bluuebunny/crossref_metadata_2025 huggingface dataset:
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

Abstract

The 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

Abstract

Echolocation 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

Abstract

Feces 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

Abstract

One 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

Abstract

This 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

Abstract

We 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

Abstract

We 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

Abstract

Twenty‐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

Abstract

Like 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).
FIELD EXPERIMENTS SHOW THAT ACOUSTIC PINGERS REDUCE MARINE MAMMAL BYCATCH IN THE CALIFORNIA DRIFT GILL NET FISHERY
Authors: Barlow Jay , Cameron Grant A.
Published: August 2006

Abstract

A controlled experiment was carried out in 1996–1997 to determine whether acoustic deterrent devices (pingers) reduce marine mammal bycatch in the California drift gill net fishery for swordfish and sharks. Using Fisher's exact test, bycatch rates with pingers were significantly less for all cetacean species combined (P< 0.001) and for all pinniped species combined (P= 0.003). For species tested separately with this test, bycatch reduction was statistically significant for short‐beaked common dolphins (P= 0.001) and California sea lions (P= 0.02). Bycatch reduction is not statistically significant for the other species tested separately, but sample sizes and statistical power were low, and bycatch rates were lower in pingered nets for six of the eight other cetacean and pinniped species. A log‐linear model relating the mean rate of entanglement to the number of pingers deployed was fit to the data for three groups: short‐beaked common dolphins, other cetaceans, and pinnipeds. For a net with 40 pingers, the models predict approximately a 12‐fold decrease in entanglement for short‐beaked common dolphins, a 4‐fold decrease for other cetaceans, and a 3‐fold decrease for pinnipeds. No other variables were found that could explain this effect. The pinger experiment ended when regulations were enacted to make pingers mandatory in this fishery.
CONSEQUENCES OF ALTERNATIVE FUNCTIONAL RESPONSE FORMULATIONS IN MODELS EXPLORING WHALE‐FISHERY INTERACTIONS
Authors: Mackinson Steven , Blanchard Julia L. , Pinnegar John K. , Scott Robert
Published: August 2006

Abstract

We evaluated the utility of Ecosim for exploring interactions between cetacean predators, their prey, and fisheries. We formulated six Ecosim parameterizations, representing alternative hypotheses of feeding interactions (functional response) between cetaceans and their main fish prey, and examined differences in the predicted responses to simulated harvesting regimes for minke whales and their prey. Regardless of the type of function response formulated, intense fishing on the main fish prey of minke whales had a longer‐lasting negative impact on minke whales than when minke whale biomass was removed directly by harvesting. Consumption rate, biomass, feeding time and mortality of minke whales were all sensitive to the type of functional response specified. Inclusion of “handling time” limited minke whales consumption at high prey densities and predicted higher consumption at low prey densities; features characteristic of a type II functional response. Predicted decline and recovery rates of minke whales were slower than when consumption rates were not limited. Addition of “foraging time” adjustments resulted in more conservative estimates of decline and recovery. However, when “other mortality” was linked to time spent foraging, exposure to higher mortality at low prey densities, and reduced mortality at high prey densities resulted in dramatic differences in predicted biomass trajectory. Sensitivity to the “other mortality” assumption is important for cetaceans whose predation mortality is only a small proportion of total mortality. Differences in the feeding and biomass dynamics were also observed when prey availability to predators was represented by changes in prey vulnerability, confirming earlier reports that Ecosim predictions are sensitive to this parameter.
SEASONAL DISTRIBUTION OF STELLER'S SEA LIONS AT ROOKERIES AND HAUL‐OUT SITES IN ALASKA
Authors: Sease John L. , York Anne E.
Published: August 2006

Abstract

The Steller's sea lion population has declined by 60%‐70% over much of Alaska since the late 1970s. Overlap in species composition and sizes of fishes consumed by sea lions and harvested by commercial fisheries, particularly during winter, has led to examination of potential interaction between commercial fisheries and Steller's sea lions. Abundance and distribution data for Steller's sea lions in Alaska were derived from aerial surveys conducted during the breeding season, mid‐June to early July 1992, 1994, and 1996. To study winter distribution of sea lions, we conducted aerial surveys during March 1993, November‐December 1994, and March 1999. We counted about one‐half as many sea lions during winter surveys compared to the breeding‐season surveys. Numbers of sea lions at rookery sites dropped off considerably during winter, whereas numbers at haul‐out sites did not. We found little evidence of large‐scale, seasonal movement, at least for the western stock of sea lions. Rather, differences between summer and winter distribution were primarily a function of sea lions dispersing to local haul‐out sites during the winter. Terrestrial sites, both rookeries and haul‐outs, clearly are important to Steller's sea lions during the entire year. Individual sites may be occupied year‐round or only during particular times of year.
APPEARANCE, DISTRIBUTION, AND GENETIC DISTINCTIVENESS OF LONGMAN'S BEAKED WHALE, INDOPACETUS PACIFICUS
Authors: Dalebout Merel L. , Baker C. Scott , Anderson R. Charles , Best Peter B. , Cockcroft Victor G. , Hinsz Harvey L. , Peddemors Victor , Pitman Robert L.
Published: August 2006

Abstract

Longman's beaked whale, Indopacetus pacificus, was known previously from only two skulls. Here we describe four new specimens of this species from strandings in the western and central Indian Ocean. Two juveniles, previously misidentified from external morphology as Hyperoodon planifrons, were identified as I. pacificus through diagnostic characteristics of mitochondrial (mt) DNA sequences derived from the holotype of this species. Images of the external appearance and teeth of the species are presented for the first time. Comparison of the color pattern of these new specimens with that of “tropical bottlenose whales” sighted in the tropical Indian and Pacific oceans confirm that those unidentified whales represent I. pacificus. Moore (1968) erected a new genus, Indopacetus, for this species (described initially as Mesoplodon pacificus) based primarily on cranial morphology. Phylogenetic analyses of short mtDNA fragments available from the specimens known to date were unable to resolve the validity of this genus. However, the diagnostic osteological features highlighted by Moore (1968) for Indopacetus were also observed in the new specimens. Rib count and number of fused cervical vertebrae may also be diagnostic. Rostrum depth at mid‐length and melon shape further distinguish this species from Mesoplodon beaked whales. As such, we see no reason on morphological grounds to overturn Moore's (1968) proposal that Longman's beaked whale is sufficiently distinct to be afforded its own genus.
SEXUAL ECOLOGY OF THE SPINNER DOLPHIN, STENELLA LONGIROSTRIS: GEOGRAPHIC VARIATION IN MATING SYSTEM
Authors: Perrin William F. , Mesnick Sarah L.
Published: August 2006

Abstract

We offer the first report for a cetacean of geographical variation in mating system based in morphology. Analysis of samples from 1,678 male spinner dolphins from the eastern Pacific revealed that testis + epididymis weight was greater (to 1,354 g) in the whitebelly form of the species than in the eastern form (to 843 g). Sexual dimorphism in dorsal‐fin shape is greater in the eastern form. The difference in testis size was strongly linked with shape of the dorsal fin on an individual basis. Only a few eastern males (0.6%) reached testis + epididymis weight at which all epididymides contain sperm, while a much larger proportion of whitebelly spinners (15.2%) reached this level, suggesting that a smaller proportion of eastern spinner males may participate in reproductive activity. This, and the fact that increased dimorphism and decreased testis size are indicative of increased polygyny in a wide variety of other mammal species, leads to the conclusion that the mating system varies geographically in the species, with a gradient from a more polygynous mating system in the eastern form to a more open or polygynandrous mating system in the whitebelly form. Differences in ovulation rate in the two forms are consistent with this conclusion.
STABILIZATION MECHANISM IN SWIMMING ODONTOCETE CETACEANS BY PHASED MOVEMENTS
Authors: Fish F. E. , Peacock J. E. , Rohr J. J.
Published: August 2006

Abstract

Propulsive movements of the caudal oscillating flukes produce large forces that could induce equally large recoil forces at the cranial end of the animal, and, thus, affect stability. To examine these vertical oscillations, video analysis was used to measure the motions of the rostrum, pectoral flipper, caudal peduncle, and fluke tip for seven odontocete cetaceans: Delphinapterus leucas, Globicephala melaena, Lagenorhynchus obliquidens, Orcinus orca, Pseudorca crassidens, Stenella plagiodon, and Tursiops truncatus. Animals swam over a range of speeds of 1.4–7.30 m/sec. For each species, oscillatory frequency of the fluke tip increased linearly with swimming speed. Peak‐to‐peak amplitude at each body position remained constant with respect to swimming speed for all species. Mean peak‐to‐peak amplitude ranged from 0.02 to 0.06 body length at the rostrum and from 0.17 to 0.25 body length at the fluke tip. The phase relationships between the various body components remain constant with respect to swimming speed. Oscillations of the rostrum were nearly in phase with the fluke tip with phase differences out of—9.4°‐33.0° of a cycle period of 360°. Pectoral flipper oscillations trailed fluke oscillations by 60.9°‐123.4°. The lower range in amplitude at the rostrum compared to the fluke tip reflects increased resistance to vertical oscillation at the cranial end, which enhances the animal's stability. This resistance is likely due to both active and passive increased body stiffness, resistance on the flippers, phased movements of body components, and use of a lift‐based propulsion. Collectively, these mechanisms stabilize the body of cetaceans during active swimming, which can reduce locomotor energy expenditure and reduce excessive motions of the head affecting sensory capabilities.
KILLER WHALE PREDATION ON BELUGAS IN COOK INLET, ALASKA: IMPLICATIONS FOR A DEPLETED POPULATION
Authors: Shelden Kim E. W. , Rugh David J. , Mahoney BarbaraA. , Dahlheim Marilyn E.
Published: August 2006

Abstract

Killer whale predation on belugas in Cook Inlet, Alaska, has become a concern since the decline of these belugas was documented during the 1990s. Accordingly, killer whale sightings were compiled from systematic surveys, observer databases, and anecdotal accounts. Killer whales have been relatively common in lower Cook Inlet (at least 100 sightings from 1975 to 2002), but in the upper Inlet, north of Kalgin Island, sightings were infrequent (18 in 27 yr), especially prior to the 1990s. Beach cast beluga carcasses with teeth marks and missing flesh also provided evidence of killer whale predation. Most observed killer whale/beluga interactions were in the upper Inlet. During 11 of 15 observed interactions, belugas were obviously injured or killed, either through direct attacks or indirectly as a result of stranding. Assuming at least one beluga mortality occurred during the other four encounters, we can account for 21 belugas killed between 1985 and 2002. This would suggest a minimum estimate of roughly 1/yr and does not include at least three instances where beluga calves accompanied an adult that was attacked.
PINNIPED LACTATION STRATEGIES: EVALUATION OF DATA ON MATERNAL AND OFFSPRING LIFE HISTORY TRAITS
Authors: Schulz Tyler M. , Bowen W. Don
Published: August 2006

Abstract

Interspecific correlations are commonly used to explore the adaptive functions of life history traits in pinnipeds. Although adaptive conclusions are improved by the use of comparative methods that account for underlying phylogenetic relationships among species, they are still dependent on the quality of life history data. We collected pinniped species estimates for 12 maternal and offspring life history traits and evaluated these estimates based on sample size, duration of study, and methods used to obtain the data. Although excellent data exist for some species, high‐quality estimates in all 33 species are not available for any of the traits studied. High‐quality estimates of maternal postpartum mass are known for 12 species, neonate birth mass for 21, pup rate of mass gain for 12, lactation length for 10, and weaning mass for 10. High‐quality estimates of milk composition, milk energy output, and maternal foraging behavior during lactation are limited to ≤ 50% of species, with a taxonomic bias favoring the larger phocid species. Obtaining data on small‐bodied phocid species will be critical to gaining a better understanding of the relative roles of body size and phylogeny in the evolution of pinniped lactation strategies.
FEEDING ECOLOGY OF THE MARINE OTTER (LUTRA FELINA) IN A ROCKY SEASHORE OF THE SOUTH OF CHILE
Authors: Medina‐Vogel Gonzalo , Rodriguez Claudio Delgado , Ricardo E. Alvarez P. , Jose Luis Bartheld V.
Published: August 2006

Abstract

The marine otter (Lutra felina) lives exclusively along exposed rocky shorelines on the South American Pacific coast from Peru (6°S), to Cape Horn, Chile (56°S), and Isla de los Estados, Argentina. L. felina diet and its relationship to prey availability and energy content was assessed by spraint and prey remains analysis, direct observation, and the use of crab pots and fish traps, at four sites on the Valdivian coast in the south of Chile, between June 1999 and June 2000. Based on spraints analysis, the diet was composed of 25 species; 52% (13/25) of the species identified were crustaceans, 40% (10/25) were fish, and 8% (2/25) were mollusks. Crustaceans were found in 78% of 475 spraints, 100% of 929 prey remains, and 90.8% of prey determined by direct observation, fish in 20% of spraints and 9.0% of prey determined by direct observation, and mollusks in 2% of spraints and 0.2% of prey determined by direct observation. Observed seasonal variation in prey availability was reflected in the otter diet. Fourteen prey species were trapped; 43% (6/14) were crustaceans and 57% (8/14) fish, crustaceans were 93% of 566 trapped individuals, fish 7%. L. felina showed opportunistic feeding behavior, selecting prey seasonally according to their availability rather than to their energy input.
RIVERINE HABITAT PREFERENCES OF BOTOS (INIA GEOFFRENSIS) AND TUCUXIS (SOTALIA FLUVIATILIS) IN THE CENTRAL AMAZON
Authors: Martin A. R. , da Silva V. M. F. , Salmon D. L.
Published: August 2006

Abstract

The distribution and density of the Amazon's two contrasting endemic dolphins–boto, or Amazon river dolphin, Inia geoffrensis, and tucuxi, Sotalia fluviatilis–were examined on two adjoining large rivers in western Brazil. Using a 17‐m river boat as a sightings platform, strip transects were used to cover areas within 150 m of the river margin and line transects were used in all other areas. Highest densities of both dolphins occurred near the margin, and lowest in the center of rivers. Seven different habitats were identified along river margins. The boto and the tucuxi differed in some elements of habitat choice, but they shared a preference for areas with diminished current and where two channels joined. Neither species favored the two most common edge types in this region of the Amazon‐mud banks and flooded forest margins. Overall, the most preferred habitat type was the least common, and known as “meeting of the waters.” In these areas a channel of sediment‐rich white water meets one carrying acidic black water; the resultant mixing produces particularly productive, and obviously attractive, conditions for dolphins. These results demonstrate that Amazonian dolphins selectively occur in areas known to be favored for gill net deployment by local fishermen, and may explain why entanglement is apparently a common cause of mortality.
DUSKY DOLPHIN (LAGENORHYNCHUS OBSCURUS) FORAGING IN TWO DIFFERENT HABITATS: ACTIVE ACOUSTIC DETECTION OF DOLPHINS AND THEIR PREY
Authors: Benoit‐Bird Kelly J. , Würsig Bernd , Mfadden Cynthia J.
Published: August 2006

Abstract

Active‐acoustic surveys were used to determine the distribution of dusky dolphins and potential prey in two different New Zealand locations. During seven survey days off Kaikoura Canyon, dusky dolphins were found within the DeepScattering Layer (DSL) at 2000 when it rose to within 125 m of the surface. As the DSL rose to 30 m at 0100, the observed depth of dolphins decreased, presumably as the dolphins followed the vertical migration of their prey. Acoustically identified subgroups of coordinated animals ranged from one to five dolphins. Time, depth of layer, and layer variance contributed significantly to predicting foraging dusky dolphin subgroup size. In the much shallower and more enclosed Admiralty Bay, dolphins noted at the surface as foraging were always detected with the sonar, but were never observed in coordinated subgroups during the brief (two‐day) study there. In Admiralty Bay dolphin abundance was correlated with mean volume scattering from potential prey in the water column; and when volume scattering, an index of prey density, was low, dolphins were rarely present. Ecological differences between the deep waters of Kaikoura Canyon and the shallow nearshore waters of Admiralty Bay may result in differences in how, when, and in what social groupings dusky dolphins forage.
PHONING HOME‐A NEW GSM MOBILE PHONE TELEMETRY SYSTEM TO COLLECT MARK‐RECAPTURE DATA
Authors: Mcconnell Bernie , Beaton Rory , Bryant Ed , Hunter Colin , Lovell Phil , Hall Ailsa
Published: August 2006

Abstract

We describe and evaluate a new telemetry system based on GSM (Global System for Mobile Communications) mobile phone technology that may provide mark‐recapture data for single year survivorship studies. These phone‐tags automatically attempt to send an SMS text message once every two days. The successful receipt of a text message ashore constitutes a resighting event within the coastal zone of GSM coverage. Haul‐out data and coastal location data are incorporated into the messages. Data are presented for a three‐month period (January‐March) following tag deployment on 59 gray seal (Halichoerus grypus) pups at the Isle of May (Scotland). An average of 15.5, 4.1, and 8.2 seals succeeded in registering within each three‐day period in January, February, and March, respectively. Tags registered with a wide geographical range of GSM radio cells on the Scottish and English east coasts, and also from Norway and Germany. Haulout records covering 54% of the animals' time were received. With future modifications to the tags, this figure should approach 100%. The median delay to network registration was 9.6 sec from a seal in the sea (not hauled out). These data show that GSM mobile phone telemetry is a useful technique to obtain haul‐out and mark‐recapture data.
GROWTH RATE AND SHEDDING OF VIBRISSAE IN THE GRAY SEAL, HALICHOERUS GRYPUS: A CAUTIONARY NOTE FOR STABLE ISOTOPE DIET ANALYSIS
Authors: Greaves Danielle K. , Hammill Michael O. , Eddington Jim D. , Pettipas Darcy , Schreer Jason F.
Published: August 2006

Abstract

Stable isotopes have become powerful tools for gathering information on food webs in marine ecosystems. The method is based on the concept that the ratio of Nitrogen‐14 to 15N (or Carbon‐12 to 13C) in the tissues of animals is directly related to the ratio found in their diet. Vibrissae provide a time series of stable isotope data as tissue is laid down sequentially over time. Here we examine the growth rate of 283 mystacial (muzzle) vibrissae of four gray seals, Halichoeruas grypus, over a five‐month period to investigate their applicability for stable isotope diet analysis. The individual vibrissae did not grow at a constant rate during the study, Fifty‐nine actively growing vibrissae were modeled to quantify the growth pattern using a three‐parameter von Bertalanffy curve, with the parameters estimated using non‐linear mixed‐effects models. This model incorporated the inherent serial correlation of these data. The growth rate was 0.024 cm/d (95% CI = 0.019–0.030), the asymptotic length differed significantly by location (F3,56=9.64, P < 0.001), but no significant trend was found with muzzle location (F3,56= 0.15, P= 0.93). The Δlength/Δtime between each measurement was calculated and most of these data fell at or near zero growth (median = 0.04 cm/d, range = 0–0.78). Individual vibrissae were shed asynchronously and without any seasonal growth trend. This has serious implications for researchers attempting to extrapolate diet data from vibrissae. Because the growth is neither continuous nor synchronous, it will be a challenge to accurately identify the dates when the isotopes were incorporated into the tissue.
CAPTURE‐RECAPTURE ANALYSIS FOR ESTIMATING MANATEE REPRODUCTIVE RATES
Authors: Kendall William L. , Langtimm Catherine A. , Beck Cathy A. , Runge Michael C.
Published: August 2006

Abstract

Modeling the life history of the endangered Florida manatee (Trichechus manatus latirostris) is an important step toward understanding its population dynamics and predicting its response to management actions. We developed a multi‐state markresighting model for data collected under Pollock's robust design. This model estimates breeding probability conditional on a female's breeding state in the previous year; assumes sighting probability depends on breeding state; and corrects for misclassification of a cow with first‐year calf, by estimating conditional sighting probability for the calf. The model is also appropriate for estimating survival and unconditional breeding probabilities when the study area is closed to temporary emigration across years. We applied this model to photo‐identification data for the Northwest and Atlantic Coast populations of manatees, for years 1982–2000. With rare exceptions, manatees do not reproduce in two consecutive years. For those without a first‐year calf in the previous year, the best‐fitting model included constant probabilities of producing a calf for the Northwest (0.43, SE = 0.057) and Atlantic (0.38, SE = 0.045) populations. The approach we present to adjust for misclassification of breeding state could be applicable to a large number of marine mammal populations.
SURVIVAL ESTIMATES FOR FLORIDA MANATEES FROM THE PHOTO‐IDENTIFICATION OF INDIVIDUALS
Authors: Langtimm Catherine A. , Beck Cathy A. , Edwards Holly H. , Fick‐Child Kristin J. , Ackerman Bruce B. , Barton Sheri L. , Hartley Wayne C.
Published: August 2006

Abstract

We estimated adult survival probabilities for the endangered Florida manatee (Trichechus manatus latirostris) in four regional populations using photoidentification data and open‐population capture‐recapture statistical models. The mean annual adult survival probability over the most recent 10‐yr period of available estimates was as follows: Northwest ‐ 0.956 (SE 0.007), Upper St. Johns River ‐ 0.960 (0.011), Atlantic Coast ‐ 0.937 (0.008), and Southwest ‐ 0.908 (0.019). Estimates of temporal variance independent of sampling error, calculated from the survival estimates, indicated constant survival in the Upper St. Johns River, true temporal variability in the Northwest and Atlantic Coast, and large sampling variability obscuring estimates for the Southwest. Calf and subadult survival probabilities were estimated for the Upper St. Johns River from the only available data for known‐aged individuals: 0.810 (95% CI 0.727–0.873) for 1st year calves, 0.915 (0.827–0.960) for 2nd year calves, and 0.969 (0.946–0.982) for manatee 3 yr or older. These estimates of survival probabilities and temporal variance, in conjunction with estimates of reproduction probabilities from photoidentification data can be used to model manatee population dynamics, estimate population growth rates, and provide an integrated measure of regional status.
ENVIRONMENTAL FACTORS INFLUENCING THE DISTRIBUTION OF SOUTHERN RIGHT WHALES (EUBALAENA AUSTRALIS) ON THE SOUTH COAST OF SOUTH AFRICA II: WITHIN BAY DISTRIBUTION
Authors: Elwen Simon H. , Best Peter B.
Published: August 2006

Abstract

Environmental factors are thought to strongly influence the distribution and predictability of the coastal distribution of southern right whales (Eubalaena australis) off South Africa. Preferred habitat had generally shallow sloping sedimentary floors and was characteristically protected from open ocean swell and prevalent seasonal winds. This study investigated whether habitat choices at smaller scales (within bays) were similar. Fine scale distribution patterns (GPS) from three years' surveys (1997, 1999, 2000) were analyzed separately within the three main concentration areas St Sebastian Bay, De Hoop, and Walker Bay (containing ∼73% of cow‐calf pairs and ∼49% of unaccompanied adults in the whole survey region). Whale density at this scale of within particular bays did not correlate well with predicted variables, but Chi‐squared analysis strongly supported results at broader scales, in all bays. Post‐hoc“choice” tests between similar areas differing in only one variable revealed that cow‐calves preferred (presumed) sandy substrates and especially protection from swell. The strength and predictability of preferences shown at fine scale (where individual movement and weather variability could have great influence) provide strong support for findings at larger scales and emphasize the importance of environmental factors in the habitat choice of wintering right whales.
EFFECTS OF WATERCRAFT NOISE ON THE ACOUSTIC BEHAVIOR OF BOTTLENOSE DOLPHINS,TURSIOPS TRUNCATUS, IN SARASOTA BAY, FLORIDA
Authors: Buckstaff Kara C.
Published: August 2006

Abstract

Watercraft may provide the greatest source of anthropogenic noise for bottlenose dolphins living in coastal waters. A resident community of about 140 individuals near Sarasota, Florida, are exposed to a vessel passing within 100 m approximately every six minutes during daylight hours. I investigated the circumstances under which watercraft traffic may impact the acoustic behavior of this community, specifically looking for short‐term changes in whistle frequency range, duration, and rate of production. To analyze whistles and received watercraft noise levels, acoustic recordings were made using two hydrophones towed from an observation vessel during focal animal follows of 14 individual dolphins. The duration and frequency range of signature whistles did not change significantly relative to vessel approaches. However, dolphins whistled significantly more often at the onset of approaches compared to during and after vessel approaches. Whistle rate was also significantly greater at the onset of a vessel approach than when no vessels were present. Increased whistle repetition as watercraft approach may simply reflect heightened arousal, an increased motivation for animals to come closer together, with whistles functioning to promote reunions. It may also be an effective way to compensate for signal masking, maintaining communication in a noisy environment.
BUFFERING CAPACITY OF THE LOCOMOTOR MUSCLE IN CETACEANS: CORRELATES WITH POSTPARTUM DEVELOPMENT, DIVE DURATION, AND SWIM PERFORMANCE
Authors: Noren Shawn R.
Published: August 2006

Abstract

Skeletal muscles of marine mammals must support the metabolic demands of exercise during periods of reduced blood flow associated with the dive response. Enhanced muscle buffering could support anaerobic metabolic processes during apnea, yet this has not been fully investigated in cetaceans. To assess the importance of this adaptation in the diving and swimming performance of cetaceans, muscle buffering capacity due to non‐bicarbonate buffers was measured in thelongissimus dorsiof ten species of odontocete and one mysticete. Immature specimens from a subset of these species were studied to assess developmental trends. Fetal and neonatal cetaceans have low buffering capacities (range: 34.8–53.9 slykes) that are within the range measured for terrestrial mammals. A lengthy developmental period, independent of muscle myoglobin postnatal development, is required before adult levels are attained. Adult cetacean buffering capacities (range: 63.7–94.5 slykes) are among the highest values recorded for mammals. Cetacean species that demonstrate extremely long dive durations or high burst speed swimming tend to have greater buffering capacities. However, the wide range of body size across cetaceans may complicate these trends. Enhanced muscle buffering capacity may enable small‐bodied species to extend breath‐hold beyond short aerobic dive limits for foraging or predator evasion when necessary.
DEVELOPMENT OF DISPERSAL, MOVEMENT PATTERNS, AND HAUL‐OUT USE BY PUP AND JUVENILE STELLER SEA LIONS (EUMETOPIAS JUBATUS) IN ALASKA
Authors: Raum‐Suryan Kimberly L. , Rehberg Michael J. , Pendleton Grey W. , Pitcher Kenneth W. , Gelatt Thomas S.
Published: August 2006

Abstract

Population declines of Steller sea lions (Eumetopias juhatus) in western Alaska (west of 144°W) may be a result of reduced juvenile survival. We used satellite telemetry to study the at‐sea distribution and movement patterns of pup (1.6–11.9 mo) and juvenile (12.0–35.1 mo) Steller sea lions. We studied trip distance, duration, and interhaul‐out movements of sea lions in relation to age, sex, and month of year in the decreasing western population (WP; Prince William Sound, Kodiak, Aleutian Islands, Alaska) and the increasing eastern population (EP; Southeast Alaska). We deployed 103 satellite transmitters (29 WP; 74 EP) on sea lions between 1998 and 2001. Round trip distance and duration increased with age, trip distance was greater in the WP than the EP, trip duration was greater for females than males, and haul‐out use was clustered. Changes in round trip distance and duration occurred from April to June for all age classes studied indicating that the annual timing of weaning may be less variable than the age of weaning. Overall, 90% of round trips were ≤ 15 km from haul‐outs and 84% were <20 h, indicating nearshore areas adjacent to haulouts are critical to the developing juvenile.
MORPHOMETRY, HEMATOLOGY, AND SERUM CHEMISTRY IN THE HAWAIIAN MONK SEAL (MONACHUS SCHAUINSLANDI)
Authors: Reif John S. , Bachand Annette , Aguirre A. Alonso , Borjesson Dori L. , Kashinsky Lizabeth , Braun Robert , Antonelis George
Published: August 2006

Abstract

We studied morphometric, hematology, and serum chemistry variables in 140 Hawaiian monk seals (Monachus schauinslandi) to establish normal baseline values for these variables among free‐living seals. We compared seals at French Frigate Shoals (FFS), Midway Atoll (MID), and Pearl and Hermes Reef (PHR) because these subpopulations differ in their rates of population recovery. Dorsal standard length and axillary girth differed significantly between immature (1–4 yr old) and adult (≥5 yr old) seals among sex and island subgroups. Immature seals at FFS were shorter than those at MID and PHR; adult seals at FFS had smaller dorsal standard lengths and axillary girths compared to the other subpopulations. The differences in size were more pronounced among adult females. Significant differences were also found for hematology and serum chemistry variables among seals at FFS, MID, and PHR. Monk seals at FFS had an absolute lymphopenia and eosinopenia compared to those at MID and PHR, compatible with a stress response. Seals at FFS also had lower blood urea nitrogen than seals at PHR, and a lower plasma potassium than seals at MID or PHR. Monk seals had an absolute and relative eosinophilia compared to previously published values. Analysis of subpopulation differences is useful for population health assessment and for long‐term monitoring of an endangered species.
DESCRIPTION OF A NEW DOLPHIN, THE AUSTRALIAN SNUBFIN DOLPHIN ORCAELLA HEINSOHNI SP. N. (CETACEA, DELPHINIDAE)
Authors: Beasley Isabel , Robertson Kelly M. , Arnold Peter
Published: August 2006

Abstract

Comparisons of the Irrawaddy dolphin, Orcaella brevirostris, between Australian and Asian sites documented geographic differences in height of dorsal fin, presence or absence of a median dorsal groove in front of the dorsal fin, and coloration (presence or absence of a dorsal cape). Analysis of genetic data provided support for two clades within the Asian samples, the Mekong River samples from Cambodia and southern Laos, and all other marine and freshwater sites from Thailand, Indonesia, and the Philippines. The major separation, however, was between sites in Asia and those from Australia (5.9% of base pair differences, compared with 1.2% for within Australia and 1.5% for within Asia). Within a 403 base segment of the mtDNA control region, Australian specimens had 17 diagnostic sites with 16 fixed base pair differences and one insertion/deletion. Consistent, statistically significant differences in skull characters of Australian specimens have previously been demonstrated and are reviewed in this paper. There was a high concordance in character differences demonstrated between O. brevirostris from all Asian sites and Australian specimens, especially in the genetic and osteological characters. Based on the range and concordance of character differences, we propose that the Australian dolphins be recognized as a new species, Orcaella heinsohni (suggested common name: Australian snubfin dolphin).