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James L. Bodkin - One of the best experts on this subject based on the ideXlab platform.
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Sea Otter foraging behavior
2021Co-Authors: Randall W. Davis, James L. BodkinAbstract:Sea Otters are marine specialists but diet generalists, which feed primarily on benthic mega-invertebrates (i.e., body dimension >1 cm). They locate and capture epibenthic and infaunal prey with their forepaws by relying on vision and tactile sensitivity during short-duration dives (generally <2 min) in shallow waters (routine dives <30 m and maximum dive depth ~100 m) of the littoral zone. Sea Otters have an elevated resting metabolic rate and small or no energy reserves in the form of blubber, so they feed every 3–4 h. Foraging dives often occur in bouts (i.e., two or more consecutive dives), which may last several hours with 1–2 min between dives, depending on the type of prey. Sea Otters consume small or soft prey entirely or use their teeth or stone tools to access the flesh of mega-invertebrates with a shell, test, or exoskeleton. The daily percentage of time that Sea Otters devote to foraging depends on age, sex, presence of a pup, time of year, and prey abundance, which varies geographically, Seasonally, and episodically. In areas occupied by Sea Otters for many years, epifaunal prey generally decline first followed by infaunal species, and this may result in greater foraging effort and diet specialization associated with density-dependent competition for food. Although prey availability strongly influences Sea Otter carrying capacity, both intrinsic and extrinsic factors influence population equilibrium density, resulting in spatiotemporal variations in foraging behavior.
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Future Directions in Sea Otter ReSearch and Management
Frontiers in Marine Science, 2019Co-Authors: Randall W. Davis, Daniel H Monson, James L. Bodkin, Heather A. Coletti, Shawn Larson, Lilian P. Carswell, Linda M. NicholAbstract:The conservation and management of Sea Otters has benefited from a dedicated reSearch effort over the past 60 years enabling this species to recover from a few thousand in the early 20th century to about 150,000 today. Continued reSearch to allow full, pre-exploitation recovery and restoration of nearshore ecosystems should focus on at least seven key challenges: 1) Defining Sea Otter populations at smaller spatial scales that reflect this species’ life history and dispersal patterns; 2) Understanding factors that regulate Sea Otter population density with a focus on index sites that are representative of the variety of littoral habitats occupied by Sea Otters around the North Pacific Rim; 3) Quantifying the effects of Sea Otters on the littoral community with a focus on how food availability limits population and ecosystem recovery and on predicting the effect of Sea Otter reoccupation on commercially valuable invertebrates; 4) Making Sea Otter monitoring programs comparable across geo-political boundaries through international collaboration to optimize survey efforts both spatially and temporally and to determine the cause of changes in Sea Otter demographics; 5) Evaluating the conservation benefits of Sea Otter reintroductions into historical habitat; 6) Assessing the socioeconomic costs and benefits of Sea Otter range expansion to anticipate and mitigate conflicts; 7) Recognizing in conservation and management plans that Sea Otters can be significantly affected by higher level predators in some circumstances. Many of these challenges will require new tools including the next generation geolocation tag technology that will allow assessments of long-range movements, dispersal and gene flow in various populations.
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Figure S1: Study location map. from Defining the risk landscape in the context of pathogen pollution: Toxoplasma gondii in Sea Otters along the Pacific Rim
2018Co-Authors: Tristan L. Burgess, James L. Bodkin, Michael J. Murray, Melissa A. Miller, Shawn Larson, Linda M. Nichol, Patricia A. Conrad, Tim M Tinker, Justin A Saarinen, Christine K. JohnsonAbstract:Map showing the location of all study regions for Northern Sea Otter (Enhydra lutris kenyoni). 1) Western Prince William Sound, Alaska; 2) Elfin Cove, Alaska; 3) Whale Bay, Alaska; 4) Nuchatlitz Inlet (Blue) and Clayoquot Sound (Green), British Columbia; 5) Olympic Peninsula, Washington. Coastal watersheds included in the study are outlined in black. See Figure 1 for Southern Sea Otter (E. lutris nereis) study regions in California
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trade offs between energy maximization and parental care in a central place forager the Sea Otter
Behavioral Ecology, 2016Co-Authors: Nicole M Thometz, James L. Bodkin, Joseph A Tomoleoni, Michelle M. Staedler, Gena B Bentall, Martin Tim TinkerAbstract:Between 1999 and 2014, 126 archival time–depth recorders (TDRs) were used to examine the foraging behavior of southern Sea Otters (Enhydra lutris nereis) off the coast of California, in both resource-abundant (recently occupied, low Sea Otter density) and resource-limited (long-occupied, high Sea Otter density) locations. Following predictions of foraging theory, Sea Otters generally behaved as energy rate maximizers. Males and females without pups employed similar foraging strategies to optimize rates of energy intake in resource-limited habitats, with some exceptions. Both groups increased overall foraging effort and made deeper, longer and more energetically costly dives as resources became limited, but males were more likely than females without pups to utilize extreme dive profiles. In contrast, females caring for young pups (≤10 weeks) prioritized parental care over energy optimization. The relative importance of parental care versus energy optimization for adult females with pups appeared to reflect developmental changes as dependent young matured. Indeed, contrary to females during the initial stages of lactation, females with large pups approaching weaning once again prioritized optimizing energy intake. The increasing prioritization of energy optimization over the course of lactation was possible due to the physiological development of pups and likely driven by the energetic deficit incurred by females early in lactation. Our results suggest that regardless of resource availability, females at the end of lactation approach a species-specific ceiling for percent time foraging and that reproductive females in the central portion of the current southern Sea Otter range are disproportionately affected by resource limitation.
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Challenges to Sea Otter Recovery and Conservation
Sea Otter Conservation, 2015Co-Authors: B E Ballachey, James L. BodkinAbstract:Similar to other species that in recent centuries experienced unregulated human exploitation, Sea Otters were extirpated throughout large portions of their historic range in the North Pacific. For most of the twentieth century, with cessation of the fur trade and because of concerted efforts at conservation, Sea Otters recovered much of their historic range and abundance. Late in the twentieth century, increased predation by killer whales in southwest Alaska drove Sea Otter populations to a few percentage points of their prior abundance, and one of the nation’s largest oil spills in south-central Alaska caused the death of several thousand animals and required more than two decades for recovery. In California, entanglement in fishing gear and environmental degradation, among other factors, have contributed to slow growth in Sea Otter abundance. We discuss the role of density dependence and spatial structuring of populations in reduced rates of Sea Otter recovery recently detected in the Northeast Pacific, and consider the potential effects of multiple low-level and cumulative threats on Sea Otter populations. The resilience demonstrated by Sea Otters over the past century will be tested in upcoming decades as human activities continue to degrade nearshore coastal areas of the North Pacific.
James A. Estes - One of the best experts on this subject based on the ideXlab platform.
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Gene transcription in Sea Otters (Enhydra lutris); development of a diagnostic tool for Sea Otter and ecosystem health.
Molecular ecology resources, 2011Co-Authors: Lizabeth Bowen, B E Ballachey, James L. Bodkin, Michael J. Murray, Martin Haulena, A. Keith Miles, Judy Tuttle, William Van Bonn, Lance Adams, James A. EstesAbstract: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 of transcripts for each gene in a group of clinically healthy captive and free-ranging Sea Otters. The 10 genes of interest represent multiple physiological systems that play a role in immuno-modulation, inflammation, cell protection, tumour suppression, cellular stress response, xenobiotic metabolizing enzymes, antioxidant enzymes and cell‐cell adhesion. The cycle threshold (CT) measures for most genes were normally distributed; the complement cytolysis inhibitor was the exception. The relative enumeration of multiple gene transcripts in simple peripheral blood samples expands the diagnostic capability currently available to assess the health of Sea Otters in situ and provides a better understanding of the state of their environment.
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Sea Otter mortality in fish and shellfish traps estimating potential impacts and exploring possible solutions
Endangered Species Research, 2011Co-Authors: Brian B Hatfield, James A. Estes, Michelle M. Staedler, Tim M Tinker, Jack A Ames, Andrew B Johnson, Michael D HarrisAbstract:Sea Otters Enhydra lutris can be bycaught and drowned in fishing pots and traps, which may pose a threat to the welfare of Otter populations. We explored this potential problem and its solu- tions using a wide variety of analyses. We exposed live California (USA) Sea Otters to finfish traps, lobster traps, and mock Dungeness crab traps in captive trials and found that the animals attempted to enter the circular and rectangular fyke openings, with some becoming entrapped. Using both live and dead Sea Otters, we found that a 3 × 9 inch (7.6 × 22.9 cm) fyke opening (1 inch narrower than the 4 × 9 inch (10.2 × 22.9 cm) openings currently used in California's commercial Dungeness crab fish- ery) would exclude most free-living (i.e. weaned from their mothers) Otters while permitting the undi- minished capture of crabs. Observer programs do not currently exist in California for these fisheries, so we calculated the effort required by an observer program to document Sea Otter bycatch over a range of hypothetical levels and evaluated the impact of those mortality rates on population growth. These analyses demonstrate that significant mortality from bycatch might easily go undetected, even with seemingly high levels of observer effort. As Sea Otters reoccupy portions of their former habitat in California, co-occurrence with finfish and shellfish traps with relatively large fyke openings will increase.
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prey choice and habitat use drive Sea Otter pathogen exposure in a resource limited coastal system
Proceedings of the National Academy of Sciences of the United States of America, 2009Co-Authors: Christine K. Johnson, Melissa A. Miller, David A. Jessup, James A. Estes, Patricia A. Conrad, Michelle M. Staedler, Martin Tim Tinker, Jonna A. K. MazetAbstract:The processes promoting diSease in wild animal populations are highly complex, yet identifying these processes is critically important for conservation when diSease is limiting a population. By combining field studies with epidemiologic tools, we evaluated the relationship between key factors impeding southern Sea Otter (Enhydra lutris nereis) population growth: diSease and resource limitation. This threatened population has struggled to recover despite protection, so we followed radio-tagged Sea Otters and evaluated infection with 2 diSease-causing protozoal pathogens, Toxoplasma gondii and Sarcocystis neurona, to reveal risks that increased the likelihood of pathogen exposure. We identified patterns of pathogen infection that are linked to individual animal behavior, prey choice, and habitat use. We detected a high-risk spatial cluster of S. neurona infections in Otters with home ranges in southern Monterey Bay and a coastal segment near San Simeon and Cambria where Otters had high levels of infection with T. gondii. We found that Otters feeding on abalone, which is the preferred prey in a resource-abundant marine ecosystem, had a very low risk of infection with either pathogen, whereas Otters consuming small marine snails were more likely to be infected with T. gondii. Individual dietary specialization in Sea Otters is an adaptive mechanism for coping with limited food resources along central coastal California. High levels of infection with protozoal pathogens may be an adverse consequence of dietary specialization in this threatened species, with both depleted resources and diSease working synergistically to limit recovery.
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using demography and movement behavior to predict range expansion of the southern Sea Otter
Ecological Applications, 2008Co-Authors: Tim M Tinker, Daniel F Doak, James A. EstesAbstract:In addition to forecasting population growth, basic demographic data combined with movement data provide a means for predicting rates of range expansion. Quantitative models of range expansion have rarely been applied to large vertebrates, although such tools could be useful for restoration and management of many threatened but recovering populations. Using the southern Sea Otter (Enhydra lutris nereis) as a case study, we utilized integro-difference equations in combination with a stage-structured projection matrix that incorporated spatial variation in dispersal and demography to make forecasts of population recovery and range recolonization. In addition to these basic predictions, we emphasize how to make these modeling predictions useful in a management context through the inclusion of parameter uncertainty and sensitivity analysis. Our models resulted in hind-cast (1989-2003) predictions of net population growth and range expansion that closely matched observed patterns. We next made projections of future range expansion and population growth, incorporating uncertainty in all model parameters, and explored the sensitivity of model predictions to variation in spatially explicit survival and dispersal rates. The predicted rate of southward range expansion (median = 5.2 km/yr) was sensitive to both dispersal and survival rates; elasticity analysis indicated that changes in adult survival would have the greatest potential effect on the rate of range expansion, while perturbation analysis showed that variation in subadult dispersal contributed most to variance in model predictions. Variation in survival and dispersal of females at the south end of the range contributed most of the variance in predicted southward range expansion. Our approach provides guidance for the acquisition of further data and a means of forecasting the consequence of specific management actions. Similar methods could aid in the management of other recovering populations.
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individual dietary specialization and dive behaviour in the california Sea Otter using archival time depth data to detect alternative foraging strategies
Deep-sea Research Part Ii-topical Studies in Oceanography, 2007Co-Authors: M. T. Tinker, James A. Estes, Daniel P. Costa, N WieringaAbstract:Abstract The existence of individual prey specializations has been reported for an ever-growing number of taxa, and has important ramifications for our understanding of predator–prey dynamics. We use the California Sea Otter population as a case study to validate the use of archival time–depth data to detect and measure differences in foraging behaviour and diet. We collected observational foraging data from radio-tagged Sea Otters that had been equipped with Mk9 time depth recorders (TDRs, Wildlife Computers, Redmond, WA). After recapturing the study animals and retrieving the TDRs it was possible to compare the two data types, by matching individual dives from the TDR record with observational data and thus examining behavioural correlates of capture success and prey species. Individuals varied with respect to prey selection, aggregating into one of three distinct dietary specializations. A number of TDR-derived parameters, particularly dive depth and post-dive surface interval, differed predictably between specialist types. A combination of six dive parameters was particularly useful for discriminating between specialist types, and when incorporated into a multivariate cluster analysis, these six parameters resulted in classification of 13 adult female Sea Otters into three clusters that corresponded almost perfectly to the diet-based classification (1 out of 13 animals was misclassified). Thus based solely on quantifiable traits of time–depth data that have been collected over an appropriate period (in this case 1 year per animal), it was possible to assign female Sea Otters to diet type with >90% accuracy. TDR data can thus be used as a tool to measure the degree of individual specialization in Sea Otter populations, a conclusion that will likely apply to other diving marine vertebrates as well. Our ultimate goals must be both to understand the causes of individual specialization, and to incorporate such variation into models of population- and community-level food web dynamics.
Tim M Tinker - One of the best experts on this subject based on the ideXlab platform.
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behavioral responses across a mosaic of ecosystem states restructure a Sea Otter urchin trophic cascade
Proceedings of the National Academy of Sciences of the United States of America, 2021Co-Authors: Joshua G Smith, Jessica A Fujii, Joseph A Tomoleoni, Michelle M. Staedler, Sophia Lyon, Tim M TinkerAbstract:Consumer and predator foraging behavior can impart profound trait-mediated constraints on community regulation that scale up to influence the structure and stability of ecosystems. Here, we demonstrate how the behavioral response of an apex predator to changes in prey behavior and condition can dramatically alter the role and relative contribution of top-down forcing, depending on the spatial organization of ecosystem states. In 2014, a rapid and dramatic decline in the abundance of a mesopredator (Pycnopodia helianthoides) and primary producer (Macrocystis pyrifera) coincided with a fundamental change in purple Sea urchin (Strongylocentrotus purpuratus) foraging behavior and condition, resulting in a spatial mosaic of kelp forests interspersed with patches of Sea urchin barrens. We show that this mosaic of adjacent alternative ecosystem states led to an increase in the number of Sea Otters (Enhydra lutris nereis) specializing on urchin prey, a population-level increase in urchin consumption, and an increase in Sea Otter survivorship. We further show that the spatial distribution of Sea Otter foraging efforts for urchin prey was not directly linked to high prey density but rather was predicted by the distribution of energetically profitable prey. Therefore, we infer that spatially explicit Sea Otter foraging enhances the resistance of remnant forests to overgrazing but does not directly contribute to the resilience (recovery) of forests. These results highlight the role of consumer and predator trait-mediated responses to resource mosaics that are common throughout natural ecosystems and enhance understanding of reciprocal feedbacks between top-down and bottom-up forcing on the regional stability of ecosystems.
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Figure S1: Study location map. from Defining the risk landscape in the context of pathogen pollution: Toxoplasma gondii in Sea Otters along the Pacific Rim
2018Co-Authors: Tristan L. Burgess, James L. Bodkin, Michael J. Murray, Melissa A. Miller, Shawn Larson, Linda M. Nichol, Patricia A. Conrad, Tim M Tinker, Justin A Saarinen, Christine K. JohnsonAbstract:Map showing the location of all study regions for Northern Sea Otter (Enhydra lutris kenyoni). 1) Western Prince William Sound, Alaska; 2) Elfin Cove, Alaska; 3) Whale Bay, Alaska; 4) Nuchatlitz Inlet (Blue) and Clayoquot Sound (Green), British Columbia; 5) Olympic Peninsula, Washington. Coastal watersheds included in the study are outlined in black. See Figure 1 for Southern Sea Otter (E. lutris nereis) study regions in California
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effects of wildfire on Sea Otter enhydra lutris gene transcript profiles
Marine Mammal Science, 2015Co-Authors: Lizabeth Bowen, James L. Bodkin, Michael J. Murray, Keith A Miles, Crystal A Kolden, Justin A Saarinen, Tim M TinkerAbstract:Wildfires have been shown to impact terrestrial species over a range of temporal scales. Little is known, however, about the more subtle toxicological effects of wildfires, particularly in downstream marine or downwind locations from the wildfire perimeter. These down-current effects may be just as substantial as those effects within the perimeter. We used gene transcription technology, a sensitive indicator of immunological perturbation, to study the effects of the 2008 Basin Complex Fire on the California coast on a sentinel marine species, the Sea Otter (Enhydra lutris). We captured Sea Otters in 2008 (3 mo after the Basin Complex Fire was controlled) and 2009 (15 mo after the Basin Complex Fire was controlled) in the adjacent nearshore environment near Big Sur, California. Gene responses were distinctly different between Big Sur temporal groups, signifying detoxification of PAHs, possible associated response to potential malignant transformation, and suppression of immune function as the primary responses of Sea Otters to fire in 2008 compared to those captured in 2009. In general, gene transcription patterns in the 2008 Sea Otters were indicative of molecular reactions to organic exposure, malignant transformation, and decreased ability to respond to pathogens that seemed to consistent with short-term hydrocarbon exposure.
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Sea Otter mortality in fish and shellfish traps estimating potential impacts and exploring possible solutions
Endangered Species Research, 2011Co-Authors: Brian B Hatfield, James A. Estes, Michelle M. Staedler, Tim M Tinker, Jack A Ames, Andrew B Johnson, Michael D HarrisAbstract:Sea Otters Enhydra lutris can be bycaught and drowned in fishing pots and traps, which may pose a threat to the welfare of Otter populations. We explored this potential problem and its solu- tions using a wide variety of analyses. We exposed live California (USA) Sea Otters to finfish traps, lobster traps, and mock Dungeness crab traps in captive trials and found that the animals attempted to enter the circular and rectangular fyke openings, with some becoming entrapped. Using both live and dead Sea Otters, we found that a 3 × 9 inch (7.6 × 22.9 cm) fyke opening (1 inch narrower than the 4 × 9 inch (10.2 × 22.9 cm) openings currently used in California's commercial Dungeness crab fish- ery) would exclude most free-living (i.e. weaned from their mothers) Otters while permitting the undi- minished capture of crabs. Observer programs do not currently exist in California for these fisheries, so we calculated the effort required by an observer program to document Sea Otter bycatch over a range of hypothetical levels and evaluated the impact of those mortality rates on population growth. These analyses demonstrate that significant mortality from bycatch might easily go undetected, even with seemingly high levels of observer effort. As Sea Otters reoccupy portions of their former habitat in California, co-occurrence with finfish and shellfish traps with relatively large fyke openings will increase.
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using demography and movement behavior to predict range expansion of the southern Sea Otter
Ecological Applications, 2008Co-Authors: Tim M Tinker, Daniel F Doak, James A. EstesAbstract:In addition to forecasting population growth, basic demographic data combined with movement data provide a means for predicting rates of range expansion. Quantitative models of range expansion have rarely been applied to large vertebrates, although such tools could be useful for restoration and management of many threatened but recovering populations. Using the southern Sea Otter (Enhydra lutris nereis) as a case study, we utilized integro-difference equations in combination with a stage-structured projection matrix that incorporated spatial variation in dispersal and demography to make forecasts of population recovery and range recolonization. In addition to these basic predictions, we emphasize how to make these modeling predictions useful in a management context through the inclusion of parameter uncertainty and sensitivity analysis. Our models resulted in hind-cast (1989-2003) predictions of net population growth and range expansion that closely matched observed patterns. We next made projections of future range expansion and population growth, incorporating uncertainty in all model parameters, and explored the sensitivity of model predictions to variation in spatially explicit survival and dispersal rates. The predicted rate of southward range expansion (median = 5.2 km/yr) was sensitive to both dispersal and survival rates; elasticity analysis indicated that changes in adult survival would have the greatest potential effect on the rate of range expansion, while perturbation analysis showed that variation in subadult dispersal contributed most to variance in model predictions. Variation in survival and dispersal of females at the south end of the range contributed most of the variance in predicted southward range expansion. Our approach provides guidance for the acquisition of further data and a means of forecasting the consequence of specific management actions. Similar methods could aid in the management of other recovering populations.
Patricia A. Conrad - One of the best experts on this subject based on the ideXlab platform.
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Figure S1: Study location map. from Defining the risk landscape in the context of pathogen pollution: Toxoplasma gondii in Sea Otters along the Pacific Rim
2018Co-Authors: Tristan L. Burgess, James L. Bodkin, Michael J. Murray, Melissa A. Miller, Shawn Larson, Linda M. Nichol, Patricia A. Conrad, Tim M Tinker, Justin A Saarinen, Christine K. JohnsonAbstract:Map showing the location of all study regions for Northern Sea Otter (Enhydra lutris kenyoni). 1) Western Prince William Sound, Alaska; 2) Elfin Cove, Alaska; 3) Whale Bay, Alaska; 4) Nuchatlitz Inlet (Blue) and Clayoquot Sound (Green), British Columbia; 5) Olympic Peninsula, Washington. Coastal watersheds included in the study are outlined in black. See Figure 1 for Southern Sea Otter (E. lutris nereis) study regions in California
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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
Parasitology, 2016Co-Authors: Karen Shapiro, Patricia A. Conrad, Andrea E Packham, Beatriz Aguilar, Elizabeth VanwormerAbstract: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 disseminated toxoplasmosis. Toxoplasma gondii and S. neurona DNA was amplified from placental tissue culture, as well as from fetal lung tissue. Molecular characterization of T. gondii revealed a Type X genotype in isolates derived from placenta and fetal brain, as well as in all tested fetal organs (brain, lung, spleen, liver and thymus). This report provides the first evidence for transplacental transmission of T. gondii in a chronically infected wild Sea Otter, and the first molecular and immunohistochemical confirmation of concurrent transplacental transmission of T. gondii and S. neurona in any species. Repeated fetal and/or neonatal losses in the Sea Otter dam also suggested that T. gondii has the potential to reduce fecundity in chronically infected marine mammals through parasite recrudescence and repeated fetal infection.
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prey choice and habitat use drive Sea Otter pathogen exposure in a resource limited coastal system
Proceedings of the National Academy of Sciences of the United States of America, 2009Co-Authors: Christine K. Johnson, Melissa A. Miller, David A. Jessup, James A. Estes, Patricia A. Conrad, Michelle M. Staedler, Martin Tim Tinker, Jonna A. K. MazetAbstract:The processes promoting diSease in wild animal populations are highly complex, yet identifying these processes is critically important for conservation when diSease is limiting a population. By combining field studies with epidemiologic tools, we evaluated the relationship between key factors impeding southern Sea Otter (Enhydra lutris nereis) population growth: diSease and resource limitation. This threatened population has struggled to recover despite protection, so we followed radio-tagged Sea Otters and evaluated infection with 2 diSease-causing protozoal pathogens, Toxoplasma gondii and Sarcocystis neurona, to reveal risks that increased the likelihood of pathogen exposure. We identified patterns of pathogen infection that are linked to individual animal behavior, prey choice, and habitat use. We detected a high-risk spatial cluster of S. neurona infections in Otters with home ranges in southern Monterey Bay and a coastal segment near San Simeon and Cambria where Otters had high levels of infection with T. gondii. We found that Otters feeding on abalone, which is the preferred prey in a resource-abundant marine ecosystem, had a very low risk of infection with either pathogen, whereas Otters consuming small marine snails were more likely to be infected with T. gondii. Individual dietary specialization in Sea Otters is an adaptive mechanism for coping with limited food resources along central coastal California. High levels of infection with protozoal pathogens may be an adverse consequence of dietary specialization in this threatened species, with both depleted resources and diSease working synergistically to limit recovery.
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transplacental toxoplasmosis in a wild southern Sea Otter enhydra lutris nereis
Veterinary Parasitology, 2008Co-Authors: Patricia A. Conrad, Erick R James, Andrea E Packham, Sharon Toychoutka, Michael E GriggAbstract:In September 2004, a neonatal Sea Otter pup was found alive on the beach in northern Monterey Bay, CA. Efforts to locate the mother were unsuccessful. Due to a poor prognosis for successful rehabilitation, the pup was euthanized. Postmortem examination revealed emaciation, systemic lymphadenopathy and a malformation of the left cerebral temporal lobe. On histopathology, free tachyzoites and tissue cysts compatible with Toxoplasma gondii were observed in the brain, heart, thymus, liver, lymph nodes and peri-umbilical adipose. The presence of T. gondii within host tissues was associated with lymphoplasmacytic inflammation and tissue necrosis. Immunofluorescent antibody tests using postmortem serum were positive for anti-T. gondii IgM and IgG (at 1:320 and 1:1280 serum dilution, respectively), but were negative for IgG directed against Sarcocystis neurona and Neospora caninum (<1:40 each). Brain immunohistochemistry revealed positive staining for tachyzoites and tissue cysts using antiserum raised to T. gondii, but not S. neurona or N. caninum. T. gondii parasite DNA was obtained from extracts of brain and muscle by PCR amplification using the diagnostic B1 locus. Restriction enzyme digestion followed by gel electrophoresis and DNA sequencing confirmed the presence of Type X T. gondii, the strain identified in the majority of southern Sea Otter infections.
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Southern Sea Otter as a Sentinel of Marine Ecosystem Health
EcoHealth, 2004Co-Authors: Melissa Miller, Jack Ames, Mike Harris, Christine Kreuder, Patricia A. ConradAbstract:The southern Sea Otter ( Enhydra lutris nereis ) is listed as “threatened” under the Endangered Species Act (ESA) and is a “keystone species,” strongly influencing the abundance and diversity of the other species within its kelp forest ecosystem. This is accomplished primarily by preying upon urchins that eat the kelp stipe and holdfast, which can reduce a kelp forest to an urchin barren. Sea Otters are very susceptible to marine pollutants such as petroleum, which may be directly toxic and/or alter their fur’s insulating properties. Sea Otters are an excellent sentinel species. They eat approximately 25% of their body weight per day in shellfish and other invertebrates, and can concentrate and integrate chemical contaminants. In addition, they appear to be susceptible to a number of diSeases and parasites that may have anthropogenic origins, and shellfish may serve as an intermediary for some of these infections. Many of the shellfish the Otters eat are also harvested for human food. In their role as sentinels, Sea Otter health has implications for human health, economic sustainability of shellfisheries, as well as overall marine ecosystem health. The recent southern Sea Otter decline has been viewed with some alarm by conservationists and, indeed, recovery seems a long way off. High mortality rather than depressed recruitment appears to underlie the decline. A good deal of debate has centered on the role of infectious diSeases and parasites, exposure to contaminants, nutrition and prey availability, net and pot fishery interactions, and other sources of mortality. Current reSearch is being done related to major classes of mortality, various types of pollutants and some specific organisms causing southern Sea Otter mortality, and their implications for marine ecosystem health and sustainability.
Daniel H Monson - One of the best experts on this subject based on the ideXlab platform.
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Sea Otter predator avoidance behavior
2021Co-Authors: Daniel H MonsonAbstract:Predators directly affect their prey as a source of mortality, and prey respond by employing antipredator strategies. Sea Otters are a keystone predator within the nearshore community, but higher trophic level avian, terrestrial, and pelagic predators (e.g., bald eagles, brown bears, wolves, white sharks, and killer whales) prey on them. Three antipredator strategies used by Sea Otters are vigilance (group or sentinel detection of danger), avoidance (seeking a location that is inaccessible to predators), and crypsis (the ability to avoid observation or detection). Vigilant behavior allowed Sea Otters to escape total extinction during the Maritime Fur Trade of the eighteenth and nineteenth centuries. Female Otters with pups practice vigilance when they reduce their foraging time and move along meandering paths. Sea Otters usually rest at Sea, and when they rest on shore, they usually haul out on offshore rocks, reefs, and small islands—possibly a behavioral response to terrestrial predators (brown bears and wolves can kill non-vigilant Sea Otters on shore). In areas where many Sea Otters haul out together, group vigilance may be important in detecting an approaching threat. Along the coast of central California, white sharks are a significant source of Sea Otter mortality, and the only antipredator strategy is avoidance or crypsis by resting in kelp beds. Despite the threat, Sea Otters still forage in open water, so the perception of risk may be low. In the western Aleutian Islands, killer whale predation is believed to be the cause of a > 90% decline in Sea Otters. As a result, Sea Otters perceive killer whales as a threat and limit their movements to shallow, complex habitats where the risk of attack is low. This behavioral response is so strong in the western Aleutian Islands that it may it limit Sea Otter dispersal among islands, with implications for the connectivity and genetic health of the small, isolated populations that remain.
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Future Directions in Sea Otter ReSearch and Management
Frontiers in Marine Science, 2019Co-Authors: Randall W. Davis, Daniel H Monson, James L. Bodkin, Heather A. Coletti, Shawn Larson, Lilian P. Carswell, Linda M. NicholAbstract:The conservation and management of Sea Otters has benefited from a dedicated reSearch effort over the past 60 years enabling this species to recover from a few thousand in the early 20th century to about 150,000 today. Continued reSearch to allow full, pre-exploitation recovery and restoration of nearshore ecosystems should focus on at least seven key challenges: 1) Defining Sea Otter populations at smaller spatial scales that reflect this species’ life history and dispersal patterns; 2) Understanding factors that regulate Sea Otter population density with a focus on index sites that are representative of the variety of littoral habitats occupied by Sea Otters around the North Pacific Rim; 3) Quantifying the effects of Sea Otters on the littoral community with a focus on how food availability limits population and ecosystem recovery and on predicting the effect of Sea Otter reoccupation on commercially valuable invertebrates; 4) Making Sea Otter monitoring programs comparable across geo-political boundaries through international collaboration to optimize survey efforts both spatially and temporally and to determine the cause of changes in Sea Otter demographics; 5) Evaluating the conservation benefits of Sea Otter reintroductions into historical habitat; 6) Assessing the socioeconomic costs and benefits of Sea Otter range expansion to anticipate and mitigate conflicts; 7) Recognizing in conservation and management plans that Sea Otters can be significantly affected by higher level predators in some circumstances. Many of these challenges will require new tools including the next generation geolocation tag technology that will allow assessments of long-range movements, dispersal and gene flow in various populations.
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long term effects of the exxon valdez oil spill Sea Otter foraging in the intertidal as a pathway of exposure to lingering oil
Marine Ecology Progress Series, 2012Co-Authors: James L. Bodkin, B E Ballachey, Heather A. Coletti, George G Esslinger, Kimberly A Kloecker, Stanley D Rice, John A Reed, Daniel H MonsonAbstract:The protracted recovery of some bird and mammal populations in western Prince William Sound (WPWS), Alaska, and the persistence of spilled 'Exxon Valdez' oil in intertidal sed- iments, suggests a pathway of exposure to consumers that occupy nearshore habitats. To evaluate the hypothesis that Sea Otter (Enhydra lutris) foraging allows access to lingering oil, we contrast spatial relations between foraging behavior and documented oil distribution. We recovered archival time-depth recorders implanted in 19 Sea Otters in WPWS, where lingering oil and de - layed ecosystem recovery are well documented. Sea Otter foraging dives ranged from +2.7 to �92 m below Sea level (MLLW), with intertidal accounting for 5 to 38% of all foraging. On average, female Sea Otters made 16 050 intertidal dives per year and 18% of these dives were at depths above the +0.80 m tidal elevation. Males made 4100 intertidal dives per year and 26% of intertidal foraging took place at depths above the +0.80 m tidal elevation. Estimated annual oil encounter rates ranged from 2 to 24 times yr �1 for females, and 2 to 4 times yr �1 for males. Exposure rates increased in spring when intertidal foraging doubled and females were with small pups. In sum- mer 2008, we found Sea Otter foraging pits on 13.5 of 24.8 km of intertidal shoreline surveyed. Most pits (82%) were within 0.5 m of the zero tidal elevation and 15% were above 0.5 m, the level above which most (65%) lingering oil remains. In August 2008, we detected oil above background concentrations in 18 of 41 (44%) pits excavated by Sea Otters on beaches with prior evidence of oil- ing, with total PAH concentrations up to 56 000 ng g �1 dry weight. Our estimates of intertidal for- aging, the widespread presence of foraging pits in the intertidal, and the presence of oil in and near Sea Otter foraging pits documents a pathway of exposure from lingering intertidal oil to Sea Otters foraging in WPWS.
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Sea Otter population status and the process of recovery from the 1989 'Exxon Valdez' oil spill
Marine Ecology Progress Series, 2002Co-Authors: James L. Bodkin, Sc Jewett, B E Ballachey, A K Fukuyama, C E O'clair, Daniel H Monson, T A Dean, L. Mcdonald, Glenn R VanblaricomAbstract:Sea Otter Enhydra lutris populations were severely affected by the 1989 'Exxon Valdez' oil spill in western Prince William Sound, AK, and had not fully recovered by 2000. Here we present results of population surveys and incorporate findings from related studies to identify current population status and factors affecting recovery. Between 1993 and 2000, the number of Sea Otters in the spill-area of Prince William Sound increased by about 600 to nearly 2700. However, at Knight Island, where oil exposure and Sea Otter mortality in 1989 was most severe, no increase has been observed. Sea Otter reproduction was not impaired, and the age and sex composition of captured Otters are consistent with both intrinsic reproduction and immigration contributing to recovery. However, low resighting rates of marked Otters at Knight Island compared to an unoiled reference area, and high proportions of young Otters in beach cast carcasses through 1998, suggest that the lack of recovery was caused by relatively poor survival or emigration of potential recruits. Significantly higher levels of cytochrome P4501A (CYP1A), a biomarker of hydrocarbons, were found in Sea Otters at Knight Island from 1996 to 1998 compared to unoiled Montague Island, implicating oil effects in the lack of recovery at Knight Island. Delayed recovery does not appear to be directly related to food limitation. Although food availability was relatively low at both oiled and unoiled areas, we detected significant increases in Sea Otter abundance only at Montague Island, a finding inconsistent with food as a principal limiting factor. Persistent oil in habitats and prey provides a source of continued oil exposure and, combined with relatively low prey densities, suggests a potential interaction between oil and food. However, Sea Otters foraged more successfully at Knight Island and young females were in better condition than those at Montague Island. We conclude that progress toward recovery of Sea Otters in Prince William Sound is evident, but that in areas where initial oil effects were greatest, recovery may be constrained by residual spill effects, resulting from elevated mortality and emigration. It is evident that internal reproduction and immigration of juveniles has been the primary means of population recovery, as opposed to broad scale redistribution of adults from outside affected areas. The result is a recovery period protracted by long-term spill effects on survival and emigration and intrinsic limits to population growth.
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changes in Sea urchins and kelp following a reduction in Sea Otter density as a result of the exxon valdez oil spill
Marine Ecology Progress Series, 2000Co-Authors: Thomas A Dean, Daniel H Monson, James L. Bodkin, Stephen C Jewett, Dennis JungAbstract:Interactions between Sea Otters Enhydra lutris, Sea urchins Strongylocentrotus droebachiensis, and kelp were investigated following the reduction in Sea Otter density in Prince William Sound, Alaska, after the Exxon Valdez oil spill in 1989. At northern Knight Island, a heavily oiled portion of the sound, Sea Otter abundance was reduced by a minimum of 50 % by the oil spill, and from 1995 through 1998 remained at an estimated 66 % lower than in 1973. Where Sea Otter densities were reduced, there were proportionally more large Sea urchins. However, except in some widely scattered aggregations, both density and biomass of Sea urchins were similar in an area of reduced Sea Otter density compared with an area where Sea Otters remained about 10 times more abundant. Furthermore, there was no change in kelp abundance in the area of reduced Sea Otter density. This is in contrast to greatly increased biomass of Sea urchins and greatly reduced kelp density observed following an approximate 90 % decline in Sea Otter abundance in the western Aleutian Islands. The variation in community response to a reduction in Sea Otters may be related to the magnitude of the reduction and the non-linear response by Sea urchins to changes in predator abundance. The number of surviving Sea Otters may have been high enough to suppress Sea urchin populations in Prince William Sound, but not in the Aleutians. Alternatively, differences in response may have been due to differences in the frequency or magnitude of Sea urchin recruitment. Densities of small Sea urchins were much higher in the Aleutian system even prior to the reduction in Sea Otters, suggesting a higher rate of recruitment.