摘要:

AbstractTo test hypotheses involving reproduction and demographics, the sex of individuals must be established, but many species of Cetacea are not obviously dimorphic. In the North Atlantic right whale,Eubalaena glacialis, population, the sex of 61 males and 55 females had been determined previously by observation of the urogenital region, and the sex of 43 more females had been inferred from repeated sightings with a calf. To confirm the sex of some of these animals and to identify the sex of mote animals, genomic DNA was isolated from skin samples of 95 individual right whales (54 from among those described above and 41 additional recognizable individuals). The DNA was surveyed using the human Y‐chromosome probe pDP1007. WithEcoRI‐digested DNA, a clear, sex‐discriminating banding pattern was apparent. This method verified the sex of all 54 animals whose sex was previously known or inferred and identified the sex of an additional 41 recognizable individuals. A total of 89 male and 111 female right whales was identified in the population. The most unbiased estimate of sex ratio available is the 36 male and 34 female calves identified by genital morphology and DNA techniques. The sex ratio of this sample does not differ significantly from unity (P = 0.811). Only 38% (58/152) of the females in the North Atlantic population are known to have been reproductively successful compared with 54% in the population of right whales in the western South Atlantic. The population growth rate reported for the North Atlantic population is only 33% of that reported for right whales in the South Atlantic. Thirteen adult North Atlantic females have been identified that have not been known to calve during the past 11 yr. These data suggest that the absence of measurable recovery may be due to a combination of fewer actively reproducing females and lower reproductive rates of some fe

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1994.tb00481.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractDevelopment, sexual dimorphism, and individual variation were examined in the skeleton of the finless porpoise in the coastal waters of western Kyushu, Japan. Skulls ceased growing by 4 yr. Postcranial skeletons ceased increasing in size at an age older than 11 yr. The finless porpoise was estimated to attain cranial maturity by 4 yr and physical maturity at 14–23 yr. Sexual dimorphism was not detectable in most of the cranial characters but was detected in more than half of the postcranial characters. Females tended to show larger values of postcranial characters. The shape of the pelvic bone was obviously different between males and females. Thus, a discriminant function was proposed to determine sex using measurements of this bone. Individual variation was greatest in the feeding apparatus such as length of the rostrum, and least in the braincas

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1994.tb00482.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractA total of 1,715 km of boat‐based surveys and 1,521 km of aircraft‐based surveys was conducted from 1986–1989 to assess the distribution, relative abundance, and ecological relationships of cetaceans in the northern Gulf of California. Seven cetacean species were seen; in decreasing frequency of groups encountered they were: bottlenose dolphins,Tursiops truncatus; vaquitas,Phocoena sinus; common dolphins,Delphinus delphis; fin whales,Balaenoptera physalus; Bryde's whales,B. edeni; gray whales,Eschrichtius robustus, and killer whales,Orcinus orca.Common dolphins were numerically dominant and bottlenose dolphins were seen most often. Bryde's whales and vaquitas had the smallest group sizes. In general, the odontocete cetaceans were separated spatially, whereas the distribution of Bryde's and fin whales overlapped conside

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1994.tb00483.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractDuring the morbillivirus epizootic that affected the Mediterranean striped dolphins (Stenella coeruleoalba)in 1990–1992, several thous and individuals are believed to have died. In order to determine the segments of the population that were affected by the event, the sex‐ and age‐frequency distributions of the animals that were washed ashore on the Spanish coasts were studied. The age of the animals was determined by counting dentine growth layer groups in the teeth. The results obtained indicate that both sexes were affected similarly by the disease and that the population component that suffered the largest mortality was that of sexually mature individuals, although substantial mortality of calves, probably still dependent on their mothers, was also observed. Juveniles, in contrast, appeared to be only slightly affected by the epizootic. This pattern of mortality is not consistent with the epidemiology of morbillivirus infections previously observed in other mammals. Possible explanations of this particular age distribution include behavioral factors, increased susceptibility to the disease in adults due to the effects of pollution, high temperatures and decreased food availability, or allopatric geographical distribution of population components and, therefore, of their associated mort

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1994.tb00484.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractWeather conditions recorded from 1956 to 1986 on St. Paul Island, Alaska, were probed to establish their influence upon the northern fur seal's life cycle (Callorhinus ursinus). Air temperatures, wind speeds, and relative humidity levels were seasonally decomposed and compared with the timing of pupping and migration. Most pups are born in early July when air temperatures and relative humidity approach their highest annual levels and wind speeds are at their lowest. Weather conditions favor growth and survival of pups from July to September but are unfavorable in June. A rapid deterioration in weather through October and November corresponds with the fall migration of pups and lactating females. The data suggest the pivotal event in the fur seal's life cycle is the timing of birth and survival of nursing pups. As such, the ultimate determinant of the precisely timed fur seal life cycle appears to be climatic seasonality during the breeding season.

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1994.tb00485.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractGross energy intake (GEI), apparent digestible efficiency (%DE), and body‐mass change were studied both in recently weaned and in subadult harp seals fed capelin (Mallotus villosus) and crustaceans (Parathemisto libellulaandThysanoessasp.)ad lib.The median %DE ofParathemisto libellula(with a wet‐weight energy density (ED) of 3.9 kJ/g) andThysanoessasp. (ED: 2.3 kJ/g) was 81% and 83%, respectively, while the median %DE of capelin (ED: 8.6 kJ/g) was 94% and 93% for subadult harp seals and one harp seal pup, respectively. No correlation between age and %DE was obtained (P>0.05). Despitead lib.access to the food, the harp seal pups were unable to maintain body mass while on a crustacean diet, and it is therefore suggested that harp seal pups most likely must supplement their crustacean diets with fish to maintain gro

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1994.tb00486.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractFood intake (PI), body mass (BM), and compartmental growth were recorded for 12 mo in four captive 2–4‐yr‐old male harp seals (Phoca groenlandica), exposed to an artificial light regime that closely resembled natural day length at 69°. In early May before molting, bothFZandBMdecreased in all four animals. Total body fat (TBF) declined from 51% ofBMin March (n = 4) to 30% in August (n = 2), while total body water (TBW) concomitantly increased from 37% to 51% and total body protein (TBP) from 11% to 17%. In JulyFIstarted to increase, whileBMstarted to increase in August.TBFincreased whileTBWandTBPdecreased from August, all three parameters reaching a stable level in October at 47%, 39%, and 12%, respectively. Thereafter, body composition was maintained rather constant until May. Between October and March/AprilFIfluctuated for all animals, whileBMshowed a fairly steady increase. Average daily amount of capelin consumed was 2.67 kg·d−1, equivalent to 25,600 kJ·d−1, or 343

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1994.tb00487.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1994.tb00488.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1994.tb00489.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1994.tb00490.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY