Coloration and Sexual Dimorphism in the Dall Porpoise

Morejohn, G. Victor; Loeb, Valerie J.; Baltz, Donald M.

doi:10.2307/1379096

Cited by 14 publications

(8 citation statements)

References 4 publications

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“…Because of their relatively offshore distribution and inconspicuous nature, they have received little attention. Much of what is known comes from a long-term study of Dall's porpoises in Monterey Bay, California, by G. V. Morejohn and his associates (Loeb 1972;Morejohn et al 1973; Morejohn 1979), and several studies of behavioral responses to survey vessels by G. C. Bouchet and his colleagues (Bouchet et al 1983Withrow et al 1985).…”

Section: Introductionmentioning

confidence: 99%

A study of the behavior of Dall's porpoise (Phocoenoides dalli) in the Johnstone Strait, British Columbia

Jefferson¹

1987

Can. J. Zool.

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JEFFERSON, T. A. 1987. A study of the behavior of Dall's porpoise (Phoc.oenoides dalli) in the Johnstone Strait, British Columbia. Can. J. Zool. 65: 736-744. The behavior of Dall's porpoise was studied in the western Johnstone Strait, British Columbia, during the summer of 1984. Observations and theodolite trackings were made from a cliff-top observation point on West Cracroft Island. Dall's porpoise was the second most common marine mammal in the study area, being seen on 63% of the days, and it was reported to be a year-round resident of the Strait. Three types of surfacing behavior were observed, with slow rolling occurring in 97% of the sightings. Swimming speed of slow rolling porpoises was 5.1 5 0.83 (SD) km/h (n = 18). Dives during travel averaged 35.9 5 26.52 (SD) s (n = 10). Deep vertical dives lasted 2 to 4 min for adults and up to 2 min for calves, and were presumed to be associated with feeding. Westward movement predominated. Dall's porpoises usually showed no obvious reaction to resident killer whales, but apparently swimming speed increases when killer whales are within 2 km. Group sizes ranged from one to over five animals (mean size = 2.6 + 1.05 (SD), n = 68). Groups that included calves tended to be larger than adult-only groups. Neither direction of travel nor time of day were significantly related to group size. The population appears to contain a high percentage of cow-calf pairs, and this suggests that the study area may be used as a calving area during the summer. JEFFERSON, T. A. 1987. A study of the behavior of Dall's porpoise (Phocoenoides dalli) in the Johnstone Strait, British Columbia. Can. J. Zool. 65 : 736-744. Le comportement du Marsouin de Dall a fait l'objet d'une etude dans le ditroit de Johnstone, Colombie-Britannique, au cours de 1'Cti 1984. Un poste d'observation comportant un theodolite a Cte install6 au sommet d'une falaise dans l'ile de West Cracroft.Parmi les mammiferes marins, le marsouin de Dall est le deuxieme plus nombreux dans cette rigion, et des individus ont Ct C observes au cours de 63% des jours d'itude; l'animal habite le dCtroit durant toute I'annie. En surface, les marsouins utilisent trois types de comportement et les roulements lents ont Ct C observis en 97% des cas. La vitesse de nage des marsouins au cours de ces roulements lents a e\C evaluie a 5,l 5 0,83 (ET) km/h (n = 18). Les plongies au cours des dkplacements duraient en moyenne 35,9 5 26,52 (ET) s (n = lo). Les plongies verticales profondes pouvaient durer de 2 a 4 min chez les adultes et jusqu'a 2 min chez les petits; ces plongees semblaient associees a I'alimentation. Les diplacements se faisaient surtout en direction ouest. Les marsouins ne paraissaient pas particulierement affectis par la prCsence d'Epaulards, mais il semble que la vitesse de nage augmente lorsque des Epaulards sont a moins de 2 km. Le nombre de marsouins dans un groupe variait de un a plus de cinq (moyenne = 2,6 2 1'05 (ET), n = 68). Les groupes qui contenaient des petits avaient tendance a etre plus grands que les groupes qui...

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Section: Introductionmentioning

confidence: 99%

A study of the behavior of Dall's porpoise (Phocoenoides dalli) in the Johnstone Strait, British Columbia

Jefferson¹

1987

Can. J. Zool.

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“…A fetus collected from a Dall's porpoise off California (illustrated in Ridgway 1966 and noted as "probably term") provides some evidence to support this hypothesis, appearing virtually identical with the hybrid fetus recorded in this study. Morejohn et al (1973) also include a drawing of a fetus with a clear mouth-to-flipper stripe, superficially similar to the hybrid fetus from our study (Fig. 1).…”

Section: Distancementioning

confidence: 98%

“…The pigmentation pattern of a Dall's porpoise neonate has been described as generally similar to that of an adult, though muted, with dark gray and light gray tones later intensifying into black and white in the adult (Jefferson 1988). There is considerable variability in this typical colour pattern (e.g., Morejohn et al 1973;Morejohn 1979), much of which relates to the amount of white on the dorsal fin and tail flukes, which varies with age and among individuals (Jefferson 1990). Unfortunately, very few descriptions or photographs of Dall's porpoise fetuses appear to exist.…”

Section: Distancementioning

confidence: 99%

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A new molecular technique for identifying field collections of zebra mussel (Dreissena polymorpha) and quagga mussel (Dreissena bugensis) veliger larvae applied to eastern Lake Erie, Lake Ontario, and Lake Simcoe

Claxton¹,

Boulding²

1998

Can. J. Zool.

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The veliger larvae of two introduced species of bivalves, the zebra mussel (Dreissena polymorpha) and the quagga mussel (Dreissena bugensis), are difficult or impossible to tell apart morphologically. We have developed specific dreissenid polymerase chain reaction (PCR) primers from dreissenid bivalve DNA sequences, which amplify a region of the cytochrome c oxidase subunit I mitochondrial gene. Non-dreissenid mtDNA, as found in field-collected veliger samples, was not amplified by these new PCR primers. The DNA sequence of this region distinguishes zebra mussel from quagga mussel larvae. Restriction digests of this region using the enzyme ScrFI showed no intraspecies variation in restriction pattern. We used this technique to distinguish the species of veliger larvae collected in eastern Lake Erie, Lake Ontario, and Lake Simcoe. In our limited study, no quagga mussel larvae were found in Lake Simcoe, suggesting that this mussel species has not yet spread to the Kawartha Lake system. No zebra mussel larvae were found in either Lake Erie or Lake Ontario. These preliminary results add to the growing evidence that the quagga mussel is replacing the zebra mussel in parts of the lower Great Lakes.

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“…Phocoenoides dalli-The commonly accepted understanding of the adult pigmentation of this species provides an instructive example of the effects and implications of post-mortem darkening. Numerous descriptions and photographs of dead animals do not indicate the presence of eye spot, eye stripe, or blowhole stripe (True 1885, Benson and Groody 1942, Cowan 1944, Scheffer 1949, Ridgway 1966, Morejohn et al 1973, Jefferson 1988, although True (1885) noted that, the eye was "blackish," and Morejohn et al (1973) depicted a large darkish eye spot in a "grayish-brown color variant" seen in the water but not captured. However, dorsal photographs of live specimens in the water taken under good photographic conditions (Quayle 1988, p. 73) show a clearly defined dark blowhole stripe.…”

Section: Other Speciesmentioning

confidence: 99%

Development and Homologies of Head Stripes in the Delphinoid Cetaceans

Perrin

1997

Marine Mammal Science

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Ontogeny and variation of head stripes were investigated in Stenella attenuata, S. longirostris, and Delphinus delphis. The eye stripe and the blowhole stripe together comprise the bridle. The Anlage of the bridle is a line extending across the back of the head in small fetuses. As the blowhole moves posteriorly and the rostrum lengthens, an inflection point develops in the line above the eye. This point moves forward, creating a progressively greater triangular area between the incipient eye and blowhole stripes. Well before birth, the inflection point is close to the apex of the melon, and the eye and blowhole stripes are narrow and well defined. This process proceeds to varying degrees in the other delphinoids. For example, in Peponocephala electra and in Cephalorhynchus spp., the inflection point migrates only part of the way to the apex of the melon, and the resulting “blowhole stripe” remains a broad caplike feature, resembling the state of development in small fetuses of Stenella and Delphinus. A simple eye spot without a stripe may be primitive, as it occurs in non‐delphinoid cetaceans. Presence of the bridle only in the delphinids and phocoenids may unite them in a clade exclusive of the monodontids.

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Coloration and Sexual Dimorphism in the Dall Porpoise

Cited by 14 publications

References 4 publications

A study of the behavior of Dall's porpoise (Phocoenoides dalli) in the Johnstone Strait, British Columbia

A study of the behavior of Dall's porpoise (Phocoenoides dalli) in the Johnstone Strait, British Columbia

A new molecular technique for identifying field collections of zebra mussel (Dreissena polymorpha) and quagga mussel (Dreissena bugensis) veliger larvae applied to eastern Lake Erie, Lake Ontario, and Lake Simcoe

Development and Homologies of Head Stripes in the Delphinoid Cetaceans

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