bluuebunny/crossref_metadata_2025_split huggingface dataset:
MOVEMENTS OF SATELLITE‐TAGGED SUBADULT AND ADULT HARBOR SEALS IN PRINCE WILLIAM SOUND, ALASKA
Authors: Lowry Lloyd F. , Frost Kathryn J. , Ver Hoep Jay M. , Delong Robert A. 
Published: August 2006

AbstractSatellite‐linked tags were attached to 49 subadult and adult harbor seals captured in Prince William Sound (PWS), Alaska, and their movements were monitored during 1992–1997. Seals were tracked for a total of 5,517 seal‐days and were located on about 80% of the days that tags transmitted. Most locations were in or near PWS, but some juvenile seals moved 300–500 km east and west into the Gulf of Alaska. While several seals travelled to 50–100 km offshore, virtually all locations were in water <200 m deep. Overall, juvenile seals moved more than adults and had larger home ranges. Movements were significantly affected by month, and age by month and sex by month interactions. In all months, mean distances between successively used haulouts were <10 km for adults and <20 km for juveniles. Mean monthly home ranges varied from <100 km2to >1,500 km2, and were smallest during June‐July. Mean haul‐out to at‐sea distance was 5–10 km for adults and generally 10–25 km for juveniles. Satellite‐linked tags provided an effective means of monitoring and describing the full range of harbor seal movements in this region, with the exception of late summer when tags were shed during the molt.
INVESTMENT IN SONS AND DAUGHTERS BY SOUTHERN ELEPHANT SEALS, MIROUNGA LEONINA, AT MARION ISLAND
Authors: Wilkinson Ian S. , van Aarde Rudi J. 
Published: August 2006

AbstractThe southern elephant seal, Mirounga leonina, exhibits extreme sexual dimorphism and polygyny and is thought to be an ideal subject to test maternal investment theory. Predictions concerning differential investment in offspring by sex were tested on M. leonina breeding at Marion Island over three austral summers. Large females produced more male pups, while small females produced more female pups, providing tentative support for the Trivers and Willard (1973) hypothesis. Maternal size had a greater influence on growth rate and weaning mass than on the sex of offspring. Differential reproductive costs to adult females were not evident in terms of future fecundity or survival. In keeping with other studies on this species, we could not demonstrate any differential investment in the two sexes. We suggest that before discounting maternal investment theories, further studies need to be undertaken to determine the benefits, if any, of size at weaning on long‐term survival and reproductive success.
MAXIMUM SWIM SPEEDS OF CAPTIVE AND FREE‐RANGING DELPHINIDS: CRITICAL ANALYSIS OF EXTRAORDINARY PERFORMANCE
Authors: Rohr J. J. , Fish F. E. , Gilpatrick J. W. 
Published: August 2006

AbstractResearch into dolphin swimming historically was guided by false assumptions pertaining to maximum speed. Accurate measurements on swimming speed and duration of effort of free‐ranging dolphins are rare. To examine the variance of maximum swimming speeds, nearly 2,000 speed measurements were obtained for both captive and free‐ranging dolphins, including Tursiops truncatus, Pseudorca crassidens, Delphinus capensis, and Delphinus delpbis. Measurements were made from videotapes of dolphins trained to swim fast around a large pool or jumping to a maximum height, videotapes of captured wild dolphins immediately after release, and sequential aerial photographs of a school of free‐ranging dolphins startled by a passing airplane. Maximum horizontal speeds for trained animals were 8.2 m/sec for T. truncatus, 8.0 m/sec for D. delphis, and 8.0 m/sec for P. crassidens. Maximum speeds for T. truncatus swimming upwards, prior to vertical leaps ranged from 8.2 to 11.2 m/sec. Wild T. truncatus demonstrated a maximum speed of 5.7 m/sec. Maximum swimming speed of free‐ranging D. capensis responding to multiple passes by a low flying airplane was 6.7 m/sec. There was no evidence that the freeranging dolphins have superior swimming capabilities to captive animals. The results of this study imply that realistic maximum swimming speeds for dolphins are lower than previous reports which were based on sparse data and imprecise measurement techniques.
HOW DO SPERM WHALES CATCH SQUIDS?
Authors: Fristrup Kurt M. , Harbison G. Richard 
Published: August 2006

AbstractVision may play a central role in sperm whale predation. Two complementary hypotheses regarding the detection and capture of prey items are presented, based on a review of mesopelagic ecology. The first hypothesis postulates that sperm whales locate their prey visually, either silhouetted against the midwater “sky,” or by searching for bioluminescence produced by the movements of their prey. The second hypothesis postulates that sperm whales create a zone of stimulated bioluminescence around the mouth, which attracts squids and other visual predators. Studies of midwater fishes and invertebrates document the importance of vision in mesopelagic communities. If sperm whales search for silhouetted prey, they should be oriented upside‐down to improve visual coverage and to facilitate the transition from search to prey capture. Prey capture events should be marked by excursions toward the surface. If they lure their prey, they should swim at a steady pace, with little rapid acceleration, and spend most of their time foraging at depths with the greatest potential for stimulated bioluminescence.
CLICK CHARACTERISTICS OF NORTHERN BOTTLENOSE WHALES (HYPEROODON AMPULLATUS)
Authors: Hooker Sascha K. , Whitehead Hal 
Published: August 2006

AbstractSounds produced by northern bottlenose whales (Hyperoodon ampullatus) recorded in the Gully, a submarine canyon off Nova Scotia, consisted predominately of clicks. In 428 min of recordings no whistles were heard which could unequivocally be attributed to bottlenose whales. There were two major types of click series, initially distinguished by large differences in received amplitude. Loud clicks (produced by nearby whales socializing at the surface) were rapid, with short and variable interclick intervals (mean 0.07 sec; CV 71%). The frequency spectra of these were variable and often multimodal, with peak frequencies ranging between 2 and 22 kHz (mean 11 kHz, CV 59%). Clicks received at low amplitude (produced by distant whales, presumably foraging at depth) had more consistent interclick intervals (mean 0.40 sec, CV 12.5%), generally unimodal frequency spectra with a mean peak frequency of 24 kHz (CV 7%) and 3 dB bandwidth of 4 kHz. Echolocation interclick intervals may reflect the approximate search distance of an animal, in this case 300 m, comparable to that found for sperm whales. The relationship between click frequency and the size of object being investigated, suggests that 24 kHz would be optimal for an object of approximately 6 cm or more, consistent with the size range of their squid prey.
ESTIMATED SOURCE LEVELS OF FIN WHALE (BALAENOPTERA PHYSALUS) VOCALIZATIONS: ADJUSTMENTS FOR SURFACE INTERFERENCE
Authors: Charif Russell A. , Mellinger David K. , Dunsmore Katherine J. , Fristrup Kurt M. , Clark Christopher W. 
Published: August 2006

AbstractWe recorded a series of 34 fin whale vocalizations using four calibrated hydrophones in a towed array. The whale's location was determined using arrival‐time differences of each call at the hydrophones. The recordings showed evidence of interference between signals propagating along direct and surface‐reflected paths (the “Lloyd Mirror”). We made preliminary estimates of source level (SL) using a spherical spreading model of transmission loss. We then applied a conservative correction for the effect of interference by subtracting the maximum possible signal enhancement from the preliminary SL estimate. These adjusted spherical spreading estimates had a median of 171 dB re 1 μPa at 1 m, with a range of 159–184 dB. These are the first SL estimates that explicitly attempt to correct for possible interference effects. We also propose a method that simultaneously estimates SL and source depth by fitting a Lloyd Mirror transmission loss curve to the measured received level, known receiver depth, and source‐to‐receiver range. Attempts to apply this method to the present data set yielded inconsistent results, probably because of the small number of hydrophones available. With more hydrophones in the interference field, this new method should produce reliable estimates of SL and depth of vocalizing whales.
ESTIMATION OF AGE‐SPECIFIC PROBABILITIES OF FIRST RETURN AND ANNUAL SURVIVAL RATES FOR THE MALE GRAY SEAL (HALICHOERUS GRYPUS) ON SABLE ISLAND FROM CAPTURE‐RECAPTURE DATA
Authors: Manske Micheline , Stobo Wayne T. , Schwarz Carl J. 
Published: August 2006

AbstractWe used a longitudinal capture‐recapture study to estimate the age‐specific probabilities of first return to the breeding colony and annual survival rates for male gray seals (Halichoerus grypus), based on resightings of seals branded as young on Sable Island. We estimated that the average age of first returns for seals born in 1969–1970 to be 9.1 (SE 0.4) yr; for seals born in 1973–1974 it is estimated to be 9.8 (SE 0.2) yr. The estimated annual survival rate of these males was estimated to be 0.976 (SE 0.003).
ASSESSMENT OF ARGOS LOCATION ACCURACY FROM SATELLITE TAGS DEPLOYED ON CAPTIVE GRAY SEALS
Authors: Vincent Cécile , Mcconnell Bernie J. , Ridoux Vincent , Fedak Michael A. 
Published: August 2006

AbstractThe Argos satellite system is commonly used to track and relay behavioral data from marine mammals, but their underwater habit results in a high proportion of locations of non‐guaranteed accuracy (location classes (LC) O, A, and B). The accuracy of these locations is poorly documented in marine mammals. We assessed the accuracy of all LCs on four juvenile gray seals fitted with Argos satellite relay data loggers and held in captivity in an outdoor tank for a total of 61 seal‐days. Four hundred and twenty‐six locations were obtained from seals in captivity, and their latitude and longitude error was assessed before and after filtering, following MConnell et al. (1992). There was significantly more error in longitude than latitude in all LCs except I. C A. The ratio of the standard deviations of longitude : latitude ranged from 1.77 (LC 3) to 2.58 (LC 1). Filtering had very little effect on errors in LCs 3‐1, but in the remaining LCs filtering resulted in error reductions ranging from 8% to 63%. In LCs O, A, and B, error reduction was greater in the 95th percentile errors, especially in longitude. The averages of the latitude and longitude 68th percentile errors and those predicted by Argos (in brackets) were 226 (150), 372 (350), and 757 (1000) m for LCs 3, 2, and 1 respectively. Both latitude and longitude errors of LCs > O were normally distributed. Both filtered and unfiltered LC A locations were of a similar accuracy to LC 1 locations, and considerably better than LC O locations.
GEOGRAPHIC VARIATION IN RATES OF VOCAL PRODUCTION OF FREE‐RANGING BOTTLENOSE DOLPHINS
Authors: Jones Guenevere J. , Sayigh Laela S. 
Published: August 2006

AbstractEcholocation and whistle production, group sizes, and activities of free‐ranging bottlenose dolphins were compared across four regions (Wilmington, NC Intracoastal Waterway [ICW]; Wilmington coastline; Southport, NC coastline; and Sarasota, FL inshore waters). Number of whistles and echolo‐cation bouts differed significantly across sites. Dolphins whistled significantly more in Southport than in the other sites, independent of group size. Unlike at the other sites, dolphin vocalizations in Southport did not vary significantly across activities; this difference may be due to the fact that Southport animals were often found behind shrimp‐trawling vessels, which may affect their behavior. Resident Sarasota dolphins vocalized significantly less than dolphins at the NC sites. At most sites, echolocation production per dolphin decreased as group size increased, supporting the idea that echolocation information is shared. In the ICW and Sarasota, echolocation production per dolphin was highest while feeding, indicating that echolocation is used in foraging. At all sites but Southport, whistle production per dolphin was highest while socializing, indicating that whistles are used in communication. Overall, these data show that dolphins have different vocal and activity patterns at different sites; thus, caution should be used when extrapolating results from one study site to another.
CLASSIFYING PREY HARD PART STRUCTURES RECOVERED FROM FECAL REMAINS OF CAPTIVE STELLER SEA LIONS (EUMETOPIAS JUBATUS)
Authors: Cottrell Paul E. , Trites Andrew W. 
Published: August 2006

AbstractFeces were collected from six Steller sea lions (Eumetopias jubatus) that consumed known amounts of Atka mackerel (Pleurogrammus monopterygius), Pacific herring (Clupea barengus), pink salmon (Oncorhynchus gorbuscha), walleye pollock (Theragra chalcogramma), and squid (Loligo opalacens). The goal was to determine the numbers and types of taxon‐specific hard parts that pass through the digestive tract and to develop correction factors for certain abundantly occurring structures. Over 20,000 fish and squid were consumed during 267 d of fecal collection. During this period, over 119,000 taxon‐specific hard parts, representing 56 different structures, were recovered. Skeletal structures and non‐skeletal structures accounted for 72% and 28% of all hard parts, respectively. The branchiocranium, axial skeleton, and dermocranium regions of the skeletal system accounted for the greatest number of hard parts recovered. Over 70% of all recovered hard parts were represented by one to six taxa specific structures for each prey type. The average number of hard parts (3.1–31.2) and structure types (2.0–17.7) recovered per individual prey varied across taxa and were used to derive correction factors (to reconstruct original prey numbers). A measure of the variability of hard part recovery among sea lions showed no difference for certain herring, pollock, and squid structures, however, there was a significant difference for salmon and Atka mackerel structures. Identifying all taxon‐ specific prey hard parts increases the likelihood of identifying and estimating the number of prey consumed.
THREE MASS STRANDINGS OF SPERM WHALES (PHYSETER MACROCEPHALUS) IN SOUTHERN AUSTRALIAN WATERS
Authors: Evans Karen , Morrice Margaret , Hindell Mark , Thiele Deborah 
Published: August 2006

AbstractOne hundred and fifteen sperm whales (97 female, 15 male, 3 unknown sex) were involved in three mass stranding events during the month of February 1998 along the west and northwest coastlines of Tasmania, Australia. Sixty‐six of these whales stranded at Ocean Beach, Strahan; 35 at Greens Beach, Marrawah; and 11 at Black River Beach, Stanley. The remaining whales stranded singly along the coastline. Three mass strandings of this species in such close temporal proximity have not been reported in this area before, and this is the first time that data have been comprehensively collected from complete or near‐complete groups of sperm whales from Tasmanian waters. Adult females dominated the three stranding groups. Total lengths ranged from 417 to 1,200 cm and ages ranged from 0.75 to 64 yr. Four females were lactating and four fetuses were found amongst the groups. Stomach contents were dominated by pelagic cephalopods.
SKIN DENSITY AND ITS INFLUENCE ON BUOYANCY IN THE MANATEE (TRICHECHUS MANATUS LATIROSTRIS), HARBOR PORPOISE (PHOCOENA PHOCOENA), AND BOTTLENOSE DOLPHIN (TURSIOPS TRUNCATUS)
Authors: Kipps E. K. , Mclellan W. A. , Rommel S. A. , Pabst D. A. 
Published: August 2006

AbstractThis study investigated how skin contributes to buoyancy control in the Florida manatee (Trichechus manatus latirostris), harbor porpoise (Phocoena phocoena), and bottlenose dolphin (Tursiops truncatus). Manatees are shallow divers and control their position in the water column hydrostatically. The two cetaceans are relatively deep divers that control their buoyancy hydrodynamically. Although the cetacean skin had been hypothesized to lower total body density (e. g., Dearolf et al. 2000, Nowacek et al. 2001), its buoyant force had not been calculated. The density of manatee skin, and its contribution to buoyancy, was unknown. Skin densities of 27 manatees, five harbor porpoises, and five bottlenose dolphins were measured volumetrically. Skin mass and density were used to calculate buoyant force. Harbor porpoise (952 kg/m3) and bottlenose dolphin (969 kg/m3) skins were less dense than seawater, and added 9 and 25 N of positive buoyant force, respectively, to total body buoyancy. By contrast, manatee skin (1,121 kg/m3) contributed 56 N of negative buoyant force, which equaled 70% of the negative buoyant force of their dense, pachyosteosclerotic ribs. Calculation of buoyant forces of the skeleton, skin and lungs demonstrates that the manatee is positively buoyant at the surface and negatively buoyant at depths of less than 10 m.
REDUCING INCIDENTAL MORTALITY OF FRANCISCANA DOLPHINPONTOPORIA BLAINVILLEIWITH ACOUSTIC WARNING DEVICES ATTACHED TO FISHING NETS
Authors: Bordino P. , Kraus S. , Albareda D. , Fazio A. , Palmerio A. , Mendez M. , Botta S. 
Published: August 2006

AbstractWe conducted a double blind experiment in an artisanal gillnet fishery in Argentina to determine the effectiveness of acoustic deterrents (pingers) at reducing bycatch of the Franciscana dolphin (Pontoporia blainvillei). The fishery was conducted by small inflatable and fiberglass vessels operating between 0.5 and 7 krn from the coast. Each vessel carried an independent observer who was rotated from vessel to vessel throughout the course of the experiment. Information on the number of dolphins captured, geographic position, depth, configuration of fishing gear, soak time, biomass of fish caught, and sea lion predation in a string/net producing any damage was recorded. Equivalent numbers of active and silent pingers were used during the experiment. A total of 45 dolphins were caught in the silent nets, and seven were caught in the active pinger nets, demonstrating a highly significant reduction in bycatch for this species. However, sea‐lions (Otaria flavescens) damaged the fish in active pinger nets significantly more than silent nets, and the damage increased over the course of the experiment. Although pingers show promise as a management tool for this species, pinniped depredation suggests that higher pinger frequencies will be needed to avoid a “dinner bell” effect.
INTERACTIONS BETWEEN CETACEANS AND THE TUNA FISHERY IN THE AZORES
Authors: Silva Mónica A. , Feio R. , Prieto R. , Gonçalves J. M. , Santos R. S. 
Published: August 2006

AbstractWe studied the operational and ecological interactions between cetaceans and the tuna‐fishery in the Azores, based on reports of observers placed on board tuna fishing vessels from 1998 to 2000. Data were collected during 617 fishing trips (representing 43% of total fishing trips) and 6,554 fishing events. Cetaceans were present during <10% of the observed fishing events, with common dolphins (Delphinus delphis) accounting for 78% of the occurrences. The presence of cetaceans during fishing varied both spatially and temporally, depending on the distribution of fishing effort and on the pattern of occurrence of each cetacean species in the region. Overall, cetaceans interfered in 5% of the fishing events. This interference resulted in a higher proportion of events with no catches. In the three years, 49 dolphins were caught in the fishing lines but were released alive, although it is impossible to determine if they survived the interaction. Annual estimates of incidental capture of cetaceans by all the tuna fleet were calculated based on total tuna landings. An estimated 55 dolphins were captured in 1999, 38 in 1998, and 16 in 2000. Overall, our results suggest a low level of interaction between cetaceans and this fishery.
MEDITERRANEAN FIN WHALE'S (BALAENOPTERA PHYSALUS) RESPONSE TO SMALL VESSELS AND BIOPSY SAMPLING ASSESSED THROUGH PASSIVE TRACKING AND TIMING OF RESPIRATION
Authors: Jahoda Maddalena , Lafortuna Claudio L. , Biassoni Nicoletta , Almirante Carla , Azzellino Arianna , Panigada Simone , Zanardelli Margherita , Di Sciara Giuseppe Notarbartolo 
Published: August 2006

AbstractTwenty‐five fin whales (Balaenoptera physalus) were individually studied in their Ligurian Sea feeding grounds to describe and measure short‐term responses to the close approach of a fast‐moving inflatable craft from which biopsy samples were collected. Passive tracking was performed with a new technique based on simultaneous determination of (1) position of the observation vessel, (2) laser‐measured distance between the target animal and the observation vessel, and (3) azimuth of the target animal with respect to the observation vessel. Tracking was combined with timing of the surfacing intervals. Two different swimming‐surfacing patterns supposed to be related to feeding and traveling, respectively, were observed. Supposed feeding whales reacted to disturbance by changing their behavior into traveling. Two different avoidance strategies were performed simultaneously by the whales: travel at increased velocity and reduction of the time spent at the surface. After the disturbance ceased, the surfacing activity never completely reverted to predisturbance conditions during one hour of post exposure control and supposed feeding behavior appeared to be suspended indefinitely. Our results suggest the need for whale watching regulations in the Ligurian Sea, particularly as far as presumed feeding whales are concerned.
INDIVIDUALITY IN THE VOICE OF FUR SEAL FEMALES: AN ANALYSIS STUDY OF THE PUP ATTRACTION CALL IN ARCTOCEPHALUS TROPICALIS
Authors: Charrier Isabelle , Mathevon Nicolas , Jouventin Pierre 
Published: August 2006

AbstractLike most otariids species, the Subantarctic fur seal breeds on land in large, dense colonies. Pups are confronted by the long and repetitive absences of their mother throughout lactation. At each mother's return, pups have to find her among several hundreds of congeners. This recognition process mainly relies on acoustic signals. We performed an acoustic analysis on 125 calls from 20 females recorded during the 1999–2000 breeding season on Amsterdam Island (Indian Ocean). Ten variables were measured in both temporal and frequency domains. To find the acoustic parameters supporting individual signature, we assessed the differences between individuals using Kruskall‐Wallis univariate analysis of variance. For each variable, we also calculated the potential of individuality coding (PIC) as the ratio between the between‐individual coefficient of variation and the mean value of the within‐individual coefficients of variation. We found that the frequency spectrum, the characteristics of the frequency modulation of the initial and middle part of the call and the call duration exhibit an important individual stereotypy (PIC values ranging between 1.5 and 3), whereas features relative to amplitude and the frequency modulation of the final part of the call are weakly individualized (PIC values between 1 and 1.2).