bluuebunny/crossref_metadata_2025_split huggingface dataset:
REPRODUCTION, SURVIVAL AND TAG LOSS IN CALIFORNIA SEA OTTERS
Authors: Siniff Donald B. , Ralls Katherine 
Published: August 2006

AbstractWe observed 40 California sea otters, Enhydra lutris, that were instrumented with implanted radio transmitters and flipper‐tagged, and obtained additional data on the reproduction of tagged female otters from the California Department of Fish and Game.The proportion of instrumented females accompanied by a pup peaked in the spring, with a secondary peak in the fall. Two methods of estimating the annual reproductive rate gave comparable values of 0.90 and 0.94. The average inter‐birth interval was 389 d. Two methods of estimating pup survival to weaning gave values of 0.46 and 0.58. Pups either remained with a female less than 80 or more than 120 d. Early mortality of dependent pups appears to be more frequent in California than in Prince William Sound, Alaska.Two methods of estimation indicated that adult females had the highest survival rates and adult males the lowest. Juvenile females had lower survival rates than adult females but juvenile males had higher survival rates than adult males. The survival rate of juvenile females was lower than that of juvenile males.The estimated annual loss rate for flipper‐tags, based on the instrumented individuals, was 0.26. More individuals lost two tags than would be expected by chance. It is unlikely that accurate estimates of sea otter survival rates can be derived from observations of tagged individuals.
SEXUAL DIMORPHISM IN NEWBORN SOUTHERN SEA LIONS
Authors: Cappozzo H. Luis , Campagna Claudio , Monserrat Jose 
Published: August 2006

AbstractMale southern sea lion, Otaria byronia, pups born at Peninsula Valdés, Argentina, were significantly heavier (13.7 ± 1.6 kg, n = 37 vs 12.3 ± 1.4 kg, n= 38) and longer (0.82 ± 0.04 m, n= 29 vs. 0.79 ± 0.03 m, n= 29) than females. The rate of mass and length gain during the first month of life did not differ between the sexes (males: 0.21 kg/d, 0.003 m/d; females: 0.20 kg/d, 0.004 m/d). Sex differences in pup body size were not reflected in female nursing behavior, attendance patterns, and duration of feeding trips. These results suggest that southern sea lion mothers invest more energy in sons than in daughters during gestation, a difference consistent with the importance of large body size to the reproductive success of males in a polygynous species.
DIET OF WEDDELL SEALS LEPTONYCHOTES WEDDELLII AT VESTKAPP, EASTERN WEDDELL SEA (ANTARCTICA), IN RELATION TO LOCAL FOOD SUPPLY
Authors: Plötz Joachim , Ekau Werner , Reijnders Peter J. H. 
Published: August 2006

AbstractThirteen Weddell seals (Leptonychotes weddellii) were collected at Vestkapp, eastern Weddell Sea coast, in austral spring 1986. All stomachs contained partially digested food. The mean wet weight of stomach contents was 7.5 kg, 3.3% of the. mean body weight of the collected seals. Twelve fish species and three cephalopod species were identified from 372 left otoliths and 25 lower beaks, representing 58.4% of 679 total prey items obtained. Composition by number of total prey was: Chionodraco myersi (15.8%), Trematomus eulepidotus (10.0%), Pagetopsis maculatus (9.7%), Racovitzia glacialis (9.6%) and Cryodraco antarcticus (4.1%). Otoliths of the seven other fish species and beaks of the three cephalopod species together represented 9.1% of total prey numbers. The pooled wet weights calculated from 13 prey species (regressions for two octopod species were not available) amounted to 43.5 kg food mass and represented 44.7% of the combined food mass in all stomachs. Composition by mass was: C. myersi (44.5%), T. eulepidotus (19.8%), squid Psychroteuthis glacialis (8.5%), P. maculates (7.9%), C. antarcticus (7.1%) and R. glacialis (6.2%). The remaining 7 fish species together represented 5.8% by mass. Temporal variation in food availability was apparent. Midwater fish Pleuragramma antarcticum was the staple food of Weddell seals from the same area during the 1985 summer, whereas it was absent in the samples taken in spring 1986. Estimates of fish biomass from net hauls demonstrate a highly variable availability of pelagic food resources for top predators in the Vestkapp area.
KILLER WHALES,ORCINUS ORCA, IN THE SOUTHEASTERN BERING SEA: RECENT SIGHTINGSandPREDATION ON OTHER MARINE MAMMALS
Authors: Frost Kathryn J. , Russell Richard B. , Lowry Lloyd F. 
Published: August 2006

ABSTRACTAn unusual number of killer whales appeared in inshore waters of the southeastern Bering Sea in summer 1989 and 1990. Multiple sightings occurred in Bristol and Kuskokwim bays where killer whales had been seen only rarely in previous years. Three animals became stranded on mud flats in Kuskokwim Bay but were able to free themselves on a high tide. Killer whales were observed interacting with salmon, harbor seals, Steller sea lions, walruses, and beluga whales. Detailed observations were made of killer whales attacking belugas in the Naknek River. Local conditions and behavioral adaptations may reduce the susceptibility of belugas to killer whale predation. Continued killer whale activity in this area would be unlikely to affect fish resources, but might have some influence on beluga whales.
CYCLIC OCULAR HYPERTENSION IN CETACEANS
Authors: Dawson William W. , Schroeder J. Pete , Dawson Judyth C. , Nachtigall Paul E. 
Published: August 2006

ABSTRACTIn the laboratory, intraocular pressure (IOP) was measured in each eye of two adult Tursiops truncatus and one Grampus griseus. Measures were made in alternation between eyes over a time span. Means and standard deviations were calculated. Mean IOP's ranged from 33.4 mm Hg (SD = 2.4) in the male Tursiops to 24.6 (SD = 2.3) in the female Tursiops. IOP in the Grampus was intermediate. Tonograph functions for the Tursiops over periods greater than 25 min had a cyclic character with maxima and minima. These cycles were fitted with a polynomial function with periods of 15 min (female) and 20 to 26 min (male). There was no significant correlation of the IOP variations with time between eyes in either Tursiops. Compared to humans, these cetaceans exhibit clinical ocular hypertension bilaterally. The range of pressures they exhibit, over time, is much greater than reported previously for several terrestrial mammals.
IMMOBILIZATION OF WALRUS WITH ETORPHINE HYDROCHLORIDE AND ZOLETIL®
Authors: Griffiths David , Wiig ØYstein , Gjertz Ian 
Published: August 2006

Abstract: The paper describes the use of the drugs Zoletil® and etorphine for the immobilization of walrus (Odobenus rosmarus rosmarus) for attachment of satellite telemetry equipment. Three animals weighing approximately 1,500 kg each were injected intramuscularly with Zoletil® at a dose between 1.4 and 2.2 mg/kg. One walrus died while the two others were adequately restrained. The induction time was between 14 and 29 minutes and the effect lasted for 75‐220 min.Thirty‐eight animals of weight 900‐1,500 kg were darted intramuscularly with etorphine at a dose between 3.3 and 8 mg/kg. Thirty‐six were immobilized although one died later. The induction time for etorphine was two to ten minutes. The action of this drug was terminated with an injection of the antidote di‐prenorphine.The use of etorphine was accompanied by convulsive movements and apnoea while Zoletil® produced a gradual and smooth entry into and withdrawal from immobilization.
VOCALIZATIONS OF A CAPTIVE JUVENILE AND FREE‐RANGING ADULT‐CALF PAIRS OF BRYDE'S WHALES, BALAENOPTERA EDENI
Authors: Edds Peggy L. , Odell Daniel K. , Tershy Bernie R. 
Published: August 2006

Abstract: Vocalizations were recorded from a captive juvenile Bryde's whale, Balaenoptera edeni, that stranded off the gulf coast of Florida (Pinellas Co.) and was held at Sea World of Florida. The most common vocalization was a pulsed moan with durations of 0.5–51 set and acoustic energy from 200–900 Ht. Although these sounds are unlike any reported previously from this species, there are similarities to moans recorded opportunistically during a feeding study of free‐ranging B. edeni in the Gulf of California (GOC). The pulsed moans recorded from Bryde's whale adults in the GOC were shorter in duration (0.7–1.4 set) than those recorded from the captive juvenile, but the frequencies were similar (165–875 Hz). In addition, a series of discrete, regularly spaced pulses (interpulse interval = 0.5–1.0 set, 700–950 Hz) were recorded only in the presence of Bryde's whale calves in the GOC.Pulse rates produced by the captive juvenile (20–70 pulses/set) were intermediate between those recorded in the presence of GOC adults (60–130/sec) and calves (10–20/set). With these limited data it is not possible to determine to what extent the intermediate qualities of the juvenile call reflect maturational differences in the sound production apparatus, a phase of learning to vocalize like an adult, or the characteristics of a context‐dependent call not recorded in the GOC.
NEW ZEALAND HERD STRANDING SITES DO NOT RELATE TO GEOMAGNETIC TOPOGRAPHY
Authors: Brabyn Mark , Frew Richard V. C. 
Published: August 2006

AbstractRecent theories relating cetacean stranding sites to geomagnetic topography were tested for the New Zealand coastline. New Zealand herd strandings showed no relationship to either perpendicular geomagnetic contours or magnetic minima, nor did whales appear to be avoiding magnetic gradients. Single‐live stranding sites also showed no geomagnetic relationship.
CETACEANS OF THE NORTHERN GULF OF CALIFORNIA: DISTRIBUTION, OCCURRENCE, and RELATIVE ABUNDANCE
Authors: Silber Gregory K. , Newcomer Michael W. , Silber Patricia C. , Pérez‐Cortés M. Héctor , Ellis Graeme M. 
Published: August 2006

AbstractA total of 1,715 km of boat‐based surveys and 1,521 km of aircraft‐based surveys was conducted from 1986–1989 to assess the distribution, relative abundance, and ecological relationships of cetaceans in the northern Gulf of California. Seven cetacean species were seen; in decreasing frequency of groups encountered they were: bottlenose dolphins, Tursiops truncatus; vaquitas, Phocoena sinus; common dolphins, Delphinus delphis; fin whales, Balaenoptera physalus; Bryde's whales, B. edeni; gray whales, Eschrichtius robustus, and killer whales, Orcinus orca. Common dolphins were numerically dominant and bottlenose dolphins were seen most often. Bryde's whales and vaquitas had the smallest group sizes. In general, the odontocete cetaceans were separated spatially, whereas the distribution of Bryde's and fin whales overlapped considerably.
DIGESTIBILITY OF CRUSTACEANS and CAPELIN IN HARP SEALS (PHOCA GROENLANDICA)
Authors: Mårtensson P.‐E. , Nordøy E. S. , Blix A. S. 
Published: August 2006

AbstractGross energy intake (GEI), apparent digestible efficiency (%DE), and body‐mass change were studied both in recently weaned and in subadult harp seals fed capelin (Mallotus villosus) and crustaceans (Parathemisto libellula and Thysanoessa sp.) ad lib. The median %DE of Parathemisto libellula (with a wet‐weight energy density (ED) of 3.9 kJ/g) and Thysanoessa sp. (ED: 2.3 kJ/g) was 81% and 83%, respectively, while the median %DE of capelin (ED: 8.6 kJ/g) was 94% and 93% for subadult harp seals and one harp seal pup, respectively. No correlation between age and %DE was obtained (P > 0.05). Despite ad lib. access to the food, the harp seal pups were unable to maintain body mass while on a crustacean diet, and it is therefore suggested that harp seal pups most likely must supplement their crustacean diets with fish to maintain growth.
ECHOLOCATION RATES OF TWO HARBOR PORPOISES (PHOCOENA PHOCOENA)
Authors: Akamatsu Tomonari , Hatakeyama Yoshimi , Kojima Takahito , Soeda Hideo 
Published: August 2006

AbstractThe rate of occurrence of click trains of two harbor porpoises (Phocoena phocoena) were counted during 14 nights. We developed an echolocation signal detection system that was harnessed to a porpoise and activated a light when the animal emitted an echolocation signal. This device, referred to as a click‐light, detects echolocation signals above 150 dB re 1 μPa in the 28–180 kHz range. Echolocation rates, i.e., occurrences of click trains, changed frequently, ranging from 0 to 25 per minute. Echolocation rates were affected by feeding, individual difference, and enclosure type such as the net enclosure and the pool. The porpoise echolocation rates seemed to show acclimation.
A COMPARISON OF SOME CYCLOHEXAMINE BASED DRUG COMBINATIONS FOR CHEMICAL RESTRAINT OF SOUTHERN ELEPHANT SEALS (MIROUNGA LEONINA)
Authors: Woods Rupert , McLean Stuart , Nicol Stewart , Burton Harry 
Published: August 2006

AbstractThis study compared the effects of drug combinations commonly used for chemical restraint of southern elephant seals. The combinations were: ketamine and diazepam, ketamine and midazolam, ketamine and xylazine, and tiletamine and zolazepam. The main aims were to gather basic information regarding the response of the animals to the different combinations, and to determine which were most useful for routine chemical restraint. All drug combinations could be used safely although apnea and whole‐body shaking occurred with each. There were significant differences in several of the responses measured. Poor muscle relaxation and prolonged apnea were associated with ketamine and diazepam use. Animals given ketamine and xylatine were more depressed, took longer to recover, had a higher incidence of thermoregulatory problems, and lower heart rate than after other combinations. Ketamine and midazolam and tiletamine and zolazepam produced fewer complications than the other drug combinations, and tiletamine and zolazepam showed greater predictability of response and ease of use, making it preferable for use by people with little experience in anesthesia of elephant seals.
FEEDING, SOCIAL AND MIGRATION BEHAVIOR OF BOWHEAD WHALES, BALAENA MYSTICETUS, IN BAFFIN BAY VS. THE BEAUFORT SEA—REGIONS WITH DIFFERENT AMOUNTS OF HUMAN ACTIVITY
Authors: Richardson W. John , Finley Kerwin J. , Miller Gary W. , Davis Rolph A. , Koski William R. 
Published: August 2006

AbstractThis paper compares the behavior of bowhead whales of the Davis Strait/Baffin Bay stock, as observed along the east coast of Baffin Island in 1979–1986, with behavior of the Bering/Chukchi/Beaufort Sea stock observed in the Beaufort Sea in 1980–1986. All data used here were collected during late summer and early autumn in the absence of acute human disturbance. The behavioral repertoires of the two populations were similar. However, quantitative differences were found for whales engaged in all three activities studied: (1) Bowheads feeding in deep water off Isabella Bay, Baffin Island, had longer dives and surfacings, on average, than noted for bowheads feeding in the Beaufort Sea. (2) Among whales socializing in shallow water, we saw sexual interactions more often at Isabella Bay than in the Beaufort Sea. Calls emitted by socializing whales off Baffin Island were similar to those heard in the Chukchi and Beaufort Seas. However, pulsed tonal calls were longer off Baffin Island, and previously undescribed mechanical “crunch” sounds were recorded there near socializing bowheads. (3) During autumn migration, “fluke‐out” dives were less common, and dive durations were longer, in the Beaufort Sea than off Baffin Island (P<0.001). Multivariate and other analyses indicated that some but not all differences can be ascribed to regional differences in the natural environment or in whale activities, However, during 1974–1986, Bering/Chukchi/Beaufort bowheads were exposed to more industrial, hunting and other human activity than Davis Strait/Baffin Bay bowheads. The “inconspicuous” behavior during autumn migration in the Beaufort may have been attributable to human activities, but causative links cannot be isolated.
DETECTION OF SEA OTTERS IN BOAT‐BASED SURVEYS OF PRINCE WILLIAM SOUND, ALASKA
Authors: Udevitz Mark S. , Bodkin James L. , Costa Daniel P. 
Published: August 2006

AbstractBoat‐based surveys have been commonly used to monitor sea otter populations, but there has been little quantitative work to evaluate detection biases that may affect these surveys. We used ground‐based observers to investigate sea otter detection probabilities in a boat‐based survey of Prince William Sound, Alaska. We estimated that 30% of the otters present on surveyed transects were not detected by boat crews. Approximately half (53%) of the undetected otters were missed because the otters left the transects, apparently in response to the approaching boat. Unbiased estimates of detection probabilities will be required for obtaining unbiased population estimates from boat‐based surveys of sea otters. Therefore, boat‐based surveys should include methods to estimate sea otter detection probabilities under the conditions specific to each survey. Unbiased estimation of detection probabilities with ground‐based observers requires either that the ground crews detect all of the otters in observed subunits, or that there are no errors in determining which crews saw each detected otter. Ground‐based observer methods may be appropriate in areas where nearly all of the sea otter habitat is potentially visible from ground‐based vantage points.
MAXIMUM NET PRODUCTIVITY LEVEL ESTIMATION FOR THE NORTHERN FUR SEAL (CALLORHINUS URSINUS) POPULATION OF ST. PAUL ISLAND, ALASKA
Authors: Ragen Timothy J. 
Published: August 2006

AbstractThe goal of this study was to assess the maximum net productivity level for the northern fur seal (Callorhinus ursinus) population of St. Paul Island, Alaska. Definitive determination of this level is not possible due to uncertainty in life table parameters and density‐dependent changes in those parameters. To account for such uncertainty, repetitive numerical simulations were used to generate frequency distributions of estimates for the maximum net productivity level and related population parameters. This approach systematically varied simulation input parameters, ran a separate simulation with each input parameter combination, and validated the simulations on the basis of comparison with historical observations. Results from validated simulations were compiled in frequency distributions to provide a measure of confidence for MNPL estimates. The distributions confirm that this population is probably well below its maximum net productivity level. Because they reflect the uncertainty in our understanding of northern fur seal population dynamics, these distributions are a more realistic basis for management than single point estimates.
AN ASSESSMENT OF CHANGES WITH TIME IN THE MARKING PATTERNS USED FOR PHOTOIDENTIFICATION OF INDIVIDUAL SPERM WHALES, PHYSETER MACROCEPHALUS
Authors: Dufault Susan , Whitehead HAL 
Published: August 2006

AbstractWe observed changes with time in the patterns of characteristic fluke markings used to identify sperm whales. Changes were categorized as minor, moderate, or major based on their severity. These change types were found to occur at rates of 0.9%, 11.8%, and 1.3% per individual per year, respectively. Gain and loss rates for each of seven different mark types were also calculated. The highest estimated rate was the gain of small nicks at 0.08 per individual per year. Most individuals identified by us possess at least a few characteristic marks and, therefore, changes of the type observed in this study are unlikely to severely affect their recognizability. For all but one mark type, gain rates were higher than loss rates, indicating that individuals may be accumulating marks with age. Over long periods this could eventually make individuals unrecognizable, with the result that population sizes calculated from these data may be overestimated. As long as photoidentification studies are conducted sufficiently often, and these changes are as gradual as they appear to be, this problem should be minimal.
REPRODUCTION IN THE FEMALE SUBANTARCTIC FUR SEAL, ARCTOCEPHALUS TROPICALIS
Authors: Bester Martháan N. 
Published: August 2006

AbstractThe reproductive tracts of 89 female subantarctic fur seals, taken at Gough Island between November 1977 and October 1978, were examined. Females started ovulating at age 4 yr and all 6‐yr‐old females were sexually mature. They are mono‐ovulatory, alternating between ovaries, and only single embryos were found. Females older than 13 yr (n= 11) showed poor follicular development and some failed to ovulate. The gestation period (first recorded ovulation to first recorded birth) was 360 d, while delayed implantation (first recorded ovulation to first recorded implantation) lasted for 139 days. Follicle numbers in the functional ovary declined sharply after ovulation while the corpus luteum increased in size until at least 1 mo prior to parturition. The number of follicles in the contralateral ovary increased after midwinter (June/July), and the mean size of the largest follicles peaked prior to ovulation in December. The mean size of the largest follicles increased in both ovaries near implantation time, after reaching a low subsequent to, ovulation. The regressing corpus albicans, conspicuous for approximately 3 mo after parturition, could not be detected macroscopically within one year postpartum. Subantarctic fur seals at Gough Island have a distinct postreproductive class of older females. The pregnancy rate for all females ≥4 yr of age was 79%, and it was 84.5% for the sexually mature group of ≥6 yr of age, while the mean age at puberty was 4.80 yr.
BLOOD CHEMISTRY OF WILD HARBOR PORPOISES PHOCOENA PHOCOENA (L.)
Authors: Koopman H. N. , Westgate A. J. , Read A. J. , Gaskin D. E. 
Published: August 2006

AbstractBlood chemistry values were measured from 31 harbor porpoises (Phocoena phocoena) released from herring weirs in the Bay of Fundy, Canada. Sodium, phosphorus, calcium, chloride, magnesium, total protein, albumin, globulin, urea, cholesterol, serum osmolality, and alanine aminotransferase levels fell within ranges reported for captive harbor porpoises and other odontocetes. Glucose, potassium, creatine kinase, aspartate aminotransferase, hemoglobin, thyroxine, bilirubin, and alkaline phosphatase levels were generally higher than those reported for captive odontocetes. Cortisol and creatinine levels were significantly higher (P= 0.0356 and 0.0174, respectively) in porpoises that were handled for longer periods and fitted with electronic tags (mean cortisol value = 314 ± 107 nmol/L, mean creatinine value = 94 ± 14 μmol/L) than those receiving roto‐tags (mean cortisol value = 222 ± 82 nmol/L, mean creatinine value = 75 ± 15 μmol/L). A more controlled study of duration of handling, time spent out of water, degree of manipulation, and method of tag attachment is required to identify which factors are responsible for the stress response.
DOLPHIN THYROID AND ADRENAL HORMONES: CIRCULATING LEVELS IN WILD AND SEMIDOMESTICATED TURSIOPS TRUNCATUS, AND INFLUENCE OF SEX, AGE, AND SEASON
Authors: St. Aubin D. J. , Ridgway S. H. , Wells R. S. , Rhinehart H. 
Published: August 2006

AbstractBiological and environmental influences on circulating adrenal and thyroid hormones were investigated in 36 wild and 36 semidomesticated Atlantic bottlenose dolphins, Tursiops truncatus, matched by age, sex, and time of year when the samples were collected. Serum concentrations of thyroxine (free [fT41 and total [tT4]), triiodothyronine (free [fT3], total [tT3], and total reverse [rT37), cortisol, and aldosterone were determined by radio‐immunoassay, Wild female dolphins had significantly higher levels of tT4, fT4 and fT3, an effect that was possibly related to reproduction and lactation. Semidomesticated females had higher tT3 than their wild counterparts. fT4 declined with age in wild dolphins, whereas rT3 was greatest in the older animals. Cortisol and aldosterone were both higher in wild animals sampled after a variable interval of up to four hours after encirclement by capture net. The pattern of adrenal hormone release suggested a mild stress response. Levels of both adrenal hormones were low in semidomesticated dolphins conditioned to present voluntarily their tails for blood sampling, an approach that appears to yield specimens representative of resting values for these constituents.