摘要:

AbstractThe distribution of blue whales,Balaenoptera musculus, in the eastern tropical Pacific (ETP) was analyzed from 211 sightings of 355 whales recorded during research vessel sighting surveys or by biologists aboard fishing vessels. Over 90% of the sightings were made in just two areas: along Baja California, and in the vicinity of the Costa Rica Dome (a large, stationary eddy centered near 9°N, 89°W), with the rest made along the equator near the Galapagos islands, the coasts of Ecuador and northern Peru. All sightings occurred in relatively cool, upwelling‐modified waters. Because these areas are the most productive parts of the ETP, and have relatively large standing stocks of euphausiids, it seems possible that blue whales select low latitude habitats which permit foraging. The waters off western Baja California were occupied seasonally, with a peak in sightings coinciding with the spring peak in upwelling and biological production. The Costa Rica Dome area was occupied year round, suggesting either a resident population, or that both northern and southern hemisphere whales visit, with temporal overlap. The modal group size was one for all areas and seasons, but the frequency of groups with two or more whales was significantly higher in sightings made near the Galapagos Islands and the coast of Ecuador and northern P

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1990.tb00357.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractNorth Atlantic right whale mortality rates range from 2% to 17% over the first four years of life. Sources of mortality in this population include ship collisions, entanglements, and natural causes. A combined analysis of stranding data, entanglement records, and photographic information indicates that approximately one third of all right whale mortality is caused by human activities. Anthropogenic sources of right whale mortality may be a significant factor inhibiting growth in the North Atlantic population.

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1990.tb00358.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractBreeding colonies of the antarctic fur sealArctocephalus gazellaon Heard Island (53°10′S, 73°30′E) are situated on the sheltered northern and eastern coasts on flat vegetated terrain near streams and pools. Pupping in the 1987/88 summer began on 21 November, with 90% of births in 26 d. The median birth date was 11 December. Pup counts at Heard Island made in seven breeding seasons from 1962/63 to 1987/88 show an exponential rate of increase of 21%, which may be inflated due to undercounting in early years. The total of 248 births in 1987/88 represents an exponential increase of 37% since the previous year, but pups may have been undercounted then. Based on the number of pups born, the breeding population is estimated at 870–1,120. During the breeding season, the largest number of animals ashore was 835. Many non‐breeding fur seals began hauling out from early January and 15,000 animals were estimated to be ashore by late February, a fat larger number than expected from the size of the breeding population. Both the breeding and non‐breeding components of the population may be augmented by immigration. The source of immigrants may be undiscovered breeding colonies of this species in the northwestern sector of the Kerguelen Archipelago or the concentration at South Georgia. Further censuses are required at Heard Island to monitor the popula

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1990.tb00359.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractSkulls of 69 bottlenose dolphins (genusTursiops) from the Indian/Banana River on the east coast of Florida were examined for evidence of sexual dimorphism. The only sexual dimorphism shown byt‐tests on 28 morphological and four meristic skull characters was that males have, on average, more teeth than females in all four arcades. Results of covariance analysis, employed to account for variation in size, indicate minor dimorphism in parietal width of the skull. Twenty body measurements of 29Tursiopsoriginating in the same area were also analysed for differences between males and females. Statistical results indicate the possibility of sexual dimorphism in the length from the snout to the umbilicus and in flipper width. No evidence was found for differences in overall skull or body length between the sexe

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1990.tb00360.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractSamples of sperm whale skin, useful for modern molecular analyses of DNA, can be obtained from living animals either by collecting skin sloughed naturally by the whales, or by using biopsy darts fired from crossbows or compound bows. Sloughed skin was found frequently in warm waters, and particular samples could often be linked to photographs which enabled individuals to be identified. However, sloughed skin seemed less available at higher latitudes. Two types of darts were found to collect skin but collected samples were very small (<4 mm2) and insufficient for repeated DNA fingerprinting analyses. Sperm whales always reacted to darting by “startling” and showing changes of behavior over the next few minutes, but we found no indications of longer‐term effects. In warm water studies, collection of sloughed skin seems to be generally effective, but for samples of sperm whale tissue at high latitudes modifications could probably be made to either of the darts in order to obtain larger‐sized

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1990.tb00361.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractMultivariate statistical analyses of 18 morphometric characters were performed in order to evaluate potential heterogeneity between predefined minke whale stock unit areas in the North Atlantic (West Greenland, Central, and Northeastern stocks). Results from principal component analyses suggested that the data cannot be regarded as random samples drawn from one uniform distribution. The overlap between groups was too substantial, however, to allow a firm conclusion concerning the question of isolated breeding stocks versus a large common breeding pool.

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1990.tb00362.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractAirborne sensing of emitted infrared (IR) was tested as a means of detecting under‐snow lairs of the ringed seal (Phoca hispida) in study areas in Resolute Passage, N.W.T. Lairs and regularly used large breathing holes could in some cases be detected by emitted IR from altitudes of up to 180 m. Lairs were more easily detected if they had thin roofs, and detectability was higher before sunrise, and under conditions of low wind, low ambient temperature and high cloud cove

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1990.tb00363.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1990.tb00364.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1990.tb00365.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

HandbookofMarine—Mammals‐Volume4: RiverDolphinsandtheLargerToothedWhales. Sam H. Ridgway and Sir Richard Harrison,

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1990.tb00366.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY