Female Sea Otters Research Articles

Advancing surrogate-rearing methods to enhance southern sea otter recovery

Recovery of wildlife and their ecosystems may require enhancement of vulnerable populations through human intervention. As a southern sea otter (Enhydra lutris nereis) enhancement strategy, surrogate rearing and releasing of stranded orphans provides these individuals with another opportunity of life in the wild, promotes species-specific development of behaviors necessary for survival and reproduction after release, and may bolster targeted populations and resiliency of nearshore ecosystems. To further advance surrogacy as a viable recovery strategy for this threatened subspecies, we comprehensively describe our methods and use a machine learning algorithm to monitor and evaluate program success. Specifically, we model 20 years (2002−2021) of rehabilitation outcomes for 64 pups (i.e., success or failure reacclimating to the wild) based on 34 parameters representing three release sites and five treatment stages: stranding, stabilization, surrogacy, pre-release, and release. We find that surrogacy is a successful rehabilitation method (75%), robust to all measured factors through release preparation, including idiosyncrasies in pup origin, age, early development, and pairings with female sea otters. Instead, key performance indicators of successful outcomes in the wild are environmental conditions experienced during release, such as favorable sea conditions and weather, localized dispersal, and minimal competition from local populations. Most importantly, success requires optimal values among all environmental conditions at chosen release sites because a decline in any one factor may result in failure. Our findings highlight the importance of continuously evaluating rehabilitation methods to enhance species recovery and may have broader application to restoring other threatened species and their ecosystems.

TRANSTHORACIC ECHOCARDIOGRAPHIC EVALUATION AND SERUM CARDIAC TROPONIN VALUES IN ANESTHETIZED HEALTHY FEMALE SOUTHERN SEA OTTERS (ENHYDRA LUTRIS NEREIS).

Information about antemortem cardiac evaluation in sea otters (Enhydra lutris) is limited, despite well-established clinical care and rehabilitation procedures and a reported elevated risk of cardiac disease for this species. Serum cardiac troponin I (cTnI) concentration and echocardiographic assessment are two ways of screening for and diagnosing cardiac disease. However, no baseline data or reference intervals for either evaluation are published for sea otters. The objectives of this prospective study were to establish serum cTnI concentrations and echocardiographic technique and quantitative measurements in anesthetized healthy female southern sea otters (Enhydra lutris nereis) (n=15). Serum cTnI values were assessed by a high-sensitivity assay. Serum cTnI concentration ranged from <0.006 to 0.038 ng/ml. A complete echocardiogram, including two-dimensional and M-mode modalities, was performed. Echocardiographic measurements for left atrial size, aorta size, left ventricular structure, and left ventricular function were reported. The median left atrial size to aorta ratio was 1.22 (range 0.80-1.59) in short-axis and 1.70 (range 1.39-2.15) in long-axis. The median left ventricular internal dimension was 3.53 cm (range 2.87-4.92 cm) when assessed in two dimensions and 3.58 cm (range 2.80-4.48 cm) by M-mode. Serum concentrations of cTnI and transthoracic echocardiography may represent valuable tools for the antemortem diagnosis of cardiac disease in sea otters.

Lactation and resource limitation affect stress responses, thyroid hormones, immune function, and antioxidant capacity of sea otters (Enhydra lutris).

Lactation is the most energetically demanding stage of reproduction in female mammals. Increased energetic allocation toward current reproduction may result in fitness costs, although the mechanisms underlying these trade‐offs are not well understood. Trade‐offs during lactation may include reduced energetic allocation to cellular maintenance, immune response, and survival and may be influenced by resource limitation. As the smallest marine mammal, sea otters (Enhydra lutris) have the highest mass‐specific metabolic rate necessitating substantial energetic requirements for survival. To provide the increased energy needed for lactation, female sea otters significantly increase foraging effort, especially during late‐lactation. Caloric insufficiency during lactation is reflected in the high numbers of maternal deaths due to End‐Lactation Syndrome in the California subpopulation. We investigated the effects of lactation and resource limitation on maternal stress responses, metabolic regulation, immune function, and antioxidant capacity in two subspecies of wild sea otters (northern: E. l. nereis and southern: E. l. kenyoni) within the California, Washington, and Alaska subpopulations. Lactation and resource limitation were associated with reduced glucocorticoid responses to acute capture stress. Corticosterone release was lower in lactating otters. Cortisol release was lower under resource limitation and suppression during lactation was only evident under resource limitation. Lactation and resource limitation were associated with alterations in thyroid hormones. Immune responses and total antioxidant capacity were not reduced by lactation or resource limitation. Southern sea otters exhibited higher concentrations of antioxidants, immunoglobulins, and thyroid hormones than northern sea otters. These data provide evidence for allocation trade‐offs during reproduction and in response to nutrient limitation but suggest self‐maintenance of immune function and antioxidant defenses despite energetic constraints. Income‐breeding strategists may be especially vulnerable to the consequences of stress and modulation of thyroid function when food resources are insufficient to support successful reproduction and may come at a cost to survival, and thereby influence population trends.

Do differences in skull morphology and bite performance explain dietary specialization in sea otters?

Intraspecific studies of morphology and performance are essential for understanding the factors that enable resource partitioning within ecological communities. The sea otter (Enhydra lutris) is one of the few mammal species in which individual-level dietary specialization has been documented, making them an ideal system to investigate the morphological basis of food resource partitioning. Here, we test if differences in food resource use within and between sea otter subspecies can be explained by differences in ecologically relevant metrics of bite performance that are mainly the product of variation in size, cranial morphology, or a combination of these traits. We use geometric morphometrics to evaluate variation in cranium size and morphology, and 2-dimensional models to estimate bite performance differences between 2 sea otter subspecies that differ in dietary ecology: the northern sea otter (Enhydra lutris kenyoni, a facultative generalist) and the southern sea otter (E. l. nereis, a specialist). We found significant differences in cranium shape and size between subspecies and between male and female sea otters. These differences were subtle yet consistent with most subspecies classifications and known sexually dimorphic traits. Cranial morphological differences did not translate into differences in estimated bite force between subspecies or sexes, but dentary strength differed significantly between male and female sea otters. Sea otters have short, blunt crania with pronounced sagittal and lambdoidal crests, and strong mandibles. These traits combine to produce high bite forces for their size. We propose that high bite performance capacity in sea otters enables resource-use variation by widening the diversity of available food resources they can procure from their environment; this allows them to behave as either generalists or specialists within different habitats.

The flehmen response and pseudosuckling in a captive, juvenile Southern sea otter (Enhydra lutris nereis).

A juvenile, female sea otter (Enhydra lutris nereis) was observed in 43 instances of the flehmen response over 19 days from May through July of 2015 at the Oregon Zoo. In all flehmen grimace observations, the juvenile sea otter engaged in nibbling, nosing, or licking the peri-mammary or anogenital areas of a non-lactating, geriatric female sea otter. The flehmen behavior observed was consisted with the sequences of behavior documented in other mammals, lifting the head, elevating the nose to the air, retracting the upper lip slightly, and manipulating her mystacial vibrissae back and forth while rapidly inspiring air through her mouth in quick succession, tongue extruded. The occurrence of this behavior was not specific to visitor density, visitor impact rating, day of the month, time of day, or exhibit zone. However, it did occur more frequently in one area of the enclosure. Among the three sea otters (two females, one male) currently housed at the Oregon Zoo, the juvenile female's flehmen response only occurred following interactions with the older female and was always preceded by the pseudosuckling or anogenital nosing, licking or nibbling behavior. Zoo Biol. 36:30-39, 2017. © 2017 Wiley Periodicals, Inc.

Sexual dimorphism in craniomandibular morphology of southern sea otters (Enhydra lutris nereis)

The niche divergence hypothesis suggests that if a species exhibits intersexual differences in diet, selection should favor divergence in the feeding apparatus between the sexes. Recent work revealed that male and female southern sea otters ( Enhydra lutris nereis ) utilize different dietary resources in response to increased population density; females exhibit more specialized diets as a function of smaller home ranges, whereas males exhibit larger home ranges, potentially allowing them to expand their dietary breadths by feeding on prey items that are not found in female home ranges. These dietary differences suggest the potential for sexual dimorphism of the feeding apparatus (i.e., the skull). Here, we tested the hypothesis that male and female southern sea otters exhibit differences in craniomandibular traits directly related to biting ability. Univariate and multivariate analyses of 12 craniomandibular traits showed that size is the primary axis of skull variation, whereas only a handful of craniomandibular traits demonstrated significant shape differences between the sexes. Relative postorbital constriction breadth, masseter in-lever length, and cranial height differed significantly between the sexes. These 3 traits can increase the surface area of jaw muscle attachment sites and thus are directly linked to the mechanics of biting ability. Collectively, these morphological differences indicate that niche divergence may be an important mechanism maintaining sexual dimorphism in southern sea otters.

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 investigated. To test the hypothesis that scaling patterns of bite force, a metric of feeding performance, differ between the sexes, we calculated theoretical bite forces for 55 naturally deceased male and female southern sea otters spanning the size ranges encountered over ontogeny. We then used standardized major axis regressions to simultaneously determine the scaling patterns of theoretical bite forces and skull components across ontogeny and assess whether these scaling patterns differed between the sexes. We found that positive allometric increases in theoretical bite force resulted from positive allometric increases in physiological cross-sectional area for the major jaw adductor muscle and mechanical advantage. Closer examination revealed that allometric increases in temporalis muscle mass and relative allometric decreases in out-lever lengths are driving these patterns. In our analysis of sexual dimorphism, we found that scaling patterns of theoretical bite force and morphological traits do not differ between the sexes. However, adult sea otters differed in their absolute bite forces, revealing that adult males exhibited greater bite forces as a result of their larger sizes. We found intersexual differences in biting ability that provide some support for the niche divergence hypothesis. Continued work in this field may link intersexual differences in feeding functional morphology with foraging ecology to show how niche divergence has the potential to reinforce sexual dimorphism in southern sea otters.

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. Concurrently, measurements were made on a non-breeding control female. Our results suggest that RMR declines during gestation. Conversely, RMR increases during lactation, reaches a peak at 3-4 months postpartum, and remains elevated until weaning. Combining these direct measurements with published data, we found the cost of pup rearing to be significantly higher than previously estimated. High baseline energy demands and limited energy reserves, combined with significant lactation and pup rearing costs, appear to necessitate metabolic and thermal lability during key reproductive stages.

Development of an altricial mammal at sea: II. Energy budgets of female sea otters and their pups in Simpson Bay, Alaska

Lactation is a critical and energetically expensive period of reproduction, especially for female sea otters (Enhydra lutris) and their pups, both of which have resting metabolic rates that are ca. 2.5-fold higher than terrestrial mammals of similar size. The simultaneous energy budgets for female Alaskan sea otters and their pups during the first three months postpartum were calculated based on published activity budgets for wild animals and metabolic rates for specific behaviors of captive sea otters. Pups were classified into three behavioral/size categories: Category 1 (C1) 0–<4wk. old; Category 2 (C2) 4–<8wk. old; and Category 3 (C3) 8–12wk. Energy for growth (Energygrowth) averaged 0.0416MJday−1 for all pups. The combined daily energy expenditure to support resting metabolism and activity (Energyr+a) for C1 and C2 pups was 1.31 and 2.61MJday−1, respectively, of which most (C1: 99%; C2: 84%) was associated with resting-equivalent behaviors (i.e., resting, nursing and being groomed by the female). Energyr+a for C3 pups was 4.62MJday−1 of which 49% was associated with resting-equivalent behaviors, while 35% was associated with active behaviors (i.e., feeding, swimming and grooming). The underlying resting metabolic rate for all behaviors represented 100% of Energyingest for C1, 94% for C2 and 85% for C3 pups. Energyr+a for all females was similar regardless of pup age and averaged 10.88MJday−1 (range 10.79–11.03). Energyr+a for C1 females was associated mainly with self-grooming and pup grooming (30%) and swimming (25%), while only 10% was associated with feeding. Energyr+a for C3 females was mainly associated with feeding (37%) with less energy devoted to swimming (10%) and grooming (14%). Lactation energy (Energylactation) in C3 females was 3.5-fold greater than in C1 females. Ingested energy for C1 females was 19.55MJday−1, which increased to 22.13MJday−1 for C2 females and 26.53MJday−1 for C3 females. As with pups, the underlying resting metabolic rate for all female behaviors represented 70% of Energyingest for C1 females and 72% for C2 and C3 females. Hence, thermogenesis dominated the metabolism of female sea otters as with their pups. These results provide a quantitative picture of the energetics of Alaskan female sea otters and their pups during early pup rearing in a species that has one of the highest mass specific resting metabolic rates of any mammal and the most altricial neonate born at sea.

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 attributable to a concurrent, independent disease process in females dying during late pup care or postweaning. We compiled detailed data for 108 adult female southern sea otters ( Enhydra lutris nereis) examined postmortem that stranded in California, US, 2005-12, and assessed pathology, reproductive status, and the location and timing of stranding. We introduce simple, grossly apparent, standardized physical criteria to assess reproductive stage for female sea otters. We also describe ELS, examine associated risk factors, and highlight female life history strategies that likely optimize reproduction and survival. Our data suggest that females can reset both the timing and energetic demands of reproduction through fetal loss, pup abandonment, or early weaning as part of specific physiologic checkpoints during each reproductive cycle. Females appear to preload nutritionally during delayed implantation and gestation to increase fitness and reproductive success. We found that ELS was a major cause of death, affecting 56% of enrolled adult females. Peak ELS prevalence occurred in late spring, possibly reflecting the population trend toward fall/winter pupping. Increasing age and number of pregnancies were associated with a higher risk of ELS. Although the proportion of ELS females was highest in areas with dense sea otter populations, cases were recovered throughout the range, suggesting that death from ELS is associated with, but not solely caused by, population resource limitation.

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 biochemical properties. We found that the sea otter TMJ disks are, in general, similar to other carnivores. Macroscopically, the TMJ disk was highly congruent, and the mandibular head was encased tightly by the mandibular fossa with a thin disk separating the joint into two compartments. Histologically, the articular surfaces were lined with dense fibrous connective tissue that gradually transitioned into one to two cell thick layer of hyaline-like cartilage. The disk fibers were aligned primarily in the rostrocaudal direction and had occasional lacuna with chondrocyte-like cells. The disk was composed primarily of collagen type 1. Biochemical analysis indicates sulfated glycosaminoglycan content lower than other mammals, but significantly higher in male sea otters than female sea otters. Finally, mechanical analysis demonstrated a disk that was not only stronger and stiffer in the rostrocaudal direction than the mediolateral direction but also significantly stronger and stiffer in females than males. We conclude that the congruent design of the TMJ, thin disk, biochemical content, and mechanical properties all reflect a structure–function relationship within the TMJ disk that is likely designed for the sea otter’s hard diet and continuous food intake.

Development of an altricial mammal at sea: I. Activity budgets of female sea otters and their pups in Simpson Bay, Alaska

Parental care is necessary for the survival of most mammalian offspring. However, this is especially true for neonatal sea otters (Enhydra lutris), which are the most altricial of marine mammals born at sea. The female not only feeds the pup but also protects it from environmental and predatory threats while maintaining the insulating properties of its fur for thermoregulation. We studied the behavior of female sea otters and their pups during the first three months postpartum in Simpson Bay, Alaska. Six behaviors for females and seven behaviors for pups were recorded to produce 24-h activity budgets. Pups were classified into three behavioral/size categories: Category 1 (C1) 0 – <4 wks old; Category 2 (C2) 4 – <8 wks old; Category 3 (C3) 8–12 wks. The percentage of time females spent feeding increased from 9% (C1) to 32% (C3) reflecting the increased nutritional requirements of the maturing pups. C1 females spent 21% of their time swimming in a meandering manner, possibly to protect young pups from predation, which decreased to 8% for females with C3 pups. The time spent resting by females (ca. 50%) was independent of pup category. C1 pups spent 83% of their day resting which decreased to 48% for C3 pups. Time spent nursing remained constant (ca. 8%) for all pup categories, but feeding on solid food provided mainly by the female increased to 17% (C3 pups). The percentage of time that pups spent swimming increased to 17% (C3 pups) as they developed strength and coordination. Our results provide a quantitative picture of the changes in female and pup behavior and activity patterns during the early and critical developmental stages of altricial pups at sea.

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(13)C) and nitrogen (δ(15)N)isotope analysis of sea otter vibrissae with long-term observational studies of five subpopulations in California. We define individual diet specialization as low ratios of within-individual variation (WIC) to total population niche width (TNW). We compare isotopic and observational based metrics of WIC/TNW for males and females to data on population densities, and movement patterns using both general linear and linear mixed-effects models. Consistent with our hypothesis, increasing population density is associated with increased individual diet specialization by females but not by males. Additionally, we find the amount of coastline in a sea otter's home range positively related with individual dietary variability, with increased range span resulting in weaker specialization for both males and females. We attribute our results to sex-based differences in movement, with females needing to specialize in their small ranges to maximize energy gain, and posit that the paradigm of individual prey specialization in sea otters with increased intraspecific competition may be a pattern driven largely by females. Our work highlights a potentially broader role of sex in the mechanistic pressures promoting and maintaining dietspecialization.

Time and energy allocation of female sea otters (Enhydra lutris) with pups in Alaska

The behavior of sea otters (Enhydra lutris kenyoni) with dependent pups was observed between May and August of 2005–2010 in Simpson Bay, Alaska using focal follows and instantaneous sampling. Six behaviors (foraging, grooming, resting, swimming, swimming slowly and interacting) were recorded during four, 6-h time periods (dawn [05:00–11:00], day [11:00–17:00], dusk [17:00–23:00] and night [23:00–05:00]) to create a 24-h activity budget. Overall, 1190 focal follows were conducted for a total of 595h. Females with dependent pups spent the greatest percentage of the day resting (42%), about equal percentages foraging (18%), grooming (15%), swimming (15%), swimming slowly (8%) and interacting (2%). Field Metabolic Rate (FMR) was estimated by using the oxygen consumption (mlO2min−1kg−1) for each behavior for captive otters (Yeates et al., 2007). The estimated FMR for females with a dependent pup was 12.69MJday−1 with the following absolute and percentage allocations for each behavior: foraging 2.38 (19%), grooming 2.70 (21%), resting 3.42 (27%), swimming 2.64 (21%), swimming slowly 1.25 (10%) and interacting 0.3 (2%). The estimated weight specific FMR was 601kJday−1kg−1, similar to that reported for territorial males in the same area. The sea otter population in Simpson Bay has been stable for at least the last 12years. It would follow then that the time spent foraging might be similar to other areas where the population is stable, but this is not the case. In Simpson Bay, the time spent foraging is more similar to areas that have been recently occupied. The relatively small amount of time spent foraging may indicate that geographic differences (structure of the near-shore community: substrate, water depth, kelp canopy, prey assemblage, and competitors) may play a greater role in determining the amount of time spent foraging than population status.

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 wild. Here, we quantified the energetic demands of immature sea otters across five developmental stages as a means of assessing the underlying energetic challenges associated with pup rearing that may contribute to poor maternal condition. Activity-specific metabolic rates, daily activity budgets and field metabolic rates (FMR) were determined for each developmental stage. Mean FMR of pre-molt pups was 2.29 ± 0.81 MJ day(-1) and increased to 6.16 ± 2.46 and 7.41 ± 3.17 MJ day(-1) in post-molt pups and dependent immature animals, respectively. Consequently, daily energy demands of adult females increase 17% by 3 weeks postpartum and continue increasing to 96% above pre-pregnancy levels by the average age of weaning. Our results suggest that the energetics of pup rearing superimposed on small body size, marine living and limited on-board energetic reserves conspire to make female sea otters exceptionally vulnerable to energetic shortfalls. By controlling individual fitness, maternal behavior and pup provisioning strategies, this underlying metabolic challenge appears to be a major factor influencing current population trends in southern sea otters (Enhydra lutris nereis).

Motherhood is no picnic for sea otter mums

Sea otters have voracious appetites, and for good reason. As the smallest marine mammals, they face unprecedented metabolic challenges just to stay warm, consuming a quarter of their own body mass each day. And there are times when the metabolic demands of sea otter females rocket even further. Nicole Thometz, from the University of California at Santa Cruz, USA, explains that in addition to the extra cost of lactation, the mums must also expend additional energy while foraging to sustain themselves and their dependents. However, no one knew the true magnitude of the metabolic burden placed on sea otter mothers: ‘neither the energetic demands of immature sea otters nor the cost of lactation for adult females have been quantified’, says Thometz. Fortunately, Thometz and her colleagues had access to the world's most successful sea otter pup rehabilitation program at the Monterey Bay Aquarium in California, where they could measure the metabolic rates of wild sea otter pups while they grew, prior to their return to the ocean, to begin to find out how much of a burden motherhood is for sea otter females (p. 2053).Measuring the metabolic rates of sea otter youngsters (ranging from tiny pre-moult pups to juveniles) as they participated in a range of activities from resting to swimming and foraging, the team discovered that their daily metabolic demands rose from 2.29 MJ day−1 during the first few weeks after birth to 7.41 MJ day−1 when the youngsters were about to begin foraging for themselves; even when the animals were beginning to fend for themselves they continued returning to mum to supplement their diet. It is only after weaning at 6 months that the mothers are truly free of their obligation.Tallying up the metabolic data, the team calculated that to supply a pup with a staggering total of 930 MJ of energy through to independence, the female's daily metabolic rate has to escalate by an extraordinary 96%. And when the team converted this colossal energy expenditure into the amount of energy reserves that a sea otter female would use if unable to increase foraging, they realised that she would consume almost 133% of her own body mass. The only way that sea otters have to make up this gigantic metabolic shortfall is to increase foraging at a time when they are already running near their metabolic limits, stretching an even tighter energy budget still further.The team suspects that this extreme exertion could account for the poor condition of many sea otter mums and their relatively high mortality rates at the end of lactation. It could also account for the relatively high numbers of abandoned pups. Thometz says, ‘Female sea otters are thought to utilize a “bet-hedging” strategy, either keeping or abandoning a pup post-partum [after birth] depending upon physiological factors.’ She explains that females that are in poor condition and unlikely to be able to provide for their young are more likely to abandon their pups after birth to give themselves a better chance of successfully raising a pup during the following breeding attempt. ‘The optimal decision may be to “cut losses”’, says Thometz. And she adds that sea otter mothers may also choose to wean their young sooner to preserve their health, rather than risk their own survival and subsequent breeding attempts by investing too heavily in the present pup, although this strategy places youngsters that were weaned early at a greater risk of mortality after independence.

Primary Cerebral T-Cell Lymphoma in a Sea Otter (&lt;i&gt;Enhydra lutris&lt;/i&gt;)

ABSTRACTA 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-cells was found in other organs. Taken together, we diagnosed this case as a primary cerebral T-cell lymphoma. To our knowledge, this is the first case of primary cerebral T-cell lymphoma in a sea otter.

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 mass with rubbery texture was firmly attached to the left maxillary region of the skull and the nasopharynx was occluded by soft neoplastic tissue. Post-mortem skull radiographs showed an oval, smoothly marginated mineralized opaque mass centered on the left maxilla, extending from the canine tooth to caudal to the molar and replacing portions of the zygomatic arch and palatine and temporal bones. The majority of the mass protruded laterally from the maxilla and was characterized by central homogeneous mineral opacity. Microscopically, the mass was characterized by fully differentiated lamellar non-osteonal bone that expanded beyond the margins of the adjacent normal osteonal bone. Sections of the nasopharyngeal mass were comprised of moderately pleomorphic cells with bony stroma. Gross, microscopical and radiological findings were compatible with maxillary osteosarcoma with concurrent osteoma.

Long-term effects of the ‘Exxon Valdez’ oil spill: sea otter foraging in the intertidal as a pathway of exposure to lingering oil

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 447:273-287 (2012) - DOI: https://doi.org/10.3354/meps09523 Long-term effects of the ‘Exxon Valdez’ oil spill: sea otter foraging in the intertidal as a pathway of exposure to lingering oil James L. Bodkin1,*, Brenda E. Ballachey1, Heather A. Coletti3, George G. Esslinger1, Kimberly A. Kloecker1, Stanley D. Rice2, John A. Reed1, Daniel H. Monson1 1US Geological Survey, Alaska Science Center, 4210 University Drive, Anchorage, Alaska 99508, USA2Auke Bay Laboratory, National Marine Fisheries Service, Juneau, Alaska 99801, USA 3Present address: SW Alaska Network, National Park Service, Anchorage, Alaska 99501, USA *Email: jbodkin@usgs.gov ABSTRACT: 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 sediments, 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 de­layed 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 16050 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 summer 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 oiling, with total PAH concentrations up to 56000 ng g−1 dry weight. Our estimates of intertidal foraging, 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. KEY WORDS: Sea otter · ‘Exxon Valdez’ · Oil spill · Enhydra lutris · Time-depth recorder · TDR Full text in pdf format See Comment and Reply Comment on this article PreviousNextCite this article as: Bodkin JL, Ballachey BE, Coletti HA, Esslinger GG and others (2012) Long-term effects of the ‘Exxon Valdez’ oil spill: sea otter foraging in the intertidal as a pathway of exposure to lingering oil. Mar Ecol Prog Ser 447:273-287. https://doi.org/10.3354/meps09523 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 447. Online publication date: February 13, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.

Lesions and Behavior Associated with Forced Copulation of Juvenile Pacific Harbor Seals (&lt;I&gt;Phoca vitulina richardsi&lt;/I&gt;) by Southern Sea Otters (&lt;I&gt;Enhydra lutris nereis&lt;/I&gt;)

Nineteen occurrences of interspecific sexual behavior between male southern sea otters (Enhydra lutris nereis) and juvenile Pacific harbor seals (Phoca vitulina richardsi) were reported in Monterey Bay, California, between 2000 and 2002. At least three different male sea otters were observed harassing, dragging, guarding, and copulating with harbor seals for up to 7 d postmortem. Carcasses of 15 juvenile harbor seals were recovered, and seven were necropsied in detail by a veterinary pathologist. Necropsy findings from two female sea otters that were recovered dead from male sea otters exhibiting similar behavior are also presented to facilitate a comparison of lesions. The most frequent lesions included superficial skin lacerations; hemorrhage around the nose, eyes, flippers, and perineum; and traumatic corneal erosions or ulcers. The harbor seals sustained severe genital trauma, ranging from vaginal perforation to vagino-cervical transection, and colorectal perforations as a result of penile penetration. One harbor seal developed severe pneumoperitoneum subsequent to vaginal perforation, which was also observed in both female sea otters and has been reported as a postcoital lesion in humans. This study represents the first description of lesions resulting from forced copulation of harbor seals by sea otters and is also the first report of pneumoperitoneum secondary to forced copulation in a nonhuman animal. Possible explanations for this behavior are discussed in the context of sea otter biology and population demographics.