COMPARISON IN COLOUR PATTERN OF TWO SPECIESOF HARBOUR SEAL IN ADJACENT WATERSOF HOKKAIDOYASUHIKO NAITO*
Ocean Research Institute, University of Tokyo

ABSTRACTThe pelage of Phoca vitulina largha shows a clear colour contrast between
the lighter ventral and the darker dorsal. On the other hand, the pelageof Phoca kurilensis shows little such contrast. There is much variation in the
pelage of both species. Sometimes Phoca kurilensis has pelage closely resemblingthat of Phoca vitulina largha, and identification by colour pattern is difficult.
Hard scars are often found on the pelage of Phoca kurilensis, which are presumably caused by fights between males during the breeding season.
INTRODUCTION
The pelage colour and pattern of the harbour seal have been reported in the literature ever since biologists have been interested in this animal. It is generally said tobe quite difficult to describe them precisely because of their endless variations.
However, in spite of the above difficulties, the importance of pelage studies of thisseal has increased all the more, in the light of recent studies on its taxonomy andzoogeography in the North Pacific.
In the North Pacific, there are three types of harbour seal; Phoca vitulina
largha, Phoca vitulina richardi, and Phoca kurilensis (i.e., Phoca insularis). These three
seals differ in their distribution, breeding grounds and habitat. P. v. richardi breeds
on sand bars or rocky shores and occurs along the Pacific coast of North America(Scheffer and Slipp, 1944; Fisher, 1952; Scheffer, 1958; King, 1964; Stutz, 1967;
Bigg, 1969). P. v. largha is an ice breeding type and occurs mainly in the Bering Sea
and the Sea of Okhotsk (lnukai, 1942 a, b; Wilke, 1954; Scheffer, 1958; King,
1964; Burns, 1970; Tikhomirov, 1971; Fay, 1972; Naito and Nishiwaki, 1972 a).
P. kurilensis breeds on rocky shores and occurs along the Kurile Islands and Hokkaido (Inukai, 1942 a, b; Belkin, 1964; Belkin et al., 1969; Naito and Nishiwaki,
1972 a). The distribution of this species is incompletely known.
It is generally recognized that the differences in the pup coat are importantcharacters that distinguish each species or subspecies. The white-coat pup of P. v.
largha, according to McLaren (1966) is one of the most important characters bywhich this seal can be regarded as an independent species (P. largha) from other P.
vitulina groups which do not bear such a pup coat. The colour and pattern of the* Present address: Kominato Marine Biological Laboratory, Tokyo University of Fisheries. 1 Uchiura,
Amatsu-Kominato, Chiba 299-54.
Sci. Rep. Whales Res. Inst.,

No. 25, 1973, 301-310.

302

NAITO

adult pelage also seem to be important. Variations among local populations of thepelage colour and pattern are reported in P. v. richardi (Stutz, 1967). However,studies on these problems in the above mentioned three types of harbour seals still
do not provide sufficient data for comparative taxonomic evaluation. Furthermore
these studies seem to be important to establish the relationship between pelage character and habitat of each type from the point of view of adaptation and speciation.
The present paper provides some new data on the pelages of P. v. largha and P.
144°E

146°E

SEA OF OKHOTSK
46°N

46°N
AREA I

44°N -HOKKAIDO

PACIFIC OCEAN
42°N

42°N
142°E

Fig. I.

144°E

146°E

Sampling areas for P. v. largha and P. kurilensis in the southern Sea of Okhotsk and
the Pacific coast of Nemuro Peninsula.

Sci. Rep. Whales Res. Inst.,
No. 25, 1973.

COLOUR PATTERN OF HARBOUR SEAL

303

kurilensis and attempts to clarify the above mentioned problems.
MATERIALS AND METHODS
Field studies on the harbour seal (P. v. largha and P. kurilensis) were made in thesouthern Sea of Okhotsk and Hokkaido from 1969 to 1971. Pelage studies were included during the same period and mostly in the same area (Fig. 1). The pelage ofP. v. largha for this study was recorded from the southern Sea of Okhotsk (area I)
and from Nemuro Strait (area II). The pelage of P. kurilensis was recorded fromarea III of Pacific coast ofNemuro Peninsula. Ninety-four skins of P. v. largha and37 of P. kurilensis were examined to establish the range of variation in pelage colour
and pattern of each .seal by studying photographs taken at the factories of fur compames.
PUP COAT OF P. KURILENSIS
It is widely reported in the literature that P. v. largha is a pagophilic seal and bears its
pup without exception with a white coat. Belkin (1964) and Belkin et al. (1969)
reported however that the pup of this seal is born with the adult type coat. P. v.
richardi is also generally recognized to bear the adult type coat pup, the white coatbeing lost in utero before birth. However, there are some reports on the pups of P. v.
richardi which still retain their white coat after birth (Scheffer and Slipp, 1944;
Fisher, 1952; Burns, 1970; Stutz, 1966). The same phenomenon is suggested forP. kurilensis (Naito and Nishiwaki, 1972 a). The present paper gives more details of
exceptional white-coat pups of P. kurilensis.
TABLE I. SOME MEASUREMENTS OF WHITE-COAT PUPS OF PHOCA
KURILENSIS AND THE EXCEPTIONAL PUP WITH THE
LARGHA-TYPE COAT OF PHOCA KURILENSIS.

white coat pup

pup with thelargha type coat

field
numberdate ofcatch

localitysex

bodylengthbodyweightNM 16

1969-5.20

Moyururi Is.

male

89cm

16kg

'70-154

1970-5.25

Daikoku Is.

female93cm

14.5 kg'70-173

1970-5 .18

Pacific coastof Nemuro P.

female

98 cm

23 k

*mean body length of P. kurilensis:gwith lOcm
umbilical cordwith 9.5cm
umbilical cordwith 5.5cm
umbilical cord

98.2±3.2cm (Naito and Nishiwaki, 1972a)

As shown in Table 1, two exceptional white-coat pups were collected from area
One was mostly covered with a white coat except for head, flippers and tail.
The colour of the hair is creamy white itself, however, as shown in Plate I, the adulttype coat under it imparts a greyish hue. The other exceptional pup possessed apartial white coat (15 cm wide) on its dorsal parts, the hair being so thin that its
existence was easily missed if the body was wet. These exceptional pups occurredamong 20 pups which possessed a fresh umbilical cord (5-10 cm).
Burns (1970) reported the retention of the white coat in early-born pups of P. v.

III.

Sci. Rep. Whales Res. Inst.,

No. 25, 1973.

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NAITO

richardi in the Alaska Peninsula, where this seal has a longer pupping season (lateMay to mid-July) than P. kurilensis in Hokkaido (mid to end of May; Naito andNishiwaki, 1972 a. According to a fisherman, the earliest record in Hokkaido is 28thof April). The birth of these exceptional pups occurred during the normal birth
season of this seal and their body size is quite normal. The frequency of appearanceof these white-coat pups is still unknown because of inadequate data, however, it issaid that the specimen of Plate I collected 20th of May 1969 was the first example in
the long experience of the fur company and the fisherman. Belkin et al. (1969)
observed more than 100 newborn pups of this seal in the southern Kuril Islands
some of which possessed fresh umbilical cords; however, they found none of theabove type of exceptional pup. Therefore, it seems that the white-coat pup is considerably rare in the southern Kuril Islands and Hokkaido.
THE PELAGE COLOUR AND PATTERN
lnukai (1942 a) and Belkin (1964) recognized the pelage colour and pattern as important characters distinguishing P. kurilensis from P. v. largha. However, in spite of
their work, the range of variation of the pelage colour and pattern of each species isstill unknown. In P. v. richardi, Stutz (1967) studied the range of variation of pelage
colour and pattern and named three basic categories: " black ", " common " and" muddy ", and suggested that these three categories typify three largely isolated
local populations. In the present study, the range of variation of the pelage colour
and pattern of P. v. largha and P. kurilensis were examined in 94 and 37 photographs
respectively.
TABLE 2.

FREQUENCY OF APPEARANCE OF EACH COLOUR TYPE
lighter <--- colour degrees ---> darker

P. v. largha numbers examined(%)
P. kurilensis numbers examined
(%)

I

2

3

4

5

Total

9
(9.6)
3
(8.1)

17
(18. l)11(29.7)

44(46.8)
14(37 .8)18(19.l)
6(16. 0)

6
(6.4)
3
(8.1)

94
37

Ninety-four pelages of P. v. largha were classified into five categories by thecolour, from lighter to darker (Plate 11), and the frequency of appearance was examined. These colour categories were chiefly determined by the number and sizeof dark spots on the ventral side. As shown in Table 2, the distribution in thesecategories seemed not to show any bias to the lighter side or blacker side. The
colour of the pelage of this seal is, as shown in Plate II, composed of two parts, adarker part on the dorsal side and a lighter part on the ventral side. The mid-lineof the dorsal side is darkest, showing black, blueish-black or dark grey, and dorsal
dark colour sharply fades out in the border parts between dorsal and ventral sides,
which show creamy white or silvery white. This contrast is clearer in the lighter
colour type. Dark spots appear all over the pelage, showing wide variation in size
Sci. Rep. Whales Res. Inst.,

No. 25, 1973.

COLOUR PATTERN OF HARBOUR SEAL

305

and form. Indistinct light marks are seen on the dark dorsal side, sometimes showing obscure small ring marks. The above-mentioned colour is not constant throughthe year. Moulting of the hair occurs in April and May, and the colour differs
markedly in the moulting season. Light parts turn to creamy or sometimes lightbrown, dark parts turn to dark brown, and spot marks become obscure.
Thirty-seven pelages of P. kurilensis were also classified into five categories fromlighter to darker. As shown in Table 2, the distribution in these categories as forP. v. largha seemed not to show any bias to lighter or darker. Plate II indicates thatthe pelage of P. kurilensis shows little or no colour contrast between dorsal and ventral side, as seen in P. v. largha. The colour of the dorsal side is black or dark brown,with dark grey or light brown on the ventral side. The pattern differs between
dorsal and ventral sides. There are several clear light ring marks on the dorsal side,sometimes on both dorsal and ventral sides, and on the ventral side many deformed
and complicated light ring marks or mottles are seen. These pelages in my observation seemed to have a good camouflage effect when the seals haul out on the rocky
shores (Plate III).
As mentioned above, most of P. v. largha and P. kurilensis are divided by pelage
colour and pattern as indicated by Inukai (1942 a) and Belkin et al. (1969). However, Plate II indicates that the darker pelage of P. v. largha (colour type 5) resembles
the lighter pelage of P. kurilensis of colour type 1, and it is suggested that it is difficult
to distinguish them completely by pelage colour and pattern. Furthermore, wecollected a strange pup of P. kurilensis, of which the pelage colour and pattern do notbelong to any colour degree of P. kurilensis but seem to belong to those of P. v. largha(Table 1). As shown in Plate IV, fig. 1, characteristic ring marks of P. kurilensis arerecognized on the dorsal side while the ventral side is silvery white with little small
spots, showing a clear colour contrast with dorsal side. It seems quite difficult to
identify this pup from pelage colour and pattern. However, this pup was identified
as P. kurilensis for the following reasons: 1) This pup possessed the incomplete hyoidbones, as the normal P. kurilensis does (Naito and Nishiwaki, 1972 b ). 2) The birthtime and place belonged to those of P. kurilensis (Naito and Nishiwaki, 1972 a).
This largha type seal occurred among 153 collection of P. kurilensis. The other example of largha type P. kurilensis like the above pup was observed in our field observation at Moyururi Island in the beginning of April 1970. In this observation, only one
such white pelage seal was found out of 92 P. kurilensis in the colony. Judging fromthe season and location, this seal was supposed to be P. kurilensis. From the above
facts it is suggested that the largha type seal of P. kurilensis is quite rare in this area.
SCARS OF PELAGE
Inukai (1942 b) reported scars on the neck oflarge males of P. kurilensis. I foundremarkable scars on the pelages of male P. kurilensis, while no scars were found on the
pelages of both sexes of P. v. largha. These scars were mainly found around theneck, the hind flippers and the tail. The larger and harder scars were found aroundthe neck (Plate IV. fig. 2). The scars were sometimes so heavy and severe that theSci. Rep. Whales Res. Inst.,
No. 25, 1973.

306

NAITO

pelage around the neck showed an uneven surface, with many old ones. The causeof these hard scars is still unknown. However, the facts that the fresh bleedingscars were found only in the breeding season (May to June) and only on adult males(Table 3) suggests that the scars are caused by fighting between males in the breeding season. This is supported by the following observations. I observed hard struggles of this seal in the breeding season during the field observation performed at
Moyururi Island in early June of 1969. However, in early April (two months before
breeding season) none of struggles were observed among 92 in the population at thesame island.
TABLE 3. LIST OF MALES OVER 140 cm IN BODY LENGTH OF
PHOCA KURILENSIS ON WHICH SCARS WERE FOUND.
densityof scars

field
numberdate ofcatch

body
lengthheavy

1970-208
1970-221
1970-223
1971-444
1971-455
1971-456
1970-224
1970-219
1970-215
1971-457
1971-447
1970-209
1971-424

1970-6.6
1970-6.16
1970-6.16
1971-6.7
1971-6.28
1971-6.28
1970-6.16
1970-6.16
1970-6.10
1971-6.28
1971-6.27
1970-5.6
1971-5.22

191.4 cm
192.5
183
183
184
180
170.5
165.5
160.0
161
152
146.5
144

mediumlight
none

estimated
age
19
10
10
8
9
4
4
3
5
3

DISCUSSION
It is revealed that shore pupping P. kurilensis bear a white-coat pup quite exceptionally. In my study, the occurrence of white-coat pups of P. kurilensis seemed to
be rare, while the occasional occurrence of a white coat in newborn pups of P. v.
richardi is reported from Alaska to as far south as California (Scheffer and Slipp,
1944; Fisher, 1952; Stutz, 1966; Burns, 1970). It would be interesting to know
which seal shows a higher frequency of white-coat pups between P. kurilensis andP. v. richardi, in consideration of the phylogenetic aspects of P. v. largha, P. v. richardi
and P. kurilensis in the North Pacific.
With regard to pelage colour and pattern, it was found that P. v. largha shows alighter phase ventrally, contrasting with a dark dorsal side; P. kurilensis has a darker
phase both ventrally and dorsally, showing less or no contrast between both sides.
The difference in pelage colour and pattern between P. v. largha and P. kurilensis asmentioned above seems to relate to differences in their habitats or hauling grounds.
P. v. largha stays on ice floes in winter and spring, occupying the edge of the pack ice(Wilke, 1954; Burns, 1970; Fay, 1972). After ice-melt, seals are highly migratory(Fay, 1972). In Hokkaido, the hauling grounds of this seal show wide topograSci. Rep. Whales Res. Inst.,.No. 25, 1973.

COLOUR PATTERN OF HARBOUR SEAL

307

phical variation. They haul out on the rocky reefs at Point Notoro and grass bars or
sand bars of the inland sea the mouth of which opens to the Sea of Okhotsk or Nemuro Strait, where such environments are often found. They are rarely seen however on the Pacific coast of Nemuro Peninsula (Fig. 1), where rocky shores prevail.
The lighter pelage of P. v. largha seems to adapt to the above mentioned lighter
circumstances, and furthermore the lighter phase of the ventral side, in contrast withdarker dorsal side, may have a camouflage effect by obliterative counter shading as
seen in pelagic fish (Lagler et al., 1962) when they migrate offshore. On the other
hand, P. kurilensis occurs on the rocky coast of Nemuro Peninsula (Naito and Nishiwaki, 1972 a), rarely penetrating the inland sea of the Nemuro Peninsula where
P. v. largha is dominant. These seals are non-migratory and are found along thecoast throughout the year, hauling out on the rocky shores of small islands (Belkin,
1964; Belkin et al., 1969). The darker colour and white ring marks of their pelages
are supposed to be well adapted to their habitat or hauling grounds as mentioned
already. We are still uncertain, but the above facts may suggest that P. v. largha andP. kurilensis select their own habitats or hauling grounds in accordance with theirpelage colour and pattern. This interpretation may be supported by their following
behaviour. According to some fisherman or hunters in Hokkaido, when P. v.
largha and P. kurilensis haul out at the same place and are hunted, P. v. largha swims
away offshore, while P. kurilensis goes along the coast where rocky reefs are welldeveloped.
Stutz (1967) classified the pelage colour and pattern of P. v. richardi
into three basic categories, " common ", " black " and " muddy ". The pelage of" common " and " black " of P. v. richardi seem to correspond to that of P. v. largha
and P. kurilensis of the present study respectively, and it is known that P. v. richardi
haul out on both sand bars of river estuaries or inland sea and rocky coast (Scheffer
and Slipp, 1944; Fisher, 1952; Fisher, Bigg, and Newby, personal communication).
However, it is still unknown whether P. v. richardi shows any tendency of habitat
segregation by the pelage colour. Newby, in private communication, informed meof the pelage colours of seals in the different areas of the state of Washington, with acomment on inadequate data. The San Juan seals that haul out on rocks aredarker than those found on the sandy beaches of the coast and inland sea.
From these findings, it appears important in future studies to consider the systematic relation between P. v. largha, P. v. richardi and P. kurilensis. Stutz (1967)
reported that his "common" pelage (resembling that of P. v. largha) appears in
15-47% in the pelages of P. v. richardi collected from some places in Alaska and British
Columbia. It was quite rare in P. kurilensis in our study. However, unfortunately
there are quite few data from the Kuril and Aluetian Islands as far east as the Alaska
Peninsula, for considering this problem genetically and zoogeographically.
The scars on the adult male pelages of P. kurilensis are of interest from the pointof view of social behaviour. P. v. largha mates in the ice floe region, displaying"family groups " (consisting of male, female and pup) which are rarely closer
together than 0.2 Km (Burns et al., 1972). P. kurilensis on the other hand breeds on
narrow rocky shores in large herds (70-90 individuals including young were obSci. Rep. Whales Res. Inst.,
No. 25, 1973.

308

NAITO

served at Moyururi Island in 1969 and 1971), and fighting was observed among
them. Ohsumi (1971) suggested that scars on the male sperm whale may indicatesocial maturity of the males in the harem. In the present study, as I am still uncertain as to the minimum ages and body size at sexual maturity in this seal, I cannot
discuss the relation between these scars and sexual maturity. Therefore, I do notknow what these scars mean. However, I can indicate that they are closely related to their breeding habitat and their social behaviour when I consider that thesexual dimorphism of this seal in body size is larger than that of P. v. largha (Naito
and Nishiwaki, 1972a). Further studies on these problems are required in P.
kurilensis and also in P. v. richardi.
ACKNOWLEDGMENTS

It is a pleasure to extend my grateful thanks to Professor M. Nishiwaki, Ocean
Research Institute, University of Tokyo, who gave me constant encouragement andstimulation. I also express my sincere thanks to Drs. T. Kajihara, K. Numachi and
T. Kasuya of my laboratory for their valuable advice and discussions. In the fieldworks, greatest thanks go to Mr. Suzuki, Engaru Fur Co. and Mr. N. Kanazawa,
Kanazawa Fur Co., who have been very helpful in producing photographs andcollecting data. Particular thanks are due to Professor H. D. Fisher, Universityof British Columbia, and Professor S. Tanaka of the same Ocean Research Institute,for their critical reading of the manuscript.
REFERENCES
BELKIN, A. N., 1964. A new species of seal-Phoca insularis n. sp.-from the Kuril Islands. Dok!. Akad.
Nauk. SSSR, 158: 1217-1219. (in Russian).
BELKIN, A. N., G. M. KosYGIN, and K. I. PANIN., 1969. Marine mammals. Akademy of Sciences ofU.S.S.R.,
Ministry of Fisheries of U.S.S.R., Moscow., 157-175. (in Russian)
BIGG, M.A., 1969. The harbour seal in British Columbia. Bull. Fish. Res. Bd. Canada, 172: 1-33.
BuRNs,J.J., 1970. Remarks on the distribution and natural history ofpagohilic Pinnipeds in the Bering and
Chukchi Seas. J. Mamm. 51 (3): 445-454.
BURNS, J.J., G. C. Ray, F. H. FAY, and P. D. SHAUGHNESSY, 1972. Adoption of a strange pup by the iceinhabiting harbour seal, Phoca vitulina largha. Ibid., 53(3): 594-598.
FAY, F. H., 1972. The role of ice in the ecology of marine mammals of the Bering Sea. International Symposium/or Bering Sea Study. Hokkaido University, Hakodate, Japan. (in press).
FISHER, H. D., 1952. The status of the harbour seal in British Columbia, with particular reference to the
Skeena River. Bull. Fish. Res. Bd. Canada, 93: 1-58.
INuKAI, T., 1942a. Hair seals in our northern waters (I). Shokubutsu Dobutsu, 10 (10): 927-932. (inJapanese).
INUKAI, T., 1942b. Hair seals in our northern waters (II). Ibid., 10 (11): 1025-1030. (in Japanese).
KING, J.E., 1964. Seals of the world. British Museum, London, 154 pp.
LAGLER, K. F., J.E. BARDACH, and R.R. MILLER, 1962. Ichthyology: The Study of.fishes. John Wiley andSons, Inc., New York. London. (Toppan Company, Ltd., Tokyo), 545 pp.
McLAREN, I. A., 1966. Taxonomy of harbour seals of the western North Pacific and evolution of certain
other hair seals. J. Mamm., 47 (3): 466-473.
NAITO, Y., and M. NISHIWAKI, 1972a. The growth of two species of the harbour seal in the adjacent waters of
Hokkaido. Sci. Rep. Whales Res. Inst., 24: 127-144.
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NAITO, Y., and M. NrsHIWAKr, 1972b. Ecology and morphology of Phoca vitulina largha and Phoca kurilensis in
the southern Sea of Okhotsk and north east of Hokkaido. Symposium on the Biology of the Seal., Universityof Guelph, Ontario Canada. (in press).
0HSUMI, S., 1971. Some investigations on the school structure of sperm whale. Sci. Rep. Whales Res. Inst.,
23: 1-25.
SCHEFFER, V. B., andJ. W. SLIPP, 1944. The harbour seal in Washington State. Am. Midland Nat., 32 (2):373-416.
SCHEFFER, V. B., 1958. Seals, sea lions, and walruses. Stanford Univ. Press, Stanford, 179 pp.
STUTZ, S.S., 1966. Foetal and postpartum white coat pelage in Phoca vitulina. j. Fish. Res. Bd. Canada,
23 (4): 607-609.
STUTZ, S.S., 1967. Pelage patterns and population distributions in the Pacific harbour seal (Phoca vitulina
richardi). Ibid., 24 (2): 541-455.
TrKHOMIROV, E. A., 1971. Body growth and development ofreproductive organs of the North Pacific Phocids.
In: Pinnipeds of the North Pacific. (Israel program for scientific translations). Keter Press, Jerusalem,
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WILKE, F., 1954. Seals of northern Hokkaido. J. Mamm., 35 (2): 218-224.

Sci. Rep. Whales Res. Inst.,
No. 25, 1973.

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NAITO

EXPLANATION OF PLATESPLATE IThe exceptional white-coat pup of Phoca kurilensis (middle). Upper, white-coat
pup of Phoca vitulina largha; lower, normal pup of Phoca kurilensis.

PLATE IIClassified five colour types from light to dark of Phoca vitulina largha (left side)and Phoca kurilensis (right side).

PLATE III
Phoca kurilensis have a camouflage effect by their pelage colour and pattern when
they haul out on the rocky shores.

PLATE IV
Fig. 1. The exceptional largha type coat pup of Phoca kurilensis (in a stuffed
specimen).
Fig. 2. The scars on the pelage of a large male of Phoca kurilensis.

Sci. Rep. Whales Res. Inst.,
No. 25, 1973.

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