bluuebunny/crossref_metadata_2025_split huggingface dataset:
MEASUREMENT OF PHOTOGRAPHIC QUALITY AND INDIVIDUAL DISTINCTIVENESS FOR THE PHOTOGRAPHIC IDENTIFICATION OF HUMPBACK WHALES, MEGAPTERA NOVAEANGLIAE
Authors: Friday Nancy , Smith Tim D. , Stevick Peter T. , Allen Judy 
Published: August 2006

AbstractAccurate identification of humpback whales from photographic identification data depends on the quality of the photographs and the distinctiveness of the flukes. Criteria for evaluating photographic quality and individual distinctiveness were developed involving judgments about overall quality or distinctiveness and about specific aspects of each. These criteria were tested for the level of agreement among judges. The distinctiveness scheme was tested for the independence of distinctiveness judgments and photographic quality. Our results show that judges could agree when evaluating specific and overall aspects of photographic quality and individual distinctiveness. The level of agreement varied for different pairs of judges, and less adept judges were identified. Ability to agree on evaluations of photographic quality was independent of the experience of the judges. Overall photographic quality and overall distinctiveness were successfully predicted from more specific variables, but the agreement between judges for these was not significantly greater than the agreement for the overall measures judged directly. There was no correlation between individual distinctiveness and photographic quality for four of the five judges, but the power of this rest may be low. Analyses of photographic identification data frequently require evaluations of photographic quality and individual distinctiveness. To obtain reliable results from such analyses, evaluation schemes and judges should be tested to ensure reliable and consistent evaluations.
A BAYESIAN ANALYSIS TO ESTIMATE LOSS IN SQUID CATCH DUE TO THE IMPLEMENTATION OF A SEA LION POPULATION MANAGEMENT PLAN
Authors: Maunder Mark N. , Starr Paul J. , Hilborn Ray 
Published: August 2006

AbstractThis study estimates the effect of a sea lion (Phocarctos hookeri) population management plan on both the sea lion population and the associated squid (Nototodarus sloanii) fishery. The goal of the management plan is to rebuild the sea lion population and involves closing the squid fishery when a threshold level of sea lions have been caught. The threshold level is calculated from a generalized simulation analysis which conservatively allows for adequate population rebuilding for a number of different species and populations. Our analysis uses Bayesian theory to describe uncertainty in the sea lion population site and squid catch under the implementation of the management plan. The priors represent this particular sea lion population, and the analysis represents expectation rather than calculating conservative levels of safe fishing‐related mortality. The results show that the squid catch is very sensitive to whether or not the squid fishery is closed when it exceeds the threshold level for sea lion bycatch. The sea lion population size is much less sensitive to the closure of the squid fishery. For an economically important fishery, the estimates of uncertainty in both loss of catch and increase in sea lion population are needed to allow informed decision‐making about trade‐offs between sea lion conservation and full exploitation of the fishery.
SEASONAL AND DIURNAL TRENDS OF CHORUSING HUMPBACK WHALES WINTERING IN WATERS OFF WESTERN MAUI
Authors: Au Whitlow W. L. , Mobley Joseph , Burgess William C. , Lammers Marc O. , Nachtigall Paul E. 
Published: August 2006

AbstractA portable data logger controlled by a Tattletale 7 microcontroller was used to record humpback whale choruses during the 1998 humpback whale winter season in Hawaii. The data logger sampled the sounds for four minutes every half hour using a digitizing rate of 2 kHz, and the data were stored on a hard disk. The results between January and April showed a peak in the sound pressure level between mid‐February and mid‐March. This peak of approximately 120 dB re 1 μPa coincided with the peak in the number of whales sighted by aerial survey on 7 March 1998. The choruses had spectral peaks at 315 Hz and 630 Hz. Some of the sounds at 630 Hz were second harmonics of the 315 Hz peak and others were not. The data also indicated a diurnal pattern in the sound pressure level, with levels at night significantly louder than the daytime levels. The sound levels began to increase during sunset and remained relatively high until sunrise, when they progressively decreased to a minimum. The nighttime peak occurred within an hour before and after midnight, and the daytime minimum occurred between 1100 and 1500. That more humpback whales appear to sing at night may reflect a switch to sexual advertisement as the primary male mating strategy at this time. It may also indicate that daylight and vision play key roles in the formation of competitive groups. It is suggested that the relative number of humpback whales in a given locale may be estimated by monitoring changes in sound pressure levels.
FUNCTIONAL REDUCTION OF THE SOUTHERN MINKE WHALE (BALAENOPTERA ACUTOROSTRATA) TESTIS DURING THE FEEDING SEASON
Authors: Mogoe Toshihiro , Suzuki Takatoshi , Asada Masatsugu , Fukui Yutaka , Ishikawa Hajime , Ohsumi Seiji 
Published: August 2006

AbstractSeasonal variation in reproductive activity in the male southern minke whales was investigated. The animals were killed and collected during the feeding season (December‐March) in the Antarctic Ocean in the eastern part of Area III (35°E‐70°E, south of 60°S) and Area IV (70°E‐130°E, south of 60°S). Blood samples, testes, epididymides, and vasa deferentia were collected from 62 males, which had testes weighing over 400 g each. Changes in testicular morphology and plasma testosterone, estradiol‐17β and LH concentrations measured by enzyme immunoassay were investigated. Reduction of testicular function associated with different capture periods was found in the summer season. From December to March, body length and body weight remained steady, but decreases in testicular weight, epididymal weight, and testicular volume were found in February. During the same period, plasma testosterone concentration also declined. A significant decrease in the number of germ cells continued during the period of feeding season. An increase in area of seminiferous tubule tended to proceed in a number of germ cells. These changes reflected the percentage of spermatozoa in the vasa deferentia; in particular, motile spermatozoa were observed in December. Based on morphological observation, spermatogenesis had also declined. These results indicate regulation of testicular function by testosterone, as in terrestrial mammals. A gradual decrease of testicular function occurred during December‐January.
DO PHOTOPERIOD AND TEMPERATURE INFLUENCE THE MOLT CYCLE OF PHOCA VITULINA IN CAPTIVITY?
Authors: Mo Giulia , Gili Claudia , Ferrando Paola 
Published: August 2006

AbstractPhotoperiod variations are the principal environmental signals entraining circannual activity in mammals, which is also believed to be influenced by changes in temperature and nutrition. Control of the molt in phocids has not been extensively studied with experimental manipulations of environmental factors, but substantial work indicates that photoperiod has a primary influence on mammalian breeding and furring mechanisms. Studies were under taken to reestablish the molt cycle in five harbor seals (Phoca vitulina) previously kept in an enclosed facility with a limited air/water temperature gradient and artificial photoperiod. The seals were exposed to an extended temperature gradient during the first period of study, and no molting was observed. The second period of study was characterized by a natural occurring photoperiod of 8 h 53 min light (L)/15 h 07 min dark (D) and a maximal 15 h 31 min L/8h 29 min D duration, and molting occurred in all individuals. These results suggest a prevalent influence of photoperiod variation on the harbor seal molt.
DIET OF HARP SEALS (PAGOPHILUS GROENLANDICUS) IN NEARSHORE NORTHEAST NEWFOUNDLAND: INFERENCES FROM STABLE‐CARBON (δ13C) AND NITROGEN (δ15N) ISOTOPE ANALYSES
Authors: Lawson John W. , Hobson Keith A. 
Published: August 2006

AbstractTrophic position, and often the source of feeding of predators in food webs, can be estimated using measurements of stable isotope ratios of nitrogen and carbon in predators and their prey. Muscle samples from 60 harp seals (Pagophilus groenlandicus) collected during May 1995 in nearshore waters of New foundland, Canada, were analyzed for δ13C and δ15N values. These values were compared with those for 63 prey samples representing seven species generally collected near the same area. Using diet‐tissue isotopic fractionation factors derived from previous studies using captive animals, we infer a greater dependence of harp seals on lower trophic‐level prey during April compared with results expected from exclusive diets of Atlantic cod (Gadus morhua), Atlantic herring (Clupea harengus), Greenland halibut (Reinhardtius hippoglossoides), or northern shrimp (Pandalus borealis). Our mean δ15N value for harp seals is lower than previous findings for seals collected on the winter whelping patch and may be a function of interannual or seasonal differences in diet. Subadult seals (aged 1‐4 yr) had significantly lower δ15N values than adults (5 + yr), suggesting that older seals were feeding at a slightly higher trophic level.
VOCAL INDIVIDUALITY IN MOTHER AND PUP SOUTH AMERICAN FUR SEALS, ARCTOCEPHALUS AUSTRALIS
Authors: Phillips Alana V. , Stirling Ian 
Published: August 2006

AbstractSouth American fur seals breeding in Peru are subjected to levels of maternal aggression, and subsequent pup mortality, that are higher than has been reported for any other otariid species. For mothers and pups to maintain contact with each other, a mutual recognition system should exist to facilitate reunion and avoid misdirection of maternal effort. We recorded vocalizations of mothers and pups at Punta San Juan, Peru, during the 1994 and 1995 breeding seasons. Sixteen acoustic variables were measured from a total of 560 calls from 15 mothers and 13 pups. Multivariate analysis showed that calls were variable in several acoustic dimensions. While calls of both mothers and pups showed low variability within and high variability among individuals, mothers' calls were more individualistic. On average, discriminant‐function analysis correctly assigned 60% of pup calls and 70% of mother calls to the individual that produced them. Characteristics of the fundamental frequency were most important for distinguishing among mothers, while pup calls, which typically contained less harmonic structure, could be differentiated by formant‐like frequency ranges. Thus, calls of mother and pup South American fur seals appear to exhibit sufficient stereotypy to allow for recognition and discrimination among individuals.
CHANGES IN THE RELATIVE ABUNDANCE AND DISTRIBUTION OF GRAY WHALES (ESCHRICHTIUS ROBUSTUS) IN MAGDALENA BAY, MEXICO DURING AN EL NIÑO EVENT
Authors: Gardner S. C. , Chávez‐Rosales S. 
Published: August 2006

AbstractThe oceanographic changes during the El Niño and La Niña of 1998–1999 have provided an opportunity to document the effects of these events on the migratory patterns of gray whales (Eschrichtius robustus). Magdalena Bay is located at the southernmost point of the gray whale's annual breeding migration along the Baja California Peninsula in Mexico. Standardized surveys were conducted for three consecutive seasons (1997–1999) in Magdalena Bay, enabling an assessment of the changes in the relative abundance of gray whales with altered temperature. The average temperature of the bay in 1998 was 4.2°C higher than in 1997 and 5.8°C higher than in 1999. The number of whale sightings during that time period was inversely related to temperature, with nearly 15 times greater relative abundance observed in 1999 than in 1998. It is hypochesized that the decreasing temperatures associated with the La Niña event of 1999 may have induced more whales to travel farther south along their migration route. Alternative hypotheses are also expiored. Comparisons of the three years are discussed with consideration of the importance of environmental conditionsversusarea fidelity as determining factors in the location of gray whale calving and breeding activities.
DISTRIBUTION OF KILLER WHALE PODS IN PRINCE WILLIAM SOUND, ALASKA 1984–1996
Authors: Scheel D. , Matkin Craig O. , Saulitis Eva 
Published: August 2006

AbstractThirteen years of encounter data (1984–1996) were used to examine killer whale distribution within Prince William Sound, Alaska. Four patterns of area use were found, which comprised differences between resident pods and transient groups and differences among resident groups. Resident pods frequented large open passages, while transient groups used the narrow passages and bays in the southwest. This dichotomy likely reflects resident use of salmon and transient use of pinniped prey resources, as well as the different foraging strategies required for these prey types. Four resident pods (AB, AI, AJ, and AN) used Knight Island Passage more than other areas of the Sound; two (AE and AK) used all areas of the Sound more evenly. Use of the Sound by the AT1 transient whales declined in the latter part of the study. Nearshore foraging for pinniped prey by the AT1 transient whales was more common in areas where these whales spend a disproportionate amount of time, suggesting that these areas were critical foraging habitat for them. No similar pattern emerged for Open‐water Foraging for cetaceans by AT1 whales, nor for foraging by the resident whales.
LABORATORY DIGESTION OF PREY AND INTERPRETATION OF WALRUS STOMACH CONTENTS
Authors: Sheffield Gay , Fay Francis H. , Feder Howard , Kelly Brendan P. 
Published: August 2006

AbstractA new approach for evaluating the potential biases of walrus (Odobenus rosmarus) diet data derived from stomach contents was examined based on the rates at which different prey types were digested. In this study controlled digestion experiments on polychaetes, echiurid and sipunculid worms, clams, snails, and crabs demonstrated that these prey items did not remain equally identifiable during digestion. Polychaetes, echiurids, and sipunculids were the least persistent prey. All worms became unidentifiable during the six‐hour digestion trials. Over 50% of the clams maintained their diagnostic tissues (i. e., foot and/or siphon). Clam viscera did not survive hour 2. Snails and crustaceans were the most persistent prey. Without a consideration of the state of digestion, a stomach sample may not accurately reflect the species composition and size of prey consumed. Volume is not a reliable measure of a prey's relative importance, as the diagnostic fragments of invertebrate prey in a stomach vary greatly in physical composition. Walruses probably consume all of the soft tissues of clams, not solely the foot and siphon.
INCREASED AVOIDANCE OF SWIMMERS BY WILD BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS) DUE TO LONG‐TERM EXPOSURE TO SWIM‐WITH‐DOLPHIN TOURISM
Authors: Constantine Rochelle 
Published: August 2006

AbstractThe responses of wild, non‐provisioned bottlenose dolphins (Tursiops truncatus) to swim attempts from commercial swim‐with‐dolphin tour boats were systematically observed during two research periods: 1994–1995 and 1997–1998. A total of 255 groups of dolphins was encountered during boat‐based surveys and 36% (n= 93) were exposed to at least one swim attempt. The operators' success with swim attempts, defined as at least one dolphin milling within 5 m of at least one swimmer, decreased from 48% in 1994–1995 to 34% in 1997–1998, and avoidance responses to swimmers increased from 22% to 31%. Dolphin response was found to vary according to swimmer placement. The greatest increase in avoidance occurred when swimmers were placed in the dolphins' path of travel. Based on sighting records of 266 individually identified dolphins, it was estimated that an average dolphin was exposed to 31 swim attempts per year. This level of exposure suggests that individual dolphins have, with cumulative experience, become sensitized to swim attempts. When a swim attempt was successful, on average it involved 19% of the group. Age‐class differences in interaction rates showed that juveniles were significantly more likely to interact with swimmers than adults. This study highlights the importance of longitudinal studies in evaluating human impact and suggests the urgent need for similar studies of potential human impact on other toothed cetaceans.
DIRECT ESTIMATION OF WITHIN‐GROUP HETEROGENEITY IN PHOTO‐IDENTIFICATION OF SPERM WHALES
Authors: Whitehead Hal 
Published: August 2006

AbstractHeterogeneity in photo‐identification rates among individuals is a potentially serious problem in many studies of cetacean biology, especially the analysis of populations. However, this heterogeneity is usually difficult to identify or measure. Two instances in which closed groups of female and immature sperm whales (Physeter macrocepbalus) were tracked and identified using fluke photographs over periods of days off the Galápagos Islands allowed direct examination of heterogeneity in identification rates. A group of nine animals followed in 1999 provided almost no evidence for heterogeneity (permutation test for heterogeneity, P= 0.48), with an estimated coefficient of variation in identification rates of 0.03 (95% CI from 1,000 bootstrap replications: 0.00–0.10). In contrast, the identification rates of a group of 22 animals followed in 1995 seemed to show potentially important differences (P= 0.058, CV = 0.20, 95% CI = 0.07–0.28). These differences were not related to the internal social structure of the group or to differences in numbers of markings on the flukes, but smaller whales had lower identification rates. Thus, young sperm whales may be underrepresented in photo‐identification studies, but adults within groups seem to have similar identification rates. Situations in which animals are photo‐identified from closed populations of known size are particularly useful for examining heterogeneity. They should be vigorously exploited by those who use photo‐identification to examine population or behavioral biology.
DIVING BEHAVIOR OF SUBADULT AND ADULT HARBOR SEALS IN PRINCE WILLIAM SOUND, ALASKA
Authors: Frost Kathryn J. , Simpkins Michael A. , Lowry Lloyd F. 
Published: August 2006

AbstractSatellite‐linked depth recorders (SDRs) were attached to 47 harbor seals in Prince William Sound, Alaska, during 1992–1996. Parameters describing diving effort, diving focus, and focal depth (depth bin to which diving was focused) were calculated from binned data on maximum dive depth and time spent at depth, and analyzed using repeated‐measures mixed models. This analysis method accounted for individual variability, temporal autocorrelation, and the binned nature of SDR data, which are often ignored using standard statistical techniques. Results indicated that diving effort remained steady from September to April, when seals spent 68%‐75% of their overall time in the water. Time spent in the water declined to 60% in May and to about 40% in July. Seals spent the most time in the water at night and the least in the morning. The diving of all seals in all months was highly focused. Overall, diving was focused to one depth bin approximately 75% of the time. Diving was more focused for females than for males and subadults. Focal dive depth was deepest in winter and shallowest during May‐July. Focal depth and diving focus varied by region. Collinearity between month and region in the focal depth model suggests that seals move in winter to regions where prey are found deeper in the water column. Variations in diving behavior presumably result from combinations of regional bathymetry, seasonal cycles in type or depth distribution of prey, and seal life‐cycle events such as reproduction and molting.
THREE‐DIMENSIONAL DIVING BEHAVIORS OF RINGED SEALS (PHOCA HISPIDA)
Authors: Simpkins Michael A. , Kelly Brendan P. , Wartzok Douglas 
Published: August 2006

AbstractDives of five freely diving ringed seals were classified into three‐dimentional movement types. Horizontally convoluted dives, defined as dives with angular velocity > 15°/sec, appeared to be foraging or social dives. Simple dives that did not include convoluted movements (angular velocity < 10°/sec) were considered to be exploration dives. Directional dives with nearly linear horizontal travel (horizontal directionality >0.6, on a scale of 0–1) were presumed to be travel dives. Each three‐dimensional dive type was observed with similar frequency in dives with two distinct time‐depth profiles: V‐shaped profiles in which ascent immediately followed descent, and U‐shaped profiles in which >7 sec were spent at depth between descent and ascent. The lack of behavioral differences between dives with distinct time‐depth profiles suggested that time‐depth profiles are not a reliable means of inferring dive behaviors for ringed seals.
DIET OF WEANED PUPS AND SEASONAL VARIATIONS IN BODY CONDITION OF JUVENILE BARENTS SEA HARP SEALS PHOCA GROENLANDICA
Authors: Nilssen Kjell Tormod , Haug Tore , Lindblom Charlotta 
Published: August 2006

AbstractData on blubber depth, body condition, and diet were collected from young of year and juvenile harp seals (Phoca groenlandica) in the Barents Sea in the periods February‐April and June‐October 1990–1997. Harp seal pups feed independently shortly after weaning. In the southern parts of the Barents Sea the diet of harp seal pups consisted mainly of euphausiids (“krill”) Thysanoessa sp. and amphipods of the genus Parathemisto. The change in body condition of harp seal pups between weaning (mid‐March) and June indicated that considerable amounts of blubber energy, deposited during suckling, were mobilized. This suggests that the early food intake of weaned pups was insufficient to meet the energy requirements. The pattern of low spring and earlysummer body condition, followed by a subsequent rapid improvement in condition during late summer and autumn appeared to occur not only among pups‐of‐the‐year, but also in one‐ and two‐year old harp seals.
MOLECULAR SYSTEMATICS OF RIVER DOLPHINS INFERRED FROM COMPLETE MITOCHONDRIAL CYTOCHROME‐B GENE SEQUENCES
Authors: Yang Guang , Zhou Kaiya , Ren Wenhua , Ji Guoqing , Liu Shan , Bastida Richardo , Rivero Laura 
Published: August 2006

Abstract1,140 bp of the complete mitochondrial cytochrome‐b gene sequences of baiji (Lipotes vexillifer), franciscana (Pontoporia blainvillei), and Ganges river dolphin (Platanista gangetica gangetica) were determined to address the systematic position and phylogeny of extant river dolphins with combination of homologous sequences of other cetaceans. The neighbor‐joining (NJ), maximum parsimony (MP), and maximum likelihood (ML) phylogenetic analyses all identified the river dolphins into three lineages, i. e., Platanista, Lipotes, and Inia+Pontoporia. The Lipotes did not have sister relationship with either Platanista or Inia+Pontoporia, which strongly supported the referral of Lipotes to a separate family, i. e., Lipotidae. There were very high sequence divergences between all river dolphin genera, suggesting a relatively longer period of separation time than those among other odontocete families.