[Show abstract][Hide abstract] ABSTRACT: A complementary approach of stomach content and stable isotope analyses was used to characterize the foraging ecology and evaluate niche overlap between pygmy (Kogia breviceps) and dwarf (K. sima) sperm whales stranded on the U.S. mid-Atlantic coast between 1998 and 2011. Food habits analysis demonstrated both species were primarily teuthophagous, with 35 species of cephalopods, and 2 species of mesopelagic fishes represented in their overall diets. Pianka's Index of niche overlap suggested high overlap between whale diets (On = 0.92), with squids from the families Histioteuthidae, Cranchidae, and Ommastrephidae serving as primary prey. Pygmy sperm whales consumed slightly larger prey sizes (mean mantle length [ML] = 10.8 cm) than dwarf sperm whales (mean ML = 7.8 cm). Mean prey sizes consumed by pygmy sperm whales increased with growth, but showed no trend in dwarf sperm whales. Significant differences were not detected in δ15N and δ13C values of muscle tissues from pygmy (10.8‰ ± 0.5‰, −17.1‰ ± 0.6‰), and dwarf sperm whales (10.7‰ ± 0.5‰, −17.0‰ ± 0.4‰), respectively. Isotopic niche widths also did not differ significantly and dietary overlap was high between the two species. Results suggest the feeding ecologies of the pygmy and dwarf sperm whales are similar and both species occupy equivalent trophic niches in the region.
[Show abstract][Hide abstract] ABSTRACT: The adjacency of 2 marine biogeographic regions off Cape Hat-teras, North Carolina (NC), and the proximity of the Gulf Stream result in a high biodiversity of species from northern and southern provinces and from coastal and pelagic habitats. We examined spatiotemporal patterns of marine mammal strandings and evi-dence of human interaction for these strandings along NC shorelines and evaluated whether the spatiotemporal patterns and species diversity of the stranded animals reflected published records of populations in NC waters. During the period of 1997–2008, 1847 stranded animals were documented from 1777 reported events. These animals represented 9 families and 34 species that ranged from tropical delphinids to pagophilic seals. This bio-diversity is higher than levels observed in other regions. Most strandings were of coastal bottlenose dolphins (Tursiops truncatus) (56%), harbor porpoises (Phocoena phocoena) (14%), and harbor seals (Phoca vitulina) (4%). Overall, strandings of northern species peaked in spring. Bottlenose dolphin strand-ings peaked in spring and fall. Al-most half of the strandings, including southern delphinids, occurred north of Cape Hatteras, on only 30% of NC's coastline. Most stranded animals that were positive for human interaction showed evidence of having been en-tangled in fishing gear, particularly bottlenose dolphins, harbor porpoises, short-finned pilot whales (Globicepha-la macrorhynchus), harbor seals, and humpback whales (Megaptera novae-angliae). Spatiotemporal patterns of bottlenose dolphin strandings were similar to ocean gillnet fishing effort. Biodiversity of the animals stranded on the beaches reflected biodiversity in the waters off NC, albeit not always proportional to the relative abundance of species (e.g., Kogia species). Chang-es in the spatiotemporal patterns of strandings can serve as indicators of underlying changes due to anthropo-genic or naturally occurring events in the source populations. Marine biogeographic boundaries are remarkable 1) for the diversity of species that occur as a result of the biogeographically distinct prov-inces on either side of the environ-mental or dispersal discontinuities (e.g., Ekman, 1953; Searles, 1984) and 2) for the long-term infl uences of these boundaries on phylogeog-raphy (e.g., Wares et al., 2001; Ad-ams and Rosel, 2006). Several ma-rine biogeographic boundaries oc-cur along the continental United States, such as at Point Concep-tion, California; Cape Canaveral, Florida; Cape Cod, Massachusetts; and Cape Hatteras, North Carolina (NC) (Briggs, 1974; Fautin et al., 2010). The faunal transition zone at Cape Hatteras results from the juxtaposition of warm waters from the northeast-fl owing Gulf Stream and cool waters from the south-fl owing Virginia Current and leads to the occurrence of both temperate
Fishery Bulletin- National Oceanic and Atmospheric Administration 01/2014; 112:1-23. · 1.14 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In 1940, Scholander suggested that stiffened upper airways remained open and received air from highly compressible alveoli during marine mammal diving. There are little data available on the structural and functional adaptations of the marine mammal respiratory system. The aim of this research was to investigate the anatomical (gross) and structural (compliance) characteristics of excised marine mammal tracheas. Here we defined different types of tracheal structures, categorizing pinniped tracheas by varying degrees of continuity of cartilage (categories 1-4) and cetacean tracheas by varying compliance values (categories 5A and 5B). Some tracheas fell into more than one category, along their length, for example, the harbor seal (Phoca vitulina) demonstrated complete rings cranially, and as the trachea progressed caudally tracheal rings changed morphology. Dolphins and porpoises had less stiff, more compliant spiraling rings while beaked whales had very stiff, less compliant spiraling rings. The pressure-volume (P-V) relationships of isolated tracheas from different species were measured to assess structural differences between species. These findings lend evidence for pressure-induced collapse and re-inflation of lungs, perhaps influencing variability in dive depth or ventilation rates of the species investigated.
Journal of Experimental Biology 12/2013; · 3.24 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: abstract : Euthanasia of stranded large whales poses logistic, safety, pharmaceutical, delivery, public relations, and disposal challenges. Reasonable arguments may be made for allowing a stranded whale to expire naturally. However, slow cardiovascular collapse from gravitational effects outside of neutral buoyancy, often combined with severely debilitating conditions, motivate humane efforts to end the animal's suffering. The size of the animal and prevailing environmental conditions often pose safety concerns for stranding personnel, which take priority over other considerations. When considering chemical euthanasia, the size of the animal also necessitates large quantities of euthanasia agents. Drug residues are a concern for relay toxicity to scavengers, particularly for pentobarbital-containing euthanasia solutions. Pentobarbital is also an environmental concern because of its stability and long persistence in aquatic environments. We describe a euthanasia technique for stranded mysticetes using readily available, relatively inexpensive, preanesthetic and anesthetic drugs (midazolam, acepromazine, xylazine) followed by saturated KCl delivered via custom-made needles and a low-cost, basic, pressurized canister. This method provides effective euthanasia while moderating personnel exposure to hazardous situations and minimizing drug residues of concern for relay toxicity.
Journal of wildlife diseases 10/2013; · 1.27 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Electronic tags have proven to be valuable tools in assessing small cetacean move-ment and behavior. However, problems associated with tag size and attachment have limited duration and damaged dorsal fins. These outcomes have motivated research-ers to develop a new satellite-linked tag design that reduces detrimental effects to tagged animals, while increasing transmission durations. The goals of this study were to review previous studies that deployed single-pin transmitters and determine factors that influence transmission duration. Then, test these factors utilizing com-putational fluid dynamics (CFD) models to identify an optimal single-pin satellite-linked tag design, and evaluate this prototype through field studies. A review of four projects, which deployed 77 single-pin radio tags, determined that tags attached along the lower third of the dorsal fin and approximately 33 mm from the trailing edge resulted in longer transmission durations and reduced negative impacts to the 1
[Show abstract][Hide abstract] ABSTRACT: Blubber has been used for decades to monitor exposure of marine mammals to persistent organic pollutants (POPs). However, little is known about POP variability as a function of blubber depth and across the body of the animal. Remote blubber biopsy sampling (e.g, projectile biopsy) is the most common technique used to acquire samples from free-swimming animals, yet such techniques may result in variable sampling. It is important to understand whether blubber stratification or body location affects POP concentration or the concentration of other important blubber constituents such as fatty acids (FA). To investigate the influence of sampling depth and location on POP concentration, full depth blubber samples were taken from one stranded bottlenose dolphin (Tursiops truncatus) at six different body sites to assess variation in FA distribution and contaminant storage with body location. Three of the samples from different body locations were separated into histologically distinct layers to examine the effect of blubber depth and body location on POPs and FAs. In this individual, both POPs and FAs were heterogeneous with blubber depth and body location. POP concentrations were significantly greater in ventral (average ΣPBDEs 1350ng/g lipid) and anterior (average ΣPCBs 28700ng/g lipid) body locations and greater in the superficial blubber layer (average ΣPCBs 35500ng/g lipid) when compared to the deep (8390ng/g lipid) and middle (23,700ng/g lipid) layers. Proportionally more dietary FAs were found in dorsal blubber and in middle and deep layers relative to other locations while the reverse was true for biosynthesized FAs. Stratification was further examined in blubber from the same body location in five additional stranded bottlenose dolphins. Although FAs were stratified with blubber depth, lipid-normalized POPs were not significantly different with depth, indicating that POP concentrations can vary in an individual with blubber depth though the direction of POP stratification is not consistent among individuals.
Science of The Total Environment 07/2013; 463-464C:581-588. · 3.26 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Post-mortem examination of dead and live stranded beach-cast pinnipeds and cetaceans for determination of a cause of death provides valuable information for the management, mitigation and prosecution of unintentional and sometimes malicious human impacts, such as vessel collision, fishing gear entanglement and gunshot. Delayed discovery, inaccessibility, logistics, human safety concerns, and weather make these events challenging. Over the past 3 decades, in response to public concern and federal and state or provincial regulations mandating such investigations to inform mitigation efforts, there has been an increasing effort to objectively and systematically investigate these strandings from a diagnostic and forensic perspective. This Theme Section provides basic investigative methods, and case definitions for each of the more commonly recognized case presentations of human interactions in pinnipeds and cetaceans. Wild animals are often adversely affected by factors such as parasitism, anthropogenic contaminants, biotoxins, subclinical microbial infections and competing habitat uses, such as prey depletion and elevated background and episodic noise. Understanding the potential contribution of these subclinical factors in predisposing or contributing to a particular case of trauma of human origin is hampered, especially where putrefaction is significant and resources as well as expertise are limited. These case criteria descriptions attempt to acknowledge those confounding factors to enable an appreciation of the significance of the observed human-derived trauma in that broader context where possible.
Diseases of Aquatic Organisms 04/2013; 103(3):229-64. · 1.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A chronically entangled North Atlantic right whale, with consequent emaciation was sedated, disentangled to the extent possible, administered antibiotics, and satellite tag tracked for six subsequent days. It was found dead 11 d after the tag ceased transmission. Chronic constrictive deep rope lacerations and emaciation were found to be the proximate cause of death, which may have ultimately involved shark predation. A broadhead cutter and a spring-loaded knife used for disentanglement were found to induce moderate wounds to the skin and blubber. The telemetry tag, with two barbed shafts partially penetrating the blubber was shed, leaving barbs embedded with localized histological reaction. One of four darts administered shed the barrel, but the needle was found postmortem in the whale with an 80º bend at the blubber-muscle interface. This bend occurred due to epaxial muscle movement relative to the overlying blubber, with resultant necrosis and cavitation of underlying muscle. This suggests that rigid, implanted devices that span the cetacean blubber muscle interface, where the muscle moves relative to the blubber, could have secondary health impacts. Thus we encourage efforts to develop new tag telemetry systems that do not penetrate the subdermal sheath, but still remain attached for many months.
[Show abstract][Hide abstract] ABSTRACT: Most marine mammals are hypothesized to routinely dive within their aerobic dive limit (ADL). Mammals that regularly perform deep, long-duration dives have locomotor muscles with elevated myoglobin concentrations and are composed of predominantly large, slow-twitch (Type I) fibers with low mitochondrial volume densities (V(mt)). These features contribute to extending ADL by increasing oxygen stores and decreasing metabolic rate. Recent tagging studies, however, have challenged the view that two groups of extreme deep-diving cetaceans dive within their ADLs. Beaked whales (Ziphius cavirostris, Cuvier and Mesoplodon densirostris, Blainville) routinely perform the deepest and longest average dives of any air-breathing vertebrate, and short-finned pilot whales (Globicephala macrorhynchus, Gray) perform high-speed sprints at depth. We investigated the locomotor muscle morphology and estimated total body oxygen stores of these cetaceans to determine whether they (a) shared muscle design features with other deep-divers and (b) performed dives within their calculated ADLs. Muscle of both cetaceans displayed high myoglobin concentrations and large fibers, as predicted, but novel fiber profiles for diving mammals. Beaked whales possessed a sprinter's fiber-type profile, composed of approximately 80% fast-twitch (Type II) fibers with low V(mt). Approximately one-third of the muscle fibers of short-finned pilot whales were slow-twitch, oxidative, glycolytic fibers, a rare fiber-type for any mammal. The muscle morphology of beaked whales likely decreases the energetic cost of diving, while that of short-finned pilot whales supports high activity events. Calculated ADLs indicate that, at low metabolic rates, both cetaceans carry sufficient onboard oxygen to aerobically support their dives.
Journal of Experimental Biology 02/2013; · 3.24 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The health of common bottlenose dolphins (Tursiops truncatus) within south-ern Georgia estuaries is of particular concern due to high levels of anthropo-genic contaminants in their tissues. Dolphins in this region have the highest 1 Corresponding author (e-mail: firstname.lastname@example.org).
[Show abstract][Hide abstract] ABSTRACT: 1. Under US policy, a stock is a group of animals shown to be demographically independent from other such groups. Evidence of demographic delineations for marine mammal stocks is gained primarily through genetic analysis. However, additional techniques play an important role in determining fine-scale ranging patterns that can be used to define a stock's geographic boundaries. In cases where genetic studies have not yet been performed, movement and ranging pattern data are essential in identifying a targeted geographic region for tissue sampling and genetic studies. 2. Photo-identification surveys, vessel-based radio telemetry, automated radio telemetry systems (ARTS), and satellite-linked telemetry are sampling techniques that have been used to determine common bottlenose dolphin ranging patterns and provide detailed insight into stock boundaries. The results of near simultaneous use of these sampling techniques are compared using data from a case study of bottlenose dolphins within the estuaries of southern Georgia. 3. Satellite-linked and radio telemetry were determined to be useful sampling techniques for identification of short-term ranging patterns. Satellite-linked telemetry had the second lowest cost per location ($122) and identified dolphin ranging patterns within and outside of the study area boundaries. Vessel-based radio telemetry was more costly ($195 per location) and had relatively limited tracking coverage. However, this sampling technique permitted visual observations of animal and tag condition. The combination of vessel-based radio telemetry and ARTS, which had the lowest cost per location ($34), was an effective method for determining ranging patterns of tagged individuals within and outside of the study area. 4. Photo-identification surveys, relative to satellite-linked and radio telemetry, were not as efficient for determination of targeted individuals' short-term ranging patterns and had the highest cost per location of the four sampling techniques ($292). However, photo-identification is more effective than any other technique for compiling data on large numbers of individuals within a designated study area. Photo-identification surveys are essential for long-term monitoring and provide additional insight into dolphin stock structure that cannot be determined through telemetry alone.
[Show abstract][Hide abstract] ABSTRACT: United States and Canadian governments have responded to legal requirements to reduce human-induced whale mortality via vessel strikes and entanglement in fishing gear by implementing a suite of regulatory actions. We analyzed the spatial and temporal patterns of mortality of large whales in the Northwest Atlantic (23.5°N to 48.0°N), 1970 through 2009, in the context of management changes. We used a multinomial logistic model fitted by maximum likelihood to detect trends in cause-specific mortalities with time. We compared the number of human-caused mortalities with U.S. federally established levels of potential biological removal (i.e., species-specific sustainable human-caused mortality). From 1970 through 2009, 1762 mortalities (all known) and serious injuries (likely fatal) involved 8 species of large whales. We determined cause of death for 43% of all mortalities; of those, 67% (502) resulted from human interactions. Entanglement in fishing gear was the primary cause of death across all species (n= 323), followed by natural causes (n= 248) and vessel strikes (n= 171). Established sustainable levels of mortality were consistently exceeded in 2 species by up to 650%. Probabilities of entanglement and vessel-strike mortality increased significantly from 1990 through 2009. There was no significant change in the local intensity of all or vessel-strike mortalities before and after 2003, the year after which numerous mitigation efforts were enacted. So far, regulatory efforts have not reduced the lethal effects of human activities to large whales on a population-range basis, although we do not exclude the possibility of success of targeted measures for specific local habitats that were not within the resolution of our analyses. It is unclear how shortfalls in management design or compliance relate to our findings. Analyses such as the one we conducted are crucial in critically evaluating wildlife-management decisions. The results of these analyses can provide managers with direction for modifying regulated measures and can be applied globally to mortality-driven conservation issues.
[Show abstract][Hide abstract] ABSTRACT: Blubber, the specialized hypodermis of cetaceans, provides thermal insulation through the quantity and quality of lipids it contains. Quality refers to % lipid content; however, not all lipids are the same. Certain deep-diving cetacean groups possess blubber with lipids - wax esters (WE) - that are not typically found in mammals, and the insulative quality of "waxy" blubber is unknown. Our study explored the influence of lipid storage class - specifically WE in pygmy sperm whales (Kogia breviceps; n=7) and typical mammalian triacylglycerols (TAG) in short-finned pilot whales (Globicephala macrorhynchus; n=7) - on blubber's thermal properties. Although the blubber of both species had similar total lipid contents, the thermal conductivity of G. macrorhynchus blubber (0.20 ± 0.01 Wm-1°C-1) was significantly higher than that of K. breviceps (0.15 ± 0.01 Wm-1°C-1; P=0.0006). These results suggest that lipid class significantly influences blubber's ability to resist heat flow. In addition, because blubber's lipid content is known to be stratified, we measured its depth-specific thermal conductivities. In K. breviceps blubber, the depth-specific conductivity values tended to vary inversely with lipid content. In contrast, G. macrorhynchus blubber displayed unexpected depth-specific relationships between lipid content and conductivity, which suggests that temperature-dependent effects, such as melting, may be occurring. Differences in heat flux measurements across the depth of the blubber samples provide evidence that both species are capable of storing heat in their blubber. The function of blubber as an insulator is complex and may rely upon its lipid class, stratified composition, and dynamic heat storage capabilities.
Journal of Experimental Biology 09/2012; · 3.24 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Understanding the scenarios whereby fishing gear entanglement of large whales induces mortality is important for the development of mitigation strategies. Here we present a series of 21 cases involving 4 species of baleen whales in the NW Atlantic, describing the available sighting history, necropsy observations, and subsequent data analyses that enabled the compilation of the manners in which entanglement can be lethal. The single acute cause of entanglement mortality identified was drowning from entanglement involving multiple body parts, with the animal's inability to surface. More protracted causes of death included impaired foraging during entanglement, resulting in starvation after many months; systemic infection arising from open, unresolved entanglement wounds; and hemorrhage or debilitation due to severe gear-related damage to tissues. Serious gear-induced injury can include laceration of large vessels, occlusion of the nares, embedding of line in growing bone, and massive periosteal proliferation of new bone in an attempt to wall off constricting, encircling lines. These data show that baleen whale entanglement is not only a major issue for the conservation of some baleen whale populations, but is also a major concern for the welfare of each affected individual.
Diseases of Aquatic Organisms 10/2011; 96(3):175-85. · 1.73 Impact Factor