bluuebunny/crossref_metadata_2025_split huggingface dataset:
OCCURRENCE, DISTRIBUTION, SITE FIDELITY, AND SCHOOL SIZE OF BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS) OFF SAN DIEGO, CALIFORNIA
Authors: Defran R. H. , Weller David W. 
Published: August 2006

AbstractThe occurrence, distribution, site fidelity, and school size of bottlenose dolphins (Tursiops truncatus) in the coastal waters of north San Diego County, California were assessed during a six‐year boat‐based photoidentification study. A total of 146 photographic surveys were conducted between January 1984 and December 1989. Dolphin schools were encountered on 79% of all surveys, and 2, 869 individuals were observed in 145 separate schools. Three‐hundred seventy‐three dolphins were individually identified. All schools were sighted within 1 km of shore, and more than two thirds of the schools were encountered in the southern half of the 32‐km long study area. School size (mean = 19.8, SD = 18.40) and the number of dolphins encountered per survey (mean = 26.8, SD = 22.30) were highly variable. Low resighting rates of known individuals provided little evidence for longterm site fidelity. When our six‐year photoidentification database was combined with previous data, 404 dolphins were identified in the study area from September 1981 to December 1989. Jolly‐Seber population estimates during the 1984‐1989 study period varied between 234 and 285. The combination of regular dolphin occurrence, low site fidelity by known individuals, and the continuous increase in the rate at which new dolphins were identified indicates that numerous different individuals were visiting the study area across and within years. The open California coastline differs in habitat structure and prey distribution from more protected study areas where bottlenose dolphins display site fidelity. These habitat differences may help to explain the observed intraspecific behavioral variability of this species.
PINNIPED POPULATION DYNAMICS IN CENTRAL CALIFORNIA: CORRELATIONS WITH SEA SURFACE TEMPERATURE AND UPWELLING INDICES
Authors: Sydeman William J. , Allen Sarah G. 
Published: August 2006

AbstractWe investigated effects of marine climate variability on pinniped populations and assessed the initial stages of recovery following implementation of the U. S. Marine Mammal Protection Act (MMPA) based on long‐term (1973‐1997) population surveys at the South Farallon Islands and Point Reyes Peninsula, central California. California sea lions increased over the study period, with peak numbers observed during and after major El Niño events. The rate of increase for California sea lions appears to have decreased in recent years. Steller sea lions decreased at the South Farallon Islands and remain depleted at Point Reyes Peninsula. Harbor seal populations increased in a logistic and non‐linear fashion at Point Reyes Peninsula and the South Farallon Islands, respectively. Harbor seals were more abundant at the South Farallon Islands during years of relatively high sea‐surface temperature, which may be related to their inability to find sufficient prey in coastal waters under these conditions. Northern elephant seal abundance increased in a logistic fashion over the study period at both the South Farallon Islands and Point Reyes Peninsula; however, productivity at the South Farallon Islands decreased in recent years. Maximum haulout numbers for elephant seals at the South Farallon Islands increased in the 1970s, maintained an asymptote throughout the 1980s and early 1990s, but recently declined; additional studies are needed to investigate which age classes are associated with this decline. Protection afforded by the MMPA has facilitated partial to full recovery of all populations except for Steller sea lion. Oceanographic relationships do not appear to confound interpretations of population recovery and may help to explain changes in the Steller sea lion population.
MONITORING THE TREND OF HARBOR SEALS IN PRINCE WILLIAM SOUND, ALASKA, AFTER THE EXXON VALDEZ OIL SPILL
Authors: Frost Kathryn J. , Lowry Lloyd F. , Ver Hoef Jay M. 
Published: August 2006

AbstractWe used aerial counts to monitor the trend in numbers of harbor seals, Phoca vitulina richardsi, in Prince William Sound, Alaska, following the 1989 Exxon Valdez oil spill. Repetitive counts were made at 25 haul‐out sites during the annual molt period each year from 1990 through 1997. A generalized linear model indicated that time of day, date, and time relative to low tide significantly affected seal counts. When Poisson regression was used to adjust counts to a standardized set of survey conditions, results showed a highly significant decline of 4.6% per year. Unadjusted counts indicated a slight, but not statistically significant, decline in the number of seals. The number of harbor seals on the trend‐count route in eastern and central PWS has been declining since at least 1984, with an overall population reduction of 63% through 1997.Programs to monitor long‐term changes in animal population sizes should account for factors that can cause short‐term variations in indices of abundance. The inclusion of such factors as covariates in models can improve the accuracy of monitoring programs.
STOMACH CONTENTS OF FALSE KILLER WHALES (PSEUDORCA CRASSIDENS) STRANDED ON THE COASTS OF THE STRAIT OF MAGELLAN, TIERRA DEL FUEGO
Authors: Alonso Mariano Koen , Pedraza Susana N. , Schiavini Adrian C. M. , Goodall R. NATALIE P. , Crespo Enrique A. 
Published: August 2006

AbstractWe examined the stomachs of 25 false killer whales collected from a mass stranding of 181 animals along both coasts of the Strait of Magellan, Chile, in March 1989. The 21 stomachs (nine males and 12 females), with food remains contained 11 prey species (nine cephalopods and two fishes) with a total of 442 individuals. Except for one case, food remains were meager, indicating that the animals had not eaten for some time or through stress had vomited on the beach. Eleven of the 21 animals had mud (often with squid beaks) in the esophagus and first stomach. The prey were identified employing squid beaks, fish otoliths and bones, and their wet weights were estimated using regressions between hard parts and known weights of species. The most important prey were the oceanic and neritic‐oceanic squids, Martialia byadesi and Illex argentinus, followed by the neritic fish, Macruronus magellanicus. Of less importance were the oceanic squid, Todaroes fillipovae, the oceanic and epipelagic octopus, Ocytboe sp., and the oceanic squid, Moroteuthis ingens. The rest of the prey were poorly represented and included four oceanic squids and one neritic fish. The prey species of these animals were subantarctic, with two antarctic species, abundant over the Patagonian shelf and adjacent oceanic waters around Tierra del Fuego.
MOTHER‐INFANT SPATIAL RELATIONS IN CAPTIVE BOTTLENOSE DOLPHINS, TURSIOPS TRUNCATUS
Authors: Gubbins Cara , Mcowan Brenda , Lynn Spencer K. , Hooper Stacie , Reiss Diana 
Published: August 2006

AbstractThe prolonged nursing period and strong, extended mother‐infant bond observed among bottlenose dolphins may reflect social and physical ontogeny critical for infant survival. This study was conducted to quantify ontogentic changes in mother‐infant contact time and the amount of time infants spent in specific spatial states with their mothers from birth to age 12 mo. These behaviors were studied through a systematic, longitudinal study of six mother‐infant pairs of captive bottlenose dolphins from three different social groups. There was a significant decrease in the time infants spent with their mothers (logistic regression, P < 0.001), following the general mammalian pattern of increasing independence with age. When with their mothers, the probability that infants would be found in “echelon” position, flanking the mother, decreased as the calf aged (logistic regression, P <0.001), possibly due to anatomical and hydrodynamic factors. The probability that infants would be found in “infant” position, underneath the mother, increased with calf age (logistic regression, P < 0.001). Results obtained in this study are consistent with similar studies of wild bottlenose dolphin mother‐infant pairs, indicating a suite of ontogenetically comparable behaviors between wild and captive bottlenose dolphins.
RISK FACTORS AFFECTING THE VAQUITA (PHOCOENA SINUS)1
Authors: Rojas‐Bracho Lorenzo , Taylor Barbara L. 
Published: August 2006

AbstractDespite the vaquita being commonly cited as one of the most endangered marine mammals in the world, there is still disagreement over which factors put the species at greatest risk of extinction. This lack of agreement hinders management decisions needed to reduce the risk to the species. To expedite decision‐making we consider four major risk factors. Habitat alteration from reduced flow of the Colorado River does not currently appear to be a risk factor because productivity remains high in vaquita habitat. Pollutant loads are low and pose low to no risk. Reduced fitness from inbreeding depression and loss of genetic variability are unlikely to pose high risk currently, though risk will increase if vaquitas remain at low abundance over long periods of time. Mortality resulting from fisheries bycatch poses high risk. Thus, short term management should not be hindered by uncertainty in estimating the risk of these factors, and primary conservation efforts should be directed to wards immediate elimination of incidental fishery mortality.
MITOCHONDRIAL DNA VARIATION IN THE CRITICALLY ENDANGERED VAQUITAPHOCOENA SINUSNORRIS AND MACFARLAND, 19581
Authors: Rosel Patricia E. , Rojas‐Bracho Lorenzo 
Published: August 2006

AbstractThe vaquita,Phocoena sinus, is one of two critically endangered cetacean species, and is listed as an endangered species in both the United States and Mexico. These listings result from a small population size, estimated to be 224 animals, and a rapid decline in abundance (18% per annum) thought to be caused by human activities. To characterize the genetic composition of the vaquita, we have sequenced a portion of the mitochondrial DNA control region from 43 individuals collected between 1985 and 1993. All animals had identical sequences. While low genetic variability has been reported for cetacean species, this complete lack of polymorphism in the control region is unique. This result is concordant with the hypothesis that the evolutionary history of the species includes a bottleneck or founder event, possibly at species inception, followed by a small long‐term effective population size. We recommend parallel studies of nuclear variability, which could provide understanding of the basic biology of the vaquita for use in conservation efforts.
BIASES IN DOLPHIN AGE STRUCTURE DUE TO AGE ESTIMATION TECHNIQUE1
Authors: Hohn Aleta A. , Fernandez Stephanie 
Published: August 2006

AbstractThe use of different tooth‐preparation techniques resulted in widely different estimates of age in a sample of bottlenose dolphins, Tursiops truncatus. Teeth from 30 animals were prepared using the two most prevalent techniques reported in the literature for this species, unstained sections and decalcified and stained thin sections, and the resulting paired counts of growth layers were compared. Estimates from the two methods were identical or at least placed the specimen in the same age class in only five cases, ranging in age from 2 to 22 yr. Otherwise, the results fell into one of two categories: when the estimates were close (± 3‐yr difference, n= 15), counts from unstained sections generally were higher (13 cases, age from unstained sections 2‐20 yr); when the counts were more disparate, estimates from stained sections always were higher (6‐31 yr difference, n= 10, age from unstained sections 12‐27 yr and corresponding ages from stained sections of 27‐47). Previous studies of age estimation in known‐age bottlenose dolphins indicate that stained sections allow accurate estimates of age and demonstrate that maximum lifespan approaches or exceeds 50 yr. In contrast, the results herein suggest that using unstained sections for age estimation may result in imprecise or biased age‐structure data.
THE SPERM WHALE'S NOSE: SEXUAL SELECTION ON A GRAND SCALE?1
Authors: Cranford Ted W. 
Published: August 2006

AbstractThe world's largest nose belongs to the sperm whale, yet its functional significance remains equivocal. In order to help shed light on its function, the head of a postmortem neonate sperm whale was subjected to CT scanning. Geometric comparisons between homologous cephalic structures in sperm whales and dolphins (normalized for body size) show extreme hypertrophy and size sexual dimorphism in the sperm whale's lipid spermaceti organ. Anatomic geometry, energetics, and behavior suggest that this immense nasal apparatus is a bioacoustical machine. Sexual selection via an acoustic display is suggested as an explanation for the size and continuous (physiologically isolated) energy investment in the construction and maintenance of the male's spermaceti organ.
MOVEMENTS OF NORTH PACIFIC BLUE WHALES DURING THE FEEDING SEASON OFF SOUTHERN CALIFORNIA AND THEIR SOUTHERN FALL MIGRATION1
Authors: Mate Bruce R. , Lagerquist Barbara A. , Calambokidis John 
Published: August 2006

AbstractThe satellite‐acquired locations of 10 blue whales (Balaenoptera musculus) tagged off southern California with Argos radio tags were used to identify (1) their movements during the late summer feeding season; (2) the routes and rate of travel for individuals on their southern fall migration; and (3) a possible winter calving/breeding area. Whales were tracked from 5.1 to 78.1 d and from 393 to 8,668 km. While in the Southern California Bight, most of the locations for individual whales were either clumped or zigzagged in pattern, suggesting feeding or foraging (searching for prey).Average speeds ranged from 2.4 to 7.2 km/h. One whale moved north to Cape Mendocino, and four migrated south along the Baja California, Mexico coast, two passing south of Cabo San Lucas on the same day. One of the latter whales traveled an additional 2,959 km south in 30.5 d to within 450 km of the Costa Rican Dome (CRD), an upwelling feature. The timing of this migration suggests the CRD may be a calving/breeding area for North Pacific blue whales. Although blue whales have previously been sighted in the Eastern Tropical Pacific (ETP), this is the first evidence that whales from the feeding aggregation off California range that far south. The productivity of the CRD may allow blue whales to feed during their winter calving/breeding season, unlike gray whales (Eschrichtius robustus) and humpbacks (Megaptera novaeangliae) which fast during that period.
RELATIVE ABUNDANCE OF LARGE WHALES AROUND SOUTH GEORGIA (1979–1998)1
Authors: Moore M. J. , Berrow S. D. , Jensen B. A. , Carr P. , Sears R. , Rowntree V. J. , Payne R. , Hamilton P. K. 
Published: August 2006

AbstractTo assess large‐whale stocks following the cessation of land‐based South Georgia whaling in 1965, we report three independent sighting databases: a cruise in 1997, observations from Bird Island (NW of South Georgia) between 1979 and 1998, and mariner sightings between 1992 and 1997. All species were rare, with sightings of southern right whales being the most common event. Two right whales photographed off South Georgia matched animals known from Peninsula Valdés, Argentina, a population known to be growing at 7%per annum. In contrast, blue and fin whales appeared to be less abundant. A single blue whale mother‐calf pair was observed off the Shag Rocks in February 1997. Extirpation of animals from this particular feeding ground is the most likely reason for ongoing low numbers of all species. Other factors may include competition for krill by traditional predators such as penguins and seals and more recently by humans, an unusually high rate of natural mortality, habitat change such as alteration in sea ice coverage, and/or the impact of ongoing whaling. The history of this critical area of large‐whale habitat and this report demonstrate the need for improved, consistent longterm monitoring of population trends for these depleted stocks.
HARBOR PORPOISE (PHOCOENA PHOCOENA) ABUNDANCE IN ALASKA: BRISTOL BAY TO SOUTHEAST ALASKA, 1991‐1993
Authors: Dahlheim M. , York A. , Towell R. , Waite J. , Breiwick J. 
Published: August 2006

AbstractBetween 1991 and 1993, Alaska harbor porpoise (Phocoena phocoena) abundance was investigated during aerial surveys throughout much of the coastal and offshore waters from Bristol Bay in the eastern Bering Sea to Dixon Entrance in Southeast Alaska. Line‐transect methodology was used, and only those observations made during optimal conditions were analyzed. Survey data indicated densities of 4.48 groups/100 km2, or approximately 3,531 harbor porpoises (95% C. I. 2,206‐5,651) in Bristol Bay and 0.54 groups/100 km2, or 136 harbor porpoises (95% C. I. 11‐1,645) for Cook Inlet. Efforts off Kodiak Island resulted in densities of 1.85 groups/100 km2, or an abundance estimate of 740 (95% C. I. 259‐2,115). Surveys off the south side of the Alaska Peninsula found densities of 2.03 groups/100 km2 and an abundance estimate of 551 (95% C. I. 423‐719). Surveys of offshore waters from Prince William Sound to Dixon Entrance yielded densities of 4.02 groups/100 km2 and an abundance estimate of 3,982 (95% C. I. 2,567‐6,177). Combining all years and areas yielded an uncorrected density estimate of 3.82 porpoises per 100 km2, resulting in an abundance estimate of 8,940 porpoises (CV = 13.8%) with a 95% confidence interval of 6,746‐11,848. Using correction factors from other studies to adjust for animals missed by observers, the total number of Alaska harbor porpoises is probably three times this number.
ASPECTS OF GROWTH IN CAPTIVE KILLER WHALES (ORCINUS ORCA)
Authors: Clark Steven T. , Odell Daniel K. , Lacinak C. Thad 
Published: August 2006

AbstractMorphometrics from 25 captive killer whales (11 captive‐born) were collected at SeaWorld parks from 1984 to 1995 to determine age‐specific growth parameters. For sexes combined, the body‐volume index was the most accurate predictor of body weight. However, predicting weight from total length was appropriate, although it may underestimate weight of pregnant animals. Among captive‐born calves, a Gompertz model was the best predictor of weight and length at age. Estimates for length and weight at birth were done using data from in utero and neonatal calves. For ages 1‐5 yr, models indicate that males grew in both weight and length at slower rates. Growth rates in males may surpass those of females at approximately 5‐6 yr of age.
CHANGES IN MORPHOLOGY WITH AGE IN MEDITERRANEAN MONK SEALS (MONACHUS MONACHUS)
Authors: Samaranch Roser , González Luis Mariano 
Published: August 2006

AbstractIn order to describe the pelage and external appearance of the Mediterranean monk seal (Monachus monachus) and prepare an age‐sex classification guide, 120 seals from the Cabo Blanco Peninsula colony in the Western Sahara/Mauritania were periodically photographed between 1993 and 1996. Analysis of the pigmentation pattern, pelage color and pattern of natural markings of each seal established 48 phenetic types, which were, in turn, arranged in five groups (morphological classes) with multivariate cluster analysis (UPGMA). The variables that best define these groups are size and color. The variation related to relative size, sex and age of 26 identified seals monitored over three years showed that: (1) after each molt, external appearance varied considerably only in non‐adults, while adult appearance was invariable; (2) marked sexual dimorphism exists in adults' external appearance; and (3) a remarkable similarity of adult and neonate pelage exists. With these results, we propose an age‐sex classification guide to facilitate monk seal identification in the field.
PUP SURVIVAL IN THE MEDITERRANEAN MONK SEAL (MONACHUS MONACHUS) COLONY AT CABO BLANCO PENINSULA (WESTERN SAHARA‐MAURITANIA)
Authors: Gazo Manel , Aparicio Fernando , Cedenilla Miguel Angel , Layna Jorge F. , González Luis Mariano 
Published: August 2006

AbstractWe surveyed pup survival in Mediterranean monk seals (Monachus monachus), at Cabo Blanco Peninsula (Western Sahara‐Mauritania) colony from May 1993 to December 1997. This species breeds and hauls out on beaches inside two main caves. During the study period we detected a total of 93 pups that died or disappeared. The survival rate of 84 pups through the age of first moult (approximately two months) was 0.47. This value is similar to those reported for other pinnipeds breeding in caves but lower than for those breeding on open beaches. Mortality varied seasonally and appeared to increase as a result of storms, large ocean swells, and high tides. Mother‐pup pair separation (and resulting pup starvation) and physical injury caused by impact against the rock walls of the cave and cliffs were established as the causes of most deaths. Beach surface area inside the caves also appeared to be a mediating factor in the effects of sea conditions. High pup mortality may be a limiting growth factor in this population, although cave dwelling protects the population from predators and human disturbance.
A KINEMATIC STUDY OF SUCTION FEEDING AND ASSOCIATED BEHAVIOR IN THE LONG‐FINNED PILOT WHALE, GLOBICEPHALA MELAS (TRAILL)
Authors: Werth Alexander 
Published: August 2006

AbstractAnalysis of videotaped feeding sequences provides novel documentation of suction feeding in captive juvenile long‐finned pilot whales (Globicephala melas). Swimming and stationary whales were videotaped while feeding at the surface, mid‐water, and bottom. The ingestion sequence includes a preparatory phase with partial gape followed by jaw opening and rapid hyoid depression to suck in prey at a mean distance of 14 cm (duration 90 msec), although prey were taken from much greater distances. Depression and retraction of the large, piston‐like tongue generate negative intraoral pressures for prey capture and ingestion. Food was normally ingested without grasping by teeth yet was manipulated with lingual, hyoid, and mandibular movement for realignment; suction was then used to transport prey into the oropharynx. Whales frequently rolled or inverted before taking prey, presumably to avoid grasping and repositioning. Prey were sucked off the bottom or sides of the pool without direct contact; lateral suction was used to ingest items from the sides of the mouth.
TEMPORAL VARIABILITY IN FEATURES USED TO PHOTO‐IDENTIFY HUMPBACK WHALES (MEGAPTERA NOVAEANGLIAE)
Authors: Blackmer Alexis L. , Anderson Scott K. , Weinrich Mason T. 
Published: August 2006

AbstractPhotographs of 99 humpback whales of known age were analyzed to assess the temporal variability and recognizability of individually distinctive fluke and dorsal fin features used for photo‐identification. Stable features tended to be morphological in nature (dorsal fin shape and edges, the trailing edge of the fluke, and the raised bumps on the caudal peduncle termed “knobs”). Transitory features typically were superficial marks (scarring, scratching, and pigmentation). The variability of several features was found to be age‐dependent as well. Young animals sometimes experienced substantial change to their fluke coloration patterns, though this feature stabilized with age. Dorsal fin edges and fluke serration peaks tended to undergo more change in males than in females, with most changes occurring following sexual maturation. Peduncle knobs were the most stable feature, with no documented change in any age interval. Given the extreme stability (and hence recognizability) of dorsal fin shape and peduncle knobs, we suggest that photographs combining the dorsal fin and the caudal peduncle provide the most consistent way to reidentify humpback whales, particularly calves following weaning.