bluuebunny/crossref_metadata_2025 huggingface dataset:
BOTTLENOSE DOLPHINS INCREASE BREATHING SYNCHRONY IN RESPONSE TO BOAT TRAFFIC
Authors: Hastie Gordon D. , Wilson Ben , Tufft Lindsay H. , Thompson Paul M.
Published: August 2006

Abstract

To minimize potential impacts of boat traffic on the behavior of cetaceans it is important to assess short‐term behavioral responses to boats and interpret the long‐term consequences of these. Anecdotal descriptions of synchronous behavior in cetaceans are particularly frequent with reports of individuals within schools surfacing to breathe in a coordinated fashion being common. However, quantitative descriptions are rare. This study begins by quantifying synchronous breathing patterns of bottlenose dolphins off northern Scotland. We investigate possible functions of synchrony such as feeding patterns and presence of calves. We then test whether the presence of boat traffic in an area used intensively by dolphins affects their breathing synchrony. Although the majority of dolphin schools observed showed random breathing patterns, 30.5 % of schools showed synchronous breathing. There was no variation in this behavior with respect to identifiable feeding activities. However, synchrony was significantly negatively telated to the presence of calves in the school (χ2= 7.17, df = 1, P = 0.007) and significantly positively related to the presence of boat traffic in the study area (χ= 13.85, df = 1, P = 0.0002). Such consistent short‐term behavioral responses by dolphins may potentially accumulate to produce longer‐term consequences both for individuals and the whole population.
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

Abstract

The 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

Abstract

Growth 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

Abstract

Elevated 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

Abstract

To 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

Abstract

Our 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

Abstract

This 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

Abstract

Several 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

Abstract

We 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

Abstract

At 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

Abstract

A 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

Abstract

We 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

Abstract

We 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

Abstract

Age 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

Abstract

Knowledge 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

Abstract

In 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

Abstract

The 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

Abstract

An 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.
ABUNDANCE OF BLUE AND HUMPBACK WHALES IN THE EASTERN NORTH PACIFIC ESTIMATED BY CAPTURE‐RECAPTURE AND LINE‐TRANSECT METHODS
Authors: Calambokidis John , Barlow Jay
Published: August 2006

Abstract

We estimated humpback and blue whale abundance from 1991 to 1997 off the west coast of the U. S. and Mexico comparing capture‐recapture models based on photographically identified animals and line‐transect methods from ship‐based surveys. During photo‐identification research we obtained 4,212 identifications of 824 humpback whales and 2,403 identifications of 908 blue whales primarily through non‐systematic small‐boat surveys along the coast of California, Oregon, and Washington. Line‐transect surveys from NOAA ships in 1991, 1993, and 1996 covered approximately 39,000 km along the coast of Baja California, California, Oregon, and Washington out to 555 km from shore. The nearshore and clumped distribution of humpback whales allowed photographic identification from small boats to cost‐effectively sample a substantial portion of the population, but made it difficult to obtain effective samples in the line‐transect surveys covering broad areas. The humpback capture‐recapture estimates indicated humpback whale abundance increased over the six years (from 569 to 837). The broader more offshore distribution of blue whales made it harder to obtain a representative sample of identification photographs, but was well suited to the line‐transect estimates. The line‐transect estimates, after correction for missed animals, indicated approximately 3,000 blue whales (CV = 0.14). Capture‐recapture estimates of blue whales were lower than this: approximately 2,000 when using photographs obtained from the line‐transect surveys as one of the samples. Comparison of the results from the two methods provides validation, as well as insight into potential biases associated with each method.
GEOGRAPHIC GENETIC STRUCTURE IN THE FRANCISCANA DOLPHIN (PONTOPORIA BLAINVILLEI)
Authors: Lázaro Marila , Lessa Enrique P. , Hamilton Healy
Published: August 2006

Abstract

The franciscana, Pontoporia blainvillei, is endemic to the South Atlantic coast of South America. The species is of conservation concern because it suffers elevated mortality rates due to incidental captures in fishing nets, and perhaps it is one of the most threatened small cetaceans in this region. Previous morphological and genetic studies have suggested the existence of at least two distinct stocks to the north and south of Santa Catarina Island in Brazil. Fixed differences were found between a sample from Rio de Janeiro and one from Rio Grande do Sul, in southern Brazil. Using 94 sequences of the control region of mitochondrial DNA, we examined the genetic structure of the species. We found no shared haplotypes between Rio de Janeiro and samples from the southern range of the species distribution. However, a phylogenetic analysis suggests that the former population is diphyletic with respect to the southern samples. This suggests that the populations have not been isolated long enough to reach reciprocal monophyly. Furthermore, genetic differentiation is broadly consistent with a simple model of isolation by distance, that therefore appears as an alternative to a model of strict isolation of two stocks. The estimated levels of gene flow are higher among neighboring populations, and decrease as more distant localities are compared. Finally, the molecular data suggest that franciscanas have expanded in Rio de Janeiro.
MAJOR HISTOCOMPATIBILITY COMPLEX I POLYMORPHISM IN A CETACEAN: THE GRAY WHALE (ESCHRICHTIUS ROBUSTUS)
Authors: Flores‐Ramirez Sergio , Miller Robert D. , Urban‐Ramirez Jorge
Published: August 2006

Abstract

Vertebrate Major Histocompatibility Complex‐I (Mbc‐I) proteins bind and display self and foreign peptides on the cell surface. Mbc‐I polymorphism is considered critical for eliciting immune responses to a diversity of antigens, and thus, for the health and conservation of a species. Based on restriction fragment length polymorphism it was concluded that whales generally have low Mbc‐I polymorphism. This was attributed to the weak pathogenic pressure in aquatic habitats. Since gray whales' habits might favor their encounter with diverse pathogens, resulting in selection pressures for Mbc variability, we searched for functional polymorphism of gray whale's Mbc‐I exon 2 sequences that encode the α‐1 protein domain of the antigen‐binding region. We sequenced twelve Mbc‐I exon 2 clones from each of seven gray whales. Most obtained sequences were similar to functional artiodactyl sequences, and their reconstructed phylogeny consistently showed three whale Mbc‐I exon 2 sequence clusters (A, B, and C). Sequences within a given cluster and from distinct clusters, showed a greater number of non‐synonymous than synonymous substitutions, that commonly shifted the physiochemical properties of the involved residue, suggesting the existence of a diverse repertoire of Mbc‐I antigen recognition sites in gray whales, and that selection maintains gray whale's Mbc‐I allelic diversity.
DETERMINING BLUBBER FATTY ACID COMPOSITION: A COMPARISON OF IN SITU DIRECT AND TRADITIONAL METHODS
Authors: Thiemann Gregory W. , Budge Suzanne M. , Iverson Sara J.
Published: August 2006

Abstract

Fatty acids (FAs) are used to make inferences about the foraging behavior and diets of free‐ranging marine mammals. However, several methods are currently available for determining the FA composition of blubber and these methods may produce different results. We compared in situ direct transesterification methods, where a small amount of tissue is sampled, with more traditional methods involving prior lipid extraction of the entire sample of interest. Using gray seal (Halichoerus grypus) and beluga whale (Delphinapterus leucas) blubber, we found that when the direct in situ method was used on a 2‐mg sample of blubber, the resulting FA profile differed significantly from that produced when traditional full‐extraction methods were employed. Regardless of where the small spot sample was taken within the blubber depth, it was not representative of the entire blubber FA composition, as blubber is non‐homogeneous throughout its depth. We also modified the in situ direct method to allow analysis of the entire blubber layer. Results of this full‐layer direct method compared quite favorably with traditional extraction methods and may provide a reasonable alternative for analyses. Although application of our full‐layer direct method will require further verification in certain marine mammal blubber samples, we conclude that the large differences obtained when using the direct method are not a consequence of the chemical method itself. Rather, they arise from non‐representative sampling of the blubber FA composition.
A STAGE‐BASED MODEL OF MANATEE POPULATION DYNAMICS
Authors: Runge Michael C. , Langtimm Catherine A. , Kendall William L.
Published: August 2006

Abstract

A stage‐structured population model for the Florida manatee (Trichechus manatus latirostris) was developed that explicitly incorporates uncertainty in parameter estimates. The growth rates calculated with this model reflect the status of the regional populations over the most recent 10‐yr period. The Northwest and Upper St. Johns River regions have growth rates (λ) of 1.037 (95% interval, 1.016–1.056) and 1.062 (1.037–1.081), respectively. The Southwest region has a growth rate of 0.989 (0.946–1.024), suggesting this population has been declining at about 1.1% per year. The estimated growth rate in the Atlantic region is 1.010 (0.988–1.029), but there is some uncertainty about whether adult survival rates have been constant over the last 10 yr; using the mean survival rates from the most recent 5‐yr period, the estimated growth rate in this region is 0.970 (0.938–0.998). Elasticity analysis indicates that the most effective management actions should seek to increase adult survival rates. Decomposition of the uncertainty in the growth rates indicates that uncertainty about population status can best be reduced through increased monitoring of adult survival rate.
METHODS FOR JOINT INFERENCE FROM MULTIPLE DATA SOURCES FOR IMPROVED ESTIMATES OF POPULATION SIZE AND SURVIVAL RATES
Authors: Goodman Daniel
Published: August 2006

Abstract

Critical conservation decisions often hinge on estimates of population size, population growth rate, and survival rates, but as a practical matter it is difficult to obtain enough data to provide precise estimates. Here we discuss Bayesian methods for simultaneously drawing on the information content from multiple sorts of data to get as much precision as possible for the estimates. The basic idea is that an underlying population model can connect the various sorts of observations, so this can be elaborated into a joint likelihood function for joint estimation of the respective parameters. The potential for improved estimates derives from the potentially greater effective sample size of the aggregate of data, even though some of the data types may only bear directly on a subset of the parameters. The achieved improvement depends on specifics of the interactions among parameters in the underlying model, and on the actual content of the data. Assuming the respective data sets are unbiased, notwithstanding the fact that they may be noisy, we may gauge the average improvement in the estimates of the parameters of interest from the reduction, if any, in the standard deviations of their posterior marginal distributions. Prospective designs may be evaluated from analysis of simulated data. Here this approach is illustrated with an assessment of the potential value in various ways of merging mark‐resight and carcass‐survey data for the Florida manatee, as could be made possible by various modifications in the data collection protocols in both programs.
HIGH PERFORMANCE TURNING CAPABILITIES DURING FORAGING BY BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS)
Authors: Maresh Jennifer L. , Fish Frank E. , Nowacek Douglas P. , Nowacek Stephanie M. , Wells Randall S.
Published: August 2006

Abstract

Large predators should have difficulty catching small prey because small animals demonstrate greater maneuverability and agility compared to large animals. The ability of a predator to capture small prey indicates locomotor strategies to compensate for inequities in maneuverability. Bottlenose dolphins (Tursiops truncatus) in Sarasota Bay, Florida feed on fish at least one order of magnitude smaller than themselves. To examine the locomotor strategies involved in prey capture, the foraging movements of these dolphins were videotaped from overhead using a remotely‐controlled camera suspended from a helium‐filled aerostat, which was tethered to an observation vessel. Dolphins were observed to rapidly maneuver during chases of fish in open water or around patches of rooted vegetation. Video analysis of the chase sequences indicated that the dolphins could move the rostrum through small radius turns with a mean value of 0.20 body lengths and with a minimum value of 0.08 body lengths. Mean rate of turn was 561.6°/sec with a maximum rate measured at 1,372.0°/sec. High turning rates with small turning radii were primarily the result of maneuvers in which the dolphin rolled 90° and rapidly flexed its body ventrally. The ability of dolphins to change body orientation in multiple rotational axes provides a mechanism to reduce turning radius and increase turning rate to catch small, elusive prey.
RETROSPECTIVE ISOTOPIC ANALYSES OF STELLER SEA LION TOOTH ANNULI AND SEABIRD FEATHERS: A CROSS‐TAXA APPROACH TO INVESTIGATING REGIME AND DIETARY SHIFTS IN THE GULF OF ALASKA
Authors: Hobson Keith A. , Sinclair Elizabeth H. , York Anne E. , Thomason James R. , Merrick Richard E.
Published: August 2006

Abstract

Stable isotope (δ15N and δ13C) values of individual tooth annuli of female Steller sea lions (n= 120) collected from the 1960s through the 1980s were used for retrospective analyses of temporal changes in food webs in the Gulf of Alaska and North Pacific Ocean. We also examined isotopically contour feathers of tufted puffins (n= 135) and crested auklets (n= 37) through this period to test for broader isotopic patterns indicative of whole food web changes. Steller sea lions decreased slightly in δ13C and increased in δ15N values, suggesting an increasing trophic level and change in foraging location or oceanographic isotopic signature. Steller sea lion first and second tooth annuli were enriched in 15N and depleted in 13C compared with subsequent annuli, indicating the effects of maternal influence through weaning. The general pattern of increasing δ15N values among Steller sea lions supports previous conclusions regarding a reduction or redistribution of forage fishes and an increase of demersal and semi‐demersal species in the North Pacific ecosystem. There were no significant changes in δ15N values for either bird species. However, δ13C values in both bird species again suggested changes in foraging location or a shift in oceanographic currents.
AQUATIC MATING STRATEGIES OF THE MALE PACIFIC HARBOR SEAL (PHOCA VITULINA RICHARDII): ARE MALES DEFENDING THE HOTSPOT?
Authors: Hayes Sean A. , Costa Daniel P. , Harvey James T. , le Boeuf BURNEY J.
Published: August 2006

Abstract

Compared to the harem and resource defense systems of terrestrial mating pinnipeds, males of aquatic mating species appear unable to monopolize females or resources. We investigated movements, acoustics, and aquatic territorial behavior of male harbor seals, Phoca vitulina richardii, in Elkhorn Slough, California, using VHF telemetry, hydrophones, and acoustic playback experiments. During the mating season 22 males increased time spent in the water and away from haul‐out locations, exhibiting activity patterns similar to Atlantic subspecies. Two acoustic display patterns were observed. At one location multiple males aggregated to display with acoustic activity peaking one month before peak estrus. At two other locations, lone males displayed primarily during peak estrus. Acoustic display areas were non‐adjacent with a mean ± SE size of 4,228 ± 576 m2, similar to harbor seal display patterns in the Moray Firth, Scotland. Underwater playbacks of male vocalizations were used to define territorial boundaries by inducing responses from territory‐holding males. Four solitary males defended adjacent territories (mean area 39,571 ± 18,818 m2) along a travel corridor, similar to observations of harbor seals at Miquelon, Newfoundland. Acoustic display stations appeared to be subcomponents of larger territories. Males exhibited site fidelity to territories for at least 2–4 yr. Females moved through territories freely. The establishment of male‐display territories along female‐traffic corridors resembles terrestrial systems described as hotspot leks.
TEMPORARY THRESHOLD SHIFTS AFTER NOISE EXPOSURE IN THE BOTTLENOSE DOLPHIN (TURSIOPS TRUNCATUS) MEASURED USING EVOKED AUDITORY POTENTIALS
Authors: Nachtigall Paul E. , Supin Alexander Ya. , Pawloski Jeffrey , Au Whitlow W. L.
Published: August 2006

Abstract

The time course of recovery from temporary threshold shift (TTS) was measured in a bottlenose dolphin, Tursiops truncatus, using an evoked‐potential procedure. The envelope‐following response (EFR), which is a rhythmic train of auditory brainstem responses (ABR) to sinusoidally amplitude‐modulated tones, was used as an indicator of the sound reception by the animal. Variation of the intensity of the stimulus allowed us to measure the animal's hearing via EFR thresholds. During each session, following an initial measure of threshold, the trained animal voluntary positioned itself within a hoop 1 m underwater while a 160 dB re 1 μPa noise of a 4–11 kHz bandwidth was presented for 30 min. After the noise exposure, thresholds were measured again at delays of 5, 10, 15, 25, 45, and 105 min. Measurements were made at test frequencies of 8, 11.2, 16, 22.5, and 32 kHz. The maximum TTS occurred 5 min after exposure and rapidly recovered with a rate of around 1.5 dB per doubling of time. TTS occurred at test frequencies from 8 to 16 kHz, with the maximum at 16 kHz. TTS was negligible at 22.5 kHz and absent at 32 kHz.
HISTORICAL OBSERVATIONS OF HUMPBACK AND BLUE WHALES IN THE NORTH ATLANTIC OCEAN: CLUES TO MIGRATORY ROUTES AND POSSIBLY ADDITIONAL FEEDING GROUNDS
Authors: Reeves Randall R. , Smith Tim D. , Josephson Elizabeth A. , Clapham Phillip J. , Woolmer Gillian
Published: August 2006

Abstract

The seasonal distributions of humpback and blue whales (Megaptera novaeangliaeandBalaenoptera musculus, respectively) in the North Atlantic Ocean are not fully understood. Although humpbacks have been studied intensively in nearshore or coastal feeding and breeding areas, their migratory movements between these areas have been largely inferred. Blue whales have only been studied intensively along the north shore of the Gulf of St. Lawrence, and their seasonal occurrence and movements elsewhere in the North Atlantic are poorly known. We investigated the historical seasonal distributions of these two species using sighting and catch data extracted from American 18th and 19th century whaling logbooks. These data suggest that humpback whales migrated seasonally from low‐latitude calving/ breeding grounds over a protracted period, and that some of them traveled far offshore rather than following coastal routes. Also, at least some humpbacks apparently fed early in the summer west of the Mid‐Atlantic Ridge, well south of their known present‐day feeding grounds. In assessing the present status of the North Atlantic humpback population, it will be important to determine whether such offshore feeding does in fact occur. Blue whales were present across the southern half of the North Atlantic during the autumn and winter months, and farther north in spring and summer, but we had too few data points to support inferences about these whales' migratory timing and routes.
ABUNDANCE OF CETACEANS IN THE OCEANIC NORTHERN GULF OF MEXICO, 1996–2001
Authors: Mullin Keith D. , Fulling Gregory L.
Published: August 2006

Abstract

The Gulf of Mexico is a subtropical marginal sea of the western North Atlantic Ocean with a diverse cetacean community. Ship‐based, line‐transect abundance surveys were conducted in oceanic waters (>200 m deep) of the northern Gulf within U. S. waters (380,432 km2) during spring from 1996 to 1997 and from 1999 to 2001. Data from these five surveys were pooled and minimum abundance estimates were based on 12,162 km of effort and 512 sightings of at least 19 species. The most commonly sighted species (number of groups) were pantropical spotted dolphin,Stenella attenuata(164); sperm whale,Physeter macrocephalus(67); dwarf/pygmy sperm whale,Kogia simalbreviceps(58); Risso's dolphin,Grampus griseus(38); and bottlenose dolphin,Tursiops truncatus(24). The most abundant species (number of individuals; coefficient of variation) wereS. attenuata(91,321; 0.16); Clymene dolphin,S. clymene(17,355; 0.65); spinner dolphin,S. longirostris(11,971; 0.71); and striped dolphin,S. coeruleoalba(6,505; 0.43). The only large whales sighted wereP. macrocephalus(1,349; 0.23) and Bryde's whale,Balaenopteraedeni(40; 0.61). Abundances for other species or genera ranged from 95 to 2,388 animals. Cetaceans were sighted throughout the oceanic northern Gulf and, whereas many species were widely distributed, some had more regional distributions.
CHANGES IN HEART RATE VARIABILITY DURING DIVING IN YOUNG HARBOR SEALS, PHOCA VITULINA
Authors: Greaves Danielle K. , Hughson Richard L. , Topor Zbigniew , Schreer Jason F. , Burns Jennifer M. , Hammill Michael O.
Published: August 2006

Abstract

We studied changes in the patterns of heart rate variability (HRV) that coincide with the development of diving skills in harbor seal pups, Phoca vitulina. Heart rate measurements were collected remotely. Spectral analysis of HRV revealed power within a mid‐frequency band (0.1–0.3 Hz) which was prominent, especially in pups less than 10 d of age. In these younger pups, the heart rate switched cyclically between a low and a high diving heart rate every 3–10 sec. Older pups exhibited a highly controlled diving bradycardia with a lower median and a lower variance when compared to younger individuals. These results provide new insight into the maturation of the bradycardia component of the dive response in harbor seal pups.
BILATERAL DIRECTIONAL ASYMMETRY OF THE APPENDICULAR SKELETON OF THE HARBOR PORPOISE (PHOCOENA PHOCOENA)
Authors: Galatius Anders , Jespersen ÅSe
Published: August 2006

Abstract

Directional asymmetry (DA) of the lengths, diameters, and masses of the scapula, humerus, radius, and ulna were analyzed on a sample of 213 harbor porpoises from Denmark and West Greenland. The levels of DA were consistent across yearlings and older animals, mature and immature animals, sexes, and populations. All investigated variables showed significant DA favoring the right side. For the pooled sample, DA of lengths ranged from 0.2% SE 0.1 (ulna) to 1.2% SE 0.1 (scapula). DAs of diameters were 1.5% SE 0.2 for the humerus, 0.6% SE 0.1 for the radius, and 1.3% SE 0.2 for the ulna. DA of mass ranged from 2.8% SE 0.5 (humerus) to 4.3% SE 0.7 (ulna). The humerus and ulna had significantly larger mean diameter/ length ratios on the right side than the left, making them more robust. The large DA of scapula length indicates larger muscle mass associated with the right flipper, while the generally more robust right humerii and ulnae may be designed for higher levels of mechanical stress. These DAs and the examples of lateralized behavior recorded in cetaceans, point to the existence of lateralized use of the flippers at the population level in harbor porpoises and possibly other cetacean species.