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Adult male and female northern fur seals (Callorhinus ursinus) are sexually segregated in different regions of the North Pacific Ocean and Bering Sea during their winter migration. Explanations for this involve interplay between physiology, predator-prey dynamics, and ecosystem characteristics, however possible mechanisms lack empirical support. To investigate factors influencing the winter ecology of both sexes, we deployed five satellite-linked conductivity, temperature, and depth data loggers on adult males, and six satellite-linked depth data loggers and four satellite transmitters on adult females from St. Paul Island (Bering Sea, Alaska, USA) in October 2009. Males and females migrated to different regions of the North Pacific Ocean: males wintered in the Bering Sea and northern North Pacific Ocean, while females migrated to the Gulf of Alaska and California Current. Horizontal and vertical movement behaviors of both sexes were influenced by wind speed, season, light (sun and moon), and the ecosystem they occupied, although the expression of the behaviors differed between sexes. Male dive depths were aligned with the depth of the mixed layer during daylight periods and we suspect this was the case for females upon their arrival to the California Current. We suggest that females, because of their smaller size and physiological limitations, must avoid severe winters typical of the northern North Pacific Ocean and Bering Sea and migrate long distances to areas of more benign environmental conditions and where prey is shallower and more accessible. In contrast, males can better tolerate often extreme winter ocean conditions and exploit prey at depth because of their greater size and physiological capabilities. We believe these contrasting winter behaviors 1) are a consequence of evolutionary selection for large size in males, important to the acquisition and defense of territories against rivals during the breeding season, and 2) ease environmental/physiological constraints imposed on smaller females.

IntroductionDomoic acid (DA) is a glutaminergic excitatory neurotoxin that causes the morbidity and mortality of California sea lions (Zalophus californianus; CSL) and other marine mammals due to a suite of effects mostly on the nervous and cardiac systems. Between 1998 and 2019, 11,737 live-stranded CSL were admitted to The Marine Mammal Center (TMMC; Sausalito, CA, USA), over 2,000 of which were intoxicated by DA. A plethora of clinical research has been performed over the past 20 years to characterize the range of toxic effects of DA exposure on CSLs, generating the largest dataset on the effects of natural exposure to this toxin in wildlife.Materials and methodsIn this study, we review published methods for diagnosing DA intoxication, clinical presentation, and treatment of DA-intoxicated CSL and present a practical, reproducible scoring system called the neuroscore (NS) to help assess whether a DA-affected CSL is fit for release to the wild following rehabilitation. Logistic regression models were used to assess the relationships between outcome (released vs. euthanized or died) and multiple variables to predict the outcome for a subset of 92 stranded CSLs.ResultsThe largest proportion of DA-intoxicated CSLs was adult females (58.6%). The proportions of acute and chronic cases were 63.5 and 36.5% respectively, with 44% of affected CSL released and 56% either dying naturally or euthanized. The average time in rehabilitation was 15.9 days (range 0–169) for all outcomes. The best-performing model (85% accuracy; area under the curve = 0.90) assessing the relationship between outcome and predictor variables consisted of four variables: final NS, change in NS over time, whether the animal began eating in rehabilitation, and the state of nutrition on admission.DiscussionOur results provide longitudinal information on the symptomatology of CSL intoxicated by domoic acid and suggest that a behavioral scoring system is a useful tool to assess the fitness for the release of DA-intoxicated CSL.

Point of care (POC) hematology testing can be valuable in triage and field settings. We assessed the accuracy between the HemoCue® WBC system and two comparative analyzers, as well as the precision of the HemoCue® WBC system in five different pinniped species: Zalophus californianus, Arctocephalus townsendi, Callorhinus urcinus, Phoca vitulina, and Mirounga angustirostris for white blood cell (WBC) quantification. In Zalophus (n = 164; 106 from U.S. Navy Marine Mammal Program (Navy); 58 from The Marine Mammal Center (TMMC)), the HemoCue® was compared to two hematology analyzers, Sysmex Xe-5000 and Vet ABC Plus. In Phoca (n = 50; TMMC), Callorhinus (n = 29; TMMC), Arctocephalus (n = 17; TMMC), and Mirounga (n = 67; TMMC), the HemoCue® was compared to Vet ABC Plus only. Bland–Altman and Passing–Bablok agreement of HemoCue® with Sysmex Xe-5000 and Vet ABC Plus analyzers were good for Zalophus, Arctocephalus, Phoca, and Mirounga but marginal with Callorhinus; bias = 0.56 × 109/L (Zalophus; Navy), −2.13 × 109/L (Zalophus; TMMC), −1.59 × 109/L (Arctocephalus), −2.48 × 109/L 0.917 (Phoca), −0.01 × 109/L (Mirounga), and −6.05 × 109/L (Callorhinus). The coefficient of variation from triplicate runs of samples were within acceptable limits for all species (2.50% ± 1.63 (Zalophus; TMMC), 3.09% ± 2.14 (Arctocephalus), 2.47% ± 1.35 (Callorhinus), 2.88% ± 1.75 (Phoca), and 3.44% ± 2.53 (Mirounga)), respectively. The presence of nucleated red blood cells (nRBC; 1–37 nRBC/100 WBC) did not significantly interfere with WBC counts in Zalophus, Callorhinus, and Phoca at the population level, but their presence should be evaluated at the individual level. The HemoCue® provides an accurate method for WBC quantification with WBC counts up to 30 × 109/L (upper limit of linearity of the analyzer) in Zalophus, Arctocephalus, Phoca, and Mirounga, but is less accurate in Callorhinus, and showed good precision in all species.

Published literature is sparse on topics associated with eared seal (otariid) dentistry. The objective of this study was to establish consensus on effective management of dental disease in otariids, using a Delphi approach. A total of 25 veterinarians with experience managing dental disease in seven species of otariids participated in the Delphi process. Oral lesions and their contributing risk factors were ranked according to perceived frequency. Consensus statements for best practices were agreed upon for a variety of topics within the categories of planning and preparation, procedural details, intervention strategies, and postoperative care. Panelist comments were collated into a Supplementary File to assist clinicians in forming their own conclusions on topics for which no consensus yet exists. Opportunities for future research include factors associated with oral lesions, ideal anesthetic management, identification of ideal candidates for endodontic therapies, ideal local and regional anesthesia, ideal suture and closure techniques, particularly with the goal of reducing dehiscence as a postoperative complication, and ideal postoperative care options.

Despite rapid advances in sensor development and technological miniaturization, it remains challenging to non-invasively record small-amplitude electrophysiological signals from an animal in its natural environment. Many advances in ecophysiology and biologging have arisen through sleep studies, which rely on detecting small signals over multiple days and minimal disruption of natural animal behavior. This paper describes the development of a surface-mounted system that has allowed novel electrophysiological recordings of sleep in wild marine mammals. We discuss our iterative design process by providing sensor-comparison data, detailed technical illustrations, and material recommendations. We describe the system’s performance over multiple days in 12 freely moving northern elephant seals ( Mirounga angustirostris ) sleeping on land and in water in captivity and the wild. We leverage advances in signal processing by applying independent components analysis and inertial motion sensor calibrations to maximize signal quality across large (> 10 gigabyte), multi-day datasets. Our study adds to the suite of biologging tools available to scientists seeking to understand the physiology and behavior of wild animals in the context in which they evolved.

Rehabilitation of marine mammals is performed throughout the world, yet the impact of rehabilitation on individuals and populations is questionable given the lack of robust information on the rehabilitation process and post-release monitoring in most cases. The goals of this study were to perform a systematic review of existing literature on marine mammal rehabilitation between 2000–2023 to determine the current state of rehabilitation and to evaluate the rehabilitation and conservation factors that could be used to build a framework to assess the health of rehabilitation programs worldwide. A total of 418 publications encompassing 52 species of marine mammal were included in the systematic review. Rehabilitation efforts focused mostly on pinnipeds, and North America was the most represented region. Data are scarce for both short- and long-term post-release survival across species. Reports about species threatened with extinction were significantly more likely to include information about conservation parameters than those species of least concern. A meta-analysis demonstrated a fairly strong fit of the dimensions of the proposed framework for a rehabilitation health index. Further refinement would strengthen the utility of this tool for both rehabilitation and conservation programs.

The nematode lungworm, (OC), is a significant cause of northern elephant seal (NES; ) mortality at The Marine Mammal Center (TMMC, Sausalito, CA). The current lack of specific antemortem diagnostic tests for pre-patent OC infection in NES makes diagnosis, proper treatment, and assessment of efficacy of medications challenging. Severe inflammation and disseminated intravascular coagulation (DIC) develop rapidly and are difficult to treat once clinical signs develop. Certain blood inflammatory and hemostasis biomarkers for early diagnosis have recently been investigated. The objective of this study was to investigate the diagnostic performance of complete blood count, serum chemistry, acute phase proteins, protein electrophoresis, and coagulation parameters for diagnosis of OC clinical infection in NES. Samples from NES with OC infection confirmed by gross pathology with blood collected antemortem during clinical disease ( = 9) and NES initially admitted for malnutrition and sampled shortly before release after successful rehabilitation ( = 20) were included in the study. Using Receiver operator characteristic (ROC) curve analysis, the diagnostic performances (area under the curve [AUC]) of albumin (0.994), albumin:globulin ratio (0.983), serum amyloid A (0.972), activated partial thromboplastin time (0.936), total bilirubin (0.975), and gamma-glutamyl transferase (0.939) were high (AUC > 0.9). These results confirm systemic inflammation and DIC, and support previously reported clinical and gross pathological findings in NES infected with OC. In addition to AUC values, this study produced cut-off points, sensitivity, specificity, confidence intervals, and predictive values for analytes with high diagnostic performance. This data will be useful in the diagnosis and clinical management of OC-infected NES and will aid in assessment of treatment efficacy.

This study establishes a relationship between positive canine heartworm (Dirofilaria immitis) test results frequently observed in California sea lions (Zalophus californianus) and infection with the filarid nematode Acanthocheilonema odendhali. Four commercially available canine heartworm antigen tests were evaluated for cross-reaction with A. odendhali in California sea lions. Sera were tested from fifteen California sea lions with A. odendhali-associated microfilaremia, confirmed by blood smear, and with no evidence of D. immitis infection at necropsy. Ninety-five percent of tests were falsely positive for D. immitis. This study also determined that the prevalence of A. odendhali infection in stranded California sea lions from central California is approximately 23% by comparing the number of findings of mircofilaremia to the total number of California sea lions sampled at The Marine Mammal Center between 2005 and 2011, inclusive. Acanthocheilonema odenhali microfilaremia in California sea lions is likely to cross-react with canine heartworm antigen tests, and clinicians should interpret results with caution.

Acute-phase proteins (APPs) are utilized to detect early inflammation in many domestic and nondomestic species, but variability exists between species and inflammatory diseases as to which APPs are most useful. Stranded juvenile northern elephant seals (NESs; Mirounga angustirostris) undergoing rehabilitation at the Marine Mammal Center experience high mortality rates due to severe arteritis caused by the lungworm, Otostrongylus circumlitis (OC), and there are currently no effective antemortem diagnostic tools for this disease. To characterize patterns of the acute-phase response in the NES, two APPs—serum amyloid A (SAA) and C-reactive protein (CRP)—were measured, and serum protein electrophoresis was performed to measure albumin and globulin fractions in 81 serum samples from 58 NESs in four different health states: healthy, malnourished, preclinical for OC infection, or clinical for OC infection. Compared to healthy NESs (median, 11.2 mg/L), SAA concentrations were significantly increased in malnourished (33.9 mg/L), preclinical (247 mg/L), and clinical OC–infected NESs (328 mg/L) (P < 0.05). CRP concentrations were increased only in clinical OC–infected NESs (median, 53.9 mg/L) and were below detectable limits in the other three groups (<0.01 mg/L). These results show that SAA and CRP are positive APPs in NESs with OC infection, and that SAA may serve as the major APP for this species. Albumin : globulin ratios were significantly increased in malnourished NESs (median, 1.26) and decreased in clinical OC–infected NESs (0.53). As a result, albumin is a negative APP in the NES, similar to other mammalian species. APP monitoring can be helpful in detecting and monitoring inflammation in rehabilitating juvenile NESs.

Ciprofloxacin is commonly selected for clinical use due to its broad-spectrum efficacy and is a frequently administered antibiotic at The Marine Mammal Center, a marine mammal rehabilitation facility. Ciprofloxacin is used for treatment of California sea lions (Zalophus californianus) suffering from a variety of bacterial infections at doses extrapolated from other mammalian species. However, as oral absorption is variable both within and across species, a more accurate determination of appropriate dosage is needed to ensure effective treatment and avoid emergence of drug-resistant bacterial strains. A pharmacokinetic study was performed to assess plasma concentrations of ciprofloxacin in California sea lions after a single oral dose. Twenty healthy California sea lions received a single 10-mg/kg oral dose of ciprofloxacin administered in a herring fish. Blood was then collected at two of the following times from each individual: 0.5, 0.75, 1, 2, 4, 8, 10, 12, 18, and 24 hr postingestion. Plasma ciprofloxacin concentration was assessed via high-performance liquid chromatography. A population pharmacokinetics model demonstrated that an oral ciprofloxacin dose of 10 mg/kg achieved an area under the concentration vs. time curve of 6.01 μg hr/ml. Absorption was rapid, with ciprofloxacin detectable in plasma 0.54 hr after drug administration; absorption half-life was 0.09 hr. A maximum plasma concentration of 1.21 μg/ml was observed at 1.01 hr, with an elimination half-life of 3.09 hr. Ciprofloxacin administered orally at 10 mg/kg produced therapeutic antibacterial exposure for only some of the most susceptible bacterial organisms commonly isolated from California sea lions.