bluuebunny/crossref_metadata_2025 huggingface dataset:
ADRENOCORTICAL FUNCTION IN PINNIPED HYPONATREMIA
Authors: St. Aubin D. J. , Geraci J. R.
Published: August 2006

Potentially fatal sodium imbalance occurs in captive and free‐ranging pinnipeds and is associated with a variety of stressors. We sought to determine the role of adrenal hormones, principally aldosterone, in the development of this condition. To induce hyponatremia, two ringed seals, Phoca hispida, were maintained in fresh water and fed a low‐sodium diet; as controls, two other ringed seals were held in salt water and received a salt‐supplemented diet. After 3–6 mo, adrenocorticotropic hormone (ACTH) was used to assess adrenocortical function. In normonatremic control seals, ACTH produced a 2‐j‐fold increase in circulating cortisol and a 7‐fold increase in aldosterone. One of the experimental seals maintained normal plasma sodium levels, and ACTH elicited an exaggerated aldosterone response. The other salt‐deprived seal became hypo‐natremic, and ACTH had little effect on plasma aldosterone levels. An ACTH stimulation test performed on a spontaneously hyponatremic harp seal, P. groenlandica, which had been maintained in a salt‐rich environment, failed to elicit cortisol or aldosterone secretion from the adrenal cortex. This study demonstrated the unusual sensitivity of the seal's zona glomerulosa to central stimulation, providing a mechanism through which the stress response might exhaust adrenal hormone reserves or desensitize the cortex to other physiological stimuli.
ATYPICAL PUP REARING STRATEGIES BY SEA OTTERS
Authors: Garshelis David L. , Garshelis Judith A.
Published: August 2006

Eight tagged sea otter (Enhydra lutris) pups in central Prince William Sound, Alaska, weighed 6–15 kg at the time of separation from their mother. Four pups weighing 15 kg were able to forage successfully on their own. Three pups weighing ≤9 kg had negligible chances of survival and apparently were abandoned by sick females. Abandonment of a pup may reduce the burden on a sick female, enabling recovery and subsequent reproduction. One of the three sick females that abandoned a pup in this study recovered and pupped again. Abandonment of pups should occur most often in populations where females are stressed by poor food resources. Reassociation with a previous offspring, as observed once in this study, also may occur most frequently in food‐limited populations where reproductive failures are most common and pup survivorship is significantly increased by additional maternal assistance.
ASSESSING NORTHERN ELEPHANT SEAL FEEDING HABITS BY STOMACH LAVAGE
Authors: Antonelis George A. , Lowry Mark S. , DeMaster Douglas P. , Fiscus Clifford H.
Published: August 2006

Abstract

Stomach lavaging was used to study the feeding habits of northern elephant seals (Mirounga angustirostris) found on San Miguel Island, California, during the spring of 1984. Fifty‐nine elephant seals were chemically immobilized with an intramuscular injection of ketamine hydrochloride. Once immobilized, an animal's stomach was intubated, filled with 3–4 liters of water to create a slurry of the undigested food items, and evacuated into a collection device. The stomachs of 57 (96.6%) of the animals lavaged contained identifiable parts of prey. Twenty‐nine different food items were identified, 12 of which have not been previously reported as prey of the northern elephant seal: two teleost fish, Coryphaenoides acrolepis (Pacific rattail) and another unidentified macrourid; two crustaceans, Pasiphaea pacifica (glass shrimp) and Euphausia sp.; six squid, Abraliopsis felis, Gonatus berryi, Histioteuthis dofleini, Cranchia scabra, Taonius pavo, and Galiteuthis sp. and two octopi, Octopus dofleini and Octopus rubescens.
ECOTOXICOLOGICAL PERSPECTIVES IN MARINE MAMMALOGY: RESEARCH PRINCIPLES AND GOALS FOR A CONSERVATION POLICY1
Authors: Reijnders Peter J. H.
Published: August 2006

In integrating ecotoxicology and marine mammalogy two principal themes are conceivable: (1) the impact of contaminants on marine mammals and (2) the feasibility of monitoring marine pollution with marine mammals. Monitoring should be an alert procedure, carried out with a sensitive sensor. Uncertainties in interpreting analyses and the low susceptibility of marine mammals to short‐term changes in pollution, make them inappropriate for pollution monitoring at present.

To answer the question whether pollutants affect marine mammals, the occurrence of contaminants and the response of the animals to those chemicals have to be assessed. In studying the occurrence of contaminants it is essential that atmospheric and riverine input, geochemical processes, and processes involved with the occurrence of natural compounds are considered. To investigate the mechanisms by which pollutants affect physiological processes the kinetics of contaminants in the animals and their clinical toxicity effects have to be studied. Comparative reference data on physical and chemical blood parameters facilitates checking for hematological disorders, electrolyte imbalance, serum biochemistry and hormonal changes. Following such a concept the retrospective study of pollution effects on marine mammals might be turned into a predictive approach.
BEHAVIORAL EVIDENCE FOR HEARING THROUGH THE LOWER JAW BY AN ECHOLOCATING DOLPHIN (TURSIOPS TRUNCATUS)
Authors: Brill Randall L. , Sevenich Martha L. , Sullivan Timothy J. , Sustman Janet D. , Witt Ronald E.
Published: August 2006

On the basis of disputed physiological evidence the fat‐filled lower jaw of odontocete cetaceans has previously been hypothesized as the primary pathway to the inner ear for acoustic signals. To gain behavioral evidence, a dolphin was trained to perform an echolocation task while wearing suction cups over its eyes and either of two neoprene robber hoods over its lower jaw. One hood allowed returning acoustic signals to pass. The other substantially attenuated such signals. The dolphin's performance was significantly hindered while wearing the attenuating hood (P <. 001, ψ2) as would be expected if the lower jaw was critically important in the reception of high frequency signals.
REBUILDING SEAL STOCKS IN THE KATTEGAT‐SKAGERRAK
Authors: Heide‐Jørgensen Mads‐Peter , Härkönen Tero J.
Published: August 2006

The harbor seal (Phoca vitulina) population in the Kattegat‐Skagerrak area has been dwindling for several centuries due to excessive hunting pressure. Corrected hunting statistics during 1890–1976 are used to estimate changes in population size over the past century. After protection was introduced in the 1960s and 1970s the harbor seal population in the area increased at an exponential rate of 0.12 and exceeded 5,000 animals in 1986. The present rate of population growth is used for modelling the influence of fertility and age‐specific mortality. It is found that the observed high rate of increase is only realistic if female fertility rate is very high, the range of juvenile mortality rate is 0.33–0.52 and adult mortality is less than 0.15. Commonly cited higher mortality rates are not realistic in the Kattegat‐Skagerrak area.
ZOOGEOGRAPHY OF OREGON COAST MARINE MAMMALS: THE LAST 3,000 YEARS
Authors: Lee Lyman R.
Published: August 2006

Mammalian faunal remains recovered from three archaeological sites on the Oregon, U.S.A. coast provide strong evidence that 18th and 19th century commercial exploitation of marine mammals had major effects on the zoogeography and demography of those taxa.Zalophus californianusandCallorhinus ursinusbred and pupped along the Oregon coast between 3,000 and 100 yr ago. About 100 yr agoEumetopias jubatusabandoned a major rookery that had been utilized since at least 400 yr ago.Phoca vitulinadoes not appear to have suffered major modifications to coastal use or demographic patterns in Oregon during the last 3,000 yr, although a minor incident of intensified utilization of one location about 1,000 yr ago is suggested. All age‐sex classes ofEnhydra lutrislived on the Oregon coast until about A.D. 1900. Oregon's prehistoric remains ofE. lutrisdisplay some dental characters similar to modern Alaskan specimens, and other dental characters similar to modern Californian specimens, conforming to a latitudinal dine reflected by historic specimens. Additional evidence for many of these observations is found in faunal remains recovered from archaeological sites on the coast of Vancouver Island, the Washington coast, and the northern California coast.
THE TAPETUM FIBROSUM IN THE EYES OF TWO SMALL WHALES
Authors: Young NinaM. , Hope G. Marion , Dawson WilliamW. , Jenkins RobertL.
Published: August 2006

Abtract

The pygmy sperm whale (Kogia breviceps) and the bottlenose dolphin (Tursiops truncatus) are equipped with a tapetum fibrosum and, with other Cetacea, are the only carnivores known to possess this typically ungulate tapetal type. Tapeta from two regions of a retina, each with a different spectral reflectance (blue and green), were found to have significantly different fibrillar diameters and inter‐fibrillar spacing. When the measured values are applied to a dielectric reflector model, the predicted wavelengths agree with the observed reflectance of the flat‐mounted tapeta. The spatial properties of the fibrils change progressively from the tapetal origin in the fibroblast layer to the pigment epithelium, suggesting that different wavelengths may be reflected systematically with tapetal depth. The very large number of reflecting layers characterizing these tapeta, relative to those of other carnivores, may provide for increased spectral purity and efficiency.
DEVELOPMENTAL PATTERN OF THE BONY FALX AND BONY TENTORIUM OF SPOTTED DOLPHINS (STENELLA ATTENUATA) AND THE RELATIONSHIP BETWEEN DEGREE OF DEVELOPMENT AND AGE
Authors: Nojima Takao
Published: August 2006

Abstract

The bony falx (BF) and bony tentorium (BT) of spotted dolphins (Stenella attenuata) at different growth stages were observed. The BF and BT were observed to have the shape of the entire falx cerebri (FC) and tentorium cerebelli (TC), respectively, in adults, but were not seen in fetuses at all. Partially formed BF and BT were observed in the young. The BF and BT of spotted dolphins are formed by ossification in the FC and TC in the course of aging. Based on age determination by means of dentinal growth layers of the maxillary teeth, the ossification in the FC and TC of spotted dolphins begins by about 1 yr of age, and is completed, except for the passage of nerves and blood vessels, by about 9 yr of age. The BF and BT of spotted dolphins are formed possibly by continual dietary intake of large amounts of calcium, phosphorus and vitamin D.
BOOTSTRAP CORRECTION FOR DIURNAL ACTIVITY CYCLE IN CENSUS DATA FOR ANTARCTIC SEALS1
Authors: Erickson Albert W. , Bledsoe Lewis J. , Hanson M. Bradley
Published: August 2006

Antarctic phocid seals and particularly the crabeater (Lobodon carcinophagus) have been observed to display a diurnal cycle in their propensity to haul out on pack ice where they are visible for census. The fact that they are not visible for much of the 24‐h period means that density estimates made over broad geographic areas at various times of the day statistically confound this cycle with geographic variability. Limitation of census observations to times of peak haulout results in extreme logistical difficulties and/or considerable reduction in sample size upon which to base population estimates. Reduced sample size results in high variability in population estimates and broad confidence bands. To develop a model with which to correct density estimates for variability due to diurnal cycle, a series of stationary censuses at fixed locations in the Antarctic continental ice pack was made over significant fractions of several days. A unimodal polynomial model for the observed density variation in any one location was statistically significant; a similar model combining multiple locations with densities standardized to peak daily values was also significant. The latter model was used to make corrections for time of day to density estimates in three test data sets taken over broad geographic areas of the Antarctic. Statistical simulation (bootstrap) methods were used to determine if variances of corrected density estimates were lower than those based on uncorrected observations taken only during the peak haulout times of the day. Results were that 95% interval estimates for corrected densities were narrowed to between 40% and 61% of the uncorrected estimates. While there are additional possible sources of variation in haulout tendency, pending further data collection and analyses, the model developed represents a considerably more precise methodology than either averaging over haulout variability or limiting observations to peak daily periods.
CRABEATER SEALS LOBODON CARCINOPHAGUS DURING THE BREEDING SEASON: OBSERVATIONS ON FIVE GROUPS NEAR ENDERBY LAND, ANTARCTICA
Authors: Shaughnessy P. D. , Kerry K. R.
Published: August 2006

Observations on five groups of crabeater seals were conducted between 29 October and 17 November 1985 in the Antarctic pack ice near 66°S 50°E, off Enderby Land. The pups studied were born in the last half of October. Two of them increased in weight at a rate of approximately 4.2kg per day. Pups were weaned in the first half of November at 80–110 kg. The lactation period was 2–3 wk and thus is one of the briefest among pinnipeds. Pups decreased in weight after weaning. The only pup visited after it left the natal floe must have been feeding, as it had lost only 2 kg in a 10–day period during which it moved 13 km. Molt of lanugo appeared to be influenced more by a pup's weight than by whether or not it was weaned.
ICE‐BASED CENSUS OF BOWHEAD WHALES MIGRATING PAST POINT BARROW, ALASKA, 1978‐1983
Authors: Krogman Bruce , Rugh David , Sonntag Ronald , Zeh Judith , Ko Daijin
Published: August 2006

Abstract

Bowhead whale (Balaena mysticetus) census data obtained during the northward spring migration are summarized for 1978–1983. Population size estimates are derived from counts made by observers standing on the seaward edge of shorefast ice in the vicinity of Point Barrow, Alaska, from mid‐April to early June. The research design utilized two counting stations: South Perch, the primary counting station, and North Perch, used to determine the number of whales missed by South Perch observers. The percentage missed is estimated for each visibility category and used here to correct the census counts. Each season's population estimate is calculated as the sum of the number of trials of several independent multinomial distributions representing different visibility conditions. Corrections are applied for unwatched hours and hours with inferior visibility. A mean estimate of the number of whales passing within view of the census station was computed as 3,674 ± 299. This estimate was based on data collected in 1978, 1981, 1982, and 1983, years with the least apparent biases. Aerial survey data provide estimates of the proportion of whales passing at various distances seaward of the census sites as follows: 0.58 from the ice edge to 2 km, 0.76 to 3 km, and 0.80 to 4 km. Correcting for whales too far offshore to be seen by the ice‐based observers results in a population estimate of over 4,200 bowheads.
A DWARF FORM OF THE SPINNER DOLPHIN (STENELLA LONGIROSTRIS) FROM THAILAND
Authors: Perrin William F. , Miyazaki Nobuyuki , Kasuya Toshio
Published: August 2006

Abstract

A very small form of the spinner dolphin has been found to inhabit the Gulf of Thailand. Ten specimens taken incidentally in a local shrimp fishery differ from specimens of this species collected elsewhere in body size and shape, skull size and shape, number of teeth and numbers of thoracic and lumbar vertebrae. Four cranially adult males were 129–137 cm long, well below the ranges for the Indian Ocean, western Pacific, central Pacific, eastern Pacific and Atlantic. The skull is also very small. Tooth counts and vertebral counts average lower than in other series. The color pattern is not significantly different from that of spinner dolphins in the central and western Pacific, Atlantic and Indian Oceans but differs from that of the small eastern spinner of the eastern Pacific. The Gulf of Thailand specimens are morphologically separable from all other specimens, but it is to be expected that when larger samples are available there will be some overlap. The dwarf form may overlap in body and skull size with small spinner dolphins taken incidentally in a gillnet fishery for sharks off northern Australia. The geographic range of the dwarf spinner may be restricted. The size and status of the population and the impact of the shrimp fishery are unknown and should be investigated. The dwarf spinner may have an ecology different from that of other spinners, feeding mainly on reef‐associated and benthic organisms rather than mesopelagic animals.
MOVEMENTS OF SOUTHERN ELEPHANT SEALS AND SUBANTARCTIC FUR SEALS IN RELATION TO MARION ISLAND
Authors: Bester Marthán N.
Published: August 2006

Abstract

Based primarily on an intensive marking/resighting program conducted at Marion Island (46°54′S, 37°45′E) in the Southern Ocean, the inter‐island movements of southern elephant seals, Mirounga leonina, and fur seals Arctocephalus spp., were investigated to elucidate their little known pelagic phase. Southern elephant seals, in particular immature animals, readily move between the proximate Marion and Prince Edward islands. Some range as far afield as Iles Crozet, approximately 1,000 km distant where they haul out for the summer molt or during an autumn resting phase. The exchange of individuals between Marion Island and Iles Crozet during the return of immatures for the molt after a winter at sea, suggests overlapping of the foraging ranges of the two populations. Despite their wanderings, the majority of M. leonina from Marion Island probably feed in the proximity of the island, and relocate onto the island for breeding, molting and resting. Of the fur seals, only a few A. tropicalis were seen away from their natal island, in some cases covering distances in excess of 2,000 km. displaying a remarkable dispersal capacity.
GROWTH LAYERS IN TEETH FROM KNOWN‐AGE, FREE‐RANGING BOTTLENOSE DOLPHINS
Authors: Hohn Aleta A. , Scott Michael D. , Wells Randall S. , Sweeney Jay C. , Irvine A. Blair
Published: August 2006

Abstract

Growth layers were examined in teeth collected from free‐ranging bottlenose dolphins, Tursiops truncatus, from Florida that have been part of a long‐term study begun in 1970; 26 of the dolphins were of known or approximately known age, and 19 were of minimum known age. A second tooth was extracted from 6 animals for examination of growth that had taken place in the interval following the initial extraction. The teeth were read for age estimates without knowledge of any data pertaining to the animals. Most of the estimated ages were the same as or close to the known and approximately known ages of the animals, ranging from 2 to 16 yr. We conclude that the structures we define as dentinal growth layer groups (GLGs) are annual, we describe sources of error in age estimates, and we provide a description of the GLG pattern that can be used by others to estimate age for dolphins.
AN INTRAPERITONEAL RADIO TRANSMITTER FOR SEA OTTERS
Authors: Ralls Katherine , Siniff Donald B. , Williams Thomas D. , Kuechle V. B.
Published: August 2006

Abstract

A small intraperitoneal radio transmitter was developed and used successfully in California sea otters. The transmitter weighs about 120 g and has an internal antenna. Thirty‐five implanted transmitters were located for an average of 526 d. The carcasses of five animals that died were recovered; there were no complications associated with the transmitters in these individuals. Reproductive performance of the adult females with implanted transmitters appeared normal. The main advantages of this transmitter are its reliability and long life. It has enabled the collection of significant new information on California sea otters.
INTER‐OBSERVER COUNT DISCREPANCIES IN A SHORE‐BASED CENSUS OF GRAY WHALES (ESCHRICHTIUS ROBUSTUS)
Authors: Rugh David J. , Ferrero Richard C. , Dahlheim Marilyn E.
Published: August 2006

Abstract

Estimations of gray whale abundance have generally assumed that shore‐based observers record all whales migrating through the viewing area during periods uncompromised by visibility. We tested the repeatability of data collected at the standard gray whale census site at Granite Canyon Marine Laboratory in central California by using pairs of observers maintaining independent sighting records. Proximal shore sites were occupied 6 d (60 h) in January 1986 where one team counted 845 whales in 427 groups while the other team counted 990 whales in 477 groups. A comparison of the records showed that the first team missed 290 whales seen by the second team, and the second team missed 204 whales seen by the first team. The total number of whales in the viewing area was calculated for each team by the Petersen estimate, using mutually sighted whale groups as “recaptures”. On average, observers recorded only 79% of the whales. More whales (68%) were missed when entire groups of whales were not seen rather than when groups were undercounted (32%). Visibility did not appear to affect observed rates of missed whales. Whales migrating at intermediate distances from the shore were less often missed than were those > 6 km or < 1 km offshore. This count discrepancy test confirms that an uncorrected calculation of population size for gray whales based on sighting records from solitary observers will be underestimated.
MAJOR DECLINE IN NUMBER OF HARBOR SEALS,PHOCA VITULINA RICHARDSI, ON TUGIDAK ISLAND, GULF OF ALASKA
Authors: Pitcher Kenneth W.
Published: August 2006

Abstract

Tugidak Island, located in the Gulf of Alaska, was once the site of one of largest local concentrations of harbor seals (Phoca vitulina richardsi) in the world. This population, which probably consisted of about 20,500 animals in the mid‐1960s declined by about 85% between 1976 and 1988. The population appeared to decline more rapidly during the late 1970s than during the 1980s. Causes for the decline are not apparent. There appear to be both similarities and dissimilarities between this decline and recent declines in abundance of northern fur seals (Callorhinus ursinus) and Steller sea lions (Eumetopias jubatus) in the Bering Sea and Gulf of Alaska.
EFFECTS OF FASTING AND FEEDING ON SERUM UREA AND SERUM CREATININE LEVELS IN POLAR BEARS
Authors: Derocher Andrew E. , Nelson Ralph A. , Stirling Ian , Ramsay Malcolm A.
Published: August 2006

Abstract

Polar bears were held in captivity and fasted for an average of 38 d prior to being fed for three days. Blood samples were collected prior to feeding and then at one and three days post‐feeding in 1984 and at one, four, and seven days post‐feeding in 1985. The ratio of serum urea to serum creatinine varied significantly in 1984, rising from a pre‐feeding mean of 11.0 (SE = 2.6) to 32.0 (SE = 3.2) on the first day post‐feeding and then dropped to 22.8 (SE =3.2) in the last sample. In 1985, the ratio of serum urea to serum creatinine increased from a pre‐feeding mean of 15.8 (SE = 2.3) to 61.2 (SE = 10.6) after three days of feeding and dropped to a mean of 29.2 (SE = 5.1) seven days after feeding ended. Serum urea levels varied over the study period in both years. No significant variation in serum creatinine levels was found in 1984, but in 1985, serum creatinine levels demonstrated significant variation, declining from the pre‐feeding mean of 1.83 mg/dl (SE = 0.29) to 0.96 mg/dl (SE = 0.12) in the last sample.

The findings suggest that polar bears can have a low serum urea to serum creatinine ratio, similar to that found in hibernating black bears, or higher ratios after feeding. Polar bears can rapidly return to a fasting serum urea to creatinine ratio after food is withheld. Polar bears may demonstrate urea conservation, similar to that found in black bears, and may be able to move between a fasting and a feeding metabolism based on food availability throughout the year, an adaptation to life on the labile sea ice.
SEX AND AGE SEGREGATION BYPHOCA VITULINA CONCOLORAT HAUL‐OUT SITES DURING THE BREEDING SEASON IN THE PASSAMAQUODDY BAY REGION, NEW BRUNSWICK
Authors: Kovacs Kit M. , Jonas Krista M. , Welke Sylvia E.
Published: August 2006

Abstract

The size and composition of groups of harbor seals at two haul‐out sites were studied during the breeding season of 1989, in the Passamaquoddy Bay region of Atlantic Canada. Evidence of segregation both by age and sex was found in the distinct composition of the two groups. One group contained mainly males and no pups, and the other had a sex ratio not significantly different from one and contained pups. The proportion of females increased at the nursery site with the onset of birthing in the region while the proportion of males increased through the breeding season at the other site. No increase in the number of adults, in total, was detected over the study period, suggesting that sexual segregation and not a change in haul‐out frequency was responsible for the disparity in the sex structure of the two groups. The proportion of juveniles was significantly greater at the male dominated site than at the nursery site.
POPULATION SIZE AND BREEDING SEASON OF THE ANTARCTIC FUR SEAL ARCTOCEPHALUS GAZELLA AT HEARD ISLAND—1987/88
Authors: Shaughnessy P. D. , Goldsworthy S. D.
Published: August 2006

Abstract

Breeding colonies of the antarctic fur seal Arctocephalus gazella on 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 population growth.
SEXUAL DIMORPHISM IN BOTTLENOSE DOLPHINS FROM THE EAST COAST OF FLORIDA
Authors: Hersh Sandra L. , Odell Daniel K. , Asper Edward D.
Published: August 2006

Abstract

Skulls of 69 bottlenose dolphins (genus Tursiops) from the Indian/Banana River on the east coast of Florida were examined for evidence of sexual dimorphism. The only sexual dimorphism shown by t‐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 29 Tursiops originating 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 sexes.
MORPHOMETRIC COMPARISON OF MINKE WHALES BALAENOPTERA ACUTOROSTRATA FROM DIFFERENT AREAS OF THE NORTH ATLANTIC
Authors: Christensen Ivar , Haug Tore , Wiig ØYstein
Published: August 2006

Abstract

Multivariate 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.
INCIDENTAL CATCH OF HECTOR'S DOLPHIN IN INSHORE GILLNETS
Authors: Dawson Stephen M.
Published: August 2006

Abstract

The incidental catch of Hector's dolphins (Cephalorhynchus hectori) in gillnets in Pegasus Bay and Canterbury Bight, New Zealand is assessed. From 1984 to 1988, at least 230 Hector's dolphins were killed in groundfish gillnets by commercial and amateur fishermen. Approximately 91% of entanglements occurred from November to February. Seasonality of catch corresponded to increased commercial gillnetting inshore in spring and summer. Most entanglements (89%) occurred within 4 nautical miles (7.4 km) of the shore, and most dolphins (86%) were caught in water less than 20 m deep. The dolphin's summer inshore movement also coincided with high levels of inshore gillnetting by amateur fishermen. The age‐frequency of net‐caught dolphins suggested that young animals were particularly vulnerable to entanglement.
MODELING AGE‐SPECIFIC MORTALITY FOR MARINE MAMMAL POPULATIONS
Authors: Barlow Jay , Boveng Peter
Published: August 2006

Abstract

A method is presented for estimating age‐specific mortality based on minimal information: a model life table and an estimate of longevity. This approach uses expected patterns of mammalian survivorship to define a general model of age‐specific mortality rates. One such model life table is based on data for northern fur seals (Callorhinus ursinus) using Siler's (1979) 5‐parameter competing risk model. Alternative model life tables are based on historical data for human females and on a published model for Old World monkeys. Survival rates for a marine mammal species are then calculated by scaling these models by the longevity of that species. By using a realistic model (instead of assuming constant mortality), one can see more easily the real biological limits to population growth. The mortality estimation procedure is illustrated with examples of spotted dolphins (Stenella attenuata) and harbor porpoise (Phocoena phocoena).
INTERACTIONS BETWEEN KURIL SEALS AND SALMON TRAP NET FISHERY IN THE COASTAL WATERS OF SOUTHEASTERN HOKKAIDO
Authors: Wada Kazuo , Hayama Shin‐Ichi , Nakaoka Toshiyasu , Uno Hiroyuki
Published: August 2006

Abstract

An annual average of 163 Kuril seals was found dead in two years in salmon trap nets along the coastal waters of the Nemuro Peninsula and adjacent areas. The seal‐caused damage to the total salmon catch at the salmon trap nets was concentrated in some of them, particularly No. 27, where seals killed or injured 5.1% of the catch in 1982, and 1.8% in 1983. Based on the proportion of Kuril seals among the dead seals in the trap nets, it was estimated that Kuril seals damaged 4.7% of the total salmon catch at No. 27 in 1982, and 1.7% in 1983. Not all seals that entered the trap net drowned; some killed or damaged salmon, and then escaped.
SURVIVAL RATES OF PHOTOGRAPHICALLY IDENTIFIED HECTOR'S DOLPHINS FROM 1984 TO 1988
Authors: Slooten Elisabeth , Dawson Stephen M. , Lad Frank
Published: August 2006

Abstract

Re‐sightings of photographically identified individuals were used to estimate survival rates for a free‐living population of Hector's dolphins Cephalorhynchus hectori, a species endemic to New Zealand waters. Most individuals were identified from injuries to the dorsal fin. Consequently, the photographic catalog contained very few young individuals. Our analysis included no newborn calves or yearlings, and provided estimates of survival rates only after the first year of life. We used two complementary methods for calculating survival rates: a modified Jolly‐Seber model, and a simpler method which corrects in a more explicit way for individual dolphins being alive but not sighted. Selection of the most reliable subset of the data had a greater effect on computed survival rates than did the difference between the two methods. We conclude that careful inspection of resighting data before analysis, and, if necessary, selection of a subset, is very important in studies of this kind. Survival rate estimates came from a population which was subject to relatively heavy mortality from gillnet entanglement. Standard errors of the survival rate estimates have been used to assess the conditional probability of population decline given three fertility scenarios. The high probability that the Banks Peninsula Hector's dolphin population was decreasing during the study period (0.78 to 0.99) suggests that gillnet entanglement constituted a serious risk to this population.
SURFACE MORPHOLOGY OF THE FOREBRAIN OF THE BOWHEAD WHALE, BALAENA MYSTICETUS
Authors: Duffield Dennis W. , Haldiman Jerrold T. , Henk William G.
Published: August 2006

Abstract

Observations were made on 11 brains from bowhead whales subsistence‐harvested by Alaskan Eskimos under International Whaling Commission guidelines. This study is part of a larger project to determine the basic morphology of this endangered species. The bowhead brain is similar to other cetacean brains, particularly that of the southern right whale. Long olfactory peduncles are reflected upon the rostrodorsal surface of the cerebral hemispheres. Olfactory bulbs have not been recovered but are presumed to exist since nerve fibers have been identified histologically in the olfactory peduncles. The induseum griseum is evident on the corpus callosum. The hippocampus proper is small but protrudes into the lateral ventricle. The cruciate sulcus runs diagonally across the rostral surface, limiting a small frontal lobe. The structure of the floor of the sylvian fissure varies from a few short gyri radiating toward the circular sulcus to a more extensive and complex two‐tiered arrangement including numerous gyri perpendicular to the gyrus bordering the paleocortex. Pineal‐body‐like tissue was present in one specimen. There is no interthalamic adhesion. The lateral geniculate body is elevated but smaller than the large medial geniculate body. The neurohypophysis was adherent on most brain specimens received.
GROWTH AND DISTRIBUTION OF A SOUTHERN ELEPHANT SEAL COLONY
Authors: Campagna Claudio , Lewis Mirtha
Published: August 2006

Abstract

In contrast with most southern elephant seal, Mirounga leonina, colonies, births at Península Valdes, Argentina, increased from 7,455 in 1982 to 9,636 in 1990. Colony size during the 1990 breeding season, including pups, was estimated at 19,000. Colony growth may respond to abundant food resources and lack of competitors. The range of distribution of elephant seals in Patagonia has not changed since at least 1972 but the spatial distribution of births along the coastline of Peninsula Valdes has varied. In 1982, 58% of the births occurred in the northeast portion of the Peninsula versus 36% in 1990. Females may prefer to give birth on broad, sandy beaches. In 1982, 56% of the females gave birth on pebble beaches and 44% on sandy beaches. In 1990, 24% bred on pebbles versus 76% on sand. Sand substrate may be preferred by females because it may confer thermoregulatory advantages in relieving heat stress.
SEGREGATIVE MIGRATION OF DALL'S PORPOISE (PHOCOENOIDES DALLI) IN THE SEA OF JAPAN AND SEA OF OKHOTSK
Authors: Amano Masao , Kuramochi Toshiaki
Published: August 2006

Dall's porpoises from the Sea of Japan population taken by a dolphin fishery vessel were examined. Estimated body lengths at sexual maturity were similar to those for the truei‐type population off the Pacific coast of Japan but larger than those for the offshore dalli‐type in the North Pacific. The Sea of Japan population is known to migrate to the Pacific coast of Japan through Tsugaru Strait and to the Sea of Okhotsk through Soya Strait in summer. From the difference of catch composition, individuals of different reproductive status in this population are considered to have different patterns of summer migration. Most of the individuals which migrate into the Pacific Ocean through Tsugaru Strait are sexually immature, while those migrating into the Sea of Okhotsk are mature. The Sea of Okhotsk is thought to be a breeding area for this population. The calving season is estimated to be May through June, which is earlier than that of the truei‐type off the Pacific coast of northern Japan. This may be an adaptation to lower water temperatures in the Sea of Japan during winter.
AN ANALYSIS OF PROCEDURES FOR IMPLEMENTING THE DYNAMIC RESPONSE METHOD
Authors: Eberhardt L. L.
Published: August 2006

Abstract: A new method, the “dynamic response method,” was developed (DeMaster et al. 1982) in an attempt to use time series data on relative population sizes to satisfy the requirements of the Marine Mammal Protection Act of 1972 for maintaining an “optimum sustainable population” of marine mammals. Three methods of implementing this approach were studied, using a computer simulation of stochastic population growth with density‐dependence operating on first‐year survival in the form of a generalized‐logistic function. Methods developed by Gerrodette (1988) and Boveng et al. (1988) appeared to be less sensitive than desirable when used with the simulated population data. The third method, developed in this study, offers better protection against “Type II error” (failing to identify populations in the optimum sustainable population range), particularly when combined with Gerrodette's (1988) approach.
COMPARISON OF THE STOMACH CONTENTS OF SOUTHERN ELEPHANT SEALS, MIROUNGA LEONINA, AT MACQUARIE AND HEARD ISLANDS
Authors: Green K. , Burton H. R.
Published: August 2006

Abstract: There are three major breeding populations of southern elephant seals centered on Macquarie Island, Kerguelen‐Heard Islands and South Georgia‐Antarctic Peninsula. The composition of the diet differs between these populations based on published data from Signy Island and data presented here from Macquarie and Heard Islands. These differences in diet appear to be linked to the location at which seals were sampled ranging from the least Antarctic (Macquarie Island) to the most Antarctic (Signy Island). The major food remains consisted of cephalopod beaks and fish eye lenses. More benthic material was found at Heard Island than at Macquarie Island. The diet at Macquarie Island differed between summer and winter and between young animals and adults. The difficulty in collecting dietary samples of southern elephant seals near their main foraging areas makes the study of the feeding ecology of this species extremely difficult in comparison with other Southern Ocean species.
BREEDING BIOLOGY OF SOUTHERN ELEPHANT SEALS IN PATAGONIA
Authors: Campagna C. , Lewis M. , Baldi R.
Published: August 2006

Abstract: Elephant seals breed in Patagonia (Península Valdés, Argentina) from late August to early November, reaching peak numbers during the first week in October. Observations of this population over the past ten years yielded similar results. Eighty percent of the pups were born by 2 October. Most (96%) of 663 females marked during three breeding seasons gave birth to a pup. Females stayed on land a mean of 28 d, gave birth 6 d after arrival, nursed their pups for 22 d, and copulated a mean of 2.5 times 20 d after parturition and 2 d before departure. Copulations peaked during the third week in October. Males spent 57–80 d on land fasting and defending harems of up to 134 females (median 11–13 females, depending on year). Most (96%) marked females that gave birth (n= 636) also weaned their pups successfully. Pup sex ratio was unity. Harems were smaller and breeding occurred about three weeks earlier in Patagonia than in other colonies. Thermal conditions, day length and food availability may explain clines in the timing of breeding events between populations, Other parameters of the breeding season for the expanding Patagonia colony are similar to those for declining southern elephant seal populations elsewhere.
IDENTIFICATION OF GEOGRAPHIC FORMS OF COMMON DOLPHIN (Delphinus delphis) FROM AERIAL PHOTOGRAMMETRY
Authors: Perryman Wayne L. , Lynn Morgan S.
Published: August 2006

Abstract: At least four morphologically distinct forms of common dolphins are found in the eastern Pacific, We compared length data for common dolphins photographed from the northern, central and southern regions as defined by Perrin et al. (1985) and found significant differences in average length for adult animals (>150 cm) and for “adult females” defined for our purposes as animals accompanied by calves. Analyses of calculated birth dates for calves demonstrated differences in timing of reproduction between the geographically adjacent forms. Length distributions from aerial photographs and samples collected from the purse seine fishery were strikingly similar. This work demonstrates a new, non‐invasive method for obtaining unbiased life history and morphological data.
LONG‐RANGE MOVEMENTS OF SOUTH ATLANTIC RIGHT WHALES EUBALAENA AUSTRALIS
Authors: Best Peter B. , Payne R. , Rowntree V. , Palazzo Jose Truda , Both Maria Do Carmo
Published: August 2006

Abstract: Movements of southern right whales between Gough Island and South Africa, and between Argentina and Tristan da Cunha, southern Brazil, and South Georgia are documented through matching of six photoidentified individuals. These include the resighting of a male in a mid‐oceanic locality some 4,424 km away from (and 11 yr after) its last sighting in a coastal area where it had been seen in six of the preceding eight years, a female photographed in mid‐Atlantic resighted with a calf in a coastal nursery area 2,769 km away, resightings of females with calves in different nursery areas 2,051 km apart in different years, and the first example of a link between a coastal nursery area and a feeding ground in high latitudes. The possible implications of these movements for estimates of calving interval and survival rate based on resightings in coastal waters are discussed. The potential for intermingling between populations on either side of the South Atlantic seems greater than was previously considered likely from a comparison of animals photographed in coastal waters.
ICEBREAKER NOISE IN LANCASTER SOUND, N.W.T., CANADA: IMPLICATIONS FOR MARINE MAMMAL BEHAVIOR
Authors: Cosens Susan E. , Dueck Larry P.
Published: August 2006

Abstract: In 1986, we recorded the MV Arctic, CCGS des Groseilliers and MV Lady Franklin during routine icebreaking operations and travel to and from the mine at Nanisivik, Baffin Island, Northwest Territories, Canada. We found that the Arctic generated more high frequency noise than did the other vessels we recorded. Monitoring of vessel noise levels indicated that belugas and, probably, narwhals should be able to detect the high frequency components of Arctic noise at least as far as 25 to 30 km from the source. The ability of whales to detect the MV Arctic at long distances may explain why belugas and narwhals in Lancaster Sound seem to react to ships at longer distances than do other stocks of arctic whales.
IMPLICATIONS OF NON‐LINEAR DENSITY DEPENDENCE
Authors: Taylor Barbara L. , Demaster Douglas P.
Published: August 2006

Abstract: Ranges of the ratio of maximum net productivity level (MNPL) to carrying capacity (K) are explored in general models for pinnipeds and odontocetes. MNPL/K is used in management of marine mammals but no empirical evidence exists to limit the range of values expected. Density dependent changes in age‐specific birth and death rates have been used to infer MNPL/K. Non‐linearities in these rates do not translate directly to population growth curves. The simple models demonstrate: (1) density dependence is likely to involve more than a single parameter (such as birth rate), (2) MNPL/K can be greatly reduced from that inferred from one strongly non‐linear parameter when changes in other parameters are linear, (3) ranges of MNPL/K depend on biological limits on ranges of fecundity and survival rates, and (4) the magnitude and sign of bias incurred by inferring MNPL/K from functional forms of single parameters cannot be determined. Given current empirical evidence the range of MNPL/K for marine mammals as a group is large. Although MNPL/K should not be inferred from single parameter non‐linearities, distributions of MNPL/K values can be generated through models which account for single species ranges for birth and death rates and maximum population growth rate.
DISTRIBUTION and NUMBERS OF STRIPED DOLPHINS IN THE WESTERN MEDITERRANEAN SEA AFTER THE 1990 EPIZOOTIC OUTBREAK
Authors: Forcada Jaume , Aguilar Alex , Hammond Philip S. , Pastor Xavier , Aguilar Ricardo
Published: August 2006

Abstract

A survey was conducted in the summer of 1991 in the western Mediterranean to map the distribution and to estimate the number of striped dolphins surviving the 1990 outbreak of the morbillivirus epizootic. The highest densities of striped dolphins were found in the Alboran Sea and the Ligurian Sea. Total numbers were estimated at 117,880 (SE: 38,962; 95% CI: 68,379–214,800). The mortality resulting from the epizootic is unknown but may have been severe because the mean size of dolphin schools observed during the epizootic outbreak was significantly smaller than that before the event. A return to larger school sizes after the 1990 outbreak is not evidence of a recovery but can be viewed as a regrouping of individuals into schools of a preferred size. Calves were observed in 24.6% of the schools. They were not seen in schools of ten or less but were present in about half the schools of 30 or more dolphins, a result which suggests segregation similar to that seen in populations of this species elsewhere in the world.
ESTIMATING SEA OTTER REPRODUCTIVE RATES
Authors: Eberhardt L. L. , Schneider K. B.
Published: August 2006

Abstract: Sea otters may give birth in any month of the year, so obtaining reproductive rates by observation is difficult. Reproductive rates may be estimated directly (births per otter‐year observed) or by determining the time interval between births. Both methods give the same result for long sequences of observations, but field data are limited to shorter periods. Monte Carlo simulations were conducted to compare the two approaches, and showed that the interval method overestimates true reproductive rates.
BOTTLENOSE DOLPHINS CAN GENERALIZE RULES and DEVELOP ABSTRACT CONCEPTS
Authors: Herman Louis M. , Pack Adam A. , Wood Amy M.
Published: August 2006

Abstract: Generalization of a rule is demonstrated if the rule governs a class of problem, and the subject, after successful experience with a limited number of problems, can apply the governing rule to new problems within that class. We show that the bottlenose dolphin (Tursiops truncatus) is capable of such generalization for classes of problems requiting the matching of one of two alternative stimuli to a “sample” stimulus to which the animal had been previously exposed, regardless of the sensory domain used: vision, passive listening, or active echolocation. We also show this generalization capability in a related class of problem requiring a judgment of whether a single “probe” stimulus is the same as, or different from, a stimulus or stimuli previously presented. Further, one dolphin was shown capable of developing a true abstract concept of same/different through its ability to categorize pairs of simultaneously presented objects as identical or not. The suggestion that such generalization ability of dolphins may be in question because of so‐called exclusion effects is shown to be not tenable when the whole body of available data is considered.