bluuebunny/crossref_metadata_2025_split huggingface dataset:
TARGET DISCRIMINATION BY AN ECHOLOCATING FINLESS PORPOISE, NEOPHOCAENA PHOCAENOIDES
Authors: Nakahara Fumio , Takemura Akira , Koido Takashi , Hiruda Hisoka 
Published: August 2006

AbstractThe 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

AbstractWe 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

AbstractWe 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

ABSTRACTLow‐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

ABSTRACTCounts 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

ABSTRACTThis 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

AbstractWe 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

AbstractLogbook 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

AbstractA 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

AbstractA 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

AbstractKelp 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

AbstractNutritional 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

AbstractThe 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.
A PROTRACTED FORAGING AND ATTENDANCE CYCLE IN FEMALE JUAN FERNÁNDEZ FUR SEALS
Authors: Francis John , Boness Daryl , Ochoa‐Acuña Hugo 
Published: August 2006

AbstractPrevious studies of fur seals suggest that the attendance patterns and consequent temporal patterning of energy transfer from mother to pup follows a latitudinal cline. While data from subpolar, tropical, and some temperate latitude species support the postulated cline, data for the temperate latitude Juan Fernández fur seal do not. Maternal foraging trips and associated visits ashore were the longest of all otariids studied to date. The first foraging trip postpartum averaged 10.2 d (n= 51 females, range 1–22.5), foraging trips combined averaged 12.3 d (n= 100, range 1.0‐25.0), and visits ashore averaged 5.3 d (n= 91, range 0.3‐15.8) over the three seasons of study. Only duration of lactation was intermediate between subpolar and tropical strategies as predicted. Dive records suggest that these females feed almost exclusively at night at depths of less than 10 m and at distances of more than 500 km offshore. The prey species of this fur seal, primarily myctophids and squid, migrate to the surface at night and are patchily distributed. Foraging trip length varied between years in conjunction with shifts in seasurface temperature and type of prey consumed. We suggest that distribution of prey, irrespective of latitude, dictates foraging patterns of fur seals and leads to the exceptionally long foraging trips and visits ashore observed in this species.
INCREASED VIGILANCE TOWARD UNFAMILIAR HUMANS BY HARBOR (PHOCA VITULINA) AND GRAY (HALICHOERUS GRYPUS) SEALS
Authors: Taylor Allison A. , Davis Hank , Boyle Glenn J. 
Published: August 2006

AbstractTwo pairs of harbor (Phoca vitulina) and three pairs of gray (Halicboeruls grypus) seals were exposed to one of three human handlers for 15 min, twice a day, for a total of six sessions. Following habituation to the familiar handler, animals were then exposed to a novel human for 7 min, and then retested for 7 min with the familiar human. In all cases, animals responded to the unfamiliar human with increased vigilant behavior, i. e., they spent more time oriented towards the unfamiliar handler during the first 2 min of the test session than during the same interval of either the final habituation session or the retest with the familiar human (P= 0.03 in all cases). There was also a tendency for seals to contact the familiar handler with their noses more rapidly than the novel human (P= 0.06). These results support the hypothesis that phocid seals are capable of discriminating between individual humans in their environment, setting the stage for human‐based Pavlovian conditioning.
ABUNDANCE OF SOUTHERN CALIFORNIA COASTAL BOTTLENOSE DOLPHINS ESTIMATED FROM TANDEM AERIAL SURVEYS
Authors: Carretta J. V. , Forney K. A. , Laake J. L. 
Published: August 2006

AbstractWe describe a tandem aerial survey method for bottlenose dolphins (Tursiops truncatus) that uses two aircraft and independent observer teams to conduct consecutive surveys of the same coastal strip one hour apart. Alternatively, one aircraft with one observer team surveys the same coastal strip twice over several hours. Using mark‐recapture analysis, we corrected survey counts for visibility bias resulting from missing dolphin groups at the surface and submerged groups. Dolphin groups were considered “recaptured” when we determined that both observer teams had detected the same group. This tandem method is highly useful for estimating abundance (and visibility bias) for species where population closure may be assumed between flights. We assumed population closure between flights and matched groups using geographic location, group size, and expected travel rates. We derive a new variance estimator of population size which incorporates group‐size variability commonly encounteted in cetacean surveys. From six tandem surveys conducted from 1991 to 1994, we estimated the abundance of southern California coastal bottlenose dolphins to be between 78 (95% CI 60‐102) and 271 (240‐306) animals, with an average of 140 (128‐154). Variability in abundance estimates is likely due to seasonal and interannual movement of animals along the California and Baja California coast. Abundance estimates from tandem surveys averaged 53% higher than dolphin counts obtained from individual survey flights, demonstrating the importance of correcting for visibility bias.