bluuebunny/crossref_metadata_2025 huggingface dataset:
DEVELOPMENT, SEXUAL DIMORPHISM, and INDIVIDUAL VARIATION IN THE SKELETON OF THE FINLESS PORPOISE, NEOPHOCAENA PHOCAENOIDES, IN THE COASTAL WATERS OF WESTERN KYUSHU, JAPAN
Authors: Yoshida Hideyoshi , Shirakihara Miki , Takemura Akira , Shirakihara Kunio
Published: August 2006

Abstract

Development, 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 braincase.
BEHAVIORAL RESPONSES OF EAST AUSTRALIAN HUMPBACK WHALES MEGAPTERA NOVAEANGLIAE TO BIOPSY SAMPLING
Authors: Brown M. R. , Corkeron P. J. , Hale P. T. , Schultz K. W. , Bryden M. M.
Published: August 2006

Abstract

The response of migrating humpback whales to biopsy sampling was investigated off North Stradbroke Island, South East Queensland. Whales were allocated a behavioral category prior to biopsy sampling according to the general behavior of their pod. Behavioral reactions were recorded after each attempt. Sex was determined using a molecular genetic technique.

Detectable reactions occurred in 41.6% of successful biopsy attempts, a significantly lower response rate than that reported by two studies carried out on the feeding and breeding grounds of the North Atlantic. There was no difference in the response rate of whales on their northward or southward migration. Pod size was not an important factor in predicting the response of an individual. Females responded to biopsy sampling at a significantly higher rate than males.

Our results indicate that a substantial difference in response rate can occur between studies. Factors such as the type of boat used and the prior exposure of whales to human impact may be of importance. Our study suggests that female humpback whales may be particularly responsive to human disturbances. Overall, however, biopsy sampling has minimal impact on humpback whales.
INTRASPECIFIC GENETIC DIFFERENTIATION IN CALIFORNIA SEA LIONS (ZALOPHUS CALIFORNIANUS) FROM SOUTHERN CALIFORNIA AND THE GULF OF CALIFORNIA
Authors: Maldonado Jesús E. , Davila Flavio Orta , Stewart Brent S. , Geffen Eli , Wayne Robert K.
Published: August 2006

Abstract

Intraspecific patterns of mitochondrial DNA sequence variation were determined among California sea lions (Zalophus califomianus californianus) from three colonies along the Pacific coast of southern and Baja California and one colony in the Gulf of California. We found no variation in 368 base pairs (bp) of cytochrome b sequence among 40 sea lions from these localities, but analysis of 360 base pairs of control region revealed eleven genotypes. The four genotypes found in the Gulf of California population were unique and phylogenetically distinct from those found in sea lions along the Pacific coast. The average sequence divergence between Gulf and Southern California genotypes was 4.3%, suggesting a relatively long period of isolation. However, colonies along the Pacific coast, which are less than 200 km apart, shared mtDNA genotypes, indicating that recent genetic exchange has occurred between them. Therefore, we suggest that regional female philopatry exists in California sea lions. Regional boundaries may be related to oceanic currents or patchiness in the distribution of resources. Further research is needed to better understand the underlying causes of genetic differentiation in the California sea lion.
INDICES OF BODY CONDITION AND BODY COMPOSITION IN FEMALE ANTARCTIC FUR SEALS (ARCTOCEPHALUS GAZELLA)
Authors: Arnould John P. Y.
Published: August 2006

Abstract

An attempt was made to develop simple, inexpensive, rapid means of determining body composition in Antarctic fur seals (Arctocephalus gazella). Measurements of total body water (TBW) and total body lipid (TBL), obtained by hydrogen isotope dilution, were compared to the results of bioelectrical impedance analysis (BIA) and morphometric indices of body condition in 52 adult females. TBW was weakly correlated with BIA measurements of resistance (v= ‐0.30, P < 0.03). Conductor volume (length2/resistance) was more highly correlated with TBW(r= 0.75, P < 0.0001) and the inclusion of mass into the predictive equation improved the correlation further (r= 0.95, P < 0.0001). A body condition index (mass/length) previously used in pinniped studies was positively correlated to TBL (r= 0.77, P < 0.0001) validating its use as a relative index of condition. However, body mass alone was highly correlated to TBW (r= 0.94, P < 0.0001) and appears to provide a simple, rapid means of estimating body composition in adult females. This technique may also be applicable to juvenile male Antarctic fur seals.
DIVING BEHAVIOR OF THE SAIMAA RINGED SEAL (PHOCA HISPIDA SAIMENSIS NORDQ.)
Authors: Hyvärinen Heikki , Hämäläinen Esa , Kunnasranta Mervi
Published: August 2006

Abstract

The activity and diving patterns of four adult Saimaa ringed seals (Phoca hispida saimensis, a landlocked subspecies living in Lake Saimaa, Finland) were examined during spring, summer, and autumn by the use of VHF‐transmitters. Over 17,000 dives were registered. The duration of the dives and diving patterns differed among individuals. The mean duration of dives increased from spring to autumn; e.g., in one individual the mean dive duration increased from 6 min in June to 10.5 min in October. The haul‐out periods of one individual in May to early June made up 46.2% of its total activity budget, but in another individual in July to August the haul‐out periods made up only 11% of the budget and the seal was submerged for 80% of the time. Periods of successive long duration dives (>10 min) were observed in three individuals in summer and autumn. The longest dive measured was 23 min. The duration of the periods containing long dives was often over three hours (maximum six hours) and the mean duration of the dives about 15 min. These long duration dives are assumed to be aerobic resting dives. Generally, the dives of the Saimaa ringed seal appear to be of longer duration than previously assumed.
RETINAL GANGLION CELL SIZE AND DISTRIBUTION PREDICT VISUAL CAPABILITIES OF DALL'S PORPOISE
Authors: Murayama Tsukasa , Somiya Hiroaki , Aoki Ichiro , Ishii Takeo
Published: August 2006

Abstract

The structure of the retina, the distribution of ganglion cells, and the extent of the tapetum lucidum were studied in Dall's porpoise (Phocoenoides dalli) with the aim of understanding the role vision plays in this species of cetacean. The basic organization of the retina was similar to that of other vertebrates. Average ganglion cell size was 21.5 μm. The distribution of the ganglion cells in the retina was not even and there were two high‐density areas, one in the temporal and one in the rostral part of the retina. Retinal resolving power was estimated using a terrestrial animal model incorporating the density of ganglion cells and other morphological data. The resolving power in the right eyes of two individuals was 2.60 and 2.64 cycles per degree. These values were close to those of other oceanic cetaceans, but inferior to those of terrestrial mammals. On the basis of amino acid analyses, it was shown that the choroid tapetum lucidum in Dali's porpoise contained collagen. The tapetum lucidum was thick at the fundal but thin at the peripheral part of the choroid.
MORBILLIVIRUS INFECTION IN TWO SPECIES OF PILOT WHALE (GLOBICEPHALA SP.) FROM THE WESTERN ATLANTIC
Authors: Duignan Padraig J. , House Carol , Geraci Joseph R. , Early Greg , Copland Heather G. , Walsh Michael T. , Bossart Gregory D. , Cray Carolyn , Sadove Samuel , Aubin David J. ST. , Moore Michael
Published: August 2006

Abstract

We report evidence of enzootic morbillivirus infection among long‐finned, Globicephala melas, and short‐finned, G. macrorhynchus, pilot whales in the western Atlantic. A retrospective serologic survey, using five morbilliviruses, was carried out on 99 G. melas from 14 stranding events between 1982 and 1993 and from 25 G. macrorhynchus stranded in 5 events between 1986 and 1994. A blood sample was also obtained from an adult G. melas by‐caught in the western North Atlantic. Tissues were collected from 24 G. melas and 15 G. macrorhynchus for histology and immunoperoxidase staining. Neutralizing antibody titers were found in 92 (92%) of 100 G. melas and 16 (64%) of 25 G. macrorynchus, and titers were highest against cetacean morbilliviruses. Seroprevalence was similar between age classes and sexes. The earliest evidence of infection was in a G. melas that stranded in 1982. Stable antibody titers were observed in pilot whales under rehabilitation for up to eight months. Clinical disease consistent with morbillivirus pneumonia was detected in a G. melas calf. Immunoperoxidase staining confirmed that viral antigen was present in the lesions.

We propose that enzootic infection in pilot whales is facilitated by population size, social structure, and migration patterns. Furthermore, through mixing with other odontocetes, pilot whales could act as vectors through the Atlantic. Clinical morbillivirus infection may precipitate mass strandings of highly social odontocetes.
SKIN BIOPSY SAMPLING OF BELUGA WHALE CARCASSES: ASSESSMENT OF BIOPSY DARTING FACTORS FOR MINIMAL WOUNDING AND EFFECTIVE SAMPLE RETRIEVAL
Authors: PATENAUDE N. J. , WHITE B. N.
Published: August 2006

Abstract

Different combinations of biopsy tip lengths (20, 25 mm) and diameters (5, 6, 7 mm), crossbow draw weights (23, 45, 68 kg) and distances (1.5–15 m) were tested on fresh beluga carcasses to determine factors affecting the success of biopsy retrieval and the extent of wounding. Tips with smaller diameters and longer lengths were found to be more likely to retrieve a skin sample, while the draw weight of the crossbow had a significant effect on the severity of the wound. The samples obtained from all biopsy darts tested yielded sufficient amounts of DNA for genetic analysis (20–109 μg) with the highest yield coming from the germinativum spinosum layer. For beluga whales we recommend using a tip of 5 mm in diameter, 25 mm in length, and a draw weight of 23 kg at close range.
LIFE IN THE FAST LANE: THE LIFE HISTORY OF HARBOR PORPOISES FROM THE GULF OF MAINE
Authors: Read Andrew J. , Hohn Aleta A.
Published: August 2006

Abstract

We describe the life history of harbor porpoises in the Gulf of Maine by examining 239 animals killed in gill net fisheries and comparing these findings with the results of previous studies from the Bay of Fundy. Most female porpoises matured at age three and became pregnant each year thereafter. Reproduction was strictly seasonal, with ovulation, conception, and parturition occurring in the spring and early summer. The oldest specimen in the sample was 17 yr of age, but most individuals were younger than 12. The findings are similar to those of earlier studies from the Bay of Fundy and support the hypothesis that these animals form a single population. Harbor porpoises represent one end of a continuum of odontocete life histories that spans a wide diversity of strategies. In comparison with other, large odontocetes, harbor porpoises mature at an earlier age, reproduce more frequently, and live for shorter periods.
BODY TEMPERATURE IN THE NEWBORN SOUTHERN ELEPHANT SEAL, MIROUNGA LEONINA, AT MACQUARIE ISLAND
Authors: Little G. J.
Published: August 2006

Abstract

Newborn southern elephant seal pups were reported by Laws (1953) to be “to some extent poikilothermic at birth.” Rectal temperatures of known age southern elephant seal pups were recorded during the 1985 pupping season at Macquarie Island. The mean pup rectal temperature was found to be 381°C ± 0.1°C SEM (n= 131, range = 36.5°‐39.1°C). Pups at two hours, six hours, and one day after birth had significantly higher rectal temperatures than pups two, three, or four days of age. Rectal temperatures of neonatal southern elephant seals were within the range observed for other pinnipeds, (but never as low as the 31°C previously observed for southern elephant seals at Signy Island in 1953). A significant though weak positive correlation was found between pup temperature and body weight. However, no correlation between pup temperature and age or any environmental factor was found. These observations demonstrated that southern elephant seal pups at Macquarie Island are homeothermic, rather than heterothermic from birth.
THE CLICK‐SOUNDS OF NARWHALS (MONODON MONOCEROS) IN INGLEFIELD BAY, NORTHWEST GREENLAND
Authors: Miller Lee A. , Pristed John , Møshl Bertel , Surlykke Annemarie
Published: August 2006

Abstract

We studied the sounds of narwhals (Monodon monoceros) foraging in the open waters in Northwest Greenland. We used a linear, vertical array of three hydrophones (depth 10 m, 30 m, 100 m) with a fourth hydrophone (depth 30 m) about 20 m from the vertical array. A smaller fifth hydrophone (depth 2 m) allowed for registering frequencies up to 125 kHz (± 2 dB) when signals were recorded at 762 mm/set on an instrumentation tape recorder. Clicks were the prevalent signals, but we heard whistles occasionally. We separated the clicks into two classes: click trains that had rates of 3‐10 clicks/sec and click bursts having rates of 110‐150 clicks/sec. The spectra of train clicks had maximum amplitudes at 48 ± 10 kHz and a duration of 29 ± 6 psec. The spectra of burst clicks had maximum amplitudes at 19 ± 1 kHz and a duration of 40 ± 3 psec. By analogy with other dolphin species, narwhals presumably use the clicks for echolocation during orientation and for locating prey. The narwhal click patterns resemble those of insectivorous bats. Click trains might correspond to bat searching signals and click bursts to the bat's terminal “buzz”, emitted just before prey capture.
PLASMA VASOPRESSIN LEVELS AND WATER CONSERVATION IN FASTING, POSTWEANED NORTHERN ELEPHANT SEAL PUPS (MIROUNGA ANGUSTIROSTRIS)
Authors: Ortiz Rudy M. , Adams Sean H. , Costa Daniel P. , Ortiz C. Leo
Published: August 2006

Abstract

Northern elephant seal pups (Mirounga angustirostris) use several physiological mechanisms to conserve water during their 8‐ 12‐wk postweaning fast. Urine was analyzed from five animals and plasma from four of those animals was sampled serially throughout the postweaning period to quantify changes in urine concentrating ability and electrolyte homeostasis at various stages of the fast (Early = 1‐4 wk, Mid = 4‐7 wk, Late = 7‐10 wk). Plasma osmolarities stayed relatively constant at 301.6 f 13.1 mOsm/kg. Urine osmolarities ranged from 1,053.5 ± 78.6 mOsm/kg (Early), to 1,585.0 ± 136.7 mOsm/kg after eight weeks, dropping to 1,214.3 ± 349.6 mOsm/kg (Late). Urine concentrations for Na+ and K+ early in the fast were 55.0 ± 14.6 mM and 180.8 ± 48.6 mM, respectively, declining to 8.2 ± 3.3 mM and 91.4 ± 29.0 mM later. Plasma vasopressin concentrations ranged from 34.8 ± 18.2 pg/ml (Early) to 4.8 ± 1.3 pg/ml (Late). The pups appear to conserve their body water by producing a concentrated urine, thus reducing urinary water loss. The significance of the antidiuretic role of vasopressin in the conservation of body water in these pups could not be conclusively determined from the results.
SUMMER FEEDING HABITS OF DALL'S PORPOISE, PHOCOENOIDES DALLI, IN THE SOUTHERN SEA OF OKHOTSK
Authors: Walker William A.
Published: August 2006

Stomach contents were analyzed from 85 Dall's porpoises, Phocoenoides dalli, taken in the southern Sea of Okhotsk during the summer of 1988. Thirteen species of fish and five species of cephalopods were identified. Fishes comprising 9 families were predominant and made up 79.9% of the total number of prey, with an overall occurrence in the stomachs of 100%. Three families of cephalopods made up 20.1% of the total number of prey ingested, with an overall occurrence of 74%. The Japanese pilchard, Sardinops sagax melanostictus, was the primary prey and represented 72.0% of the total prey in 97.3% of the stomachs examined. The gonatid squid, Berryteuthis magister, ranked second and made up 16.9% of the total prey in 61.6% of the stomachs. Walleye pollock, Theragra chalcogramma, was the third most abundant prey item consumed and represented 6.0% of the total, with an occurrence of 53.4%. Composition of the sample by the calculated total mass and caloric intake supports the numeric findings on the relative importance of the three major prey species to the DaIl's porpoise diet. The Japanese pilchard was clearly dominant using these indices and constituted 65.4% of the total mass and 80.7% of the caloric intake. Berryteuthis magister made up 26.8% of the mass and 15.5% of the caloric intake. Walleye pollock contributed the least to the diet with 7.9% of the total mass and 3.8% of the caloric intake. Volumetric data indicate that porpoises are feeding heavily on Japanese pilchard throughout the daylight hours. Berryteuthis magister was probably fed upon in the late night or early morning hours. Occurrence of both Dall's porpoise and Japanese pilchard in the coastal waters of the southern Sea of Okhotsk is seasonal. The summer movements of Dall's porpoise into this region may be related to the seasonal migration and abundance of the Japanese pilchard.
LIFE HISTORY OF FRASER'S DOLPHIN, LAGENODELPHIS HOSEI, BASED ON A SCHOOL CAPTURED OFF THE PACIFIC COAST OF JAPAN
Authors: AMANO Masao , Miyazaki Nobuyuki , Yanagisawa Fumio
Published: August 2006

Life history of Fraser's dolphin, a little known delphinid species, was examined based on 108 specimens from a school captured by the driving fishing method in Japan. The sex ratio was approximately 1:1, and mature dolphins of both sexes formed the bulk of the school. The oldest animals were two males and a female of 17.5 yr. Age and body length at sexual maturity were estimated at 7–10 yr and 220–230 cm in males and 5–8 yr and 210–220 cm in females. Mature males were larger in body length than mature females and showed apparent secondary sexual features: deepening of the tail stock and widening and darkening of the lateral dark stripe. The annual ovulation rate was 0.49. The estimated neonatal length (110 cm) predicts a gestation period of about 12.5 mo and calving peaks in spring and probably also in fall. The calving interval was estimated to be about 2 yr. These life history parameters are similar to those of the striped and pantropical spotted dolphins, except for longevity. The reproductive rate of this species may be lower than that of other pelagic delphinids, if the observed shorter longevity is real.
INTERCHANGE AND ISOLATION OF HUMPBACK WHALES OFF CALIFORNIA AND OTHER NORTH PACIFIC FEEDING GROUNDS
Authors: Calambokidis John , Steiger Gretchen H. , Evenson Joseph R. , Flynn Kiirsten R. , Balcomb Kenneth C. , Claridge Diane E. , Bloedel Prentice , Straley Janice M. , Baker C. Scott , Ziegesar Olga VON , Dahlheim Marilyn E. , Waite Janice M. , Darling James D. , Ellis Graeme , Green Gregory A.
Published: August 2006

Humpback whales feed in several high‐latitude areas of the North Pacific. We examined the interchange of humpback whales between one of these areas, off California, and those in other feeding grounds in the eastern North Pacific:. Fluke photographs of 597 humpback whales identified off California between 1986 and 1992 were compared with those off Oregon and Washington (29); British Columbia (81); southeastern Alaska (343); Prince William Sound, Alaska (141); Kodiak Island, Alaska (104); Shumagin Islands, Alaska (22); and in the Bering Sea (7). A high degree of interchange, both inter‐and intrayear, was found among humpback whales seen off California, Oregon, and Washington., A low rate of interchange was found between British Columbia and California.: two whales seen near the British Columbia/Washington border were photographed off California in a different year, No interchange was found between California and the three feeding areas in Alaska. Humpback whales off California, Oregon, and Washington form a single intermixing feeding aggregation with only limited interchange with areas farther north. These findings are consistent with photographic identification studies in the North Atlantic and with genetic studies in both the North Atlantic and North Pacific.
UNDERSTANDING AND INTERPRETING HEMATOCRIT MEASUREMENTS IN PINNIPEDS
Authors: Castellini J. M. , Meiselman H. J. , Castellini M. A.
Published: August 2006

Hematocrit data are relatively easily obtained from blood samples of pinnipeds but differences in methodology and variable physiological conditions of the subjects can significantly alter their values. This two‐fold problem makes comparative data and modeling efforts difficult. To quantify the difficulty of obtaining accurate and representative hematocrit values in pinnipeds, hematocrit was measured by both microcentrifugation and Coulter counter methods in a range of pinnipeds under a variety of physiological and handling conditions. The data show that the Coulter counter hematocrit values were 4%‐15% higher than those measured by microcentrifugation. In addition, blood samples from restrained animals showed consistently elevated hematocrit values relative to resting subjects. A significant difference was also found between hematocrit values from pups and adults. Finally, hematocrit was shown to decline over the course of isofluorane anesthesia. Taken together, these results suggest that laboratory methodology, developmental state, and animal handling techniques can significantly alter hematocrit values in pinnipeds. Thus, modeling efforts that require representative hematocrit values, such as calculations of total blood oxygen stores, can be markedly impacted by variations in hematocrit measurement techniques and sampling regimes.
ASSESSMENT OF HETEROGENEITY IN SIGHTING PROBABILITIES OF HUMPBACK WHALES WITHIN VIEWING RANGE OF CAPE VIDAL, SOUTH AFRICA
Authors: Findlay K. P. , Best P. B.
Published: August 2006

Abstract

The migrations of humpback whales on the African east coast were monitored between 1988 and 1991 at Cape Vidal, South Africa. Shore‐based surveys of the northward migration were undertaken each winter, and a survey of the southward migration was undertaken in 1990, from an approximately 60‐m‐high vantage point on a headland. Independent‐observer surveys were carried out in both 1990 (22 d) and 1991 (51 d) to determine the proportion of the population within the survey area that were being missed by observers using a single mark‐release model. Results were stratified into three distance intervals from the shore and three sighting condition intervals; there were constant sighting probabilities from the south tower under different sighting conditions, while those from the north tower increased slightly as sighting conditions improved. Sighting probabilities from both towers were highest in the intermediate distance interval and decreased in both the inshore and offshore regions.
ESTIMATES OF THE NUMBERS OF HUMPBACK WHALES OBSERVED MIGRATING PAST CAPE VIDAL, SOUTH AFRICA, 1988–1991
Authors: Findlay K. P. , Best P. B.
Published: August 2006

Abstract

A recovery‐monitoring program of the African east coast humpback whale population was carried out through shore‐based visual surveys from Cape Vidal, northern Natal. Surveys of the northward migration were undertaken each winter from 1988 to 1991, and a survey of the southward migration was undertaken in 1990. Independent observer surveys were undertaken during June 1990 and during the entire 1991 survey. Hourly densities of groups sighted each day were adjusted for groups missed by observers with distance from the shore and under different sighting conditions. Densities were multiplied by 24 h and the mean group size of the survey year to give resulting daily densities of individuals, which were summed to provide totals of whales sighted during each year's survey. The best estimate of population size was 1,711 (made during the northward migration of 1990), although this is likely to be biased downwards by a proportion of the population passing outside of observers’view. Bootstrapping of the 1991 daily data resulted in CVs between 11.4% and 12.2%. The numbers sighted show the population to have undergone considerable recovery since protection in October 1963.
EPIDEMIOLOGY OF POXVIRUS IN SMALL CETACEANS FROM THE EASTERN SOUTH PACIFIC
Authors: Bressem Marie‐Françloise Van , Waerebeek Koen Van
Published: August 2006

Abstract

The prevalence of‘tattoo’skin lesions, characteristic of poxvirus infection, was examined in 339 small cetaceans captured in gillnet fisheries off coastal Peru: 196 Lagenorhynchus obscurus (34.7%, CI 29.0%–41.8%), 54 Delphinus capensis (61.1%, CI 46.6%–74.1%), 77 Phocoena spinipinnis (62.3%, CI 50.5%–73.2%) and 12 offshore Tursiops truncatus (41.6%, CI 15.2%–72.3%). Sexual variation in tattoo prevalence was significant only in P spinipinnis with males two times more infected than females. Prevalence of poxvirus infection was correlated with the body length class in all species. It peaked around weaning age, supposedly in part due to the loss of maternal protection, and then gradually decreased as immunity developed in the delphinids, but remained high in the porpoise. This pattern is indicative of an endemic infection equivalent to a children's viral disease. The generalized distribution of the tattoos in several animals suggests that viremia may occur. Indications are that the incidence of the disease in L. obscurs and P. spinipinnis may have increased since 1990, however additional research is needed to confirm this trend.
BEHAVIORAL SIGNIFICANCE OF UNDERWATER VOCALIZATIONS OF CAPTIVE LEOPARD SEALS, HYDURGA LEPTONYX
Authors: Rogers T. L. , Cato Douglas H. , Bryden M. M.
Published: August 2006

Abstract

Two groups of underwater vocalizations were identified in a three‐year study of two captive leopard seals, Hydurga leptonyx (one female and one male at Taronga Zoo, Sydney). This was supplemented by recordings over three months from a male at Marineland, New Zealand. The sexual state of the seals at Taronga was deduced from serum hormonal concentrations: the female was considered to be in estrus at specific times during the breeding season. The seal at Marineland, New Zealand was assumed to be sexually mature on the basis of size and age. Of 12 different underwater sound types recorded, six were produced by the seals at Taronga Zoo during agonistic interactions (local calls) and were heard through most of the year. The other six sound types were produced by lone seals. These broadcast calls were produced by the female only when sexually receptive, and by the mature male during December and January, months believed to be the breeding season of wild leopard seals. We propose that underwater acoustic behavior is important in the mating system of this species, and that broadcast calls are used by mature females to advertise their sexual receptivity, and possibly by mature males in search of mates.
STATUS OF THE PACIFIC WALRUS POPULATION, 1950–19891
Authors: Fay F. H. , Eberhardt L. L. , Kelly B. P. , Burns J. J. , Quakenbush L. T.
Published: August 2006

Abstract

The Pacific walrus (Odobenus rosmarus divergens) population is an important ecological and economic resource of the Bering Sea region. We describe population change, beginning with a low in 1950, through a high in about 1980, and ending in 1989. Estimates of abundance for the years after 1989 were not attempted due to the lack of harvest data and other population parameters. Selective hunting practices resulted in biased data regarding population composition and reproductive performance. Rates of reproduction had to be estimated from ovarian data, which indicated a dramatic drop in the 1980s. High harvests in the 1980s likely contributed to a decline in the population, but uncertainties as to accuracy of population estimates and other data raise reasonable doubts, especially with respect to the number of males, for which the most recent (1985) population estimate suggests a sharp decline. Past population estimates were revised upwards to compensate for walruses underwater and not seen in aerial surveys. The weaknesses in the available data make it clear that effective management of the population will require many improvements in collection of data regarding harvests, population structure, reproduction, and population trend.
TARGET DISCRIMINATION BY AN ECHOLOCATING FINLESS PORPOISE, NEOPHOCAENA PHOCAENOIDES
Authors: Nakahara Fumio , Takemura Akira , Koido Takashi , Hiruda Hisoka
Published: August 2006

Abstract

The ability of a finless porpoise (Neophocaena phocaenoides) to discriminate the material and size of a target by echolocation was investigated. The porpoise was required to choose a standard target of a 15‐mm diameter solid steel cylinder from two stimuli, a standard and a comparison target, presented simultaneously. The porpoise could distinguish a standard cylinder from acrylic resin and brass targets, but had difficulties distinguishing it from an aluminum cylinder. In size discrimination, the porpoise could distinguish the standard from 12‐, 18‐, and 20‐mm diameter cylinders, but had difficulties distinguishing it from a 14‐mm diameter cylinder. Echo measurements suggest that the porpoise is able to detect: (1) time difference between two echo highlights to within approximately 1 μS, (2) frequency shifts of approximately 7 kHz in a broadband echo having a peak frequency of nearly 140 kHz, (3) time‐separation pitch of approximately 30 kHz, and (4) target strength differences of approximately 1 dB.
DEVELOPMENT OF HEMOGLOBIN, HEMATOCRIT, AND ERYTHROCYTE VALUES IN GALÁPAGOS FUR SEALS
Authors: Horning Markus , Trillmich Fritz
Published: August 2006

Abstract

We studied the ontogeny of hemoglobin concentration, hematocrit and erythrocyte counts in the Galapagos fur seal (Arctocephalus galapagoensis, Heller 1904). Two hundred and fifty‐three animals were sampled between the ages of 22 d and > 8 yr, of which 46 were adult females. Body mass increased steadily with age from 6.1 ± 1.2 kg in 1‐mo‐old pups (n= 27) to 28.5 ± 3.3 kg in adult females. Even adult females increased in mass with age. Hemoglobin (Hb), hematocrit (Hct), and red blood cell (RBC) values all increased in a logarithmic fashion with age up to 2 yr. Blood values for pups were Hct: 35.5 ± 4.1%; Hb: 12.9 ± 1.3 g/dl; RBC: 4.1 ± 0.3·106/μl. Half‐year‐old fur seals (Hct: 42.1 ± 3.2%; Hb: 15.7 ± 1.3 g/dl; RBC: 4.9 ± 0.5·106/μl; n= 50) were the oldest age group to show significantly lower blood values than adult females (P < 0.001 for all three parameters). Yearling blood values (Hct: 47.2 ± 3.6%; Hb: 17.3 ± 1.6 g/dl; RBC: 5.6 ± 0.4·106/μl; n= 56) did not differ significantly from those of adult females (P < 0.32; P < 0.26; P < 0.23, respectively). Blood values of adult females were lower than those of 2‐yr‐olds (Hct: 49.6 ± 2.4%; Hb: 18.5 ± 1.2 g/dl; RBC: 5.7 ± 0.3·106/μl; n= 31). These differences were significant only for RBCs (P < 0.003). Up to the age of 1 yr, age was the best predictor for blood values, thereafter mass tended to be a better predictor. Female juveniles between the ages of 150 and 600 d had higher blood values than same‐age males. The relationship of blood value development to diving activity is briefly described and the results are compared to values of other marine mammals. Ontogeny is discussed in relation to the development of these blood values in terrestrial mammals.
INVESTIGATING TROPHIC RELATIONSHIPS OF PINNIPEDS IN ALASKA AND WASHINGTON USING STABLE ISOTOPE RATIOS OF NITROGEN AND CARBON
Authors: Hobson Keith A. , Sease John L. , Merrick Richard L. , Piatt John F.
Published: August 2006

Abstract

We measured stable‐nitrogen (δ15N) and stable‐carbon (δ13C) isotope ratios in muscle and hair from 7 northern fur seals (Callorhinus ursinus) from the Pribilof Islands, Alaska, and 27 Steller sea lions (Eumetopias jubatus), and 14 harbor seals (Phoca vitulina) from the Gulf of Alaska and coast of Washington State, in order to contrast dietary information derived from isotopic vs. available conventional dietary studies. Stable‐nitrogen‐isotope analysis of muscle revealed that harbor seals were enriched over sea lions (mean δ15N = 18.6‰vs. 17.5‰) which were in turn enriched over northern fur seals (mean δ15N = 16.6‰). Trophic segregation among these species likely results primarily from differential reliance on herring (Clupea harengus), Atka mackerel (Pleurogrammus monopterygius), and large vs. small walleye pollock (Theregra chalcogramma). According to their δ15N values, adult male Steller sea lions showed a higher trophic position than adult females (mean δ15N: 18.0‰vs. 17.2‰), whereas adult female northern fur seals were trophically higher than juvenile male fur seals (mean δ15N: 16.5‰vs. 15.0‰). Each of these observed differences likely resulted from differential reliance on squid or differences in the size range of pollock consumed. Three northern fur seal pups showed higher δ15N enrichment over adults (mean 17.7‰vs. 15.8‰) due to their reliance on their mother's milk. Stable‐carbon isotope measurements of hair revealed a cline toward more negative values with latitude. Segregation in hair δ13C between Steller sea lions and harbor seals off the coast of Washington (mean δ13C: −13.6‰vs.−15.0‰) reflected the greater association of harbor seals with freshwater input from the Columbia River. Our study demonstrates the utility of the stable isotope approach to augment conventional dietary analyses of pinnipeds and other marine mammals.
BLUE WHALE, BALAENOPTERA MUSCULUS, VOCALIZATIONS FROM THE WATERS OFF CENTRAL CALIFORNIA
Authors: Rivers Julie A.
Published: August 2006

Low‐frequency calls produced by blue whales, Balaenoptera musculus, were recorded in the northeastern Pacific Ocean off central California. Two blue whales were sighted during a vessel‐based marine mammal survey, and when sonobuoys were subsequently deployed, blue whale calls were recorded. A third recording was obtained during the survey from a blue whale that was not seen. Recordings with 15, 25, and 55 min of calls were obtained from these individuals. The three recordings all contain two‐part, low‐frequency calls with slight interindividual variation. The calls consist of an amplitude modulated (AM) signal with a mean center frequency of 16.5 Hz, followed by a downsweep whose mean center frequency sweeps from 18.2 Hz to 16.6 Hz. The recordings are compared with blue whale recordings from the Pacific and Atlantic Oceans. The geographic variability suggests that blue whale calls may be used as an acoustic indicator of stock identity.
COMPARISON OF VERTICAL AERIAL PHOTOGRAPHIC AND GROUND CENSUSES OF STELLER SEA LIONS AT AÑO NUEVO ISLAND, JULY 1990‐1993
Authors: WESTLAKE ROBIN L. , PBRRYMAN WAYNE L. , ONO KATHRYN A.
Published: August 2006

Counts of Steller sea lion (Eumetopias jubatus) pups and non‐pups (adults and juveniles) from aerial photographs of rookeries at Año Nuevo Island between 1990 and 1993 were significantly higher than those made on the ground. Based on regression of natural logs of photographic counts versus year, the number of pups declined at a rate of −0.099yr while non‐pup numbers declined at −0.315/yr. Examination of ground count data for the same period revealed a significant decline in non‐pups (−0.139/yr), but no trend was detected in the ground counts of pups. The regression coefficients from photographic and ground counts of non‐pups did not differ significantly. Power analyses using the program TRENDS indicated that detectable rates of change in abundance from four annual surveys were much lower for counts of pups than counts of non‐pups where sampling precision was based on fits to linear models.
SUCCESSFUL USE OF A TRANSLOCATION PROGRAM TO INVESTIGATE DIVING BEHAVIOR IN A MALE AUSTRALIAN FUR SEAL, ARCTOCEPHALUS PUSILLUS DORIFERUS
Authors: HINDELL MARK A. , PEMBERTON DAVID
Published: August 2006

This study reports some of the first foraging behavior data collected for male fur seals. A nonbreeding male Australian fur seal, Arctocephalus pusillus doriferus, captured at a commercial salmon farm in southern Tasmania, Australia, was relocated 450 km from the site of capture. The animal was equipped with a geolocating time‐depth recorder that recorded diving behavior and approximate location for the 14.4 d that it took the seal to travel down the east coast of Tasmania and be recaptured at the salmon farm. During its time at sea, the seal spent most of its time over the relatively shallow shelf waters. It spent 30% of its time ashore on a number of different haul‐out sites. The deepest dive was 102 m and the maximum duration was 6.8 min. “Foraging” type dives made up 31.2% of the time at sea and had a median duration of 2.5 min and a median depth of 14 m. The seal performed these dives more commonly during the latter part of its time at sea, while it was on the east coast. Unlike other fur seal species studied to date, there was no evidence of a diurnal foraging pattern; it made dives at all times of the day and night.
LOW VARIATION IN BLOOD δ13C AMONG HUDSON BAY POLAR BEARS: IMPLICATIONS FOR METABOLISM AND TRACING TERRESTRIAL FORAGING
Authors: Hobson Keith A. , Stirling Ian
Published: August 2006

Abstract

We investigated the use of stable‐carbon isotope analysis of serum and cellular fractions of blood to detect the extent of terrestrial feeding in polar bears on land during the ice‐free period in western Hudson Bay. We compared blood in bears that were restricted entirely to coastal areas, who showed no evidence of terrestrial feeding, with blood in bears sampled at inland locations and who were known to have fed on berries ofVaccinium uliginosumandEmpetrum nigrum. Despite a separation of approximately 9‰ between terrestrial and marine foods, we found no statistical difference in blood 613C values between these two groups of bears. This suggests that (1) carbon pathways associated with feeding on berries result in minor incorporation of terrestrial‐based carbon into bulk plasma or cellular fractions of blood, (2) bears feed insignificantly on berries despite observational evidence to the contrary, or (3) carbon mobilized from endogenous lipid reserves overwhelmed the terrestrial signal or could not be segregated isotopically from carbon derived from berry carbohydrates. We discuss evidence for each of these scenarios and suggest that a more effective approach to using stable‐carbon isotope analysis to delineate the importance or use of terrestrial foods to polar bears on land in Hudson Bay during the ice‐free period might be through the isotopic analysis of exhaled carbon dioxide rather than blood components.
CATCHES OF HUMPBACK AND OTHER WHALES FROM SHORE STATIONS AT MOSS LANDING AND TRINIDAD, CALIFORNIA, 1919–1926
Authors: Clapham Phillip J. , Leatherwood Stephen , Szczepaniak Isidore , Brownell Robert L.
Published: August 2006

Abstract

Logbook data from California shore whaling stations at Moss Landing (1919–1922 and 1924) and Trinidad (1920 and 1922–1926) are analyzed. The logs for the two stations record the taking of 2,111 whales, including 1,871 humpbacks, 177 fin whales, 26 sei whales, 3 blue whales, 12 sperm whales, 7 gray whales, 1 right whale, 1 Baird's beaked whale, and 13 whales of unspecified type (probably humpbacks). Most whales were taken from spring to autumn, but catches were made in all months of some years. The sex ratios of humpback, fin, and sei whales (the three species with sufficient sample sizes to test) did not differ from parity. Primary prey, determined from stomach contents, included sardines and euphausiids for both humpback and fin whales, and ‘plankton’ (probably euphausiids) for sei whales. The prevalence of pregnancy was 0.46 among mature female humpbacks and 0.43 among mature female fin whales, although these values are reported with caution. Information on length distribution for all species is summarized. Analysis of the catch data for this and other areas supports the current view that humpback whales along the west coast of the continental United States comprise a single feeding stock and also suggests that the present population is well below pre‐exploitation levels.
CALCULATING LIMITS TO THE ALLOWABLE HUMAN‐CAUSED MORTALITY OF CETACEANS AND PINNIPEDS
Authors: Wade Paul R.
Published: August 2006

Abstract

A simulation method was developed for identifying populations with levels of human‐caused mortality that could lead to depletion, taking into account the uncertainty of available information. A mortality limit (termed the Potential Biological Removal, PBR, under the U. S. Marine Mammal Protection Act) was calculated as the product of a minimum population estimate (NMIN), one‐half of the maximum net productivity rate (RMAX), and a recovery factor (FR). Mortality limits were evaluated based on whether at least 95% of the simulated populations met two criteria: (1) that populations starting at the maximum net productivity level (MNPL) stayed there or above after 20 yr, and (2) that populations starting at 30% of carrying‐capacity (K) recovered to at least MNPL after 100 yr. Simulations of populations that experienced mortality equal to the PBR indicated that using approximately the 20th percentile (the lower 60% log‐normal confidence limit) of the abundance estimate for NMIN met the criteria for both cetaceans (assuming RMAX= 0.04) and pinnipeds (assuming RMAX= 0.12). Additional simulations that included plausible levels of bias in the available information indicated that using a value of 0.5 for FR would meet both criteria during these “bias trials.” It is concluded that any marine mammal population with an estimate of human‐caused mortality that is greater than its PBR has a level of mortality that could lead to the depletion of the population. The simulation methods were also used to show how mortality limits could be calculated to meet conservation goals other than the U. S. goal of maintaining populations above MNPL.
A NEW HYBRID BETWEEN A BLUE WHALE, BALAENOPTERA MUSCULUS, AND A FIN WHALE, B. PHYSALUS: FREQUENCY AND IMPLICATIONS OF HYBRIDIZATION
Authors: Bérubé Martine , Aguilar Alex
Published: August 2006

Abstract

A female hybrid between a fin (Balaenoptera physalus) and a blue whale (B. mnusculus) was caught in whaling operations in 1984 off northwestern Spain. Its coloration and body proportions were intermediate between those of a fin and a blue whale, although it was anomalously large (19.4 m) when compared to fin whales of similar age (4 yr). It was sexually immature, concomitant with its age but not its length if it were a fin whale. Molecular analyses revealed that the mother of the hybrid was a blue whale and the father a fin whale. Examination of data for the five fin‐blue whale hybrids in the literature, plus other anecdotal reports, indicates that hybridization between these two species occurs in various geographic regions and is relatively frequent, notably in light of the absence of reported hybrids between other mysticetes. Either species may act as father or mother, and there does not appear to be a selection for a given sex among the hybrids. The reproductive capacity of these hybrids remains unknown, although incidence of reproductive impairment appears to be higher in hybrid males than in hybrid females.
INCREASED HARASSMENT OF RIGHT WHALES (EUBALAENA AUSTRALIS) BY KELP GULLS (LARUS DOMINICANUS) AT PENÍNSULA VALDÉS, ARGENTINA
Authors: Rowntree V. J. , Mcguinness P. , Marshall K. , Payne R. , Sironi M. , Seger J.
Published: August 2006

Abstract

Kelp gulls at Península Valdés, Argentina, have recently developed the habit of feeding on pieces of skin and blubber that they gouge from the backs of southern right whales. In response, the whales flinch violently, submerge, and swim rapidly away underwater. The level of harassment in 1995 was almost five times higher than when first studied in 1984 by Thomas (1988). In 1995, 67% of attacks were aimed at large white lesions on the whales' backs. The proportion of whales with lesions increased from 0.01 in 1974 to 0.32 in 1990. Mother‐calf pairs that were attacked traveled at medium and fast speeds for 3.1 h per day, compared to 0.8 h for undisturbed pairs. Mother‐calf pairs are estimated to spend approximately 24% of their daylight hours in states of gullinduced disturbance. Little food is available at Península Valdés, so mothers must rely on blubber reserves to support their calves' growth, behavioral development, and migration to the feeding grounds. Even when undisturbed by gulls, mothers often curtail their calves' play and nursing bouts, suggesting that their energy reserves are limited. Increasingly intense harassment by gulls may therefore compromise calf development and might even induce right whales to abandon Península Valdés for other calving grounds.
REDUCED BODY SIZE OF FEMALE STELLER SEA LIONS FROM A DECLINING POPULATION IN THE GULF OF ALASKA
Authors: Calkins Donald G. , Becker Earl F. , Pitcher Kenneth W.
Published: August 2006

Abstract

Nutritional stress is a leading hypothesis behind the decline in numbers of Steller sea lions in the Gulf of Alaska, the Aleutian Islands, and the Bering Sea. To evaluate this hypothesis we compared body growth of female Steller sea lions 1.0–13.9 yr of age collected in the Gulf of Alaska during two time periods, 1975–1978 just prior to or early in the decline and 1985–1986 when the decline was well established. We found that growth, as measured by standard length, axillary girth, and mass, was reduced during the 1980s, supporting the undernutrition hypothesis. We also found a suggestion of reduced growth in our 1970s and 1980s samples when compared to a collection of Steller sea lions obtained from the Gulf of Alaska in 1958. However, no direct link has been demonstrated between undernutrition and the actual decline in numbers.
DISTRIBUTION AND INNERVATION OF FACIAL BRISTLES AND HAIRS IN THE FLORIDA MANATEE (TRICHECHUS MANATUS LATIROSTRIS)
Authors: Reep R. L. , Marshall C. D. , Stoll M. L. , Whitaker D. M.
Published: August 2006

Abstract

The distribution and anatomy of sirenian perioral bristles (modified vibrissae) and facial hairs are of interest because of their use during feeding and tactile exploration. In the present study we have identified six fields of perioral bristles on the face of the Florida manatee (T. manatus latirostris), four (U1‐U4) on each side of the upper lips and oral cavity, and two (L1‐L2) on each side of the lower lip pad, inside the oral cavity and rostral to the horny mandibular pad. Each field has a characteristic location, number of bristles, and range of bristle length and diameter. There is a mean of 110 (± 19) bristles per side, with no left‐right differences. Branches of the infraorbital nerve innervate the bases of the largest bristles (U2 group) on the upper bristle pad, and the inferior alveolar nerve supplies the bristles of the lower bristle pad. The dorsal and ventral buccal branches of the facial nerve innervate the superficial facial musculature, which is likely to be involved in bristle eversion and other movements which constitute feeding behavior.

Hair is denser in the facial region than on the remainder of the body. Within the face, hair is denser on the oral disk than on the supradisk. The oral disk contains bristle‐like hair, whereas the supradisk region possesses hair that is similar in length and diameter to that on the postcranial body. The mean total of bristles and hairs per face was 1,942. Means for the subregions were 220 (± 39) bristles on the perioral bristle pads, 601 (± 115) bristlelike hairs in the oral disk region, 710 (± 229) typical hairs in the supradisk region, and 411 (± 108) typical hairs on the chin. There were no significant differences between left and right side counts. Facial hair density was inversely correlated with facial area and body size.

These data provide new information on the anatomical basis of the exceptional orofacial activities characteristic of manatees during feeding and tactile exploration.