Search Results (18)

California sea lions (Zalophus californianus) are susceptible to various ocular diseases, with some literature suggesting a heightened risk for those kept in freshwater pools as opposed to saltwater. Given the potential implications of housing conditions on animal health, we wanted to analyze the ocular health of two distinct groups of California sea lions kept at Nuremberg Zoo, one housed in freshwater and the other in saltwater. Data extracted from the animals’ medical records during a ten-year period were used to compare the incidence of eye conditions and other medical conditions observed. The results revealed no significant difference in the overall occurrence of eye diseases between the two environments. However, a distinct seasonal pattern was noted: California sea lions kept in freshwater exhibited a peak in eye disorders during the summer months, while those in saltwater displayed a more uniform distribution of the occurrence of ocular diseases throughout the year. These findings suggest that sun exposure and water quality are potentially more influential factors in the development of ocular diseases in pinnipeds than salinity. Further studies are necessary to elucidate the underlying mechanisms and optimize care practices for these marine mammals. Full article

California sea lion (CSL, Zalophus californianus) abundance has declined in different localities across this species’ Mexican distribution. However, Los Islotes rookery in the southwestern Gulf of California (GoC) deviates from this pattern. It is vital to gather ecological knowledge of this CSL settlement and its surroundings to better understand its population in the GoC. This study aimed to determine the foraging habits of different CSL sex and age classes. Sixty-five CSL samples were collected in Los Islotes and its surroundings for stable isotope analysis (δ¹³C and δ¹⁵N). The data were analyzed using a hierarchical Bayesian model, and isotopic areas were estimated using the SIBER package in R. Our findings evidenced resource partitioning. Adult females had lower δ¹⁵N values than most classes, reflecting the regional ¹⁵N-enrichment of the GoC. Conversely, subadult males showed low δ¹⁵N values, carrying foraging information from the ¹⁵N-depleted Pacific Ocean into the GoC. Adult males presented the highest δ¹⁵N values (after pups), suggesting a higher trophic position than adult females and values corresponding to the GoC. Moreover, juveniles had the most negative δ¹³C values and the largest isotopic areas, indicating offshore foraging habits and a mixed consumption of maternal milk and their first prey. Pups showed the highest mean δ¹⁵N value due to maternal milk consumption, reflecting the mother’s δ¹⁵N value and their enrichment. Our findings suggest that segregation is explained by unique life history traits and a possible strategy to avoid potential competition Full article

Biotoxins produced by harmful algal blooms (HABs) are a substantial global threat to ocean and human health. Domoic acid (DA) is one such biotoxin whose negative impacts are forecasted to increase with climate change and coastal development. This manuscript serves as a review of DA toxicosis after environmental exposure in humans and wildlife, including an introduction to HAB toxins, the history of DA toxicosis, DA production, toxicokinetic properties of DA, susceptibility, clinical signs, DA detection methods and other diagnostic tests, time course of toxicosis, treatment, prognostics, and recommendations for future research. Additionally, we highlight the utility of California sea lions (CSLs; Zalophus californianus) as a model and sentinel of environmental DA exposure. Full article

While researchers have made notable progress in bio-inspired swimming robot development, a persistent challenge lies in creating propulsive gaits tailored to these robotic systems. The California sea lion achieves its robust swimming abilities through a careful coordination of foreflippers and body segments. In this paper, reinforcement learning (RL) was used to develop a novel sea lion foreflipper gait for a bio-robotic swimmer using a numerically modelled computational representation of the robot. This model integration enabled reinforcement learning to develop desired swimming gaits in the challenging underwater domain. The novel RL gait outperformed the characteristic sea lion foreflipper gait in the simulated underwater domain. When applied to the real-world robot, the RL constructed novel gait performed as well as or better than the characteristic sea lion gait in many factors. This work shows the potential for using complimentary bio-robotic and numerical models with reinforcement learning to enable the development of effective gaits and maneuvers for underwater swimming vehicles. Full article

Otariidae are the only marine mammals that use their foreflippers for propulsion, and the combination of hydrofoil and paddle propulsion makes them excellent hunters and swimmers. Therefore, it is of great scientific significance and engineering value to develop a novel underwater propulsion technology inspired by the propulsion mode of Otariidae foreflippers. At present, research on the Otariidae foreflipper-inspired propulsion is still in the initial stage and needs to be explored further in terms of both theory and technology. The bionic underwater robot team led by Prof. Liu of Tianjin University has made some achievements in this regard. Taking the California sea lion as a bionic prototype, they developed the first-generation biomimetic robotic sea lion foreflipper propulsion mechanism (Rob-flipper-I for short). In this study, the Rob-flipper-II is developed through the optimization of the Rob-flipper-I, which is composed of a driving mechanism and a pair of bionic foreflippers. The driving mechanism consists of a wobbling disk mechanism and a spatial linkage mechanism that are connected in series, and the bionic foreflippers have similar flexibility and mechanical properties to those of the sea lion foreflippers. The Rob-flipper-II can reproduce the spatial trajectory and attitude of the sea lion foreflippers by a single drive only. Based on the kinematics analysis of the Rob-flipper-II, the formulas for calculating the thrust and lift of the bionic foreflipper are derived, and the functional relationship between the motion speed of the bionic sea lion robot and the flapping frequency of the bionic foreflippers are obtained. In addition, the propulsive efficiency of the Rob-flipper-II is calculated. The tank experiment shows that the average thrust and propulsive efficiency of the Rob-flipper-II are higher than those of the Rob-flipper-I. Full article

Reproductive success is an important aspect of marine mammals’ population health, as it is an indicator of the trajectory for the population into the future. The aim of this study is to provide additional relevant data on fetus–maternal ultrasonographic monitoring in sea lion species, in order to evaluate possible fetal distress or abnormalities. From 2018 to 2023, serial ultrasonographic scans of two healthy California sea lion females (16 ± 4 years old), kept under human care, were performed over the course of two pregnancies for each female. Animals were monitored from the ovulation to the delivery. Ultrasonography was performed weekly, and, during the last month, daily images were recorded using Logiq Versana Active, General Electric, with a 2–5 MHz curvilinear transducer, and Logiq V2, General Electric, with a 2–5 MHz curvilinear transducer. Right and left lateral recumbencies have been used during the examination. To the author’s knowledge, this is the first study describing in detail the sea lion organogenesis and their correlation with the stage of pregnancy. Full article

Cognitive enrichment is becoming more prevalent in professional marine mammal facilities. Research with dolphins has suggested that such enrichment provides more welfare benefits than enrichment that does not incorporate cognitive challenge. However, there is little research supporting the use of cognitive enrichment as a means to improve the welfare of sea lions. Recently, a novel form of technological cognitive enrichment, the Enclosure Video Enrichment (EVE) system, was introduced to a population of California sea lions at the US Navy’s Marine Mammal Program as a means to enhance welfare. Two of the initial focal animals introduced to EVE were selected based on their health history and the possible benefits of cognitive enrichment in improving health measures. To evaluate this, information regarding the animals’ consumption of their offered diet was compared to other animals in the population of similar age and the absence of a similar health history. Subsequently, the total diet consumption of the targeted animals was evaluated in the two years prior to the introduction to EVE and compared to the total diet consumption during the initial 2 years of regular EVE sessions. There was a significant decrease in the number of days in which the sea lions did not consume their entire offered diet in the two years after implementing regular EVE sessions, an increase in participation and performance of voluntary husbandry behaviors, and a reduction in the number of days animals were clinically ill. This study provides evidence of cognitive enrichment as a management tool to improve animal health and welfare as well as performance in training sessions. Full article

Many wild otariids (sea lions and fur seals) strand along the California coast annually with seizures following presumed exposure to harmful algal blooms (HABs). This is a long-term case study of a stranded subadult male Guadalupe fur seal (Arctocephalus townsendi) that stranded in 2001 and within days after admission began demonstrating seizure activity. The epilepsy was stabilized with antiepileptic drug (AED) therapy and advanced imaging was performed. Magnetic resonance (MR) scans showed signs of encephalopathy consistent with domoic acid (DA) toxicosis. This fur seal was deemed “non-releasable” and over the following 19 years, he received supportive veterinary care and AED treatment at a permitted facility. In the summer of 2020, the fur seal showed progressive behavioral and functional deterioration whereupon humane euthanasia was performed. Post-mortem MR and diffusion tensor images (DTI) were acquired. A volumetric comparison with historic scans showed evidence of severe progressive unilateral right hippocampal atrophy. Histopathology confirmed severe chronic right and mild left hippocampal atrophy. The progressive degenerative brain changes demonstrate how adaptive brain function can be with neuronal atrophy secondary to DA exposure. This case highlights some considerations and decision-making processes needed for the rehabilitation and placement of wild stranded otariids with acquired epilepsy secondary to DA toxicity. Full article

Environmental enrichment devices (EEDs) have been proven to promote positive wellbeing in zoos and aquariums, and support animals’ reintroduction success; however, their use in rehabilitation centers is still limited. This pilot study investigated the safety and efficacy of three EEDs, Artificial Kelp, Horse KONG^™ and Wubba Kong^™, and their ability to decrease and/or eliminate undesired stereotypic behaviors or looking at staff/staff areas in seven wild California sea lions (CSLs) and eight northern elephant seals (NESs) undergoing rehabilitation in Southern California. Observers conducted instantaneous sampling once a minute during a 30-min baseline, followed by a 30-min EED implementation on one focal animal at a time. The data were analyzed with generalized linear mixed models (GLMM). All three EEDs were found to be durable and safe throughout the study. Our results show a significant reduction in stereotypical behaviors compared to no EED treatments in CSLs, with the most significant effect being with the Horse KONG^™. The Wubba KONG™ and Artificial Kelp provisions also reduced the undesired behavior in both species of being focused on human caretakers. Individual preferences for specific EEDs were found within species and between species, with the NESs using EEDs more than the CSLs. This study highlights the beneficial aspect of EEDs for pinnipeds in rehabilitation centers for improving their quality of life. Full article

Cognitive enrichment for professionally managed species has become more prevalent in recent years in both zoological and research settings and has been encouraged as a means of welfare enhancement. However, the task’s difficulty must be specifically tailored as it can impact the successful nature of the sessions, as tasks that are too simple or difficult may not be perceived as enriching by the animals. While pinnipeds are common in zoos, aquariums, and research facilities, few studies have explored the use of cognitively challenging enrichment in this species, and the level of difficulty and presence of failure on animal success and engagement in this type of session has not been assessed. In this study, gameplay strategies during computerized enrichment sessions were evaluated before and after a game that introduced failure, or the loss of opportunity to complete a level for a reward after an incorrect movement. Interest in participation during the session, measured as the latency without contact, was also tested as a proxy for this enrichment’s effect on welfare. When incorrect movements resulted in a short pause and removed the opportunity to finish individual levels for a reward, all three sea lions tested significantly reduced the amount of time spent on each of several strategies they employed, but significantly increased the number of button presses per strategy, suggesting the animals focused on more precise movements as their proficiency improved. Two sea lions also showed a significant decline in latency without contact following the introduction of failure in the form of a single opportunity to complete a task for a reward after previously having unlimited opportunities, while one maintained a low latency without contact across both test conditions. The results suggest that more cognitively challenging tasks incorporating failure did not cause a reduction in gameplay performance and session interest in sea lions. Individual variation was also noted in strategy use, emphasizing the importance of evaluating the individual in terms of enrichment provision. Full article

The marine algal toxin domoic acid is an important threat to marine mammal health, and exposure can lead to both acute neurologic signs and a chronic epileptic syndrome in California sea lions (Zalophus californianus). Phenobarbital has been used for several decades to manage seizures, although reports are limited correlating dosing, serum monitoring and clinical efficacy in this species. This report details serum monitoring over 33 months in an 8-year-old male sea lion. Seizure control was achieved when phenobarbital concentrations were above 18 μg/mL, and sedation and ataxia were noted when concentrations were above 35 μg/mL. There was no clinically significant difference between phenobarbital concentrations resulting from once-daily versus twice-daily dosing. Serum levels remained detectable as far as 101 days after administration, and remained stable during periods of prolonged anorexia, although dramatic decreases in serum concentrations were noted immediately after normal eating resumed. For this animal, a serum phenobarbital target range of 20–30 μg/mL was achievable with a dose of 1.5 mg/kg once daily followed by therapeutic monitoring, and this is a reasonable recommended concentration and initial dose for clinicians treating this species. Long-term seizure control may be difficult to achieve with anti-epileptic drugs such as phenobarbital alone, and further research is needed to make novel options useful for clinical management of biotoxin-related neurologic disease in this aquatic species. Full article

California sea lions are among the most agile of swimming mammals. Most marine mammals swim with their hind appendages—flippers or flukes, depending on the species—whereas sea lions use their foreflippers for propulsion and maneuvering. The sea lion’s propulsive stroke generates thrust by forming a jet between the flippers and the body and by dragging a starting vortex along the suction side of the flipper. Prior experiments using robotic flippers have shown these mechanisms to be possible, but no flow measurements around live sea lions previously existed with which to compare. In this study, the flow structures around swimming sea lions were observed using an adaptation of particle imaging velocimetry. To accommodate the animals, it was necessary to use bubbles as seed particles and sunlight for illumination. Three trained adult California sea lions were guided to swim through an approximately planar sheet of bubbles in a total of 173 repetitions. The captured videos were used to calculate bubble velocities, which were processed to isolate and inspect the flow velocities caused by the swimming sea lion. The methodology will be discussed, and measured flow velocities will be presented. Full article

Urogenital carcinoma in California sea lions (Zalophus californianus) is the most common cancer of marine mammals. Primary tumors occur in the cervix, vagina, penis, or prepuce and aggressively metastasize resulting in death. This cancer has been strongly associated with a sexually transmitted herpesvirus, otarine herpesvirus 1 (OtHV1), but the virus has been detected in genital tracts of sea lions without cancer and a causative link has not been established. To determine if OtHV1 has a role in causing urogenital carcinoma we sequenced the viral genome, quantified viral load from cervical tissue from sea lions with (n = 95) and without (n = 163) urogenital carcinoma, and measured viral mRNA expression using in situ mRNA hybridization (Basescope^®) to quantify and identify the location of OtHV1 mRNA expression. Of the 95 sea lions diagnosed with urogenital carcinoma, 100% were qPCR positive for OtHV1, and 36% of the sea lions with a normal cervix were positive for the virus. The non-cancer OtHV1 positive cases had significantly lower viral loads in their cervix compared to the cervices from sea lions with urogenital carcinoma. The OtHV1 genome had several genes similar to the known oncogenes, and RNA in situ hybridization demonstrated high OtHV1 mRNA expression within the carcinoma lesions but not in normal cervical epithelium. The high viral loads, high mRNA expression of OtHV1 in the cervical tumors, and the presence of suspected OtHV1 oncogenes support the hypothesis that OtHV1 plays a significant role in the development of sea lion urogenital carcinoma. Full article

An emaciated subadult free-ranging California sea lion (Csl or Zalophus californianus) died following stranding with lesions similar to 11 other stranded animals characterized by chronic disseminated granulomatous inflammation with necrotizing steatitis and vasculitis, involving visceral adipose tissues in the thoracic and peritoneal cavities. Histologically, affected tissues had extensive accumulations of macrophages with perivascular lymphocytes, plasma cells, and fewer neutrophils. Using viral metagenomics on a mesenteric lymph node six mammalian viruses were identified consisting of novel parvovirus, polyomavirus, rotavirus, anellovirus, and previously described Csl adenovirus 1 and Csl bocavirus 4. The causal or contributory role of these viruses to the gross and histologic lesions of this sea lion remains to be determined. Full article