A RECORD OF THE BEARDED SEAL WANDERING WITH
SPECIAL REFERENCE TO THE WANDERING SPEED
YASUHIKO NAITO
National Institute of Polar Research, Tokyo

The south and north bound wandering around the Boso Peninsula of the bearded
seal (Erignathus barbatus) was recorded in 1977. Many examples of the seal wandering had been reported in many places where so far apart from normal habitat(Richardson, 1975; King, 1975; Naito, 1976; etc.), and the wandering of seal itself
is not so much worth of special mention. However, this record might be of someinterest to report here due to the most far south record in the western North Pacificand its consequent observation made possible an estimation of wandering speed.
One seal was first observed by fishermen in the Amatsu fisheries harbor at
4: 00 PM, 6 September 1977 (Table 1). At this time I could fortunately observe
the seal at 20 meters distance. It was easily identified as the bearded seal fromits outer looking such as characteristic profusion of moustachial whiskers, andanterior insertion of the foreflippers. The sex was also identified as male fromexistence of opening of male genital organ. The seal was roughly estimated to beas large as 1.5 m and its age was supposed as a young animal. The body color
was muddy on dorsal side and brownish yellow on ventral side. The seal disappeared after about one hour stray in the harbor. On the next morning a fisherman found the seal occurred in the Chikura harbor at nine in the morning. Ivisited Chikura harbor as quickly as possible, however, the seal was already outof the harbor before my arrival. According to the fisherman's information on
the body size and color, it was supposed that this seal was the same as I saw theday before. Following informations on the seal were brought from Kisarazu andthen from Funabashi in a few days. Therefore, the wandering way of this seal
was recorded as shown in Fig. 1 and in Table l. However, after sighting at Funabashi, the seal was missed and no information was received.
According to Naito (1976), 16 examples of seal wandering were recorded along
the coast of Japan (except Hokkaido) since 1949, and only two out of 16 examples
were the bearded seals. One was recorded at Tennou-cho Akita Prefecture(39°53'N, 139°57'£) and the other was at Niigata City (38°13'N, 139°24'£). Bothwere recorded at Japan Sea coast. Therefore, this is the first time for the recordof the bearded seal wandering along the Pacific coast of Japan. Futhermore, thisobservation (Chikura; 34°37'N, 139°58'£) seems to be confirmed as the most far
south record in the western North Pacific. However, according to Wang ZheMao(personal communication), one specimen of this species was collected in China.
Therefore, being still uncertain where it was collected in China, this collection
may be the most far south record. Since the seal was observed at four locations
during its wandering as mentioned above, the wandering speed was roughly esSci. Rep. Whales Res. Inst.,
No. 31, 1979, 121-123

122

NAITO
140°EFunabashi
0N

TOKYO BAY/.•/////I
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BOSO PENINSULAkl

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I

I

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35°N

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\35°N

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______ .....
' '':>..-~..;-PACIFIC OCEAN
102030km

140°E

Fig. 1. The bearded seal first appeared at Amatsu and was successfully tracked
at Chikura, Kisarazu and Funabashi.

timated. The minimum distance between each location, time lag of occurrencesin each location, and the calculated wandering speed are shown in Table 2. Thewandering speed between Amatsu and Chikura, and between Chikura and Kisarazu are almost the same, however, between Kisarazu and Funabashi it took about
three times longer than that of the former. This difference in the wandering speed
may be resulted from the undesirable environmental condition that may caused
the unsmooth wandering between Kisarazu and Funabashi e.g. the artificiallycomplicated channels, dirty waters, numerous numbers of ships and a lot of piers.
Sci. Rep. Whales Res. Inst.,
No. 31, 1979

WANDERING OF THE BEARED SEAL

123

TABLE I. THE OBSERVED LOCALITY AND TIME OF APPEARANCE AND
DISAPPEARANCE WHILE THE BEARDED SEAL WONDEREDAROUND THE BOSO PENINSULA IN 1977
Locality

DateTimeAmatsu
ChikuraKisarazu
Funabashi

6 September
7 September
9 September
13 September

16: 00-18: 00
9:00-11:00
16: 00-18: 00
13: 00TABLE 2. MINIMUM DISTANCE BETWEEN EACH LOCATION AND TIMESPENT TO REACH EACH LOCATION WERE CALCULATEDTO INDUCE THE WONDERING SPEED
Location

Minimumdistance

Wonderinghours

Wonderingspeed

Amatsu-Chikura
Chikura-Kisarazu
Kisarazu-Funabashi
Amatsu-Funabashi (total)

26.1 km
79.1
36.9
14:U

16 hours
5391
160

1.63 kmjhr
1.49
0.41
0.88

On the other hand, the areas between Amatsu and Chikura, and between Chikura
and Kisarazu are all or partly facing to the Pacific Ocean, and it seems to be clean
enough for the seal to make smooth wandering. Therefore, it may be possible topresume that the minimum distance was followed between Amatsu and Kisarazu
which is 105.2 km, and the average speed was 1.52 km per hour. This average
speed is comparable to neither the swimming speed nor the migration speed, but
as a whole it means the minimum moving speed during wandering. The seal may
not swim directly on the minimum distance route but may stray here and there
during locomotion from location to location. Futhermore the seal may take restoccasionally. Therefore, it is likely that normal swimming speed itself may be
several times faster than the wandering speed.
In this study, I was very much indebted to the staff of the Kamogawa Sea
World to pursue the seal. They kindly provided me the informations I needed.
REFERENCERICHARDSON, D. T., 1975. Hooded seal whelps at South Brocksville, Maine. J. Mamm., 56 (2): 698-699.
KING, J.E., 1975. Leopared seals on Lord Howe Island. J. Mamm., 56 (1): 251-252.
NAITO, Y., 1976. The occurrence of the phocid seals along the coast of Japan and possible dispersal of pups.
Sci. Rep. Whales Res. Inst., 28: 175-185.

Sci. Rep. Whales Res. Inst.,
No. 31, 1979