bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE ABUNDANCE OF HARBOR SEALS IN THE GULF OF ALASKA
Authors: Boveng Peter L. , Bengtson John L. , Withrow David E. , Cesarone Jack C. , Simpkins Michael A. , Frost Kathsyn J. , Burns John J. 
Published: August 2006

AbstractThe abundance of harbor seals (Phoca vitulina richardii) has declined in recent decades at several Alaska locations. The causes of these declines are unknown, but there is concern about the status of the populations, especially in the Gulf of Alaska. To assess the status of harbor seals in the Gulf of Alaska, we conducted aerial surveys of seals on their haul‐out sites in August‐September 1996. Many factors influence the propensity of seals to haul out, including tides, weather, time of day, and time of year. Because these “covariates” cannot simultaneously be controlled through survey design, we used a regression model to adjust the counts to an estimate of the number of seals that would have been ashore during a hypothetical survey conducted under ideal conditions for hauling out. The regression, a generalized additive model, not only provided an adjustment for the covariates, but also confirmed the nature and shape of the covariate effects on haul‐out behavior. The number of seals hauled out was greatest at the beginning of the surveys (mid‐August). There was a broad daily peak from about 1100–1400 local solar time. The greatest numbers were hauled out at low tide on terrestrial sites. Tidal state made little difference in the numbers hauled out on glacial ice, where the area available to seals did not fluctuate with the tide. Adjusting the survey counts to the ideal state for each covariate produced an estimate of 30,035 seals, about 1.8 times the total of the unadjusted counts (16,355 seals). To the adjusted count, we applied a correction factor of 1.198 from a separate study of two haul‐out sites elsewhere in Alaska, to produce a total abundance estimate of 35,981 (SE 1,833). This estimate accounts both for the effect of covariates on survey counts and for the proportion of seals that remained in the water even under ideal conditions for hauling out.
AGE, GROWTH, AND REPRODUCTION IN NEW ZEALAND FUR SEALS
Authors: Dickie GailS. , Dawson Stephen M. 
Published: August 2006

AbstractGrowth and reproductive biology of New Zealand fur seals (Arctocephalus forsteri) were studied by examining 127 seals (57 females, 64 males) killed incidentally in fishing gear in New Zealand waters in 1996. Tooth sections were used to age the animals, and male and female reproductive organs were examined macroscopically and histologically. The maximum age observed was 22 yr for females and 12 yr for males. Males were significantly larger than females, but growth was similar up to 5 yr. Males reached sexual maturity between 5 and 9 yr of age, whereas females did so between 4 and 6 yr. The mean pregnancy rate in females was 0.69 (95% CI = 0.54–0.81).
CAUSES OF MORTALITY IN CALIFORNIA SEA OTTERS DURING PERIODS OF POPULATION GROWTH AND DECLINE
Authors: Estes JamesA. , Hatfield Brian B. , Ralls Katherine , Ames Jack 
Published: August 2006

AbstractElevated mortality appears to be the main reason for both sluggish growth and periods of decline in the threatened California sea otter population. We assessed causes of mortality from salvage records of 3,105 beach‐cast carcasses recovered from 1968 through 1999, contrasting two periods of growth with two periods of decline. Overall, an estimated 40%‐60% of the deaths were not recovered and 70% of the recovered carcasses died from unknown causes. Nonetheless, several common patterns were evident in the salvage records during the periods of population decline. These included greater percentages of (1) prime age animals (3–10 yr), (2) carcasses killed by great white shark attacks, (3) carcasses recovered in spring and summer, and (4) carcasses for which the cause of death was unknown. Neither sex composition nor the proportion of carcasses dying of infectious disease varied consistently between periods of population increase and decline. The population decline from 1976 to 1984 was likely due to incidental mortality in a set‐net fishery, and the decline from 1995 to 1999 may be related to a developing live‐fish fishery. Long‐term trends unrelated to periods of growth and decline included a decrease in per capita pup production and mass/length ratios of adult carcasses over the 31‐yr study. The generally high proportion of deaths from infectious disease suggests that this factor has contributed to the chronically sluggish growth rate of the California sea otter population.
SIZE‐AND AGE‐CLASS SEGREGATION OF BOWHEAD WHALES SUMMERING IN NORTHERN FOXE BASIN: A PHOTOGRAMMETRIC ANALYSIS
Authors: Cosens Susan E. , Blouw Andries 
Published: August 2006

AbstractTo determine whether Hudson Bay‐Foxe Basin bowhead whales segregate on the basis of age, whales summering in northern Foxe Basin, were aerially photographed in August of 1996, 1997, and 1998. Image lengths on either the negatives or contact prints were measured and total body lengths were estimated. In all three years the majority of whales photographed were ≤13.5 m long. Calves and juveniles made up 89.3%, 96.6%, and 79.3% of the total number of measured whales in 1996 (n = 28), 1997 (n = 30) and 1998 (n = 29) respectively. The number of bowheads >13.5 m, the approximate size at which females reach sexual maturity, that were photographed was directly proportional to the number of calves photographed. Our results indicate that northern Foxe Basin bowheads are part of a more widely distributed stock. Adult males and resting adult females apparently summer in another part of the range, probably northwestern Hudson Bay. Northern Foxe Basin appears to be used as a summer feeding area by cows with young‐of‐the‐year calves and by juveniles.
NEW INFORMATION ON THE NATURAL HISTORY, DISTRIBUTION, AND SKULL SIZE OF THE EXTINCT (?) WEST INDIAN MONK SEAL,MONACHUS TROPICALIS
Authors: Adam Peter J. , Garcia Gabriela G. 
Published: August 2006

AbstractOur knowledge of the extinct West Indian monk seal,Monachus tropicalis, is scant due to heavy exploitation following European colonization of the New World. We present previously unknown accounts of the species, including unpublished field notes of biologist E. W. Nelson, who observed a small number of wild seals in June of 1900. Records indicate thatM. tropicalismay have had a long pupping season, occurred in large groups (up to 100) when abundant, probably ate fish and crustaceans, were preyed upon by sharks, and that young and adult seals may have assorted themselves into different age groups when hauled out. Additional records extend the known range ofM. tropicalisto include the north coast of South America as far east as Guyana. We also present previously unavailable measurements from a large series of adult skulls and mandibles (n= 48). Two cases of histocytosis X, carcinoma, or other disease of the hard palate are documented from among these specimens.
VARIATION IN THE FORAGING LOCATION OF ANTARCTIC FUR SEALS (ARCTOCEPHALUS GAZELLA) AND THE EFFECTS ON DIVING BEHAVIOR
Authors: Staniland I. J. , Boyd I. L. 
Published: August 2006

AbstractThis study investigated how female Antarctic fur seals adapt their foraging behavior, over time scales of days, to spatial unpredictability in the distribution of their food. Lactating Antarctic fur seals are central‐place foragers that feed on highly patchy but spatially and temporally dynamic food. We measured the foraging distribution of 28 fur seals to test whether variation in foraging trip durations was reflected in variation in the location of foraging and the diving behavior of seals at sea. Based on the maximum distance travelled from the breeding beach, three categories of foraging trips were denned: those to the continental shelf area (n= 12, median = 71 km), to oceanic water (n= 11, median =164 km), and to farther offshore oceanic waters (n= 5, median = 260 km). Trip duration and mean surface speed were positively correlated with the maximum distance travelled from the breeding beach. Seals on longer trips spent proportionally less of their time submerged, but there was no significant difference in the total number of dives or the total time spent foraging by seals in relation to trip duration. Evidence from this study and previous work investigating energy gain suggests that an animal on a longer foraging trip could potentially have a higher mean energy return per dive than a similar animal on a shorter foraging trip. Evidence presented suggests that the type of foraging trip (near or far) is not predetermined by the animal but may be a simple response to the stochastic distribution of the resources available.
A THREE‐STAGE ALGORITHM FOR FILTERING ERRONEOUS ARGOS SATELLITE LOCATIONS
Authors: Austin Deborah , McMillan J. I. , Bowen W. D. 
Published: August 2006

AbstractSeveral methods have been used to identify erroneous animal locations based on Argos satellite data. Using 15,987 satellite locations for 37 gray seals (Haliockoerus grypus), we tested a three‐stage filtering algorithm designed to address shortcomings of other filters. In stage 1, for each location, four rates of travel were calculated—the rate to each of the two previous locations and the two subsequent locations. If all four rates exceeded 2 m/sec (95th percentile of our data), the location was removed (7.25% of total locations). Stage 2 incorporated the filtering algorithm developed by McConnell et al. (1992) resulting in the rejection of 22.75% of total locations based on reasonable assumptions of straight‐line travel. At stage 3, the remaining data were evaluated against a distance threshold, defined as the 99th percentile of realized distance traveled over a period of seven days. Locations exceeding this threshold‐were rejected (0.69% of total locations). Overall, the three‐stage filter eliminated fewer locations (30.7 ± 1.62%), than the stage 2 filter alone. Most standard locations were retained, but 85.7% of location class 0, 76.6% of A, and 41.9% of B were also retained. These location classes account for most of data routinely collected but not used.
REPRODUCTIVE SEASONALITY OF WESTERN ATLANTIC BOTTLENOSE DOLPHINS OFF NORTH CAROLINA, U.S.A.
Authors: Thayer Victoria G. , Read Andrew J. , Friedlaender Ari S. , Colby David R. , Hohn Aleta A. , McLellan William A. , Pabst D. Ann , Dearolf Jennifer L. , Bowles Nan I. , Russell John R. , Rittmaster Keith A. 
Published: August 2006

AbstractWe describe reproductive seasonality of bottlenose dolphins in North Carolina (NC), U.S.A., using strandings data from the entire coast of NC and sighting data from Beaufort, NC and by estimating dates of birth of known females. We found a strong peak of neonate strandings in the spring (April‐May), and low levels of neonate strandings in the fall and winter. The distribution of neonate strandings was significantly different from a uniform distribution (P < 0.001, K= 3.8). We found a unimodal distribution of 282 sightings of neonates with a diffuse peak in the summer. The temporal distribution of sightings of neonates departed significantly from a uniform distribution (P < 0.001, K= 5.1). Estimated birth dates of neonates from known females occurred in May (n= 6) and June (n= 4), with a single fall birth. These methods shed light on bottlenose reproductive patterns and underscore the value of using information from multiple types of data. Clarification of bottlenose dolphin reproductive patterns, such as the seasonality of birth, may enhance our understanding of the population structure of this species in the mid‐Atlantic region.
TWO TYPES OF BLUE WHALE CALLS RECORDED IN THE GULF OF ALASKA
Authors: Stafford Kathleen M. 
Published: August 2006

AbstractAt one time blue whales were found throughout the Gulf of Alaska, however, none have been sighted there in post‐whaling era surveys. To determine if blue whales (Balaenoptera musculus) might now occur in the Gulf of Alaska, an array of hydrophones was deployed there in October 1999. Data were retrieved in May 2000 and in June 2001. Spectrograms from a random subsample comprising 15% of the ∼63,000 h of data were visually examined for blue whale calls. Call types attributed to both northeastern and northwestern Pacific blue whales were recorded. Both of these call types were recorded seasonally from the initial deployment date in October 1999 through the third week of December 1999 and then from July 2000 through mid‐December 2000. Both call types were regularly recorded on the same hydrophone at the same time indicating clear temporal and spatial overlap of the animals producing these calls. Two blue whale call types were recorded in the Gulf of Alaska suggesting that perhaps two stocks use this area. The northeastern call type has now been documented from the equator up to at least 55°N in the eastern North Pacific.
LOCALIZATION OF NORTH ATLANTIC RIGHT WHALE SOUNDS IN THE BAY OF FUNDY USING A SONOBUOY ARRAY
Authors: Laurinolli Marjo H. , Hay Alex E. , Desharnais Francine , Taggart Christopher T. 
Published: August 2006

AbstractA free‐drifting 14‐sonobuoy array was used to localize North Atlantic right whales (Eubalaena glacialis) in the Grand Manan Basin area of the Bay of Fundy. This area is a primary summer/autumn right whale habitat and overlaps an international shipping lane. The three‐hour deployment on a single day provided two‐dimensional localization of 94 right whale sounds based on arrival time differences determined from spectrogram cross‐correlation analysis. The sounds were of two distinct types: tonal and gunshot. Maximum detection distances were about 30 km for both types of sound. The mean RMS location error was 1.8 km for tonal‐type sounds and 2.5 km for gunshot‐type sounds. The average RMS error was 20% of the average distance from the receiving hydrophones, the primary source of error being uncertainty in the sonobuoy positions.
QUANTIFYING ERRORS ASSOCIATED WITH USING PREY SKELETAL STRUCTURES FROM FECAL SAMPLES TO DETERMINE THE DIET OF STELLER'S SEA LION (EUMETOPIAS JUBATUS)
Authors: Tollit Dominic J. , Wong Mandy , Winship Arliss J. , Rosen David A. S. , Trites Andrew W. 
Published: August 2006

AbstractWe examined the digestion and passage times of bones and other hard parts from pollock, herring, salmon, and sandlance recovered from two juvenile captive Steller's sea lions (Eumetopias jubatus) subjected to varying activity levels. Key bones that could be identified to species were distributed over an average of 3.2 scats (range 1–6) following a single meal, with pollock remains occurring in significantly more scats than other species. Relying on otoliths alone to determine the presence of prey resulted in significantly fewer prey being identified than if other structures were also used (such as vertebrae, jaw bones, and teeth), particularly for salmon. Using either technique, there were significant differences in the likelihood that bones would be recovered from the series of scats produced following a meal, with pollock recovery exceeding herring (by three‐fold) and sandlance (by eight‐fold). Differences between species were reduced when recovery was calculated on a per scat basis rather than over multiple scats. Active animals passed greater numbers of bones, but the overall effect on prey recovery estimates was not significant. Defecation times of prey structures from a meal were variable and ranged from an initial 2–56 h to a final 28–148 h. The time interval to pass 95% of recovered structutes varied by a factor of two among prey species, and was highest for pollock due to retention beyond 65 h.
STABILITY IN THE PROPORTION OF HARBOR SEALS HAULED OUT UNDER LOCALLY IDEAL CONDITIONS
Authors: Simpkins Michael A. , Withrow David E. , Cesarone Jack C. , Boveng Peter L. 
Published: August 2006

AbstractWe monitored the haul‐out behavior of 68 radio‐tagged harbor seals (Phoca vitulina) during the molt season at two Alaskan haul‐out sites (Grand Island, August‐September 1994; Nanvak Bay, August‐September 2000). For each site, we created a statistical model of the proportion of seals hauled out as a function of date, time of day, tide, and weather covariates. Using these models, we identified the conditions that would result in the greatest proportion of seals hauled out. Although those “ideal conditions” differed between sites, the proportion of seals predicted to be hauled out under those conditions was very similar (81.3% for Grand Island and 85.7% for Nanvak Bay). The similar estimates for both sites suggest that haul‐out proportions under locally ideal conditions may be constant between years and geographic regions, at least during the molt season.
REPRODUCTION IN MALE ATLANTIC WALRUSES (ODOBENUS ROSMARUS ROSMARUS) FROM THE NORTH WATER (N BAFFIN BAY)
Authors: Born E. W. 
Published: August 2006

AbstractAge at sexual maturity and timing of the mating season were determined in male Atlantic walruses (Odobenus rosmarus rosmarus, L.) from the “North Water” subpopulation in northern Baffin Bay. Testes and epididymides of 174 male walruses (between 0 and 30 yr old) from NW Greenland (1987–1990) were studied macroscopically and a subset of 57 specimens was analyzed microscopically. In physically mature bulls (i.e., ≥12 yr old), sperm or apparently ripe spermatids were found between 9 November and 12 July. In younger walruses these signs of fertility were found in a few specimens (7–11 yr old) collected between 9 January and 28 May. The mating season seems to peak in January—April. The youngest sexually mature individual was 7 yr old and the oldest apparently immature individual was 13 yr old. Average age of sexual maturity was 10.9 yr (95% C.I.: 9–6–12.2 yr) and all were sexually mature by the time they were 14 yr old. The non‐spermiogenetic testes and epididymides showed accelerated growth between about the 5–6th and about the 12–15th year of life, indicating that sexual maturation occurs during these years. The length of the baculum increased gradually until about 12–15 yr of age, when physical maturity was reached.
CRANIAL SEXUAL DIMORPHISM AND GEOGRAPHIC VARIATION IN ERASER'S DOLPHIN, LAGENODELPHIS HOSEI
Authors: Perrin William F. , Dolar M. Louella L. , Amano Masao , Hayano Azusa 
Published: August 2006

AbstractKnowledge of geographic variation is important to questions of population assessment and management. Fraser's dolphins have been exploited in two regions in the western Pacific. Analysis of 137 skulls from the Philippines, Japan, Taiwan, Australia, Indonesia, Malaysia, South Africa, France, the U.S., St. Vincent and the Grenadines, and the eastern tropical Pacific revealed sexual dimorphism in 5 of 26 measurements (difference of 1.9%‐5.8% between males and females), similar to levels of cranial dimorphism in other small pelagic delphinids. Males had a larger braincase and temporal fossae and smaller external nares than females. Sexually dimorphic characters were excluded, and male and females samples were pooled to examine geographic differences in the remaining characters. Multivariate analyses yielded significant differences between the Philippine and Japanese series within the North Pacific and between a pooled North Pacific series and a North Atlantic series. The Japanese skulls were on average broader and had a wider rostrum, larger orbit, larger internal nares, and longer braincase than the Philippine skulls. These differences suggest that Fraser's dolphins exploited in Japanese and Philippine waters in directed fisheries or as by catch belong to different populations and should be assessed and managed separately.
IMPROVING MANAGEMENT OF OVERLAPPING BOTTLENOSE DOLPHIN ECOTYPES THROUGH SPATIAL ANALYSIS AND GENETICS
Authors: Torres Leigh G. , Rosel Patricia E. , D'Agrosa Caterina , Read Andrew J. 
Published: August 2006

AbstractIn the Northwest Atlantic the distribution of coastal bottlenose dolphins (Tursiops truncatus) overlaps with that of the offshore ecotype. We hypothesized that the distribution of the two ecotypes could be delineated by depth and/or distance from shore, facilitating their identification during surveys. We obtained 304 skin biopsy samples and identified each as either coastal or offshore using analysis of mitochondrial DNA. We then interpreted the spatial distribution of coastal and offshore forms using spatial analysis. Using a Classification and Regression Tree (CART) analysis, we found a statistically significant break in ecotype distribution at 34 km from shore. In waters beyond 34 km from shore and deeper than 34 m, all bottlenose dolphins were of the offshore ecotype. Within 7.5 km of shore, all 65 samples were of the coastal ecotype. Between these two areas only nine samples were collected, so the genetic composition of bottlenose dolphins in this area remains poorly known. To enhance our understanding of the spatial distribution of the two ecotypes, future research should obtain more biopsy samples in this zone. Nevertheless, our results indicate that a conservative abundance estimate for the coastal ecotype could be generated from surveys of bottlenose dolphins within 7.5 km of shore.
RESPONSE OF NORTH ATLANTIC RIGHT WHALES (EUBALAENA GLACIALIS) TO PLAYBACK OF CALLS RECORDED FROM SURFACE ACTIVE GROUPS IN BOTH THE NORTH AND SOUTH ATLANTIC
Authors: Parks Susan E. 
Published: August 2006

AbstractThe surface active group (SAG) is the most obvious social interaction of the North Atlantic right whale (Eubalaena glacialis). SAGs are typically composed of an adult female with two or more males engaged in social behavior near the surface. Distinct calls, believed to be produced by the female, are associated with these groups. Calls recorded from three North Atlantic right whale SAGs and three South Atlantic right whale (Eubalaena australis) SAGs were played back to North Atlantic right whales to determine if these sounds are sufficient to attract males to the groups. Playbacks of gunshot sounds produced by North Atlantic right whales were used as a control stimulus. Thirty‐six trials were carried out from 1999 to 2001 in the Bay of Fundy, Canada. Whales approached 27 of 31 SAG playbacks and 0 of 5 gunshot playbacks. Where sex was determined (n= 28), all approaches to North Atlantic SAG recordings were by males. Individuals (n= 22) of all age and sex classes approached South Atlantic SAG playbacks. These trials indicate that SAG calls from both populations are sufficient to attract right whales to SAGs and that males and females respond differently to stimuli from the North Atlantic. The difference in response to North and South Atlantic SAG stimuli was unexpected. Novelty, species differences in calls, and different seasonal or behavioral context for the recorded stimuli may be responsible for the differences in response.
SEASONAL OCCURRENCE OF SPERM WHALE (PHYSETER MACROCEPHALUS) SOUNDS IN THE GULF OF ALASKA, 1999–2001
Authors: Mellinger David K. , Stafford Kathleen M. , Fox Christopher G. 
Published: August 2006

AbstractAn acoustic survey for sperm whales was conducted in the Gulf of Alaska. Six autonomous hydrophones continuously recorded sound signals below 500 Hz from October 1999 to May 2001. After recovery, recordings were processed using an automatic process to detect usual clicks of sperm whales. The detection algorithm equalized background noise, summed the data in a frequency band, and then used autocorrelation to detect the whales' highly regular clicks. Detections were checked manually, revealing that 98% of detections did contain clicks. Results indicate that sperm whales are present in the Gulf of Alaska year‐round; this result extends what is known from whaling data, which were gathered principally in summer. Sperm whales were more common in summer than winter by a factor of roughly two, and occurred less often at the westernmost site surveyed (52°N, 157°W) than elsewhere in the Gulf. This is the first study of sperm whales based exclusively on remote acoustic sensing. This methodology is feasible because sperm whale clicks extend to frequencies (∼100 Hz) low enough to be recorded by low‐sample‐rate instruments that operate continuously, and because the detection algorithm has a low false‐detection rate. The methodology may be replicated to facilitate comparisons between different time periods and geographic regions.