Japan Cetology
Online ISSN : 2434-1347
Print ISSN : 1881-3445
Showing 1-6 articles out of 6 articles from the selected issue
  • Hajime Ishikawa
    2013 Volume 0 Issue 23 Pages 1-5
    Published: 2013
    Released: December 04, 2019
    JOURNALS OPEN ACCESS
    A questionnaire survey on the local names of finless porpoise Neophocaena phocaenoides was conducted to fishery cooperatives in Yamaguchi prefecture, Japan. A small scale hearing survey was also conducted. A total of 20 different local names of finless porpoise was collected from 49 answers. These names were clearly divided into two groups distributed in the east and the west of the prefecture. In the eastern region, the most common local name was “De-gondo” and followed by “Re-gondo” and both include a word “Gondo” (Japanese name for pilot whales). Most of other names in the eastern region seem to be modification of them. On the other hand, in the western region, most common name was “Name” or “Nametto”, and most of other names include a word “Name”. “Bohzu” was collected from both regions, though it was rather rare. Investigation of old literature suggested that names with “Name” were old and common in Japan, whereas names with “Gondo” seemed to be originated from a name “Ze-gondo” which was used at central area of the Chugoku region in Edo era.
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  • Satoshi T. Yamamoto, Akiko Yatabe
    2013 Volume 0 Issue 23 Pages 7-12
    Published: 2013
    Released: December 04, 2019
    JOURNALS OPEN ACCESS
    “Telescoping” is a unique morphological feature of cetacean skulls which previous studies have suggested is the result of aquatic adaptation of abilities such as breathing, sound production, and feeding. We think these abilities are necessary for both newborns and adults, but telescoping is not yet complete at birth. Hence we examined changes to shape during the growth process, and why those changes occurred, through observation of external features and actual measurements of the skulls of 93 common dolphins (Delphinus delphis) in different stages of growth, from newborns to adults. According to observation of external features on the dorsal aspect of the skull, in young common dolphins the braincase was relatively large compared to the rostrum, and large areas of the interparietal, parietal and frontal bones were visible. These results are the same as for previous studies. According to the measurements, condylobasal length (CBL) and length of rostrum (LR), and CBL and distance from tip of rostrum to external nares (DRE) had an almost linear positive correlation. However, the ratios of LR and DRE to CBL did not increase constantly, having a tendency to increase in three phases. This was especially the case for the ratio of DRE to CBL. In the first phase, the braincase extended little due to the interparietal bone being overlapped by the frontal bone. Extension of the rostrum was faster than the braincase after the first phase, and in the last phase, rostrum and braincase extended with proportions maintained. These results suggest that the interparietal bone has an effect on the braincase appearing relatively large and on changing proportions throughout growth. One merit of incomplete telescoping of the skull, given that frontal bone and interparietal bone are components of the braincase, would be to ensure brain volume. On the other hand, a possible demerit is insufficient ability to perform echolocation given that the concave part of the skull, which functions as an acoustic mirror for echolocation sounds, is incomplete. However, this demerit may have little effect on newborns, which are nursed by their parents. We considered the possibility that the incomplete telescoping of a newborn’s skull is due to ensuring brain volume having priority over feeding-related organs and all abilities.
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  • Mizuki Murakami, Yoshiki Koda
    2013 Volume 0 Issue 23 Pages 13-20
    Published: 2013
    Released: December 04, 2019
    JOURNALS OPEN ACCESS
    A right periotic of Albireonidae (Cetacea, Delphinoidea), from the Pliocene Na-arai Formation of Chiba, central Japan, is described. The albireonid specimen is the second reported from the western North Pacific and the first recorded from the Pliocene. Thus, this discovery largely extends our knowledge of paleobiogeography of Albireonidae. The Na-arai specimen shares following features with the type species of Albireo: having the large aperture for the cochlear aqueduct; the trapezoidal cochlear portion and the large angle between the caudal tympanic process and the lateral edge of the cochlear portion in ventral view; the mediolaterally narrow posterior bullar facet; shallow grooves on the posterior bullar facet. However, the present specimen probably belongs to different species from the type species because of differences of morphology in the internal acoustic meatus and anterior process. The fossil ear bone assemblage of Delphinoidea from the Na-arai Formation provides important data for comparing Pliocene delphinoid faunas of the western North Pacific with those from other areas of the Pacific. The paleoclimate of the Na-arai Formation was probably more similar to those of delphinoid localities in the eastern regions of the North and South Pacific than to those of other fossil localities in the western North Pacific.
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  • Yoshiharu Honma, Masahiko Iwashita
    2013 Volume 0 Issue 23 Pages 21-22
    Published: 2013
    Released: December 04, 2019
    JOURNALS OPEN ACCESS
    Following the previous paper (Honma and Iwashita, 2012), sighting records of whales by Sado Kisen (Sado Line) jetfoils and car ferry boats operating in the Niigata- Ryoutsu-route, Sea of Japan, was compiled from January to December, 2012. Comparison was made among the instances of previous years investigated 1994- 2011. Thirty-four instances, comprising 9 car ferrys and 25 jetfoil observations were enumerated. The site of sightings was concentrated between the points 3.0 and 4.0 points in the Sado lane, divided into 5 points. The greatest number of sightings was in March, one month earlier than those of ordinary year. The time zone of higher frequency was concentrated in 10:00 a.m., 2:00 p.m. and 5 p.m., but sighting were thoroughly obtained in the daytime, from early morning to evening. It was usual that only single individual was observed by a sighting, but, the large numbers of one school was several tens animals for one occasion, absolutely consisting of Grampus griseus. The directions in which the whales were swimming (= migrating route) were noted 9 south and 5 north. Fortunately, there was no collision with cetaceans and other unknown large subjects in 2012.
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  • Yoshiharu Honma, Hajime Iwao, Kazuhiro Minowa, Yukihiro Nakamura, Akir ...
    2013 Volume 0 Issue 23 Pages 23-27
    Published: 2013
    Released: December 04, 2019
    JOURNALS OPEN ACCESS
    Following a previous paper (Honma et al. 2011b), stranding, entangling, and sighting records of marine mammals along the beach and offshore regions of Niigata Prefecture, the Sea of Japan, were compiled from January 2010 to May 2012, in order to made comparison among the instances of previous years investigated 1994-2009. As a result, 27 incidences of stranding and sighting were noted on the beach. The incidences were consisted of 6 Pacific white-sided dolphins, 4 Risso’s dolphins, 5 Stejneger’s beaked whales, 4 Minke whale, 7 northern fur seals and a spotted seal. Compared with previous years, in 2012, increased sightings of northern fur seals on the beach and Naoetsu – Ogi route were remarkable. Two newborn infants of the Stejneger’s beaked whale were stranded on the beaches of Kashiwazaki City in 2012. Combined data with previous years suggested that offshore areas of this City might be important areas for parturitions and growth of Stejneger’s beaked whales.
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  • Taichi Ichimori, Shunsuke Suzuki, Senri Kojima, Kentaro Ishimori, ...
    2013 Volume 0 Issue 23 Pages 29-33
    Published: 2013
    Released: December 04, 2019
    JOURNALS OPEN ACCESS
    The cetacean sighting records from 375 sighting survey in the Tsugaru Strait for ten years were compiled and the seasonal variability and yearly trend of cetacean encounter was examined. A total of 1876 school 19065 individuals were observed, and at least 7 species are identified such as Pacific white-sided dolphin, Dall’s porpoise, Habour porpoise, Minke whale, Bottle nosed dolphin, Common dolphin, and Killer whale. Except for Killer whale, the encounter of all of the cetacean were peaked during April to June. The encounter is rare during August and October, and no encounter has been recorded for this season for 10 years except for Pacific white-sided dolphin and Habour porpoise. The encounter rate of Harbour porpoise has been significantly increased. No encounter of Common dolphin and Bottle-nosed dolphin has been recorded after 2004, and the encounter to Killer whales had been occurred after 2009.
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