A PYGMY SPERM WHALE STRANDED AT
TOKAIMURA, IBARAGI, JAPANHIDEO OMURA AND YUKO TAKAHASHIWhales Research Institute

It was informed that on 29 September 1979 a pygmy sperm whale was foundstranded on beach of Tokaimura, Ibaragi. One of the authors (Y.T.) went thereon 2 October 1979 and confirmed that the whale was a young male Kogia. The
body of the whale was already half-decomposed, but she made measurements ofbody proportions (Table 1) and brought back the head of that whale for precise
identification of the species. The skull of the whale was obtained by boiling thehead at WRI and the species was identified as Kogia breviceps, based upon the key
characters of Handley (1966).
For long years most workers accepted that there was a single but variable
species in the genus Kogia, while as many as seven species have been described.
Following works by Ogawa (1936-37) and Yamada (1954), Handley (1966) established that there are two well-defined species, the pygmy sperm whale Kogia breviceps
Blainville, 1838 and the dwarf sperm whale, Kogia simus Owen, 1866.
Recently Ross (1979) made extensive study of pygmy and dwarf sperm whales,
using at least 80 animals recorded on the southern African coast up to the end of
1975. He compared the material of K. breviceps and K. simus and confirmed Handley's (1966) distinction of the two species based on cranial and external characters,with the exception of the relative height of the foramen magnum and the positionof the dorsal fin relative to body length, which should be used with caution in
specific identification.
Handley (1966) listed up distinguishing characteristics of Kogia breviceps andK. simus in his Table 1. The majority of these differences refer to features of thecranium and mandible. According to Ross (1979) the most distinctive cranialcharacters are the shape of the dorsal sagittal septum near the vertex and thedorsal cranial fossae. In K. breviceps the sagittal septum near the vertex is broad,whereas in K. simus it is narrow. The shape of the dorsal cranial fossae of thetwo species is different in that that in K. breviceps the left fossa is conspicuously narrower than the right, and each fossa slopes gradually from the dorsal rim of theskull. In K. simus dorsal rim of the cranial fossae is sub-spherical, and the posteriorwall of each fossa is steep, giving a cupped appearance to the skull.
In the characters listed above the Tokaimura specimen (Figs 1-4) agrees wellto those of K. breviceps. In the mandible Handley (1966) noted the number ofmandibular teeth, 12-16 pairs in K. breviceps and 8-11 pairs in K. simus. He noted,
however, in rare case 10 or 11 pairs in the former and 13 pairs in the latter. The
length of mandibular symphysis is longer in K. breviceps than in K. simus.
The Tokaimura specimen had 24 teeth in all and this was estimated thatSci. Rep. Whales Res. Inst.,

No. 33, 1981, 119-124.

120OMURA AND TAKAHASHI

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Sci.Rep.Jl"halesRes.Inst・3
λro.33,1981

PYGMY SPERM WHALE
TABLE 1.

BODY PROPORTION OF THE TOKAIMURA SPECIMEN
OF KOGIA BREVICEPS
Measurements

1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.

121

Tip of snout to notch of flukes (Total length)
Tip of snout to center of eye
Tip of snout to blowhole
Tip of snout to ant. insertion of flipper
Tip of snout to ant. insertion of dorsal fin
Tip of snout to tip of dorsal fin
Length of gape
Length of blowhole
Length of eye
Notch of flukes to umbilicus
Notch of flukes to genital slit (male)
Notch of flukes to anus
Girth on transverse plane at ant. insertion of dorsal fin
Girth on transverse plane at anus
Length flipper, ant. insertion to tip
Length flipper, axilla to tip
Height, dorsal fin
Length, dorsal fin
Width of flukes, tip to tip
Anterior border of flukes to notch
Anterior border of flukes to tip

TABLE 2.

in mm% of
Total length

2,480
270
240
430
1,370
1,515
66
40
42
1,570
1,455
685
1,960
980
325
260
83165580
170
400

100
10.9
9.7
17.3
55.2
61.1
2.7
1.6
1. 7
63.3
58.7
27.6
79.0
39.5
13.1
10.5
3.3
6.7
23.4
6.9
16.1

CRANIAL MEASUREMENTS OF THE TOKAIMURASPECIMEN OF KOGIA BREVICEPS
in mm% ofTotal length

337
126
158
113
277
288
278
217
25
197

100
37.4
46.9
33.5
82.2
85.5
82.5
64.4
7.4
58.5

11.
12.
13.
14.
15.
16.

Total (condylobasal) length*
Rostrum, length**
Rostrum basal width**
Rostrum, width at its middle**
Breadth across pre-orbital angles of supra-orbital processesBreadth across post-orbital processes
Zygomatic width
Height to vertex
Width of vertex
Width of supra-occipital at narrowest part between posterior
margins of temporal fossae
Tip rostrum-left naris
Height of ventral border of foramen magnum
Length maxillary toothgroove-right
Length maxillary toothgroove-leftWidth outer margins occipital condyles
Tip rostrum-hind margin pterygoids

163
75
64+
52+
78
181

48.4
22.3

23. l
53.7

24.

Height dorsal border of foramen magnum to vertex

105

31.2

Measurements
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.

* 20 mm added for breakage.
** Measured ventrally.

Sci. Rep. Whales Res. Inst.,
No. 33, 1981

122OMURA AND TAKAHASHI

close to his upper ranges.
The cranial measurements of Kogia, however, subject to wide ranges of individual variation, judged from figures in Tables 26 and 27 of Ross (1979), and it
seems very difficult to separate both species from cranial measurements alone. In
some cases, however, condylobasal length of the skull may useful. Handley (1966)
gives condylobasal length of adult specimens of K. breviceps and K. simus as 391469 mm and 262-302 mm respectively. The condylobasal length of the Tokaimura specimen was estimated 337 mm as shown in Table 2. This length is muchlarger than those of K. simus, but still this whale was judged to be immature andbones of skull are fused loosely. The largest tooth measures 19 mm in length andpulp cavity is not closed. In K. breviceps, however, the pulp cavity appears toremain open at the base of tooth throughout life (Ross, 1979).
Body proportion or external measurements of the Tokaimura specimen of K.
breviceps ·(Table l) are compared to Table 3 of Ross ( 1979) and found slight differences between those, but we can not conclude anything at this moment andfurther collection of material is needed. According to Table 3 of Ross (1979) no
distinct difference was observed between K. breviceps and K. simus, excepting theheight of dorsal fin. This value is 2.3-4. 7% of total body length in K. breviceps(12 specimens) and 5.4-10.0% in K. simus (19 specimens), the latter species having
quite taller dorsal fin than the former. This height of dorsal fin of the Tokaimura
specimen is 3.3% of the body length and this value is within the ranges of those ofK. breviceps (Table 1).
Yamada (1954) gives measurements of body proportions of his specimen nos
3, 4, 5 and 6. Among them total length was not measured in nos 5 and 6. We
calculated, therefore, percentage figures of the height of the dorsal fin against total
body length for his specimen nos 3 and 4, and got the value of 6. 7 and 5.9% respectively. These are all within the ranges for K. simus.
Further he presents cranial photographs of the specimen nos 1, 2, 4, 5 and 6.
Judged from these photographs we assumed that his no. 4 specimen is K. simus, being
the sagittal septum near the vertex is very narrow and the cranial fossae giving acupped appearance of the skull.
In this way we can further assume that his specimen no. 1 is probably K.
simus and nos 2, 5 and 6 to be K. breviceps. This can be checked by the length ofmandibular symphysis. According to Ross (1979) this length is 13.7-26.3% of theskull length in K. breviceps, whereas the corresponding figures in K. simus is 11.115.8 %. We calculated this value for nos 1, 2, 4, 5 and 6 from his Table 3. Theseare 12.3, 15.2, 11.1, 15.8 and 15.2% of their skull length respectively. Our conclusion is, therefore, Yamada's specimen nos 1, 3 and 4 are probably assigned toK. simus and nos 2, 5 and 6 to K. breviceps.
From the coast of Japan Kogia was first reported by Van Beneden and Gervais(1868-1879). The species of this Kogia (du Japan) is judged to be K. breviceps
from drawings shown in PL. LXI of their report. The left dorsal cranial fossa ismuch narrower than the right and the posterior wall of each fossa seems to slope
gradually from the dorsal rim of the skull. The condylobasal length of the skull
Sci. Rep. Whales Res. Inst.,
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PYGMY SPERM WHALE

123

is estimated to be 342 mm (measured length from the drawing was multiplied by3). Width of the vertex was estimated as wide as 18 mm and this is 5.3% of thetotal length. This value is smaller than that of the Tokaimura specimen (Table2), but still within the ranges of values given by Ross (1979), or 5.0-11.9% in 22
specimens. Further right mandible has 13 teeth and no maxillary tooth present.
Honda (1928) reported a Kogia was stranded on the coast of Tsudanuma,Chiba, on I October 1927. This whale had 13 pairs of teeth on mandibles. Nomaxillary tooth present. Sex was determined as male and he gives general description, external as well as internal, of the whale body. He collected skull andother bones of this whale. The skull was studied later by Ogawa (1936-37) andit is possible that the species is K. breviceps.
Hirasaka (1936) reported stranding of a Cogia (Kogia) breviceps at Ishigakijima, Okinawa, on 8 March 1935. He gives a photograph of this whale andreports that the body length was said as 8 shaku (2.4 m), and no further information available. From the photograph shown in his paper it is true that the animal
belongs to the genus Kogia, but the species can not be identified from this photograph alone.
Hirasaka (1937), however, obtained skull and post-cranial bones of this whale
later and identified the species as Kogia breviceps. According to him, however, heperceived several characters similar to those of the simus-type but there are someothers that contradict them, showing the general characteristics of the breviceps. His
opinion was that the younger individual with a skull of under 300 mm (skull lengthof his speciemen is 290.5 mm) gradually change to a general type (of breviceps) after
accomplishing a certain period of growth.
He gives, however, photographs of the skull of his Kogia. Judged from thesephotographs we consider this whale would be a Kogia simus. The dorsal rim of
the cranial fossae is sub-spherical and the posterior wall of each fossa seems steep,giving a cupped appearance. The dorsal sagittal septum near the vertex is notbroad. The number of alveoli in each mandible is 9 and the length of symphysis
is 14.8% of the skull length.
Ogawa (1936-1937) studied five skulls and other bones, including those obtained by Honda (1928). He recognized both K. breviceps and K. simus occur on
the coast of Japan. He thought that his specimen nos 2, 3 and 4 whales are K.
breviceps and nos I and 5 whales are K. simus. These are supported by his description and photographs in his paper. He was also of opinion that the Kogia (duJapan) reported by Van Beneden and Gervais (1868-1879) should be assigned toK. breviceps.
Yamada (1954) studied six specimens of Kogia taken at Taiji, Wakayama andmeasured external as well as cranial proportions. His specimens are smaller inlength in general and the condylobasal length ranged 276-302 mm. The highest
number of teeth on one mandible is eleven and others are 8-10. Maxillary tooth
is common in all specimens. His report was preliminary and no definite conclusion was stated as to the distinction between K. breviceps and K. simus. He stressed,
however, a strong opposition against the dominant opinion of recent (then) time
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OMURA AND TAKAHASHI

that the younger animals of initial resemblance with K. simus turn into the general
type of K. breviceps as they grow. Then his paper was followed by Handley (1966)
as stated before. We also commented Yamada's paper (1954) in some extent asstated already. In this case, however, the number of teeth was not a good criterion
in separating the two species.
Since then no scientific paper on the genus Kogia has been appeared in Japanto our knowledge.
Our sincere thanks are due to Dr A. Okata and his staff of the Ibaragi Prefectural Fisheries Experimental Station. They kindly informed us the stranding of
this whale and gave us great help in measuring the body proportions and sampling of the head of this whale for study of the skull.
REFERENCESHANDLEY, C. 0. JR., 1966. A synopsis of the genus Kogia (pygmy sperm whale). pp. 62-69. In: K. S.
Norris (ed.) Whales, dolphins and porpoises. Univ. California Press, Berkeley and Los Angels. 789 pp.
HIRASAKA, K., 1936. A pigmy sperm-whale (in Japanese with English synopsis). The Z,oological Magazine,
48: 72-74.
HrRASAKA, K., 1937. On the pigmy sperm-whale, Kogia breviceps (Blainville). Mem. Fae. Sci. Agr. Taihoku
Imp. Univ., XIV (5): 117-142.
HONDA, K., 1928. On a toothed whale captured at Tsudanuma, Chibaken (in Japanese). The :(,oologicalMagazine, 40: 504-505.
OGAWA, T., 1936-37. Studien uber die Zahnwale in Japan. VI. Cogia. Botany and Zoology, 4: 2017-2024,
5: 25-28.
Ross, G.J.B., 1979. Records of pygmy and dwarf sperm whales, genus Kogia, from southern Africa, withbiological notes and some comparisons. Ann. Cape Prov. Mus. (nat. Hist.), 11 (14): 259-327.
VAN BENEDEN and P. GERVAIS, 1868-1879. Osteographie des Cetaces vivants et fossiles. Arthus Bertrand,Paris. 634 pp+64 pl.
YAMADA, M., 1954. Some remarks on the pygmy sperm whale, Kogia. Sci. Rep. Whales Res. Inst., 9: 37-58.

Sci. Rep. Whales Res. Inst.,

No. 33, 1981