SEGREGATION OF TWO FORMS OF SHORT-FINNEDPILOT WHALES OFF THE PACIFIC COAST OF JAPAN*

TOSHIO KASUYA**, TOMIO MIYASHITA** AND FUJIO KASAMATSU***
ABSTRACTTwo forms of the short-finned pilot whale are known off the Pacificcoast of Japan. The northern form, having larger body size, distinct saddle
mark and round contour of the head seen from the top, inhabits the coastal
waters between fronts of the cold Oyashio Current and warm Kuroshio
Current, or l2°-24°C in surface water temperature and 35°-43°N inlatitude. The southern form, having smaller body size, indistinct saddle
mark and square shaped contour of adult male head, is known from wide
range of the coastal and offshore waters south of the Kuroshio Front (overl 8°C and south of 39°N) with some degree of possible density gap within
the range. Their geographical ranges may occasionally overlap in theboundary area, but mixed schools of two forms are believed to be very
rare. The geographical and social segregation, individually identifiablemorphological differentiation, and similarity in their life history characteristics suggest that they can be dealt as separate subspecies or local stocksof the short-finned pilot whale. Although north/south segregation of thecorresponding forms might exist in the eastern North Pacific, current
information is insufficient for further consideration.
INTRODUCTION

Yamase (1760) described two kinds of pilot whales off Taiji on the Pacificcoast of central Japan, the one Shiho goto was larger and had white dorsal
patch, and the other Naisa goto was smaller and had no dorsal mark. Grayreferred similar distinction for Japanese pilot whales, and named his Naisa
gota (appeared in his 1846 and 1866 papers) or Naisa goto (in his 1846 paper)as G. sieboldii Gray, 1846 and Shiba golo (in 1846, 1866 and 1871 papers) as G.
sibo Gray, 1871. The minor difference in the spelling is not important. The
Ohnan goto of Yamase (1760) and Gray (1866) is now considered to represent
the false killer whale Pseudorca crassidens (Owen, 1846). Recent Japanesewhalers who hunted pilot whales also distinguished two pilot whales Tappa* Early version of the manuscript was submitted to the 38th annual meeting of the Scientific Committee of theInternational Whaling Commission in Bournemouth in May 1986 with document no. IWCISC/38/SMJ2.
** Far Seas Fisheries Research Laboratory, 5-7-1, Orido, Shimizu-ski, Shizuoka-ken, 424 Japan.
*** Japan Whaling Association, 3-2-4, Kasumigaseki, Chiyoda-ku, Tokyo, JOO Japan. Present address: The Instituteof Cetacean Research, 3-32-ll, Ohjima, Koto-ku, Tokyo, 136 Japan.
Sci. Rep. Whales Res. Inst.,!Vo.39,1988, 77-90

78

KASUYA, MIYASHITA AND KASAMATSU

naga (=having long flipper) off northern Japan and Ma-gondo (=common
pilot whale) off central and southern Japan. Since the last century this caused
confusion for Japanese whale taxonomists, and caused the use of various
scientific names as reviewed by Hawley (1960) and Kasuya (1975).
Nishiwaki, Kasuya, Brownell and Caldwell ( 1967) examined pilot whale
skulls taken off Izu coast (34°30'N) and Taiji (33°35'N) to find that the pilot
whales off the Pacific coast of central Japan which was called by the vernacularname of Ma-gondo and had been considered to represent Globicephala melaena(Traill, 1809) was actually G. macrorhynchus Gray, 1846. Kasuya (1975) examinedstatistics of pilot whale catch by Japanese small-type whaling and the skulls
taken by the fishery off the Pacific coast of northern Japan, found that all the
specimens examined by him possessed characteristics of rostral region of G.
macrorhynchus described by Bree ( 1971 ), and concluded, acknowledging thepossibility of presence of some local stocks, that G. macrorhynchus is the only
confirmed member of recent pilot whale fauna in the western North Pacific.
Although G. melaena survived in the northern Sea of Japan till the 12th
century and the current existence was not fully denied (Kasuya, 1975), no
supporting evidence was collected after the study and there was accumulated
indications suggesting the absence of G. melaena in the Bering Sea and northern
North Pacific (see below).
In 1982, some of the Japanese small-type whalers resumed harvesting
pilot whales off the southern part (38°N to 40°N) of the Sanriku region(Pacific coast of northern Japan between 38°N to 41°30'N) as reviewed by
Kasuya and Tai (1986), and some of the catch were examined by Miyazaki(1983). He reported that two kinds of pilot whales were taken in the season.
The one (southern form of this study) was a type that was common off the
Pacific coast of central and southern Japan (Izu and Taiji) and studied by
Nishiwaki et al. (1967), Yonekura, Matsui and Kasuya (1980), Kasuya andMatsui (1984), Kasuya and Marsh (1984) and Marsh and Kasuya (1984). The
other (northern form of this study) was new to him. Although, both forms
shared skull characteristics of G. macrorhynchus described by Bree (1971), thelatter was easily distinguished from the former by distinct saddle mark andlarger body size (Miyazaki, 1983; Kasuya, l 986b).
In the present study, we analyze distribution and segregation of the twoforms of short-finned pilot whales using sighting records in the western
North Pacific collected since the finding of Miyazaki (1983), and some additional records of previous sightings, some of which are identifiable to two
forms based on photographic or other records.
MATERIALS AND METHODS

Ident~fication of two forms
The short-finned pilot whale identified in this study as "northern form"
represents those being recognized by Japanese whalers as Tappa-naga, and its
Sci. Rep. Whales Res. Inst.,
No. 39, 1988

SEGREGATION OFSHORT‑F
INNEDPILOTWHALE
S

79

F
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80

KASUYA, MIYASHITA AND KASAMATSU
TABLE 1. LIST OF CRUISES CONDUCTED BY THE JAPAN FISHERY AGENCY
AND USED TO COLLECT DATA IN FIG. 2 OF THIS STUDYName of vessel

Year

Month

Pilot whalesightings*

Reference for cruise
track line

Konanmaru No. 25
Toshimaru No. 15
Toshimaru No. 15
Toshimaru No. 15
Toshimaru No. 25
Shonanmaru
Toshimaru No. 25
Shonanmaru

1982
1983
1984
1985
1986
1983
1983
1984

1-3
1-3
1-3
1-3
5-6
6-7
6-8
6-8

present
absentpresent
absentpresent
present
present
absentToshimaru No. 25

1984

6-9

present

Toshimaru No. 25
Toshimaru No. 18
Shonanmaru
Toshimaru No. 15
Toshimaru No. 15
Kankimaru No. 58

1985
1986
1985
1985
1986
1986

6-9
6-9
7-9
9-10
9-10
9-10

present
present
present
absentpresent
present

Miyashita (l 986b)
Miyashita (l 986b)
Miyashita (l 986b)
Miyashita (I 986b)
Miyashita and Kasuya ( 1987)
Miyashita (1985)
Miyashita (1985)
Miyashita (I 986a,b)
Kasuya (I 986a)
Miyashita (I 986a,b)
Kasuya (I 986a)
Miyashita (1986b)
Miyashita and Kasuya ( 1987)
Miyashita (I 986b)
Miyashita (l 986b)
Miyashita and Kasuya ( 1987)
Miyashita and Kasuya (1987)• Pilot whale sightings in the area indicated in Fig. 2.

peduncle. The posterior and ventral boundaries of the saddle mark of thesouthern form gradually fades into the black body color making it difficult todefine the boundary. The saddle marks of live pilot whales in Figs 1 and 2 ofPlate I in Yonekura et al. ( 1980) are now clear to represent those of northern
forms, but other photographs of the carcasses and a drawing in text-Fig. 2 of
their study represent the southern form.
Using above criteria, Kasuya (1986b) could identify all the postnatal
northern forms used in his study (about 300 individuals over 1.5 years old),and found no individuals that could be considered as intermediate of the twoforms of the short-finned pilot whale. However, none of the four full term
fetuses of northern form (165 to 185 cm in body length) had recognizablesaddle mark (Kasuya, unpublished) and the distinction of the two forms
appeared to be difficult except for the larger body size of the northern form
(Kasuya, l 986b). This suggests that the distinction of two forms by the saddle
mark becomes possible at an age between 0 and 1.5 years or well before themean age at weaning 2.4-3.1 years (Kasuya, l 986b), which causes no difficultyin the identification of northern form schools.
Source of sighting data
Main body of the data used in this study was the results of whale sighting
cruises conducted by Ja pan Fishery Agency in 1982 through 1986 (Table 1).
Sci. Rep. Whales Res. Inst.,
No. 39, 1988

SEGREGATION OF SHORT-FINNED PILOT WHALES

81

TABLE 2. DALL'S PORPOISE SIGHTINGS AND HARPOONING CRUISES IN THE WESTERNNORTH PACIFIC AND BERING SEA, WHICH PROVIDED INFORMATIONON PILOT WHALE DISTRIBUTION FOR THE PRESENT STUDYName of vessel

Year

Month

Hoyomaru No. 67
Hoyomaru No. 12

1979
1982

6-8
8-9

Hoyomaru No. 12
Hoyomaru No. 53
Hoyomaru No. 12
Hoyomaru No. 12

1983
1984
1985
1986

8-9
5-6
8-9
8-10

Pilot whalesightings

Reference for cruise
track linenone*
2 schools
off Japan
none
none
none
present

Miyazaki, Jones and Beach (1984)
Kasuya and Ogi ( 1987)
Kasuya and Ogi (1987)
Miyazaki and Fujise (1985)
Kasuya and Ogi (1987)
Yoshioka et al. (1987)• Personal communication of Dr N. Miyazaki.

In these cruises the sighting of whales was conducted along pre-fixed trackline using the method that had been used in the Antarctic minke whale
assessment cruise (Best and Butterworth, I 980), and all the marine mammalsightings were recorded. The trackline was designed systematically to coverevenly the survey area. Instruction was given since I 984 to biologist on board
or to captain of the vessel to distinguish the two forms of short-finned pilot
whales and to take photographs of those individuals for later confirmation.
Some additional photographs or sketches were left by observers of earlier
cruises at voluntary base.
Additional information was available from published reports of five cruises
conducted by Japan Fishery Agency for Dall's porpoise sightings and harpooning in the western North Pacific (Table 2). Among these cruises pilot
whales were sighted only during the I 982 and I 986 cruises, but information
obtained from other cruises was also valuable as the indication of absence ofpilot whales in the surveyed area. Biologists were on board of these five cruises.
In addition to above cruises, sightings data collected during 4 cruises ofthe Hakuhomaru and 4 cruises of the Tanseimaru (both were conducted by
the Ocean Research Institute, University of Tokyo), and each cruise of the
Hayachinemaru and Koeimaru were used. These cruises (conducted in I 967 toI 985) were selected from many other similar kind of cruises by the presenceof at least one pilot whale sighting. Kasuya or some trained observers were on
board of these cruises to collect records of whale sightings. Two schools of thenorthern form and one school of unidentified form were cited from Ogi(pers. commn in 1985) and Kuroda (1956), respectively. Some of these sightings
were identified to the whale types using photographs.
Catch of drive fisheries or of small-type whaling in Kasuya and Marsh(I 984) or in Kasuya and Tai (I 986) were used as well as a stranding in Kasuya
and Marsh (1984) as the indication of occurrence of the species.
The surface water temperature was recorded at the position of sighting
for many of the above records.
Sci. Rep. Whales Res. Inst.,
No. 39, 1988

82

KASUY A, MIY AS HITA AND KASAMATSU

140"E

ISO"E

1600E

140°E

150"E

160"E

Fig. 2. Sightings of short-finned pilot whales and surveyed area (inside of the shaded
area indicated by one degree squares). Open triangle: school of northern form,
Closed triangle: school of southern form, Star: school of unidentified form. Marksinside the coast line represent catch or stranding. The isotherms indicate ten years
mean of surface water temperature in March, .July, September, and December(Japan Oceanographic Data Center, 1978).

RESULTS

Geographical segregation

The surveyed area and sightings of pilot whales are indicated by seasonsin Fig. 2. In winter Qanuary to March), the sighting effort was limited to thesouth of 37°N. Northern forms were sighted twice off the Boso Peninsula at
between 35°N and 36°N. In spite of extended sighting effort no southern
forms were sighted to the north of 30°N, but several sightings were recorded
to the south of the latitude (Table 4, for further details of these sightings see
Miyashita (1986b)). In this season the drive fishery off Taiji (33°35'N) captured
schools of the southern form, indicating their presence in the coastal waters
Sci. Rep. Whales Res. Inst.,
No. 39, 1988

SEGREGATION OF SHORT-FINNED PILOT WHALES

83

of the latitude.
In spring (April to June), the sighting effort expanded to wider geographicalarea, although the total surveyed areas was still limited. Northern forms weresighted off northern Japan at latitudes between 40°N and 41°N. A school ofsouthern form was sighted at about 34°N. Several additional sightings of theform were recorded to the south of 30°N (Miyashita, l 986b). Drive fishery at
Taiji (33°35'N) and at Arari (34°50'N) on the Izu coast captured schools of
the southern form in this season. These suggest a northward expansion of theconcentration of southern form whales in the spring season. A school ofunidentified form in Fig. 2 (5th May 1986) in the coastal waters in 36°-37°N
and 141°-142°£ was recorded by the captain of the Toshimaru No.25 as thesouthern form. Although the surface water temperature at the position(8.6°C) appeared to be too low for the southern form, this position was justto the inshore colder side of a very distinct water front (surface water temperature decline of 12.3°C in 24 n.m.), and both forms could have been present
at the spot. Since the correctness of the identification could not be supportedby photographs or subsequent sightings (the cruise had only one sighting ofpilot whales), we tentatively dealt the school as unidentified.
In summer months (July to September), the sighting effort expandedwidest. Northern forms were sighted in the Japanese coastal waters between
36°N and 43°N, and west of l 49°E longitude. Most of these sightings wereconcentrated within about I 00 nautical miles from the coast. In spite ofconsiderable amount of sighting effort (three 40 to 45 days cruises in Augustthrough September, and two similar cruises in May through August), there
were no sightings of pilot whales in the Bering Sea and western North Pacificwest of l 75°E in the Subarctic Convergence Zone and north of it (Table 2).
Pilot whales of unidentified form were sighted south of the Subarctic Convergence in the central North Pacific in August (Table 3). These data suggestthat short-finned pilot whales do not usually enter into the Subarctic Convergence Zone in the North Pacific and the long-finned pilot whale does notexists in the Bering Sea and northern North Pacific.
In the same season, southern forms were sighted to the south of 37°N.
Segregation between the two forms is clear (Fig. 2). At Taiji (33°35'N), thedrive fishery captured southern form schools. Although density seemed to be
low south of 25°N or east of 152°E suggesting the maximum range of the
population in the western North Pacific (IWC, 1987), firm conclusion was
hard to be drawn due to the limited sighting effort in the offshore waters. In
addition to this, there is an apparent density hiatus in the Kuroshio Current
area and the distribution seems to be discontinuous between coastal area andoffshore Kuroshio Counter Current area. The sighting trackline was arranged
systematically for even coverage of the area, so the density hiatus does notseem to be an artifact of uneven sighting effort (for details see Miyashita,
l 986b). Further study is needed to confirm more than one stocks of thesouthern form short-finned pilot whales in the western North Pacific.
Sci. Rep. Whales Res. Inst.,
No. 39, 1988

84

KASUYA, MIYASHITA AND KASAMATSU

TABLE 3. SIGHTINGS OF PILOT WHALES DURING THE CRUISES DEALT IN THE PRESENTSTUDY, OUTSIDE OF THE RANGE IN FIG. 2 AND NORTH OF 35°N.
NONE OF THE WHALE TYPES WERE IDENTIFIED
Date ofsighting
2 Aug. 1967
2 Aug. 1967
3 Aug. 1967
28 Aug. 1971

Position ofsighting
42°04'N,
41°57'N,
41°56'N,
39°04'N,

175°00'E
171°54'E
165°17'£134°36'E

Area
w. N. Pac.
w. N. Pac.
w. N. Pac.

S.ofJapan

Water
temp.

Name ofvessel19.6°C
22.9°C
19.9°C
24.5°C

Hakuhomaru
Hakuhomaru
Hakuhomaru
Hakuhomaru

In autumn months (October to December), sighting effort was limited to
the Pacific coast between 34°N and 39°N, and there were sighted three schoolsof northern forms (to the north of 36°N). Northern forms were caught byJapanese small-type whaling off the Pacific coast in October and November
in latitudes between 37°N and 40°N (Miyazaki, 1983; Kasuya and Tai, 1986).
Southern forms were not sighted in the coastal waters south of 36°N in thisseason, but the presence was indicated by the stranding of a school at Choshi(35°43'N), and frequent catch by the drive fishery on Izu coasts (34°40'N) andat Taiji (33°35'N) (Kasuya and Marsh, 1984). Miyazaki (1983) reported catchof the southern form by small-type whaling off Sanriku (38°N to 40°N) in
October 1982. However, this was possibly a rare incident for the region in thisseason, because such case did not occur during the following four pilot
whaling seasons (Kasuya, 1986; unpublished; Kasuya and Tai, 1986) andbecause it was the first case for the gunner to hunt such short whales of adultshape (Mr Y. Toba, pers. commn in 1983).
There are reasons to believe that northern forms may occasionally occur
off Taiji (33°35'N) on the Pacific coast of central Japan (see Discussion).
In the Sea of Japan, we have only one record of sighting of pilot whalesof unknown form (Table 3). The species seems to be uncommon in the area
as already mentioned by Kasuya (1975). We do not have data to indicate
which form of pilot whales are distributed in the Sea of Japan.
Thermal segregation
Table 4 shows number of short-finned pilot whale sightings by surface
water temperature, type of whales and season. Southern forms were sighted
at the water temperature between 24° and 31°C in summer, and between 20°
and 24°C in winter. The observed seasonal difference of the low temperature
limit was 4°C (lower in winter), while the geographical northern range shiftedto the south by about 9° in latitude. The actual thermal difference in the
ha_bitat between winter and summer must have been larger, because there
were frequent winter drives of this form at Taiji (33° 35'N) where surface
water temperature could be below 20°C (Fig. 2). This indicates that theseasonal change of the geographical range of southern form short-finned
Sci. Rep. Whales Res. Inst.,
No. 39, 1988

85

SEGREGATION OF SHORT-FINNED PILOT WHALESTABLE 4. MONTHLY SURFACE WATER TEMPERATURE ATTHE POSITION OF SHORT-FINNEDPILOT WHALE SIGHTING IN FIG. 2 (WITHOUT PARENTHESIS) AND
THOSE IN THE WATERS SOUTH OF 30°N LATITUDE MADE
BY CRUISES LISTED IN TABLE I (IN PARENTHESES)
Northern form

W.T.*
(oC)

1-3

4-6

7-9

Unidentified

Southern form

10-12

1-3

7-9

10-12

4-6

7-9

10-12

I**

8
14
15
16

17
18
19

6

20
21
22

23
24
25

(2)
(3)

4
4

2

(2)

(I)

4
I

26

2(2)

27
28

5(7)

4(1)

29

(2)

30

(I)

(I)

(2)

• Water temperatures between n° and n+ l°C indicated by n (n being integer).

* * Captain of the research vessel (Toshimaru No. 25 cruise in I 986) recorded this as a southern form school(see text).

pilot whales is not large enough to retain a constant surface water temperatureenvironment for the stock. In other words, some additional factors such as
basithermo structure or food availability is also controlling the distribution
and their distribution does not always cover the whole geographical range
permitted by their thermal tolerance.
Northern forms, on the other hand, were sighted at the surface watertemperature between l9°C and 24°C in summer, and at between 15°C andl8°C in other seasons (Table 4). Accumulation of more data may give wider
thermal range, especially for the lower limit. Kasuya and Tai (1986) reported
that the water temperature at the position of northern form catch (38°N to40°N) in October and November ranged from 12°C to 21°C with a peakfrequency of catch at l6°-l 7°C. The surface water temperature of 10°-l5°C
corresponds to the front of the cold Oyashio Current in the area. The summer
sightings of three pilot whale schools of unidentified form at 41° -43°N will
represent the northern form. We consider that northern forms move in thefall to the southern wintering ground (north of 35°N and south of the Oyashio
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Front) from their summering range expanded probably up to 43°N accompanying the seasonal shift of the Oyashio Front. Their southern range does
not change seasonally so much as the northern range, and they endure theseasonal change of the surface water temperature between 12° and 24 °C(Fig. 2).
The segregation between the northern and southern forms of short-finned
pilot whales is usually distinct geographically and thermally. Although there
exist some examples of geographical or possible social intermingling, suchcases seem to be rare and unusual as discussed below.
DISCUSSION

The characteristics that we have used in the present study to separate twoforms of short-finned pilot whales off the Pacific coast of Japan are similar to
those used by Yamase (1760) to describe two kinds of pilot whales off Taiji(33°35'N) on the Pacific coast of Japan. Cray's (1846; 1866) description of thepilot whales off Japan is almost identical to that of Yamase (1760). This lead
us to consider that our "southern form" is equivalent to their Naisa goto or
Naisa gota which was named as G. sieboldii Gray, 1846, and our "northernform" is equivalent to their Shiho goto or Shibo golo named as G. sibo Gray,
1871. Both of these scientific names have been correctly considered by Bree
(I 971) to be junior synonyms of G. macrorhynchus Gray, 1846.
The next question will be if the northern form individuals still occur off
Taiji which situates further south of the ordinally range of the northern form
confirmed in the present study. There are evidences supporting this. In
winter, a belt of cold coastal water below l 8°C extends from 35°N (the ordinary
southern range of the northern form in both summer and winter) to 33°N
(south of Taiji at 33°35'N) along the Pacific coast of Japan. Thus it is expected
for some northern form individuals to stray to the waters off Taiji. An exwhaler and a present dolphin meat dealer Mr M. Mizutani of Taiji Town and
Mr Y. Seko of the Taiji Fish Market gave us the description of the northern
form correctly and told their belief that one of the small-type whaling vessels
at Taiji caught the northern form pilot whale (their tappa-naga) once (Mizutani)or several times (Seko) after World War II. Since the meat of southern forms
is esteemed over that of northern forms, their identification can be trusted.
As the small-type whaling ceased operation off Taiji since 1978, the catch
could have been before the date.
In their sample of more than 500 southern form short-finned pilot whales,
Kasuya and Marsh (1984) found only one male of putative northern formand excluded it from their analysis. This male was found in an aggregationof about 230 southern form individuals caught at Taiji in June 1975, andexamined by their colleague. It was 5.8 m in body length, or 0.6 m larger thanthe largest southern form in their sample. The testis (1.7 kg) was at the lower
limit of the testis weight (l.7-3.0 kg) of southern forms measuring over 5 m
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87

in body length, but it was of reasonable weight for the northern form of thatbody size (Kasuya, I 986b). The lack of observation of saddle mark or age
estimate inhibited reliable classification of the whale type. Yonekura et al.
( 1980) did not recognize among their sample of 211 individuals (most of themwere not included in Kasuya and Marsh (1984)) any individuals which could
be classified to the northern form.
Only confirmed records of southern forms off the Sanriku coast (33°-37°N)
were seven individuals taken by a small-type whaling vessel at Ayukawa(38°15'N) on 5th November 1982, examined by Dr N. Miyazaki (1983) andaged by Kasuya (1986b). These individuals were apparently taken from aschool of the same form (Y. Toba, pers. commn in 1984). These were no
additional records of such incidence during the five years operation of thewhaling in October and November, 1982 to 1986. Kasuya (1986b) identified
about 300 individuals taken by the small-type whaling off Sanriku during
the period as the northern form based on the pigmentation, and confirmed
it using body length on age relationship. These suggest that the two formsof short-finned pilot whales rarely form a common school even though
their range of distribution may occasionally situate close or overlap in theboundary area.
Although there exist opinions to consider that the saddle mark of theshort-finned pilot whale may change brightness or shape by growth orphysiological conditions (see below), currently available data indicate that thefeature of saddle mark we have described above is a stable characteristics toidentify individually two forms of short-finned pilot whales off Japan withpossible exception of newborn individuals. The whale type of newborns is
identifiable only by body size assisted by the age information (Kasuya, 1986b).
The life history of northern form short-finned pilot whales off Japan differsfrom that of the southern form (Kasuya and Marsh, 1984) only in the larger
body size and later mating peak (May vs. September), and all the life history
characteristics that were found by them to be peculiar to the short-finned
pilot whale are shared by both northern and southern forms (Kasuya, 1986b).
Kasuya (I 986b) speculated from these some ecological mechanisms whichmight inhibit free interbreeding between the two forms, and considered thatthe degree of differentiation between the two forms will be at the level ofsubspecies or local stocks. Wada ( 1988) arrived at the similar conclusion
through the analysis of isoenzymes.
Two types of short-finned pilot whales have been distinguished in theeastern North Pacific using various independent characteristics, e.g. bodysize and head shape (Mitchell, 1975) and skull morphology (Polisini, 1980).
Published studies on the pigmentation of short-finned pilot whales in thesewarters are confusing. Yablokov and Evans (1981) described individual variation of the saddle mark of short-finned pilot whales in the southern California
Bight, and Leatherwood, Reeves, Perrin and Evans (1982) and Evans, Thomas
and Kent (1984) questioned its stability and the usefulness for stock identifiSci. Rep. Whales Res. Inst.,
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KASUYA, MIYASHITA AND KASAMATSU

cation. The latter authors, however, suggested in the same study a possibilityof geographical variation of the pigmentation pattern, indicating that the
short-finned pilot whales in the eastern tropical Pacific usually have no or
only faint markings on the dorsal surface. The apparent disagreement of
opinions probably came from the mixing of some minor individual variationof pigmentation in a single population and more stable difference between
stocks.
A short-finned pilot whale photographed off Baja California and the Gulf
of California by T. Amborn (pers. commn in 1986) and Leatherwood et al.
(1982) had saddle mark similar to that of the present northern form, and aschool of 35 pilot whales sighted off Seattle (48°28'N, 133°5l'W) in August
had apparently similar saddle mark with the northern form sighted off Japan(39°50'N, 145°42'E) in August during the same cruise (Yoshioka, Ogura andShikano, 1987). We confirmed the photographic records of these sightings.
While describing the external morphology of G. scammonii, which was identified
by Bree (1971) as a junior synonym of G. macrorhynchus, Scammon (1874)
made no comment on the saddle mark of the type specimen taken by him off
Baja California (31°N). His detailed description of the variation of killer whale
saddle mark in the same book suggests that he would have mentioned thesaddle mark of the type specimen if it had such clear one as found on shortfinned pilot whales off northern Japan or off the coast of North America.
These suggest, as well as a comment in Evans et al. (1984), the presence ofgeographical segregation of two forms of the short-finned pilot whale in theeastern North Pacific. Although information on other biological feature ofthese individuals is needed for further consideration, there is a possibility thateach of them corresponds to the southern and northern forms off Japan.
The short-finned pilot whale in the North Pacific could have evolved two
geographical forms (or subspecies), one in the tropical waters and the otherin the temperate waters north of it.
We do not have information on the morphology of pilot whales sighted
in the central northern North Pacific (Table 3). The latitudes of sightings(39°-42°N), which were just to the south of the Subarctic Convergence Zone,
leave possibility for them being either of the two forms of the present study.
However, in view of the concentration of northern forms in the Japanese
coastal waters and tht; apparent discontinuity of distribution in the offshore
waters, we consider that the Japanese coastal individuals of the northern form
will constitute a local stock of relatively small population size. Miyashita (l 986b)
estimated the population as about 5,000 individuals.
ACKNOWLEDGEMENTS

Thanks are due to many anonymous scientists and crew on board of theresearch vessels who cooperated in collecting sighting records of pilot whales.
Drs T. Amborn, H. Ogi, C. Shikano, M. Yoshioka provided photographs andSci. Rep. Whales Res. Inst.,
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records of sightings of short-finned pilot whales for the present study. Dr N.
Miyazaki critically read the manuscript. Mr S. Matsui helped us in collecting
information on the historical records of the northern form catch in Taiji. Dr
A.A. Hohn advised us in references. Mrs Y. Yamamoto and Mrs M. Ikeya
helped us in data analysis and drawings.
REFERENCES
BEST, P.B. and D.S. BUTTERWORTH, 1980. Report of the southern hemisphere minke whale assessment
cruise. 1978/79. Rep. int. Whal. Commn, 30: 257-283.
BREE, P.J. H. VAN, 1971. On Globicephala sieboldii Gray, 1846, and other species of pilot whales. Beaufortia,
19(247): 79-87.
EVANS, W. E.,]. A. THOMAS and D. B. KENT, 1984. A study of pilot whales (Globicephala macrorhynchus) in thesouthern California Bight. National Marine Fisheries Ser. Administrative Rep. LJ-84-38C, 47 pp.
GRAY, J.E., 1846. The Zoology of the voyage of H.M.S. Erebus and Terror. 1: 13-53, 37 pls.
GRAY, J.E., 1866. Catalogue of Seals and Whales in the British Museum. Trustees British Museum, London. 402 pp.
GRAY, ]. E., 1871. Supplement to the Catalogue of Seals and Whales in the British Museum. Trustees British
Museum, London. 99 pp.
HAWLEY, F. 1960. Miscellanea Japonica II, Whales and Whaling in Japan, vol.l, part 1. 354 + Xpp. Publishedby the author.
IWC, 1987. Report of the sub-committee on small cetaceans. Rep. int. Whal. Commn, 37: 121-128.
JAPAN OCEANOGRAPHIC DATA CENTER, 1978. Marine Environmental Atlas, Northwestern Pacific Ocean II (Seasonal,
Monthly). Japan Hydrogr. Ass., Tokyo. 157 pp.
KASUYA, T. 1975. Past occurrence of Globicephala melaena in the western North Pacific. Sci. Rep. Whales Res.
Inst., 27: 95-110.
KASUYA, T. l 986a. Distribution and behavior of Baird's beaked whales off the Pacific coast of Japan. Sci.
Rep. Whales Res. Inst., 37: 61-83.
KASUYA, T. l 986b. Comparison of life history parameters between two stocks of short-finned pilot whales
off the Pacific coast of Japan. IWC/SC38/SM10. 32 pp.
KASUYA, T. and H. MARSH, 1984. Life history and reproductive biology of the short-finned pilot whale,
Globicephala macrorhynchus, off the Pacific coast of Japan. Rep. int. Whal. Commn, (special issue 6):259-310.
KASUYA, T. and S. MATSUI, 1984. Age determination and growth of the short-finned pilot whale off the
Pacific coast of Japan. Sci. Rep. Whales Res. Inst., 35: 57-91.
KASUYA, T. and H. 0GI, 1987. Distribution of mother-calf Dall's porpoise pairs as an indication of calving
grounds and stock identity. Sci. Rep. Whales Res. Inst., 38: 125-140.
KASUYA, T. and S. SHIRAGA, 1985. Growth of Dall's porpoise in the western North Pacific and suggested
geographical growth differentiation. Sci. Rep. Whales Res. Inst., 36: 139-152.
KASUYA, T. and S. TAI, 1986. Operation of Japanese small-type whaling on the short-finned pilot whale off
the northeastern Japan. IWC/SC38/SM16. 16 pp.
KURODA, N. 1956. Records of marine mammals in the northern North Pacific.]. Mamm. Soc. Japan, 1(3):35-39. (in Japanese with English summary)
LEATHERWOOD, S., R.R. REEVES, W.F. PERRIN and W.E. EVANS, 1982. Whales, Dolphins and Porpoises of theEastern North Pacific and Adjacent Arctic Waters, a Guide to Their Identification. NOAA Tech. Rep.
NMFS. Circular 444. 245 pp.
MARSH, H. and T. KAsUYA, 1984. Change in the ovaries of the short-finned pilot whale, Globicephalamacrorhynchus, with age and reproductive activity. Rep. int. Whal. Commn, (special issue 6): 311-335.
MITCHELL, E.D. 1975. Report of the meeting of smaller cetaceans, Montreal April 1-11, 1974, Subcommittee
on Small Cetaceans, Scientific Committee, International Whaling Commission.]. Fish. Res. Bd Can.,32(7): 889-983.

Sci. Rep. Whales Res. Inst.,
No. 39, 1988

90

KASUYA, MIYASHITA AND KASAMATSUMIYASHITA, T. 1986a. Sighting estimate for the Bryde's whale stock in the western North Pacific. Rep. int.
Whal. Commn, 36: 249-252.
MIYASHITA, T. 1986b. Abundance of some globicephalid cetaceans in the adjacent waters of Japan.
IWC/SC38/SM17. 18 pp.
MIYASHITA, T. and F. KASAMATSU, 1985. Population assessment of the western North Pacific stock of Bryde's
whales. Rep. int. Whal. Commn, 35: 363-368.
MIYASHITA, T. and T. KASUYA, 1988. Distribution and abundance of Dall's porpoises off Japan. Sci. Rep.
Whales Res. Inst., 39: 121-150.
MIYAZAKI, N. 1983. On pilot whales off Kinkazan Island. Abstracts of Papers Read in the Autumn Meeting
Japanese Soc. Sci. Fisheries. p. 55. (in Japanese).
MIYAZAKI, N. and Y. FUJISE, 1985. Outline of the survey of dolphins and porpoises by the Hoyomaru No. 53
dedicated for Dall's porpoise study (JO May to 20 June 1984). Far Seas Fisheries Res. Laboratory.
Shimizu. 47 pp. (in Japanese).
MIYAZAKI, N., L.L. Jones and R. BEACH, 1984. Some observations on the schools of dalli- and truei-type
Dall's porpoises in the northwestern Pacific. Sci. Rep. Whales Res. Inst., 35: 93-105.
N1sHIWAKI, M., T. KASUYA, R.L. BROWNELL and D.K. CALDWELL, 1967. On the taxonomy of Globicephala in
the Japanese coastal waters. Abstracts of Papers Read in the Annual Meeting ofJapanese Soc. Sci. Fisheries,
p. 15. (in Japanese)
OG1, H., H. TANAKA, T. KuRAMOCHI and Y. YAMAMOTO, 1986. Outline of the research by the dedicated vessel
Hoya Maru No. 12 in 1985. Document submitted to the meeting of Scientific Subcommittee of the
Ad Hoe Committee on Marine Mammals, International North Pacific Fisheries Commission, Tokyo,
March 1986. 26 pp. (in Japanese with English translation of text).
PousINI, 1980. A comparison of Globicephala macrorhyncha (Gray, 1846) with the pilot whale of the North
Pacific Ocean: An analysis of the skull of the broad-rostrum pilot whales of the genus Globicephala.
Doctoral thesis presented to Fae. Graduate School, Univ. Southern Cali[., 299 pp.
SCAMMON, C.M., 1874. The Marine Mammals of the North-western Coast of North America. Carmany, San Francisco.
319 pp.
WADA, S., 1988. Genetic differentiation between two forms of short-finned pilot whales off the Pacific coastof Japan. Sci. Rep. Whales Res. Inst., 39: 91-102
YABLOKov, A. V. and W. E. EVANS, 1981. On the benefit of external appearance. Science and Life, 3: 76-81.
(in Russian).
YAMASE, H. 1760. Geishi [Natural History of Whales]. Osakashorin, Osaka. 70 pp. (in Japanese).
YoNEKURA, M., S. MATSUI and T. KASUYA, 1980. On the external characters of Globicephala macrorhynchus off
Taiji, Pacific coast of Japan. Sci. Rep. Whales Res. Inst., 32: 67-95.
YOSHIOKA, M., M. 0GURA and C. SHIKANO, 1987. Results of the transpacific Dall's porpoise research cruiseby the Hoyomaru No. 12 in 1986. Document submitted to the meeting of the Scientific Committee,
Ad Hoe Committee on Marine Mammals, International North Pacific Fisheries Commission, Tokyo,
March 1987. 22 pp.

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