Publications

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adaptation to hard-object feeding in sea otters and hominins.the large, bunodont postcanine teeth in living sea otters (enhydra lutris) have been likened to those of certain fossil hominins, particularly the 'robust' australopiths (genus paranthropus). we examine this evolutionary convergence by conducting fracture experiments on extracted molar teeth of sea otters and modern humans (homo sapiens) to determine how load-bearing capacity relates to tooth morphology and enamel material properties. in situ optical microscopy and x-ray imaging during simulated ...201121474163
genetic characterisation of toxoplasma gondii in wildlife from north america revealed widespread and high prevalence of the fourth clonal type.little is known of the genetic diversity of toxoplasma gondii circulating in wildlife. in the present study wild animals, including dolphins, from the usa were examined for t. gondii infection. tissues of naturally exposed animals were bioassayed in mice for isolation of viable parasites. viable t. gondii was isolated from 31 animals including, to our knowledge for the first time, from a bald eagle (haliaeetus leucocephalus), five gray wolves (canis lupus), a woodrat (neotoma micropus), and five ...201121802422
sarcocystis neurona retinochoroiditis in a sea otter (enhydra lutris kenyoni).sarcocystis neurona is an important cause of fatal disease in sea otters in the usa. encephalitis is the predominant lesion and parasites are confined to the central nervous system and muscles. here we report retinochoroiditis in a sea otter (enhydra lutris kenyoni) found dead on copalis beach, wa, usa. salient lesions were confined to the brain and eye. multifocal nonsuppurative meningoencephalitis was present in the cerebrum and cerebellum associated with s. neurona schizonts. the retina of on ...201121782345
assessment of clinical pathology and pathogen exposure in sea otters (enhydra lutris) bordering the threatened population in alaska.northern sea otter (enhydra lutris kenyoni) abundance has decreased dramatically over portions of southwest alaska, usa, since the mid-1980s, and this stock is currently listed as threatened under the endangered species act. in contrast, adjacent populations in south central alaska, usa, and russia have been stable to increasing during the same period. sea otters bordering the area classified in the recent decline were live-captured during 2004-2006 at bering island, russia, and the kodiak archi ...201121719822
serological evidence of toxoplasma gondii infection in captive marine mammals in mexico.toxoplasma gondii infection in marine mammals is important because they are considered as a sentinel for contamination of seas with t. gondii oocysts, and toxoplasmosis causes mortality in these animals, particularly sea otters. serological evidence of t. gondii infection was determined in 75 captive marine mammals from four facilities in southern and central geographical regions in mexico using the modified agglutination test (mat). antibodies (mat, 1:25 or higher) to t. gondii were found in 55 ...201121944844
mustelid herpesvirus-2, a novel herpes infection in northern sea otters (enhydra lutris kenyoni).oral ulcerations and plaques with epithelial eosinophilic intranuclear inclusions were observed in northern sea otters (enhydra lutris kenyoni) that died or were admitted for rehabilitation after the 1989 exxon valdez oil spill (evos) in alaska, usa. transmission electron microscopy demonstrated the presence of herpesviral virions. additionally, a serologic study from 2004 to 2005 found a high prevalence of exposure to a herpesvirus in live-captured otters. tissues from 29 otters after the evos ...201222247388
quantifying population-level risks using an individual-based model: sea otters, harlequin ducks, and the exxon valdez oil spill.ecological risk assessments need to advance beyond evaluating risks to individuals, largely based on toxicity studies on a few species under laboratory conditions, to assessing population-level risks to the environment, including considerations of variability and uncertainty. two individual-based models (ibms), recently developed to assess current risks to sea otters and seaducks in prince william sound more than two decades after the exxon valdez oil spill (evos), are used to explore population ...201222275071
genotypic characterization of streptococcus infantarius subsp. coli isolates from sea otters with infective endocarditis and/or septicemia and from environmental mussel samples.pulsed-field gel electrophoresis (pfge) was used to type 128 streptococcus infantarius subsp. coli isolates from sea otters and mussels. six smai pfge groups were detected, with one predominant group representing 57% of the isolates collected over a wide geographic region. several sea otter and mussel isolates were highly related, suggesting that an environmental infection source is possible.201223052307
temporal association between land-based runoff events and california sea otter (enhydra lutris nereis) protozoal mortalities.toxoplasma gondii and sarcocystis neurona have caused significant morbidity and mortality in threatened southern sea otters (enhydra lutris nereis) along the central california coast. because only terrestrial animals are known to serve as definitive hosts for t. gondii and s. neurona, infections in otters suggest a land to sea flow of these protozoan pathogens. to better characterize the role of overland runoff in delivery of terrestrially derived fecal pathogens to the near shore, we assessed t ...201222493114
epidemiology and potential land-sea transfer of enteric bacteria from terrestrial to marine species in the monterey bay region of california.marine mammals are at risk for infection by fecal-associated zoonotic pathogens when they swim and feed in polluted nearshore marine waters. because of their tendency to consume 25-30% of their body weight per day in coastal filter-feeding invertebrates, southern sea otters (enhydra lutris nereis) can act as sentinels of marine ecosystem health in california. feces from domestic and wildlife species were tested to determine prevalence, potential virulence, and diversity of selected opportunistic ...201222740531
'natural experiment' demonstrates top-down control of spiders by birds on a landscape level.the combination of small-scale manipulative experiments and large-scale natural experiments provides a powerful approach for demonstrating the importance of top-down trophic control on the ecosystem scale. the most compelling natural experiments have come from studies examining the landscape-scale loss of apex predators like sea otters, wolves, fish and land crabs. birds are dominant apex predators in terrestrial systems around the world, yet all studies on their role as predators have come from ...201222970126
sarcomas in three free-ranging northern sea otters (enhydra lutris kenyoni) in alaska.three sarcomas were diagnosed in wild northern sea otters (enhydra lutris kenyoni) during the mid- to late 1990s. histologically, the tumors were a chondrosarcoma and two low-grade fibrosarcomas with myofibroblastic cell differentiation. the three sea otters were surviving in the wild and were killed by hunters.201222493127
genetic diversity and population parameters of sea otters, enhydra lutris, before fur trade extirpation from 1741-1911.all existing sea otter, enhydra lutris, populations have suffered at least one historic population bottleneck stemming from the fur trade extirpations of the eighteenth and nineteenth centuries. we examined genetic variation, gene flow, and population structure at five microsatellite loci in samples from five pre-fur trade populations throughout the sea otter's historical range: california, oregon, washington, alaska, and russia. we then compared those values to genetic diversity and population ...201222403635
sound production and reception in southern sea otters (enhydra lutris nereis).because of their dependence on a highly restricted coastal habitat, enhydra lutris is especially vulnerable to a variety of different environmental and anthropogenic threats. this species is presently listed as threatened and is protected throughout the northern and southern portions of its range.resource managers are presently faced with uncertainty when responding to and prioritizing potential threats to these animals due to insufficient understanding of the factors that may disturb or disrupt ...201222278472
gene transcription in sea otters (enhydra lutris); development of a diagnostic tool for sea otter and ecosystem health.gene transcription analysis for diagnosing or monitoring wildlife health requires the ability to distinguish pathophysiological change from natural variation. herein, we describe methodology for the development of quantitative real-time polymerase chain reaction (qpcr) assays to measure differential transcript levels of multiple immune function genes in the sea otter (enhydra lutris); sea otter-specific qpcr primer sequences for the genes of interest are defined. we establish a 'reference' range ...201221848762
setting realistic recovery targets for two interacting endangered species, sea otter and northern abalone.failure to account for interactions between endangered species may lead to unexpected population dynamics, inefficient management strategies, waste of scarce resources, and, at worst, increased extinction risk. the importance of species interactions is undisputed, yet recovery targets generally do not account for such interactions. this shortcoming is a consequence of species-centered legislation, but also of uncertainty surrounding the dynamics of species interactions and the complexity of mode ...201223083059
a comparison of dragon kelp, eualaria fistulosa, (phaeophyceae) fecundity in urchin barrens and nearby kelp beds throughout the aleutian archipelago(1).the aleutian archipelago coastal ecosystem has undergone a dramatic change in community composition during the past two decades. following the removal of ∼99% of the sea otters, enhydra lutris, from the ecosystem, changes to the benthic communities resulted in widespread losses to most of the region's kelp beds and corresponding increases in the prevalence of urchin barrens. within the urchin barrens, the few kelps that have remained are exposed to elevated light, nutrients and currents, all of ...201227009000
contemporary evolution of sea urchin gamete-recognition proteins: experimental evidence of density-dependent gamete performance predicts shifts in allele frequencies over time.species whose reproductive strategies evolved at one density regime might be poorly adapted to other regimes. field and laboratory experiments on the sea urchin strongylocentrotus franciscanus examined the influences of the two most common sperm-bindin alleles, which differ at two amino acid sites, on fertilization success. in the field experiment, the arginine/glycine (rg) genotype performed best at low densities and the glycine/arginine (gr) genotype at high densities. in the laboratory experi ...201222671542
organochlorine contaminants in coastal marine ecosystems of southern alaska: inferences from spatial patterns in blue mussels (mytilus trossulus).we measured the concentrations and chemical structures of persistent organochlorines (ocs) in blue mussels (mytilus trossulus) from 44 sites across southwest and southeast alaska in an effort to determine both the sources of these compounds and the extent to which this region might be contaminated. high pcb concentrations were detected at amchitka, adak, and unalaska islands (83, 430, and 2800μgkg(-1) dry weight, respectively) in the aleutians with relatively low concentrations elsewhere (7.1-51 ...201222579453
structure and mechanism of diet specialisation: testing models of individual variation in resource use with sea otters.studies of consumer-resource interactions suggest that individual diet specialisation is empirically widespread and theoretically important to the organisation and dynamics of populations and communities. we used weighted networks to analyze the resource use by sea otters, testing three alternative models for how individual diet specialisation may arise. as expected, individual specialisation was absent when otter density was low, but increased at high-otter density. a high-density emergence of ...201222414160
which states matter? an application of an intelligent discretization method to solve a continuous pomdp in conservation biology.when managing populations of threatened species, conservation managers seek to make the best conservation decisions to avoid extinction. making the best decision is difficult because the true population size and the effects of management are uncertain. managers must allocate limited resources between actively protecting the species and monitoring. resources spent on monitoring reduce expenditure on management that could be used to directly improve species persistence. however monitoring may prev ...201222363398
the distribution of 4-nonylphenol in marine organisms of north american pacific coast estuaries.one of the chemical breakdown products of nonylphenol ethoxylates, 4-nonylphenol (4-np), accumulates in organisms and is of concern as an environmental pollutant due to its endocrine disrupting effects. we measured 4-np levels in the seawater, sediment, and twelve organisms within the california estuary, morro bay, and examined biomagnification of 4-np using stable isotope abundances (δ(15)n and δ(13)c) to quantify trophic position. 4-np concentrations in organisms from morro bay included 25000± ...201222257992
tool use by aquatic animals.tool-use research has focused primarily on land-based animals, with less consideration given to aquatic animals and the environmental challenges and conditions they face. here, we review aquatic tool use and examine the contributing ecological, physiological, cognitive and social factors. tool use among aquatic animals is rare but taxonomically diverse, occurring in fish, cephalopods, mammals, crabs, urchins and possibly gastropods. while additional research is required, the scarcity of tool use ...201324101631
operationalizing a one health approach to global health challenges.the one health approach, which recognizes the interconnectedness of human, animal and ecosystem health, encourages collaboration between diverse disciplines to address complex health problems. the advantages and challenges posed by these interdisciplinary collaborations are described in this review. learning networks where diverse participants can openly share processes, best practices, and case studies are discussed as a strategy for conducting transdisciplinary one health research and tackling ...201323711930
preliminary findings of fecal gonadal hormone concentrations in six captive sea otters (enhydra lutris) after deslorelin implantation.the sea otter (enhydra lutris) is a popular exhibit animal in many zoos and aquariums worldwide. captive sea otters from these populations are owned by the united states fish and wildlife service (usfws). the usfws has requested that these sea otters be prevented from breeding in order to save captive space for wild rescued animals. sea otters are often housed in mixed sex groups, therefore a chemical contraceptive method or surgical removal of gonads must be used to prevent potential pregnancy. ...201322753108
modified-closed castration: a novel technique for sea otter (enhydra lutris nereis) orchiectomies.a novel surgical technique was used in the routine castrations of two intact male southern sea otters, enhydra lutris nereis, housed at the georgia aquarium (atlanta, georgia, usa). this technique involved incising the parietal vaginal tunic to allow placement of double ligation of the ductus deferens, testicular artery, and pampiniform plexus en masse. after ligating and transecting these structures, they were introduced back into the tunic, which was closed with a circumferential ligature. the ...201324063115
recovery of a top predator mediates negative eutrophic effects on seagrass.a fundamental goal of the study of ecology is to determine the drivers of habitat-forming vegetation, with much emphasis given to the relative importance to vegetation of "bottom-up" forces such as the role of nutrients and "top-down" forces such as the influence of herbivores and their predators. for coastal vegetation (e.g., kelp, seagrass, marsh, and mangroves) it has been well demonstrated that alterations to bottom-up forcing can cause major disturbances leading to loss of dominant vegetati ...201323983266
primary cerebral t-cell lymphoma in a sea otter (enhydra lutris).a 10-year-old female sea otter exhibited convulsions, arrhythmia, hyperthermia, forced breathing and anorexia and died after a week. histopathological examination revealed neoplastic proliferation of small round cells with scant cytoplasm and round or oval nuclei distributed mainly in the thalamus. the proliferation of neoplastic cells was observed in the cerebral parenchyma and perivascular areas. the neoplastic cells were immunopositive for cd3, but not cd20. no neoplastic proliferation of t-c ...201323955395
osteoarthritis of the temporomandibular joint in southern sea otters (enhydra lutris nereis).museum skull specimens (n = 1,008) of southern sea otters (enhydra lutris nereis) were examined macroscopically according to defined criteria for the presence, severity and characteristics of temporomandibular joint osteoarthritis (tmj-oa). the specimens were from stranded young adult to adult animals. overall, 4.1% of the specimens had findings consistent with tmj-oa. of these, 61.0% were from females and 39.0% were from males. in addition, 85.4% of the affected specimens were from adults and 1 ...201323721871
sea otters homogenize mussel beds and reduce habitat provisioning in a rocky intertidal ecosystem.sea otters (enhydra lutris) are keystone predators that consume a variety of benthic invertebrates, including the intertidal mussel, mytilus californianus. by virtue of their competitive dominance, large size, and longevity, m. californianus are ecosystem engineers that form structurally complex beds that provide habitat for diverse invertebrate communities. we investigated whether otters affect mussel bed characteristics (i.e. mussel length distributions, mussel bed depth, and biomass) and asso ...201323717697
prolonged recovery of sea otters from the exxon valdez oil spill? a re-examination of the evidence.sea otters (enhydra lutris) suffered major mortality after the exxon valdez oil spill in prince william sound, alaska, 1989. we evaluate the contention that their recovery spanned over two decades. a model based on the otter age-at-death distribution suggested a large, spill-related population sink, but this has never been found, and other model predictions failed to match empirical data. studies focused on a previously-oiled area where otter numbers (~80) stagnated post-spill; nevertheless, pos ...201323639486
the dental pathology of southern sea otters (enhydra lutris nereis).skulls (n = 1,205) of southern sea otters were examined macroscopically according to defined criteria. the museum specimens, acquired from strandings, varied in age from juvenile to adult, with an equal sex distribution. the results from all young adult and adult specimens were pooled according to tooth type. ninety-two percent of teeth were available for examination, with 6.5% artifactually absent, 0.6% deemed absent due to acquired tooth loss and 0.03% deemed congenitally absent. all teeth wer ...201323348015
a new pathogen transmission mechanism in the ocean: the case of sea otter exposure to the land-parasite toxoplasma gondii.toxoplasma gondii is a land-derived parasite that infects humans and marine mammals. infections are a significant cause of mortality for endangered southern sea otters (enhydra lutris nereis), but the transmission mechanism is poorly understood. otter exposure to t. gondii has been linked to the consumption of marine turban snails in kelp (macrocystis pyrifera) forests. it is unknown how turban snails acquire oocysts, as snails scrape food particles attached to surfaces, whereas t. gondii oocyst ...201324386100
toxoplasma gondii, source to sea: higher contribution of domestic felids to terrestrial parasite loading despite lower infection prevalence.environmental transmission of toxoplasma gondii, a global zoonotic parasite, adversely impacts human and animal health. toxoplasma is a significant cause of mortality in threatened southern sea otters, which serve as sentinels for disease threats to people and animals in coastal environments. as wild and domestic felids are the only recognized hosts capable of shedding toxoplasma oocysts into the environment, otter infection suggests land-to-sea pathogen transmission. to assess relative contribu ...201324048652
sarcocystis neurona infection in gamma interferon gene knockout (ko) mice: comparative infectivity of sporocysts in two strains of ko mice, effect of trypsin digestion on merozoite viability, and infectivity of bradyzoites to ko mice and cell culture.the protozoan sarcocystis neurona is the primary cause of equine protozoal myeloencephalitis (epm). epm or epm-like illness has been reported in horses, sea otters, and several other mammals. the gamma interferon gene knockout (ko) mouse is often used as a model to study biology and discovery of new therapies against s. neurona because it is difficult to induce clinical epm in other hosts, including horses. in the present study, infectivity of three life cycle stages (merozoites, bradyzoites, sp ...201323375195
pathogen exposure and blood chemistry in the washington, usa population of northern sea otters (enhydra lutris kenyoni).northern sea otters (enhydra lutris kenyoni) from washington state, united states were evaluated in 2011 to determine health status and pathogen exposure. antibodies to brucella spp. (10%) and influenza a virus (23%) were detected for the first time in this population in 2011. changes in clinical pathology values (serum chemistries), exposure to pathogens, and overall health of the population over the last decade were assessed by comparing 2011 data to the data collected on this population in 20 ...201324502716
novel bartonella infection in northern and southern sea otters (enhydra lutris kenyoni and enhydra lutris nereis).since 2002, vegetative valvular endocarditis (vve), septicemia and meningoencephalitis have contributed to an unusual mortality event (ume) of northern sea otters in southcentral alaska. streptococcal organisms were commonly isolated from vegetative lesions and organs from these sea otters. bartonella infection has also been associated with bacteremia and vve in terrestrial mammals, but little is known regarding its pathogenic significance in marine mammals. our study evaluated whether streptoco ...201424629902
aquatic polymers can drive pathogen transmission in coastal ecosystems.gelatinous polymers including extracellular polymeric substances (epss) are fundamental to biophysical processes in aquatic habitats, including mediating aggregation processes and functioning as the matrix of biofilms. yet insight into the impact of these sticky molecules on the environmental transmission of pathogens in the ocean is limited. we used the zoonotic parasite toxoplasma gondii as a model to evaluate polymer-mediated mechanisms that promote transmission of terrestrially derived patho ...201425297861
using molecular epidemiology to track toxoplasma gondii from terrestrial carnivores to marine hosts: implications for public health and conservation.environmental transmission of the zoonotic parasite toxoplasma gondii, which is shed only by felids, poses risks to human and animal health in temperate and tropical ecosystems. atypical t. gondii genotypes have been linked to severe disease in people and the threatened population of california sea otters. to investigate land-to-sea parasite transmission, we screened 373 carnivores (feral domestic cats, mountain lions, bobcats, foxes, and coyotes) for t. gondii infection and examined the distrib ...201424874796
phocine distemper virus: current knowledge and future directions.phocine distemper virus (pdv) was first recognized in 1988 following a massive epidemic in harbor and grey seals in north-western europe. since then, the epidemiology of infection in north atlantic and arctic pinnipeds has been investigated. in the western north atlantic endemic infection in harp and grey seals predates the european epidemic, with relatively small, localized mortality events occurring primarily in harbor seals. by contrast, pdv seems not to have become established in european ha ...201425533658
bartonella spp. exposure in northern and southern sea otters in alaska and california.since 2002, an increased number of northern sea otters (enhydra lutris kenyoni) from southcentral alaska have been reported to be dying due to endocarditis and/or septicemia with infection by streptococcus infantarius subsp. coli. bartonella spp. dna was also detected in northern sea otters as part of mortality investigations during this unusual mortality event (ume) in kachemak bay, alaska. to evaluate the extent of exposure to bartonella spp. in sea otters, sera collected from necropsied and l ...201425514118
serologic evidence of influenza a(h1n1)pdm09 virus infection in northern sea otters. 201424751396
locally acquired disseminated histoplasmosis in a northern sea otter (enhydra lutris kenyoni) in alaska, usa.histoplasmosis of local origin has not been reported in humans or wildlife in alaska, and the disease has never been reported in a free-ranging marine mammal. in 2005 a northern sea otter (enhydra lutris kenyoni) was found on kodiak island, alaska, at 57° latitude north, far outside the known distribution of histoplasma capsulatum. the animal died of disseminated histoplasmosis. microorganisms consistent with histoplasma sp. were observed on histopathology, and h. capsulatum was identified by pc ...201424484503
innervation patterns of sea otter (enhydra lutris) mystacial follicle-sinus complexes.sea otters (enhydra lutris) are the most recent group of mammals to return to the sea, and may exemplify divergent somatosensory tactile systems among mammals. therefore, we quantified the mystacial vibrissal array of sea otters and histologically processed follicle-sinus complexes (f - scs) to test the hypotheses that the number of myelinated axons per f - sc is greater than that found for terrestrial mammalian vibrissae and that their organization and microstructure converge with those of pinn ...201425400554
hearing in the sea otter (enhydra lutris): auditory profiles for an amphibious marine carnivore.in this study we examine the auditory capabilities of the sea otter (enhydra lutris), an amphibious marine mammal that remains virtually unstudied with respect to its sensory biology. we trained an adult male sea otter to perform a psychophysical task in an acoustic chamber and at an underwater apparatus. aerial and underwater audiograms were constructed from detection thresholds for narrowband signals measured in quiet conditions at frequencies from 0.125-40 khz. aerial hearing thresholds were ...201425249386
interactions of marine mammals and birds with offshore membrane enclosures for growing algae (omega).omega is an integrated aquatic system to produce biofuels, treat and recycle wastewater, capture co2, and expand aquaculture production. this system includes floating photobioreactors (pbrs) that will cover hundreds of hectares in marine bays. to assess the interactions of marine mammals and birds with pbrs, 9 × 1.3 m flat panel and 9.5 × 0.2 m tubular pbrs were deployed in a harbor and monitored day and night from october 10, 2011 to janurary 22, 2012 using infrared video. to observe interactio ...201424955238
energetic demands of immature sea otters from birth to weaning: implications for maternal costs, reproductive behavior and population-level trends.sea otters (enhydra lutris) have the highest mass-specific metabolic rate of any marine mammal, which is superimposed on the inherently high costs of reproduction and lactation in adult females. these combined energetic demands have been implicated in the poor body condition and increased mortality of female sea otters nearing the end of lactation along the central california coast. however, the cost of lactation is unknown and currently cannot be directly measured for this marine species in the ...201424920834
novel poxvirus infection in northern and southern sea otters (enhydra lutris kenyoni and enhydra lutris neiris), alaska and california, usa.small superficially ulcerated skin lesions were observed between october 2009 and september 2011 during captive care of two orphaned sea otter pups: one northern (enhydra lutris kenyoni) in alaska and one southern (enhydra lutris nereis) in california. inclusions consistent with poxviral infection were diagnosed by histopathology in both cases. virions consistent with poxvirus virions were seen on electron microscopy in the northern sea otter, and the virus was successfully propagated in cell cu ...201424807180
assessing risks to sea otters and the exxon valdez oil spill: new scenarios, attributable risk, and recovery.the exxon valdez oil spill occurred more than two decades ago, and the prince william sound ecosystem has essentially recovered. nevertheless, discussion continues on whether or not localized effects persist on sea otters (enhydra lutris) at northern knight island (nki) and, if so, what are the associated attributable risks. a recent study estimated new rates of sea otter encounters with subsurface oil residues (ssor) from the oil spill. we previously demonstrated that a potential pathway existe ...201424587690
sea otter dental enamel is highly resistant to chipping due to its microstructure.dental enamel is prone to damage by chipping with large hard objects at forces that depend on chip size and enamel toughness. experiments on modern human teeth have suggested that some ante-mortem chips on fossil hominin enamel were produced by bite forces near physiological maxima. here, we show that equivalent chips in sea otter enamel require even higher forces than human enamel. increased fracture resistance correlates with more intense enamel prism decussation, often seen also in some fossi ...201425319817
novel poxvirus discovered in sea otters. 201425158347
generational spreading speed and the dynamics of population range expansion.some of the most fundamental quantities in population ecology describe the growth and spread of populations. population dynamics are often characterized by the annual rate of increase, λ, or the generational rate of increase, r0. analyses involving r0 have deepened our understanding of disease dynamics and life-history complexities beyond that afforded by analysis of annual growth alone. while range expansion is quantified by the annual spreading speed, a spatial analog of λ, an r0-like expressi ...201526655354
kelp forest size alters microbial community structure and function on vancouver island, canada.bacteria are ubiquitous and important components of marine ecosystems, yet the interaction between bacteria and higher trophic levels remain poorly understood. the trophic cascade involving sea otters, urchins, and kelp in the north pacific is a classic case of altered ecosystem states; however, its impacts on microbial communities are unknown. we investigated the response of microbial communities to variation in kelp abundance between regions with and without sea otter populations along the wes ...201526236881
fishers' knowledge about fish trophic interactions in the southeastern brazilian coast.data derived from studies of fishers' local ecological knowledge (lek) can be invaluable to the proposal of new studies and more appropriate management strategies. this study analyzed the fisher's lek about trophic relationships of fishes in the southeastern brazilian coast, comparing fishers' lek with scientific knowledge to provide new hypotheses.201525889226
ontogeny of oxygen storage capacity and diving ability in the southern sea otter (enhydra lutris nereis): costs and benefits of large lungs.small body size, large lungs, and dense pelage contribute to the unique challenges faced by diving sea otters (enhydra lutris) when compared to other marine mammals. here we determine the consequences of large lungs on the development of diving ability in southern sea otters (enhydra lutris nereis) by examining the ontogeny of blood, muscle, and lung oxygen stores and calculating aerobic dive limits (cadl) for immature and mature age classes. total oxygen storage capacity matures rapidly in sea ...201525860829
pathogenesis of streptococcus infantarius subspecies coli isolated from sea otters with infective endocarditis.the gram positive bacterial coccus streptococcus infantarius subspecies coli is increasingly linked with development of fatal vegetative infective endocarditis and septicemia in humans, sea otters (enhydra lutris) and other animals. however, the pathogenesis of these infections is poorly understood. using s. infantarius subsp. coli strains isolated from sea otters with infective endocarditis, this study evaluated adherence and invasion of epithelial and endothelial cells, adherence to extracellu ...201525838157
comparative functional anatomy of hindlimb muscles and bones with reference to aquatic adaptation of the sea otter.although the sea otter (enhydra lutris) is a complete aquatic species, spending its entire life in the ocean, it has been considered morphologically to be a semi-aquatic animal. this study aimed to clarify the unique hindlimb morphology and functional adaptations of e. lutris in comparison to other mustelidae species. we compared muscle mass and bone measurements of five mustelidae species: the sea otter, eurasian river otter (lutra lutra), american mink (neovison vison), japanese weasel (mustel ...201525715875
the cost of reproduction: differential resource specialization in female and male california sea otters.intraspecific variation in behavior and diet can have important consequences for population and ecosystem dynamics. here, we examine how differences in reproductive investment and spatial ecology influence individual diet specialization in male and female southern sea otters (enhydra lutris nereis). we hypothesize that greater reproductive constraints and smaller home ranges of females lead to more pronounced intraspecific competition and increased specialization. we integrate stable carbon (δ(1 ...201525669450
timescales alter the inferred strength and temporal consistency of intraspecific diet specialization.many populations consist of individuals that differ substantially in their diets. quantification of the magnitude and temporal consistency of such intraspecific diet variation is needed to understand its importance, but the extent to which different approaches for doing so reflect instantaneous vs. time-aggregated measures of individual diets may bias inferences. we used direct observations of sea otter individuals (enhydra lutris nereis) to assess how: (1) the timescale of sampling, (2) under-s ...201525656583
the interaction of intraspecific competition and habitat on individual diet specialization: a near range-wide examination of sea otters.the quantification of individuality is a common research theme in the fields of population, community, and evolutionary ecology. the potential for individuality to arise is likely context-dependent, and the influence of habitat characteristics on its prevalence has received less attention than intraspecific competition. we examined individual diet specialization in 16 sea otter (enhydra lutris) populations from southern california to the aleutian islands in alaska. because population histories, ...201525645269
testing the nutritional-limitation, predator-avoidance, and storm-avoidance hypotheses for restricted sea otter habitat use in the aleutian islands, alaska.sea otters (enhydra lutris) inhabiting the aleutian islands have stabilized at low abundance levels following a decline and currently exhibit restricted habitat-utilization patterns. possible explanations for restricted habitat use by sea otters can be classified into two fundamentally different processes, bottom-up and top-down forcing. bottom-up hypotheses argue that changes in the availability or nutritional quality of prey resources have led to the selective use of habitats that support the ...201525416538
characterization of the temporomandibular joint of southern sea otters (enhydra lutris nereis).the structure-function relationship of the temporomandibular joint (tmj) of southern sea otter has largely not been described. this study aims to describe the histological, biochemical, and biomechanical features of the tmj disk in the southern sea otter. the tmj disks from fresh cadaver heads of southern sea otter adult males (n = 8) and females (n = 8) acquired from strandings were examined. following macroscopical evaluation, the tmjs were investigated for their histological, mechanical, and ...201526664997
evaluating potential conservation conflicts between two listed species: sea otters and black abalone.population consequences of endangered species interacting as predators and prey have been considered theoretically and legally, but rarely investigated in the field. we examined relationships between spatially variable populations of a predator, the california sea otter, enhydra lutris nereis, and a prey species, the black abalone, haliotis cracherodii. both species are federally listed under the endangered species act and co-occur along the coast of california. we compared the local abundance a ...201527070027
indirect effects of sea otters on rockfish (sebastes spp.) in giant kelp forests.sea otters are a classic example of a predator controlling ecosystem productivity through cascading effects on basal, habitat-forming kelp species. however, their indirect effects on other kelp-associated taxa like fishes are poorly understood. we examined the effects of sea otter (enhydra lutris) reintroduction along the west coast of vancouver island, canada on giant kelp (macrocystis pyrifera) distributions and the trophic niches and growth of two common kelp forest fishes, black (sebastes me ...201527070008
divergent skull morphology supports two trophic specializations in otters (lutrinae).variation in terrestrial mammalian skull morphology is known to constrain feeding performance, which in turn influences dietary habits and ultimately fitness. among mustelids, otters have evolved two feeding specializations: underwater raptorial capture of prey (mouth-oriented) and capture of prey by hand (hand-oriented), both of which have likely associations with morphology and bite performance. however, feeding biomechanics and performance data for otters are sparse. the first goal of this st ...201526649575
oral papillomatosis caused by enhydra lutris papillomavirus 1 (elpv-1) in southern sea otters (enhydra lutris nereis) in california, usa.the southern sea otter (enhydra lutris nereis) is a threatened marine sentinel. during postmortem investigations of stranded sea otters from 2004 to 2013 in california, us, papillomas were detected in the oral cavity of at least seven otters via necropsy and histopathology. next-generation sequencing of viral particles purified from a single papilloma revealed a novel papillomavirus, enhydra lutris papillomavirus 1 (elpv-1). the genome of elpv-1 was obtained, representing the first fully sequenc ...201525647597
sea otter health: challenging a pet hypothesis.a recent series of studies on tagged sea otters (enhydra lutris nereis) challenges the hypothesis that sea otters are sentinels of a dirty ocean, in particular, that pet cats are the main source of exposure to toxoplasma gondii in central california. counter to expectations, sea otters from unpopulated stretches of coastline are less healthy and more exposed to parasites than city-associated otters. ironically, now it seems that spillover from wildlife, not pets, dominates spatial patterns of di ...201526155464
concentration and retention of toxoplasma gondii oocysts by marine snails demonstrate a novel mechanism for transmission of terrestrial zoonotic pathogens in coastal ecosystems.the parasite toxoplasma gondii is an environmentally persistent pathogen that can cause fatal disease in humans, terrestrial warm-blooded animals and aquatic mammals. although an association between t. gondii exposure and prey specialization on marine snails was identified in threatened california sea otters, the ability of kelp-dwelling snails to transmit terrestrially derived pathogens has not been previously investigated. the objective of this study was to measure concentration and retention ...201526033089
epidemiology and pathology of toxoplasma gondii in free-ranging california sea lions (zalophus californianus).the coccidian parasite toxoplasma gondii infects humans and warm-blooded animals worldwide. the ecology of this parasite in marine systems is poorly understood, although many marine mammals are infected and susceptible to clinical toxoplasmosis. we summarized the lesions associated with t. gondii infection in the california sea lion (zalophus californianus) population and investigated the prevalence of and risk factors associated with t. gondii exposure, as indicated by antibody. five confirmed ...201525588007
coccidioidomycosis and other systemic mycoses of marine mammals stranding along the central california, usa coast: 1998-2012.a wide range of systemic mycoses have been reported from captive and wild marine mammals from north america. examples include regionally endemic pathogens such as coccidioides and blastomyces spp., and novel pathogens like cryptococcus gattii, which appear may have been introduced to north america by humans. stranding and necropsy data were analyzed from three marine mammal stranding and response facilities on the central california coast to assess the prevalence, host demographics, and lesion d ...201525647598
coxiella burnetii exposure in northern sea otters enhydra lutris kenyoni.valvular endocarditis has been well described in northern sea otters enhydra lutris kenyoni of alaska and in many cases no cause has been identified. it is also one of the most common conditions observed in people with chronic coxiella burnetii infection. given the high levels of c. burnetii exposure in marine mammals distributed throughout the same geographic range as the northern sea otter, and the presence of valvular lesions seen in otters, the objective of this study was to determine the le ...201525958809
sarcocyst development in raccoons (procyon lotor) inoculated with different strains of sarcocystis neurona culture-derived merozoites.sarcocystis neurona is considered the major etiologic agent of equine protozoal myeloencephalitis (epm), a neurological disease in horses. raccoon ( procyon lotor ) is considered the most important intermediate host in the life cycle of s. neurona in the united states; s. neurona sarcocysts do mature in raccoon muscles, and raccoons also develop clinical signs simulating epm. the focus of this study was to determine if sarcocysts would develop in raccoons experimentally inoculated with different ...201525811893
an update on sarcocystis neurona infections in animals and equine protozoal myeloencephalitis (epm).equine protozoal myeloencephalitis (epm) is a serious disease of horses, and its management continues to be a challenge for veterinarians. the protozoan sarcocystis neurona is most commonly associated with epm. s. neurona has emerged as a common cause of mortality in marine mammals, especially sea otters (enhydra lutris). epm-like illness has also been recorded in several other mammals, including domestic dogs and cats. this paper updates s. neurona and epm information from the last 15 years on ...201525737052
a systematic review of changes in marine mammal health in north america, 1972-2012: the need for a novel integrated approach.marine mammals are often cited as "sentinels of ocean health" yet accessible, synthesized data on their health changes that could effectively warn of ocean health changes are rare. the objectives of this study were to 1) perform a systematic review of published cases of marine mammal disease to determine spatial and temporal trends in disease from 1972-2012, including changes in regions and taxa affected and specific causes; and 2) compare numbers of published cases of neoplasia with known, hosp ...201526579715
prevalence, pathology, and risk factors associated with streptococcus phocae infection in southern sea otters (enhydra lutris nereis), 2004-10.recent studies have implicated beta-hemolytic streptococci as opportunistic pathogens of marine mammals, including southern sea otters (enhydra lutris nereis), but little is known about their prevalence or pathophysiology. herein, we focus on risk factors for sea otter infection by a single beta-hemolytic streptococcal species, streptococcus phocae. streptococcus phocae was first identified as a marine mammal pathogen in 1994, and the first report in southern sea otters was in 2009. its broad ho ...201626555115
concentration and retention of toxoplasma gondii surrogates from seawater by red abalone (haliotis rufescens).small marine snails and abalone have been identified as high- and low-risk prey items, respectively, for exposure of threatened southern sea otters to toxoplasma gondii, a zoonotic parasite that can cause fatal encephalitis in animals and humans. while recent work has characterized snails as paratenic hosts for t. gondii, the ability of abalone to vector the parasite has not been evaluated. to further elucidate why abalone predation may be protective against t. gondii exposure, this study aimed ...201627573192
evolutionary relationships between digeneans of the family brachycladiidae odhner, 1905 and their marine mammal hosts: a cophylogenetic study.cophylogenetic studies examine the congruence between host and parasite phylogenies. there are few studies that quantify the relative contribution of coevolutionary events, i.e. duplication, loss, failure-to-diverge, host-switching and spreading in trophically-transmitted parasites at the marine realm. we addressed this issue in the brachycladiidae, a cosmopolitan digenean family specific to marine mammals. we used, for the first time, distance-based and event-based methods to explicitly test th ...201626721312
detection and characterization of diverse coccidian protozoa shed by california sea lions.tissue-cyst forming coccidia in the family sarcocystidae are etiologic agents of protozoal encephalitis in marine mammals including the federally listed southern sea otter (enhydra lutris). california sea lions (zalophus californianus), whose coastal habitat overlaps with sea otters, are definitive hosts for coccidian protozoa provisionally named coccidia a, b and c. while coccidia a and b have unknown clinical effects on aquatic wildlife hosts, coccidia c is associated with severe protozoal dis ...201627141438
california mussels (mytilus californianus) as sentinels for marine contamination with sarcocystis neurona.sarcocystis neurona is a terrestrial parasite that can cause fatal encephalitis in the endangered southern sea otter (enhydra lutris nereis). to date, neither risk factors associated with marine contamination nor the route of s. neurona infection to marine mammals has been described. this study evaluated coastal s. neurona contamination using california mussels (mytilus californianus) as sentinels for pathogen pollution. a field investigation was designed to test the hypotheses that (1) mussels ...201627003262
dual congenital transmission of toxoplasma gondii and sarcocystis neurona in a late-term aborted pup from a chronically infected southern sea otter (enhydra lutris nereis).toxoplasma gondii and sarcocystis neurona are protozoan parasites with terrestrial definitive hosts, and both pathogens can cause fatal disease in a wide range of marine animals. close monitoring of threatened southern sea otters (enhydra lutris nereis) in california allowed for the diagnosis of dual transplacental transmission of t. gondii and s. neurona in a wild female otter that was chronically infected with both parasites. congenital infection resulted in late-term abortion due to dissemina ...201626494610
antidog igg secondary antibody successfully detects igg in a variety of aquatic mammals.serological tests play an important role in the detection of wildlife diseases. however, while there are many commercial assays and reagents available for domestic species, there is a need to develop efficient serological assays for wildlife. in recent years, marine mammals have represented a wildlife group with emerging infectious diseases, such as influenza, brucellosis, and leptospirosis. however, with the exception of disease-agent-specific assays or functional assays, few reports describe t ...201628080908
pharmacokinetic indices for cefovecin after single-dose administration to adult sea otters (enhydra lutris).seven sea otters received a single subcutaneous dose of cefovecin at 8 mg/kg body weight. plasma samples were collected at predetermined time points and assayed for total cefovecin concentrations using ultra-performance liquid chromatography and tandem mass spectrometry. the mean (±sd) noncompartmental pharmacokinetic indices were as follows: cmax (obs) 70.6 ± 14.6 μg/ml, tmax (obs) 2.9 ± 1.5 h, elimination rate constant (kel ) 0.017 ± 0.002/h, elimination half-life (t1/2kel) 41.6 ± 4.7 h, area ...201627212054
morphological analysis of long bones in semi-aquatic mustelids and their terrestrial relatives.the locomotor environment and behavior of quadrupedal mammals exert functional constraints on their limbs. therefore long bone shapes are thought to reflect at least partially the species' locomotor ecology. semi-aquatic species move through two media with distinct density and viscosity and their locomotor apparatus should therefore reflect a trade-off between the divergent functional constraints it faces. adaptation to a semi-aquatic lifestyle occurred independently in otters (lutrinae) and min ...201627794537
ontogenetic scaling of theoretical bite force in southern sea otters (enhydra lutris nereis).sexual dimorphism attributed to niche divergence is often linked to differentiation between the sexes in both dietary resources and characters related to feeding and resource procurement. although recent studies have indicated that southern sea otters (enhydra lutris nereis) exhibit differences in dietary preferences as well as sexual dimorphism in skull size and shape, whether these intersexual differences translate to differentiation in feeding performances between the sexes remains to be inve ...201627617357
comparison of human and southern sea otter (enhydra lutris nereis) health risks for infection with protozoa in nearshore waters.cryptosporidium and giardia spp. are waterborne, fecally-transmitted pathogens that cause economic loss due to gastroenteritis and beach closures. we applied quantitative microbial risk assessment (qmra) to determine the health risks for humans and sea otters due to waterborne exposure of cryptosporidium and giardia spp. when swimming in three types of surface waters: river, stormwater and wastewater effluent during the wet and dry seasons in the central coast of california. this is the first ap ...201627525585
the high cost of reproduction in sea otters necessitates unique physiological adaptations.superimposed on inherently high basal metabolic demands, the additional energetic requirements of reproduction can push female sea otters beyond physiological limits. indeed, the resulting energy imbalance contributes to disproportionately high rates of mortality at the end of lactation in this species. to examine and quantify metabolic changes associated with reproduction, we measured the resting metabolic rate (rmr) of a female sea otter across gestation, lactation and non-reproductive periods ...201627489214
the high cost of motherhood: end-lactation syndrome in southern sea otters (enhydra lutris nereis) on the central california coast, usa.sea otters ( enhydra lutris ) have exceptionally high energetic requirements, which nearly double during lactation and pup care. thus, females are extremely vulnerable to caloric insufficiency. despite a number of compensatory strategies, the metabolic challenge of reproduction culminates in numerous maternal deaths annually. massive depletion of energy reserves results in a case presentation that we define as end-lactation syndrome (els), characterized by moderate to severe emaciation not attri ...201626967137
accounting for size-specific predation improves our ability to predict the strength of a trophic cascade.predation can influence the magnitude of herbivory that grazers exert on primary producers by altering both grazer abundance and their per capita consumption rates via changes in behavior, density-dependent effects, and size. therefore, models based solely on changes in abundance may miss key components of grazing pressure. we estimated shifts in grazing pressure associated with changes in the abundance and per capita consumption rates of sea urchins triggered by size-selective predation by sea ...201626941943
auditory sensitivity and masking profiles for the sea otter (enhydra lutris).sea otters are threatened marine mammals that may be negatively impacted by human-generated coastal noise, yet information about sound reception in this species is surprisingly scarce. we investigated amphibious hearing in sea otters by obtaining the first measurements of absolute sensitivity and critical masking ratios. auditory thresholds were measured in air and underwater from 0.125 to 40 khz. critical ratios derived from aerial masked thresholds from 0.25 to 22.6 khz were also obtained. the ...201626610978
sea otters, kelp forests, and the extinction of steller's sea cow.the late pleistocene extinction of so many large-bodied vertebrates has been variously attributed to two general causes: rapid climate change and the effects of humans as they spread from the old world to previously uninhabited continents and islands. many large-bodied vertebrates, especially large apex predators, maintain their associated ecosystems through top-down forcing processes, especially trophic cascades, and megaherbivores also exert an array of strong indirect effects on their communi ...201626504217
prevalence of algal toxins in alaskan marine mammals foraging in a changing arctic and subarctic environment.current climate trends resulting in rapid declines in sea ice and increasing water temperatures are likely to expand the northern geographic range and duration of favorable conditions for harmful algal blooms (habs), making algal toxins a growing concern in alaskan marine food webs. two of the most common hab toxins along the west coast of north america are the neurotoxins domoic acid (da) and saxitoxin (stx). over the last 20 years, da toxicosis has caused significant illness and mortality in m ...201628073526
of mussels and men.some species are more equal than others. robert t. paine (american ecologist, 1933-2016) discovered that if you remove starfish - what he called a "keystone species" - from a tide pool, the complex ecosystem collapses. without the predator starfish, mussels choke out other animals and plants. this phenomenon is general. sea otters eat the sea urchins that eat the kelp that provides food and habitat for other species. on the vast serengeti plains, wildebeest "mow" the grass, protecting habitat fo ...201627585022
permissible home range estimation (phre) in restricted habitats: a new algorithm and an evaluation for sea otters.parametric and nonparametric kernel methods dominate studies of animal home ranges and space use. most existing methods are unable to incorporate information about the underlying physical environment, leading to poor performance in excluding areas that are not used. using radio-telemetry data from sea otters, we developed and evaluated a new algorithm for estimating home ranges (hereafter permissible home range estimation, or "phre") that reflects habitat suitability. we began by transforming si ...201627003710
a unique feeding strategy of the extinct marine mammal kolponomos: convergence on sabretooths and sea otters.mammalian molluscivores feed mainly by shell-crushing or suction-feeding. the extinct marine arctoid, kolponomos, has been interpreted as an otter-like shell-crusher based on similar dentitions. however, neither the masticatory biomechanics of the shell-crushing adaptation nor the way kolponomos may have captured hard-shelled prey have been tested. based on mandibular symphyseal morphology shared by kolponomos and sabre-toothed carnivores, we hypothesize a sabretooth-like mechanism for kolponomo ...201626936242
novel finding of widespread occurrence and accumulation of bisphenol a diglycidyl ethers (badges) and novolac glycidyl ethers (noges) in marine mammals from the united states coastal waters.bisphenol a diglycidyl ether (badge)- and bisphenol f diglycidyl ether (bfdge)-based epoxy resins have a broad range of applications, including serving as inner coatings of food and beverage cans and as protective coatings in marine construction. prior to this study, no studies had examined the occurrence and bioaccumulation of badges or bfdges in aquatic organisms. in this study, badge, bfdge, and nine of their derivatives were determined in 121 tissue (liver, kidney, blubber, and brain) sample ...201626800265
osteosarcoma of the maxilla with concurrent osteoma in a southern sea otter (enhydra lutris nereis).southern sea otters (enhydra lutris nereis) are threatened marine mammals that belong to the family mustelidae and are native to the coast of central california. neoplasia is reported infrequently in sea otters. an adult female free-ranging southern sea otter was found alive at pebble beach, monterey county, california, on january 1st, 1994 and died soon after capture. the carcass was submitted to the us geological survey - national wildlife health center for necropsy examination. grossly, a mas ...201622520807
trophic cascades on the edge: fostering seagrass resilience via a novel pathway.despite widespread degradation, some coastal ecosystems display remarkable resilience. for seagrasses, a century-old paradigm has implicated macroalgal blooms stimulated by anthropogenic nutrient, loading as a primary driver of seagrass decline, yet relatively little attention has been given to drivers of seagrass resilience. in elkhorn slough, ca, an estuarine system characterized by extreme anthropogenic nutrient loading and macroalgal (ulva spp.) blooms, seagrass (zostera marina) beds have re ...201627167224
organization of the retinal ganglion layer and retinal resolution in the sea otter (enhydra lutris). 201610833638
mitogenomes and relatedness do not predict frequency of tool-use by sea otters.many ecological aspects of tool-use in sea otters are similar to those in indo-pacific bottlenose dolphins. within an area, most tool-using dolphins share a single mitochondrial haplotype and are more related to each other than to the population as a whole. we asked whether sea otters in california showed similar genetic patterns by sequencing mitogenomes of 43 otters and genotyping 154 otters at 38 microsatellite loci. there were six variable sites in the mitogenome that yielded three haplotype ...201728330975
brucella infection in asian sea otters (enhydra lutris lutris) on bering island, russia.infection with brucella spp., long known as a cause of abortion, infertility, and reproductive loss in domestic livestock, has increasingly been documented in marine mammals over the past two decades. we report molecular evidence of brucella infection in asian sea otters (enhydra lutris lutris). brucella dna was detected in 3 of 78 (4%) rectal swab samples collected between 2004 and 2006 on bering island, russia. these 78 animals had previously been documented to have a brucella seroprevalence o ...201728715292
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