, considering their body length (Ohsumi,
Nishiwaki & Hibiya, 1958: Laws, 1961). The larger calf might be feeding on theplanktons with his mother, as the body length is about 46 feet which is estimated102

T. NEMOTO

4

4

3

3

2

2

0

0

:"
0
\I)

>CJ

"'
Q_
0

u:;

5

9

5

10

Number of Fin Whales

Fig. 3. Formation and separation in the number of whales in the school of fin whalesin the Antarctic (Left) and North Pacific by the marking research.

M

D

N

5

10

20

Number of fin Whales

Fig. 4. Formatin and separation in the school of fin whales in the Antarctic by themarking research. The _marks are recovered within the summer Antarctic season ofeach case.

103

SCHOOL OF BALEEN WHALES

after the weaning. When the mother fin whales recaptured in the feeding areas
in summer, they have five and nine months' foetuses calculated from the body length(Ohsumi, Nishiwaki & Hibiya, 1958). They must have copulated five and ninemonths in the late winter respectively. January and October are the possible
breeding months for them and the grown calves might be free from the motherfin whales before the time of those copulations because there are few cases of theother whales joining in the pair of cow and calf schools. The fin whales seperated
with males after copulation between the fertilization and being caught.
Au.

Ju.

Ap.

Fe .
...c

g De.

:2
Oc.

Au.

Ju.
5

10

15

20

Number of Fin Whales

Fig. 5. Formation and separation in the number of whales in the school of fin whalesin the North Pacific by the marking research. The mark are recovered within theseason of each case.

The number of baleen whales in a school has been examined by the marking
research too. As it is discussed in the former part, the single swimming fin whales
are considered to decrease with the proceeding of the summer season in the observation of the catch log. But the marked fin whales in a school of many whales partwith the parties, and they are found in the schools of smaller number. This would
deary show the breaking down of the school of fin whales in the feeding areasin the summer season too. Considering these two facts together, the school of fin
whales may be inconstant in the feeding areas in the summer. It is not clear
which is more important factor from the ecological point of view. The clear tendency
to form the school of male and female pairs and some pecurial sex ratio should beconsidered again as one of the significant point in the school of fin whales in thefeeding grounds.
If it is supposed that fin whales migrate south to breed, the formation ofschools in the feeding areas may be very usefull. On the other hand, the se-

104

T. NEMOTO

peration of the sexually mature fin whales from the other younger whales in theschool may break the school. It is considered to be natural that mutual affection is
one reason to form or break the schools among the sexually mature fin whales. This
type of the seperation in the school of fin whales in the feeding grounds has been
observed in the Antarctic too. The case of the formations in the school also havebeen observed, however, available examples are less than those of the seperations.
To make up the gap of the above described results by the observations by catch
log and the marking research, futher accumulations of the materiales are necessary.
And it should be considered that the pregnant females, sometimes feeding alone
in the feeding areas as discussed in the former part, leave the north sea feedingarea earlier than other whales (Laws, 1959). The schools consist of many fin whales
may seperate and form each party by some reasons such as affections, and younger
agers assemblage keep their schools still in the feeding grounds. These schools
consist of comparatively many small whales are sometimes observed in the marking research in the North Pacific and the Antarctic.
The variation of the number of the whales in a school for a long time also has
been checkd by the marking the results of which are shown in Fig. 3, In these
examinatins, many schools of fin whales decrease the number of the party in theschools, but some schools have the participipants, between the time being marked and caught.
Besides fin whales, the marking data on the schools of other baleen whales arerather scarce. In the North Pacific, a school of three blue whales is observed on
20thJuly and one of them, the marked whale, is found solitary after twelve days, on
24th July.
Five blue whales observed in a school in the Antarctic on 13th Dec. and they
have six members in the next year, namely 22nd January, after the lapse of nineteendays. One of a pair of blue whales marked on 19th December in 1958 is caught
on 8th February 1959 when the blue whale is swimming solitary.
There is one case of humpback whales in 1958. The pair of humpback whales
marked on 25th December in the Antarctic and found in the next year in the same
number pair of two on lst February.
The ecological habit such as the forming or the breaking of schools must
be connected with the very characteristic feeding migration in baleen whales. The
solution of this origin and history may be one key to the problem (Marr, 1962).
SCHOOL OF DIFFERENT WHALE SPECIESSchool of blue and fin whales
Sometimes baleen whales swim with different species of whales in the same school.
Gunther (1949) describes the case of one blue whale swimming with four fin whales
in a school in the Antarctic. From the data collected in the Antarctic from theyear 1957 to 1958, it is rep.orted five cases composed of blue and fin whales (Nemoto,1959). In that paper, that the sexually immature blue whales swim with the sexual-

SCHOOL OF BALEEN WHALES

105

ly mature fin whales and the number of blue whales are always less than fin whales or
the same number, is described. The followings descuss the problem chiefly according to the marking and the catch results.
School composed of fin and blue whales
There are eleven schools composed of fin and blue whales up to these days as given
in Table 20, five of which were already reported in the previous paper (Nemoto,1959). The number of blue whales are the same or less than fin whales, and the
body length estimated by the crew of catcher boats shows the possible sexual
immaturity as described by me. The school composed of less fin and more blue
whales in number has not been observed in the records yet.
TABLE 20. THE OCCURRENCES OF THE SCHOOL COMPOSED OF FIN
AND BLUE WHALES OBSERVED BY JAPANESE WHALE MARKING CRUISE
IN THE ANTARCTIC FROM 1954 TO 1961

Number of whales
Estimated bodylength in feet
Total number ofwhales in a school
Number of whales
Estimated bodylength in feet
Total number ofwhales in a school,---"'-,,---"'-,,---"'-,,---"'-,

Blue
1

Fin

Blue

Fin

Blue
1

Blue

62

71

70

68

73

2

2

60-63

,..---"---.

_____....._,,

Blue Fin
1
4

Blue Fin
1
4

Blue Fin
1 5

80

70

65-67

65-70
6

5

,---"'-,

Fin
2

78

Blue
1

Fin
3

72

63-65

3

3

,..---"---.

5

Fin
2

..----...-

Blue Fin
4
2
64-65

73

4

_____....._,,_____....._,,

Blue Fin
2
6Blue Fin
2 Ca 10? 50-65

60

Ca 12

8

6

70

TABLE 21. THE OCCURRENCES OF THE SCHOOL COMPOSEDOF FIN AND SEI WHALES IN THE FEEDING GROUNDSNorth Pacific
Antarctic_____...__.....
,-----"--o,Number of whales
Estimated length of whales in feet
Total number of whales in a school

Fin

Sei

2

2

60

45
4

Fin
2
56-57

Sei
4
45-48

6

~

Fin
I
58

Sei
2
3

School of fin and sei whales
There have been three cases of fin whales swim with sei whales in the records.
In 1960, a school of two fin and two sei whales is observed in 56-32 S, 77-06W
in the Antarctic, and two cases observed in the North Pacific. The latter cases
are composed of two fin and four sei whales in one and one fin and two sei whales
in another case. The body sizes of fin whales are cmparatively small, andthey are estimated to be sexually immature or just matured. On the contraly
to this, the body length of sei whales are large and possibly sexually mature. I
would consider this is the same tendency with the case of blue and fin whales andthat the larger baleen whales sometimes swim with the different smaller species ofbaleen whales in the case that they are sexually immature and the number is thesame or the less. The sexual potensiality may be the one reason to join a school106

T. NEMOTO

of different baleen whales in the feeding areas. This tendency is considered
common m Balaenoptera whales both in the Antarctic and the North Pacific.
School of sei and bryde's whales
A school of sei and bryde's whales is obserevd in the adjacent waers to Japan in
1961. About 180 miles from Kinkazan, the north-east part of the Pacific coast ofJapan, one mature male bryde's whale, testis of which are both 1.6 kg, is foundswimming with a immature sei whale and those two whales are caught by catcher
boat.
School of fin and little piked whales
A little piked whale (Balaenoptera acutorostrata) is observed in a school of fin whales
on 13th Dec. in 1959, 59-17S, 82-52W in the Antarctic. But it may be acceptedthat the little piked whale only follows the school of fin whales a little while.
There has been no record of the school composed of Balaenoptera and Megaptera
whales. Sometimes it is observed that humpback whales feed with Balaenoptera
whales in the same feeding areas in the very near place and seem to be in the sameschool, but they are split into respective species after a while by the chasing. The
swimming speed and the general diving depth may have the relation with the formation of schools in the case. And frequent turning in humpback whales is also one
reason of the seperation too.
Mackintosh (1942) and others (Matthews, 1938: Nemoto, 1959: 1962b) pointout that the pecurial migrating time to the feeding areas and segregation in the
distribution in the feeding areas both in the southern and the northern waters
is observed in each baleen whale species. One example in the North Pacific isshown in Fig. 6. There are differences among the distributions of baleen whales
according to species, and the primary preferances of their foods is considered as thefirst reason for their distributions. Blue whales feed only on euphausiids, and sei
whales prefer copepods especially Calanus plumchrus, but they rarely take Calanus
cristatus in these waters (Nemoto, 1959). Fin whales feed on euphausiids as wellas copepoda, Calanus cristatus, but they rarely take Calanus plumchrus (Nemoto, 1959).
These selections of foods and different oceanographic conditions for each foodspecies may form such distriutions, however, the feeding range in each speciesof baleen whales and the occupation is considered if it is fixed within a certain time.
Thus the two types of ecological segregations (Miyaji & Mori, 1953) are recognizedin these distributions. In the previous report (Nemoto, 1959), I suggest the possible
biological strength, numbers and migration time between two baleen whalescause some segregations in the feeding grounds. The case that the habit of feeding
is affected also by the number of each species is pointed out by Elton on the land
animal Buffalo (Bos cajfer) in Africa (Elton, 1927).
These types of the segregations in the feeding grounds have been observed
between blue and fin whales, fin and sei whales. In recent years, the distributions of
fin whales become tdifferent from the former days, and sei whales also penetrate
into the Antarctic high latitudes and waters of pack ice. This is partly attrubut-

SCHOOL OF BALEEN WHALES

107

able to the numbers of individuals and biological strength among baleen whales
as suggested by Nemoto (1959). These biological strength may be confirmed by
the presence of the school of different species as disscused in the former part.
There is another explanation for the fact that the different species baleen whalesof the same size may sometimes swim togather in the feeding grounds. But considereing the number of baleen whales in a school, that the larger whales are usuallyless than the smaller species, the former is more suitalbe explanatin for the problem.

"'!:'·=t-=-=-=-~~===~~========~~-=-~~=-~--~-------~~~~·
Fig. 6. Distributions of baleen whales in the North Pacific in July in 1960, showing thedifferent patterns in distributions of baleen whales by species. Open circle-Fin
whales : Black circle-sei whales : Cross-Blue whales.

COW AND CALF PAIR

It seem rather rare that the pair of cow and calf swims with other whales evenin the same species. Gunther (1949) describes a case that a cow and a calf swim
with other whales but it is only one case in his report. Slijper (1958) also states
the maintenance of the family in blue and right whales, however, the sources ofwhich are not indicated.
Both in the Antarctic and North Pacific, the cases that the pair of cow and calf
is found with other whales are rather scarce as illustrated in Table 22. But inhumpback whales, the calves sometimes are accompanied not only by their motherwhales but also other adults (Chittleborough, 1953).
In the Balaenoptera whales, only females give protections to their calves after
their parturition. The new born calves in Balaenoptera whales can swim perfectrywith their mother but the family of Balaenoptera whales consists only of females and108

T. NEMOTO

their calves in general. Those pregnant whales in feeding grounds might migrate
to the south single or with other whales but they will be alone after their parturition.
Chittleborough (1953) observes two cases of cow and calf pairs of fin whales
but no other whale in them in the waters off Australia in the lower latitudes.
TABLE 22.

THE SCHOOL OF COW AND CALF PAIR AND OTHER WHALESFOUND WITH THE PAIR IN THE FEEDING GROUNDS
Number of other whales with the pair
Numberof Cow& calfAntarctic
Blue whales
Fin whales
Humpback whales
North PacificBlue whales
Fin whales
Sei whales
Humpback whales
Bryde's whales

+l

+3

+2

+5

+6

+9

6
14

9

4

2

3
16

2

9
8
2 years

Less than 2
years ?

-5~9months-

Cow & Calf

0

/

0

0

8

+4

Weaning

Pregnant00Seperotion

Poturition

Feeding &Nursing

WinterSummer()_/Pairing

Copulation

8~
Feeding~
WinterSummer

WinterSummerFig. 7 Schema of the cycle of cow and calf fin whales in the North Pacific by the marking
research. The marks were hitin 1955 and recovered in 1957 both in summer seasons.

The pair of cow and calf in humpback whales sometimes swims with other
adult whales. This tendency is given in Table 22 too. Chitteleborough (1953) also
describes that a calf usually accompanies a single adults, but sometimes two adults
were present. This confirmes the results in the Antarctic area in Table 22. If
the starting of the pair of cow and calf to the south only by themselves, the formationof the school may be done in the route or in the feeding areas where the range in

SCHOOL OF BALEEN WHALES

109

the distribution is rather small and they may contact with each other more often
than other baleen whales. The companionship is built in their migraion and feeding, however, the sex of the members are still unknown.
The pair of cow and calf have been observed in a considerable number in thefeeding areas. But it is very rare to be found with other whales besides thefamily. Namely cow and calf form the family by themselves. The nursing duration is about seven in fin whales, and fin whales uaually do not form the school ofmany whales with the family within it, as a conclusion.
It is clear from above facts, that Balaenoptera baleen whales do not accept thefamily (cow and calf) in their school although the calf of Balaenoptera is able toswim with their mother and adults.
SUMMARY

The preliminary consideration on the school of baleen whales in the feeding areas
are made based on the Antarcic and the North Pacific baleen whales caught by theJapanese whaling and the whale marking data. The important points are as
follows.
1. The number of baleen whales in a school is examined on fin, blue, sei, humpback, right and grey whales. The seasonal change in the number of fin whales
in a school is suggested.
2. The sex ratio and sexual combinaions are studied on the school of baleen
whales especially in fin whales. From the catch of the pair fin whales, the combination of male and male, and male and female fin whales are more than the oneof both females. The sexual combinations of members of the trio and otherschools of fin whales are also investigated.
3. Based on the marking research, the following up to the number of baleen whales
in a school is done both in the Antarctic and in the North Pacific. The numberof fin whales in a school varies and the breaking up of the school is observed in thefeeding grounds. Two pregnant fin whales are caught which had been marked
when they swam with calves, and they are feeding solitary, suggesting one type ofthe formation and seperation of breaking the school in fin whales.
4. The pecurial feature of the school of different species of baleen whales aredescribed. These schools are observed in fin and blue whales, fin and sei whales,and sei and bryde's whales. Among these combinations, the larger species ofwhales are the same or less in number than the smaller baleen whales in a school.
The estimated body lengths of the blue whales in the school of fin and blue whales
are comparatively short, and fin whales also small in the school of fin and sei whales
and the possible reason, sexual potentiality, is suggested for the combination of different whale species.
5. The family of fin whales, cow and calf, is examined. It seems that the fin whales
do not accept the family (cow and calf) into the school, and this tendency may begenerally observed in Balaenoptera baleen whales.

110

T. NEMOTO

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BROWN, S.G. (1957). Whales observed in the Indian Ocean. Noted on their distribution. Marine. Obs.,
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CLARKE, R & Ruun, J.T. (1954). International co-operation in Antarctic whale marking the voyage of the
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ELTON, C. (1927). Animal ecology. London
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IMANISHI, K. (1951). Ningen izen no Shakai. [Society before the man.] Tokyo.
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