An Anatomical and Pathological Examination of the First Recorded Stranding of a Fraser\u27s Dolphin (Lagenodelphis hosei) in the Northwestern Gulf of Mexico

Reports on Fraser\u27s dolphin (Lagenodelphis hosei) strandings in the Gulf of Mexico are uncommon. The only recorded strandings from the Gulf of Mexico, both of which occurred in Florida, consist of one mass stranding and a single stranding. This report represents the first record of a Fraser\u27s dolphin stranding, dead or alive, in the northwestern Gulf of Mexico, Results presented here provide the first available data on blood hematology and chemistry values, detailed anatomy of internal organs and structures, thoracic and abdominal organ weights, blubber thickness, external morphometries, and pathological findings for this species in the western Gulf of Mexico

Digestive Efficiencies Of Ex Situ And In Situ West Indian Manatees (Trichechus Manatus Latirostris)

Digestive efficiencies (Dm) of ex situ and in situ manatees (Trichechus manatus latirostris) were, for the first time, assessed using manganese (Mn2) as a naturally occurring marker. The Dm of ex situ manatees determined using [Mn2+] did not differ significantly from the Dm assessed using lignin, supporting the efficacy of the manganese approach. Gastrointestinal tract samples, obtained from recently dead animals, showed [Mn2+] concentrations were lowest in the stomach and remained low in the duodenum and small intestine but increased in the cecum, colon, and rectum, consistent with colonic digestion and absorption. In situ manatees consuming marine vegetation had significantly lower Dm (mean ± SE, 46.9% ±1.8%; n = 8) than did in situ manatees consuming freshwater vegetation (77.8% ±2.6%; n = 7), which in turn had significantly lower values than did ex situ manatees consuming lettuce (84.0% ±0.7%; n = 37). In situ manatees eating seagrasses had significantly higher Dm than did long-term ex situ animals consuming seagrass for short periods of time (46.9% ±1.8% vs. 36.2% ±1.2%, respectively), suggesting potential modification of gut flora over time. One significant ramification of our results is that manatees consuming seagrasses would require a greater standing biomass to support their needs than would be required if they were eating freshwater vegetation. This reinforces the critical need to implement habitat conservation and protection before considering downlisting or delisting manatees as an endangered species. © 2013 by The University of Chicago. All rights reserved

Skull Morphometry Of Bottlenose Dolphins (Tursiops Truncatus) From The Gulf Of Mexico

Skull morphometry of 206 stranded juvenile and adult bottlenose dolphins (Tursiops truncatus) from Texas and Florida were examined. Juveniles differed significantly from adults in both Texas and Florida populations. Sexual dimorphism was present in skulls from Texas but not from Florida. Regional differences in females from Texas and Florida were apparent, especially in braincase height, whereas male bottlenose dolphins did not differ between regions. Females could be distinguished accurately to region (90% classification success) using skull morphometry. Cranial morphometrics of T. truncatus are concrete values that may aid in identification of a type specimen for each population. Furthermore, these results can be used as a standard for Tursiops in the Gulf of Mexico

An Isotopic Assessment Of The Feeding Habits Of Free-Ranging Manatees

There is relatively little information available on how the relative importance of fresh, brackish, or marine environments may vary geographically or individually with respect to manatee Trichechus manatus latirostris feeding ecology. As a first application of stable isotope analysis to determine diet composition of wild manatees, skin from 25 manatee carcasses and leaf tissue from 25 plant species were collected from 4 regions in Florida and analyzed for relative values of stable carbon (δ13C) and nitrogen (δ15N) isotopes. Values of δ13C and δ15N measured in plants ranged from -0.8 ± 1.0 to 6.4 ± 0.0 ‰ and in manatee tissues from -8.7 ± 0.2 to -28.3 ± 0.1 ‰, respectively. A mixing model was applied to estimate manatee diet composition across different geographic regions, and results (mean, all manatees, all regions) indicated that, overall, Florida manatees consumed 44 % of their diet from marine and/or estuarine sources. Manatees living along the central east coast obtained 100% of their diet from marine and/or estuarine sources, while animals recovered from the St. John\u27s River system (NE region) obtained ∼50% of their diet from freshwater sources, suggesting that some time had been spent outside of the river basin. In conclusion, results of the stable isotope analysis suggest that, even though manatees have a physiological requirement to ingest fresh water, marine and estuarine environments supply a significant fraction of their food resources. © Inter-Research 2006

Stratification And Intra- And Inter-Specific Differences In Fatty Acid Composition Of Common Dolphin (Delphinus Sp.) Blubber: Implications For Dietary Analysis

Sixty-five fatty acids were quantified in the blubber of common dolphins (Delphinus delphis, D. capensis) incidentally caught off the coast of southern California. Dolphins were grouped by sex, reproductive status and species, and a blubber sample was collected at a mid-lateral site located caudal to the trailing edge of the dorsal fin. Samples were divided horizontally into inner, middle and outer layers and gradients in fatty acid content (mass percent) were observed across the depth of the blubber. Levels of monounsaturated fatty acids were greatest in the outer layer, whereas levels of saturated and polyunsaturated fatty acids were greatest in the inner layer. Degree of stratification was greatest in sexually mature dolphins. Blubber of sexually immature, but physically mature, male dolphins was also highly stratified, suggesting that this difference may be attributed to differences in diet. Classification and regression tree analysis resulted in the fewest misclassifications when dolphins were grouped by species, possibly indicating that these closely related animals forage on different prey species. Dietary-derived fatty acids were typically selected as splitting criteria in classification and regression tree analyses, suggesting that the observed differences in fatty acid composition between the various groups of dolphins may be attributed to differences in diet. © 2006 Elsevier Inc. All rights reserved

Variability In Fatty Acid Composition Of Bottlenose Dolphin (Tursiops Truncatus) Blubber As A Function Of Body Site, Season, And Reproductive State

Odontocete blubber has been shown to be variable in composition and can be separated into strata visually, histologically, and biochemically. The purpose of this study was to examine fatty acid composition of bottlenose dolphin (Tursiops truncatus (Montagu, 1821)) blubber, and determine if differences exist between body sites, reproductive states, and (or) seasons. The influence of these variables on blubber composition could aid in the creation of a model that would use fatty acid signature analysis to evaluate diet in free-ranging populations. Blubber samples were obtained from freshly dead animals along the Texas and Louisiana coastlines. Samples from nine body sites were analyzed to investigate site variability, and from one site to evaluate differences due to season, reproductive state, and blubber layer. All body sites of animals sampled in the winter were statistically indistinguishable, indicating that biopsy samples could be obtained from any location on the animal for fatty acid analysis during this season; however, three distinct blubber layers were identifiable, and reproductive states were significantly different in terms of fatty acid composition. Seasonal differences in fatty acid composition were also highly significant for all one-site inner blubber layer samples. Ultimately, the differences in fatty acid composition could have resulted from dietary or physiological factors and need to be examined further. © 2004 NRC Canada

Alternative Method For Subsampling Annual Dentin Layers In Small Mammalian Teeth For Stable Isotope Analysis

Several techniques have been used to sample annual dentin layers in mammalian teeth for stable isotope analysis. However tooth size in smaller animals and the conical arrangement of the dentin layers have constrained precision of subsampling and collection of adequate sample from each annual growth layer. We tested an alternative subsampling technique using teeth from Risso\u27s dolphins (n = 15) that involved cutting out the annual dentin growth layer groups (GLGs) from 300 to 500 μm longitudinal sections from one half of a demineralized tooth and comparing the results to those obtained using a standard micromilling process on the other half of the same tooth. Subsamples were analyzed for elemental C and N content and for stable C and N isotopes. Subsamples obtained from cutting out the GLGs showed more consistent wt%N, wt%C, and atomic C/N ratios that were significantly different (P\u3c0.0001) from those obtained by micromilling. Consequently, the δ15N and δ13C values differed significantly between methods with values from the former method being more concordant with the expected variations in the early years of Risso\u27s dolphins. Deviations in δ13C values in the micromilled subsamples were large enough to create possible errors in interpretation of dietary sources. Cutting out the dentin layers reduced sample processing time by 90% and yielded ~10% more collagen than micromilling. These results suggest that cutting out the annual dentin layers can produce greater yield of samples of better collagen quality with a much shorter processing time than the micromilling process and is, therefore, an effective method to subsample small mammalian teeth

Tracing Migratory Movements Of Breeding North Pacific Humpback Whales Using Stable Isotope Analysis

North Pacific humpback whales Megaptera novaeangliae are migratory animals with a complex population structure, segregating into geographically distinct aggregations on high-latitude feeding grounds. Several feeding aggregations may converge on a common breeding ground for mating and calving. Understanding how feeding and breeding habitats are linked is critical to understanding humpback whale life history and addressing management and conservation efforts. In a continued effort to explore the population structure of North Pacific humpback whales through the analysis of stable carbon (δ13C) and nitrogen (δ15N), the present study extends on a previous study of feeding animals to describe migratory linkages to breeding grounds (Witteveen et al. 2009). Skin samples (n = 597) collected from 4 known breeding regions were analyzed for δ13C and δ15N. Breeding regions differed in both δ13C (F3, 585 = 62.3, p \u3c 0.001) and δ15N (F3, 585 = 37.2, p \u3c 0.001). Breeding values reflected the foraging locations for 46 ind. sampled on both habitats; the relationship between the breeding and feeding stable isotope ratios was significant and positive for both δ13C (F 1, 44 = 10.3, r2 = 0.19, p = 0.002) and δ15N (F1, 44 = 40.9, r2 = 0.48, p \u3c 0.001). Furthermore, individual breeding and feeding values did not differ for δ15N (t45 = 1.41, p = 0.17) or δ13C (t45 = -1.15, p = 0.26) in pairwise comparisons. We used δ13C and δ15N in a classification tree analysis to describe probable migratory linkages to 6 previously described feeding groups. Stable isotope ratios predicted regional patterns of movement, and assignments of breeding individuals to feeding grounds differed by 12% on average from photographic matching. Our results indicate this technique can be used to help understand the population structure and ecology of North Pacific humpback whale populations, especially when used in combination with other research techniques. © 2009 Inter-Research

Resource Partitioning Among South African Delphinids

In order to better understand trophic relationships among four species of coastal delphinids, we compared isotopic composition of skin to attempt to assess potential inter- and intra-specific resource partitioning. Skin samples were collected from Indo-Pacific bottlenose dolphins (Tursiops aduncus) (n=132), long-beaked common dolphins (Delphinus capensis) (n=78), humpback dolphins (Sousa chinensis) (n=27), and striped dolphins (Stenella coeruleoalba) (n=3) along the coastline of South Africa. While the latter species tends to be found offshore, the other species have overlapping distributions and feed on similar prey, carbon (δ13C) and nitrogen (δ15N) isotope analyses revealed resource partitioning with differences in diet and habitat use. Striped dolphin δ13C values (-16.97±0.25‰, SD) were consistent with evidence that they typically forage offshore, while δ13C values of humpback dolphins reflected their use of inshore habitats (-15.16±0.65‰). Common and bottlenose dolphins had δ13C (-15.48±0.66‰ and -15.76±0.71‰ respectively) values that fell between these two extremes. Mean values for δ15N ranged from 11.92±0.20‰ for striped dolphins to 15.19±0.73‰ for humpback dolphins, suggesting either that these species were feeding at different trophic levels or that they were feeding in different trophic systems. Common and bottlenose dolphins had δ15N values of 13.49±0.50‰ and 14.40±0.74‰ respectively. Male bottlenose dolphins were significantly more enriched in δ15N compared to females suggesting dietary differences. No sex related differences were found in other species. Isotopic niche width determinations using corrected standard elliptical area (SEAc) were calculated. Humpback and bottlenose dolphins had the largest SEAc reflecting a broader trophic niche, while striped dolphins had the smallest SEAc reflecting a more specialized niche. Overall, these sympatric species appear to reduce potential competitive pressure through a combination of differing prey selection and habitat utilization. © 2014 Elsevier B.V