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Anthropogenic noise is an increasing threat to marine mammals that rely on sound for communication, navigation, detecting prey and predators, and finding mates. Auditory masking is one consequence of anthropogenic noise, the study of which is approached from multiple disciplines including field investigations of animal behavior, noise characterization from in-situ recordings, computational modeling of communication space, and hearing experiments conducted in the laboratory. This paper focuses on laboratory hearing experiments applying psychophysical methods, with an emphasis on the mechanisms that govern auditory masking. Topics include tone detection in simple, complex, and natural noise; mechanisms for comodulation masking release and other forms of release from masking; the role of temporal resolution in auditory masking; and energetic vs informational masking.

Comparative cognition, as an interdisciplinary field, should utilize a holistic approach for studying cognitive mechanisms. We suggest that research with species of interest should employ both work with animals under human care and in the field. This complimentary approach allows for a better understanding of functional cognitive mechanisms themselves (i.e., comparative cognition regarding processes), and how these skill sets can relate to a particular species' ecological niche. We suggest that research evidence for equivalence classification, learning by exclusion, and long-term memory in pinnipeds can provide a foundation for discussion and implementation of a two-pronged methodological approach utilizing 'lab' and field' work. First, we describe evidence from research with pinnipeds under human care supporting each of these cognitive abilities, then follow this with evidence for implications of these mechanisms from complimentary field research. Lastly, we provide a brief discussion of implementation of a purposeful and two-pronged research approach as an understanding of pinnipeds' high levels of cognitive flexibility may underlie their success for navigating the ever-changing, and often human-altered, natural environment.

Histopathological and immunohistochemical methods were used to diagnose round cell tumors in 2 subantarctic fur seals Arctocephalus tropicalis with marked anemia. Although wild-born, both individuals were placed under human care while juveniles in a Brazilian aquarium. Both pinnipeds were PCR tested for herpesvirus, and 1 was infected with otariid gammaherpesvirus 5 (OtHV-5), previously described in a subantarctic fur seal stranded in Brazil. Although some gammaherpesviruses can cause sarcomas and other neoplasms, it was not possible to definitively associate OtHV-5 with the neoplasm. To our knowledge, these are the first neoplasm records in subantarctic fur seals.

Secondarily aquatic tetrapods have many unique morphologic adaptations for life underwater compared with their terrestrial counterparts. A key innovation during the land‐to‐water transition was feeding. Pinnipeds, a clade of air‐breathing marine carnivorans that include seals, sea lions, and walruses, have evolved multiple strategies for aquatic feeding (e.g., biting, suction feeding). Numerous studies have examined the pinniped skull and dental specializations for underwater feeding. However, data on the pinniped craniofacial musculoskeletal system and its role in aquatic feeding are rare. Therefore, the objectives of this study were to conduct a comparative analysis of pinniped craniofacial musculature and examine the function of the craniofacial musculature in facilitating different aquatic feeding strategies. We performed anatomic dissections of 35 specimens across six pinniped species. We describe 32 pinniped craniofacial muscles—including facial expression, mastication, tongue, hyoid, and soft palate muscles. Pinnipeds broadly conform to mammalian patterns of craniofacial muscle morphology. Pinnipeds also exhibit unique musculoskeletal morphologies—in muscle position, attachments, and size—that likely represent adaptations for different aquatic feeding strategies. Suction feeding specialists (bearded and northern elephant seals) have a significantly larger masseter than biters. Further, northern elephant seals have large and unique tongue and hyoid muscle morphologies compared with other pinniped species. These morphologic changes likely help generate and withstand suction pressures necessary for drawing water and prey into the mouth. In contrast, biting taxa (California sea lions, harbor, ringed, and Weddell seals) do not exhibit consistent craniofacial musculoskeletal adaptations that differentiate them from suction feeders. Generally, we discover that all pinnipeds have well‐developed and robust craniofacial musculature. Pinniped head musculature plays an important role in facilitating different aquatic feeding strategies. Together with behavioral and kinematic studies, our data suggest that pinnipeds’ robust facial morphology allows animals to switch feeding strategies depending on the environmental context—a critical skill in a heterogeneous and rapidly changing underwater habitat., Pinnipeds (seals, sea lions, and walruses) have strong, powerful craniofacial muscles that reflect their aquatic habitat and underwater feeding strategies. Their well‐developed facial expression, mastication, tongue, and hyoid muscles allow pinnipeds to successfully capture prey in dynamic marine ecosystems across the globe.

Brucella ceti has been recovered from a number species of cetaceans worldwide over the last 25 yr. Here we report, for the first time, the recovery of B. ceti from a Risso’s dolphin Grampus griseus and a killer whale Orcinus orca. Recovery from an abdominal mass in the dolphin provides further evidence of the systemic pathogenic potential for B. ceti infection in cetaceans. The isolation of B. ceti ST23 (porpoise cluster) from a killer whale from a group known to eat other marine mammals raises the possibility of infection via ingestion. This report takes the number of cetacean species in UK coastal waters from which B. ceti has been isolated to 11 and highlights the value of routine, comprehensive and specific screening for significant pathogens such as Brucella sp. by strandings networks.

Pinnipedia, an order of semi-aquatic marine mammals, adapted a body design that allows for efficient aquatic locomotion but limited terrestrial locomotion. Otariids, like the California sea lion (Zalophus californianus), have enlarged forelimbs and can bring their hindlimbs under the body to locomote quadrupedally on land, but phocids (true seals) have reduced forelimbs and are unable to bring their hindlimbs beneath them during terrestrial locomotion. Because of these differences, phocids are expected to have greater energetic costs when moving on land compared with otariids. The mechanical costs of transport (COT) and power outputs of terrestrial locomotion were first obtained from one male and two female adult California sea lions through video recording locomotion sequences across a level runway. The center of mass, along with six other anatomical points, were digitized to obtain variables such as velocity (V), amplitude of heave (A) and the frequency (f) of oscillations during the locomotion cycle. These variables represent the principal parameters of a biomechanical model that computes the power output of individuals. The three California sea lions in this study averaged a power output of 112.04 W and a COT of 0.63 J kg−1 m−1. This footage was compared against video footage previously recorded of three phocid species (harbor seal, gray seal and northern elephant seal). Power output and mechanical COT were compared for all four pinniped species by tracking the animals' center of mass. The quadrupedal gait of sea lions showed lower vertical displacements of the center of mass, and higher velocities compared with the terrestrial gait of phocids. Northern elephant seals, gray seals and harbor seals showed significantly higher COT and power outputs than the sea lions. California sea lions locomote with lower energetic costs, and thus higher efficiency compared with phocids, proving that they are a mechanically intermediate species on land between terrestrial mammals and phocids. This study provides novel information on the mechanical energy exerted by pinnipeds, particularly California sea lions, to then be used in future research to better understand the limitations of these aquatic mammals.

In this theme issue, our multidisciplinary contributors highlight the cognitive adaptations of marine mammals. The cognitive processes of this group are highly informative regarding how animals cope with specifics of and changes in the environment, because, not only did modern marine mammals evolve from numerous, non-related terrestrial animals to adapt to an aquatic lifestyle, but some of these species regularly move between two worlds, land and sea. Here, we bring together scientists from different fields and take the reader on a journey that begins with the ways in which modern marine mammals (whales, dolphins, seals, sea lions and manatees) utilize their perceptual systems, next moves into studies of the constraints and power of individuals’ cognitive flexibility, and finally showcases how those systems are deployed in social and communicative contexts. Considering the cognitive processes of the different marine mammals in one issue from varying perspectives will help us understand the strength of cognitive flexibility in changing environments—in marine mammals and beyond.

Concentrations of 15 trace elements (aluminum, arsenic, cadmium, chromium, cobalt, copper, iron, lead, manganese, mercury, nickel, selenium, tin, vanadium, and zinc) were determined in vibrissae (whiskers) and serum of two sympatric pinniped species, the Peruvian fur seal population (PFS; Arctocephalus australis Peruvian subpopulation) and South American sea lion (SASL; Otaria byronia) at Punta San Juan, Peru during 2011-19 sampling events. Element concentrations were 2-20 times higher in vibrissae than in serum. Vibrissae and serum concentrations of several elements, including aluminum, arsenic, and lead, suggest that environmental contaminants may affect the health of pinnipeds at Punta San Juan. Although toxicity thresholds are unknown in pinnipeds, high concentrations of some elements (especially aluminum, arsenic, and lead) may have adverse impacts on their health such as immunosuppression and impaired reproduction. Arsenic was the only element that increased in mean vibrissae concentration throughout the study period. Female SASL vibrissae contained a mean arsenic concentration three times higher than the male SASL vibrissae mean arsenic concentration, and twice as high as the arsenic mean for all PFS vibrissae. The mean male SASL vibrissae cadmium concentration was five times higher than the vibrissae cadmium mean for both PFS males and females and nearly three times higher than the vibrissae cadmium mean for SASL females. Serum concentrations of aluminum, arsenic, copper, and manganese were significantly higher during moderate to extreme El Niño years compared to La Niña years. With stronger and more frequent El Niño-Southern Oscillation events predicted in the future, it is vital to understand how these trace elements may affect pinniped population health.

Marine mammals, regarded as sentinels of aquatic ecosystem health, are exposed to different pathogens and parasites under natural conditions. We surveyed live South American fur seals Arctocephalus australis and South American sea lions Otaria flavescens in Uruguay for Leptospira spp., canine distemper virus (CDV), Mycobacterium spp., Toxoplasma gondii, and Neospora caninum. Samples were collected from 2007 to 2013. The seroprevalence of Leptospira spp. was 37.6% positive, 50.9% negative, and 11.5% suspect for A. australis (n = 61) while for O. flavescens (n = 12) it was 67% positive, 25% negative, and 8% suspect. CDV RNA was not detected in any of the analyzed samples. Most animals tested seropositive to tuberculosis antigens by WiZo ELISA (A. australis: 29/30; O. flavescens: 20/20); reactivity varied with a novel ELISA test (antigens MPB70, MPB83, ESAT6 and MPB59). Seroprevalence against N. caninum and T. gondii was 6.7 and 13.3% positive for O. flavescens and 0 and 2.2% positive for A. australis respectively. To evaluate possible sources of infection for pinnipeds, wild rats Rattus rattus and semi-feral cats Felis catus were also tested for Leptospira spp. and T. gondii respectively. Water samples tested for Leptospira revealed saprofitic L. bioflexa. Pathogenic Leptospira were detected in the kidneys of 2 rats, and cats tested positive for T. gondii (100%). These results represent a substantial contribution to the study of the health status of wild pinnipeds in Uruguay., CSIC (Council for Scientific Research) of the Universidad de la Republica.

Marine mammals have undergone a dramatic series of morphological transformations throughout their evolutionary history that facilitated their ecological transition to life in the water. Pinnipeds are a diverse clade of marine mammals that evolved from terrestrial carnivorans in the Oligocene (∼27 million years ago). However, pinnipeds have secondarily lost the dental innovations emblematic of mammalian and carnivoran feeding, such as a talonid basin or shearing carnassials. Modern pinnipeds do not masticate their prey, but can reduce prey size through chopping behavior. Typically, small prey are swallowed whole. Nevertheless, pinnipeds display a wide breadth of morphology of the post-canine teeth. We investigated the relationship between dental morphology and pinniped feeding by measuring the puncture performance of the cheek-teeth of seven extant pinniped genera. Puncture performance was measured as the maximum force and the maximum energy required to puncture a standardized prey item (Loligo sp.). We report significant differences in the puncture performance values across the seven genera, and identify three distinct categories based on cheek-teeth morphology and puncture performance: effective, ineffective and moderate puncturers. In addition, we measured the overall complexity of the tooth row using two different metrics, orientation patch count rotated (OPCR) and relief index (RFI). Neither metric of complexity predicted puncture performance. Finally, we discuss these results in the broader context of known pinniped feeding strategies and lay the groundwork for subsequent efforts to explore the ecological variation of specific dental morphologies.

Physio-logging methods, which use animal-borne devices to record physiological variables, are entering a new era driven by advances in sensor development. However, existing datasets collected with traditional bio-loggers, such as accelerometers, still contain untapped eco-physiological information. Here, we present a computational method for extracting heart rate from high-resolution accelerometer data using a ballistocardiogram. We validated our method with simultaneous accelerometer–electrocardiogram tag deployments in a controlled setting on a killer whale (Orcinus orca) and demonstrate the predictions correspond with previously observed cardiovascular patterns in a blue whale (Balaenoptera musculus), including the magnitude of apneic bradycardia and increase in heart rate prior to and during ascent. Our ballistocardiogram method may be applied to mine heart rates from previously collected accelerometery data and expand our understanding of comparative cardiovascular physiology.

Allocation of energy to thermoregulation greatly contributes to the metabolic cost of endothermy, especially in extreme ambient conditions. Weddell seal (Leptonychotes weddellii) pups born in Antarctica must survive both on ice and in water, two environments with very different thermal conductivities. This disparity likely requires pups to allocate additional energy toward thermoregulation rather than growth or development of swimming capabilities required for independent foraging. We measured longitudinal changes in resting metabolic rate (RMR) for Weddell seal pups (n=8) in air and water from one to seven weeks of age, using open-flow respirometry. Concurrently, we collected molt, morphometric and dive behavior data. Absolute metabolic rate (MR) in air followed the expected allometric relationship with mass. Absolute MR in water was not allometric with mass, despite a 3-fold increase in mass between one and seven weeks of age. Developmental stage (or molting stage), rather than calendar age, determined when pups were thermally capable of being in the water. We consistently observed post-molt pups had lower RMR in air and water (6.67±1.4 and 7.90±2.38 ml O2 min−1 kg−1, respectively) than pre-molt (air: 9.37±2.42 ml O2 min−1 kg−1, water: 13.40±3.46 ml O2 min−1 kg−1) and molting pups (air: 8.45±2.05 ml O2 min−1 kg−1, water: 10.4±1.63 ml O2 min−1 kg−1). RMR in air and water were equivalent only for post-molt pups. Despite the increased energy cost, molting pups spent three times longer in the water than other pups. These results support the idea of an energetic trade-off during early development; pups expend more energy for thermoregulation in water, yet gain experience needed for independence.

A fundamental question in animal behaviour is the role of vocal communication in the regulation of social interactions in species that organise themselves into social groups. Context dependence and seasonality in vocalizations are present in the communication of many species, although very little research has addressed this dependence in marine mammals. The study presented here examined variations in the rate at which free-ranging dyads of bottlenose dolphins emit social-signals in an effort to better understand the relationship between vocal communication and social context. The results demonstrate that changes in the social-signal production in bottlenose dolphins are related to the sex of the partner, mating season and social affiliation between the components of the dyad. In a context of foraging behaviour on the same feeding ground, mixed (male-female) dyads were found to emit more pulsed burst sounds during the mating season. Another relevant aspect of the study seems to be the greater production of agonistic social-signals in the dyads formed by individuals with a lower degree of social affiliation. Overall, this study confirms a clear relationship between dyad composition and context-specific social-signals that could reflect the motivational state of individuals linked to seasonal changes in vocal behaviour.

BACKGROUND: The last Pinniped species update was in 2010, as part of the list of the terrestrial and marine biota from the Azores. This list includes a chapter dedicated to marine mammals, based on previously published bibliography. NEW INFORMATION: No new species were added since that list was published. However, there were new occurrences since the last update. Funding Institutions: AZORESBIOPORTAL – PORBIOTA (Azores PO 2020 - ACORES-01-0145-FEDER-000072) TOTAL BUDGET: €299,901.83 EU Support: €254, 916.56. This project was financed by FEDER in 85% and by Azorean Public funds by 15% through the Operational Programme Azores 2020. This work is also funded by FEDER funds through the COMPETE 2020 Programme and National Funds through FCT - Portuguese Foundation for Science and Technology under the Research Infrastructure PORBIOTA - Portuguese E-Infrastructure for Information and Research on Biodiversity, project number POCI-01-0145-FEDER-022127. For the period 2022-2023- Portal da Biodiversidade dos Açores (2022-2023) - PO Azores Project - M1.1.A/INFRAEST CIENT/001/2022. Open access will be supported by the project FCT-UIDB/00329/2020-2024 (Thematic Line 1 – integrated ecological assessment of environmental change on biodiversity). info:eu-repo/semantics/publishedVersion

During 1992 and 1993, a bacterial disease occurred in a seawater Atlantic salmonSalmo salarfarm, causing serious mortalities. The causative agent was subsequently named asOceanivirga salmonicida, a member of theLeptotrichiaceae. Searches of 16S rRNA gene sequence databases have shown sequence similarities betweenO. salmonicidaand uncultured bacterial clones from the digestive tracts of marine mammals. In the current study, oral samples were taken from stranded dolphins (common dolphinDelphinus delphis, striped dolphinStenella coeruleoalba) and healthy harbour sealsPhoca vitulina. A bacterium with growth characteristics consistent withO. salmonicidawas isolated from a common dolphin. The isolate was confirmed asO. salmonicida, by comparisons to the type strain, using 16S rRNA gene,gyrB, groEL,andrecAsequence analyses, average nucleotide identity analysis, and MALDI-TOF mass spectrometry. Metagenomic analysis indicated that the genusOceanivirgarepresented a significant component of the oral bacterial microbiomes of the dolphins and seals. However, sequences consistent withO. salmonicidawere only found in the dolphin samples. Analyses of marine mammal microbiome studies in the NCBI databases showed sequences consistent withO. salmonicidafrom the common dolphin, striped dolphin, bottlenose dolphinTursiops truncatus, humpback whaleMegaptera novaeangliae, and harbour seal. Sequences from marine environmental studies in the NCBI databases showed no sequences consistent withO. salmonicida. The findings suggest that several species of marine mammals are natural hosts ofO. salmonicida.

Visual landmarks are defined as objects with prominent shape or size that distinguish themselves from the background. With the help of landmarks, animals can orient themselves in their natural environment. Yet, the way in which landmarks are perceived and encoded has previously only been described in insects, fish, birds, reptiles and terrestrial mammals. The present study aimed to provide insight into how a marine mammal, the harbour seal, encodes goals relative to landmarks. In our expansion test, three harbour seals were trained to find a goal inside an array of landmarks. After diagonal, horizontal or vertical expansion of the landmark array, the search behaviour displayed by the animals was documented and analyzed regarding the underlying encoding strategy. The harbour seals mainly encoded directional vector information from landmarks and did neither search arbitrarily around a landmark nor used a rule-based approach. Depending on the number of landmarks available within the array, the search behaviour of some harbor seals changed, indicating flexibility in landmark-based search. Our results present the first insight into how a semi-aquatic predator could encode landmark information when swimming along the coastline in search of a goal location.

Among pinnipeds, four Otariidae species (eared seals) have been reported as occasional or frequent vagrants along the coast of Brazil, mainly in the southern region. These animals usually arrive debilitated during winter and are directed to rehabilitation. Nevertheless, available information on sanitary aspects of stranded pinnipeds in Brazil is limited. Increased fur seal strandings (n=23) were recorded during the 2018 winter season in southeast Brazil (Iguape, Ilha Comprida, and Ilha do Cardoso, Sao Paulo State) compared to 2017 (n=2). Of these 23 fur seals, two were found dead and were in a good postmortem condition, and four died during rehabilitation and were subsequently necropsied. The remaining fur seals were not analyzed due to advanced decomposition (9/23) or successful rehabilitation (8/23). Herein, we report the antemortem hematology (n=4) and postmortem pathologic, parasitologic, and molecular analysis results as well as the most likely cause of stranding and/ or death (CSD) in five free-ranging juvenile South American fur seals (Arctocephalus australis) and one free-ranging juvenile subantarctic fur seal (Arctocephalus tropicalis). All animals were males, and all but one had poor body condition. Pathologic examinations revealed a variety of lesions, predominantly hemodynamic disturbances, endoparasitism, and inflammatory disease processes of suspected infectious nature. Molecular analyses detected gammaherpesvirus infections in two South American seals and one subantarctic fur seal, Sarcocystis sp. in one subantarctic fur seal, and Neospora spp. in two South American fur seals. All seals were PCR-negative for morbillivirus, flavivirus, and Toxoplasma gondii. The most likely CSDs were: starvation (2), aspiration pneumonia (1), asphyxia (1), predator attack (1), and presumed systemic infectious disease (1). These findings expand the geographic range of various pathogens of pinnipeds and may be of value to first responders, clinicians, and diagnosticians.

The higher carnivoran taxa significantly differ in the morphology of the auditory bulla, but little is known about its non-ectotympanic elements and their contribution to phylogenetically informative bullar characters. The ventral entotympanic sinus, a principal hypotympanic compartment unique to Canidae, expands in post-ossification ontogeny from a distinct portion, rather than the whole, of what is considered the ‘caudal entotympanic’. To trace the earlier development of this sinus and to clarify the potential roles of individual entotympanics in formation of the canid auditory bulla, osteological observations were made on younger skulls of Canis lupus and four additional species. The ventral entotympanic sinus was found to invariably originate at a separate bone provisionally designated the ventral entotympanic. The rest of the caudal entotympanic is a fusion of the posterior (or the proper) caudal entotympanic ossifying near the tympanohyal, and the anterior caudal entotympanic ossifying between the ectotympanic and rostral entotympanic. Examination of the rostral entotympanic also revealed previously unknown details. In sum, the canid auditory bulla includes at least four rather than earlier recognised two (or suspected three) entotympanics. Based on these findings, the composition of the canid intrabullar septum and the homologies of the carnivoran entotympanics are discussed. Within the established phylogenetic framework, the rostral entotympanic and posterior caudal entotympanic appear as plesiomorphic for crown-group Carnivora, while the anterior caudal entotympanic is synapomorphic for Caniformia, and the ventral entotympanic is autapomorphic for Cynoidea. This hypothesis implies that the carnivoran entotympanic patterns may have emerged before complete fusions of bullar bones observed in the fossil record.

Pinniped vibrissae are well-adapted to sensing in an aquatic environment, by being morphologically diverse and more sensitive than those of terrestrial species. However, it is both challenging and time-consuming to measure vibrissal sensitivity in many species. In terrestrial species, the infraorbital foramen (IOF) area is associated with vibrissal sensitivity and increases with vibrissal number. While pinnipeds are thought to have large IOF areas, this has not yet been systematically measured before. We investigated vibrissal morphology, IOF area, and skull size in 16 species of pinniped and 12 terrestrial Carnivora species. Pinnipeds had significantly larger skulls and IOF areas, longer vibrissae, and fewer vibrissae than the other Carnivora species. IOF area and vibrissal number were correlated in Pinnipeds, just as they are in terrestrial mammals. However, despite pinnipeds having significantly fewer vibrissae than other Carnivora species, their IOF area was not smaller, which might be due to pinnipeds having vibrissae that are innervated more. We propose that investigating normalized IOF area per vibrissa will offer an alternative way to approximate gross individual vibrissal sensitivity in pinnipeds and other mammalian species. Our data show that many species of pinniped, and some species of felids, are likely to have strongly innervated individual vibrissae, since they have high values of normalized IOF area per vibrissa. We suggest that species that hunt moving prey items in the dark will have more sensitive and specialized vibrissae, especially as they have to integrate between individual vibrissal signals to calculate the direction of moving prey during hunting.

In recent years, nonhuman ancient DNA studies have begun to focus on larger sample sizes and whole genomes, offering the potential to reveal exciting and hitherto unknown answers to ongoing biological and archaeological questions. However, one major limitation to such studies is the substantial financial and time investments still required during sample screening, due to uncertainty regarding successful sample selection. This study investigates the effect of a wide range of sample properties including latitude, sample age, skeletal element, collagen preservation, and context on endogenous content and DNA damage profiles for 317 ancient and historic pinniped samples collected from across the North Atlantic and surrounding regions. Using generalised linear and mixed‐effect models, we found that a range of factors affected DNA preservation within each of the species under consideration. The most important findings were that endogenous content varied significantly within species according to context, the type of skeletal element, the collagen content and collection year. There also appears to be an effect of the sample's geographic origin, with samples from the Arctic generally showing higher endogenous content and lower damage rates. Both latitude and sample age were found to have significant relationships with damage levels, but only for walrus samples. Sex, ontogenetic age and extraction material preparation were not found to have any significant relationship with DNA preservation. Overall, skeletal element and sample context were found to be the most influential factors and should therefore be considered when selecting samples for large‐scale ancient genome studies.

Campylobacter pinnipediorum was described recently for isolates recovered from pinnipeds. The novel species was further split into 2 subspecies based on host and geography, with C. pinnipediorum subsp. pinnipediorum recovered from otariid seals in California (USA) and C. pinnipediorum subsp. caledonicus recovered from phocid seals in Scotland. We report details of the infections of 7 pinnipeds from which C. pinnipediorum was isolated: C. pinnipediorum subsp. caledonicus was isolated from 2 harbour seals Phoca vitulina and a single grey seal Halichoerus grypus, and C. pinnipediorum subsp. pinnipediorum was isolated from California sea lions Zalophus californianus. Six of the isolates were recovered from samples collected at post-mortem investigation. In 2 of the Scottish seals and in 3 of the California seals, C. pinnipediorum was the sole bacterial isolate recovered from abscesses present and suggests they may have resulted from conspecific or intraspecific bite wounds.

Marine mammals endure extended breath-holds while performing active behaviors, which has fascinated scientists for over a century. It is now known that these animals have large onboard oxygen stores and utilize oxygen-conserving mechanisms to prolong aerobically supported dives to great depths, while typically avoiding (or tolerating) hypoxia, hypercarbia, acidosis and decompression sickness (DCS). Over the last few decades, research has revealed that diving physiology is underdeveloped at birth. Here, I review the postnatal development of the body's oxygen stores, cardiorespiratory system and other attributes of diving physiology for pinnipeds and cetaceans to assess how physiological immaturity makes young marine mammals vulnerable to disturbance. Generally, the duration required for body oxygen stores to mature varies across species in accordance with the maternal dependency period, which can be over 2 years long in some species. However, some Arctic and deep-diving species achieve mature oxygen stores comparatively early in life (prior to weaning). Accelerated development in these species supports survival during prolonged hypoxic periods when calves accompany their mothers under sea ice and to the bathypelagic zone, respectively. Studies on oxygen utilization patterns and heart rates while diving are limited, but the data indicate that immature marine mammals have a limited capacity to regulate heart rate (and hence oxygen utilization) during breath-hold. Underdeveloped diving physiology, in combination with small body size, limits diving and swimming performance. This makes immature marine mammals particularly vulnerable to mortality during periods of food limitation, habitat alterations associated with global climate change, fishery interactions and other anthropogenic disturbances, such as exposure to sonar.

The long-term fidelity of pinniped hosts to their natal rookery site suggests the genetic architecture of their Uncinaria spp. hookworms should be strongly structured by host breeding biology. However, historical events affecting host populations may also shape parasite genetic structure. Sequences of the mitochondrial cytochrome c oxidase 1 (COI) gene of 86 Uncinaria lucasi individuals were obtained to assess genetic variation and structure of nematodes from 2 host species (68 hookworms from northern fur seals; 18 hookworms from Steller sea lions) and rookeries from 3 widely separated geographic regions: the western Bering Sea and Sea of Okhotsk, eastern Bering Sea, and the eastern Pacific Ocean. High COI haplotype (h = 0.96-0.98) and nucleotide (π = 0.014) diversity was found. The haplotype network showed a star-shaped pattern with a large number of haplotypes separated by few substitutions. The network did not show separation of U. lucasi by geographic region or host species. Fst values between U. lucasi individuals representing geographic regions showed no differentiation, consistent with the absence of genetic structure. At face value, this lack of genetic structure in U. lucasi suggests high gene flow but could also be explained by recent (post-glacial) population expansions of northern fur seals and their hookworms.

The challenge of identifying cause of death in discarded bycaught marine mammals stems from a combination of the non-specific nature of the lesions of drowning, the complex physiologic adaptations unique to breath-holding marine mammals, lack of case histories, and the diverse nature of fishing gear. While no pathognomonic lesions are recognized, signs of acute external entanglement, bulging or reddened eyes, recently ingested gastric contents, pulmonary changes, and decompression-associated gas bubbles have been identified in the condition of peracute underwater entrapment (PUE) syndrome in previous studies of marine mammals. We reviewed the gross necropsy and histopathology reports of 36 cetaceans and pinnipeds including 20 directly observed bycaught and 16 live stranded animals that were euthanized between 2005 and 2011 for lesions consistent with PUE. We identified 5 criteria which present at significantly higher rates in bycaught marine mammals: external signs of acute entanglement, red or bulging eyes, recently ingested gastric contents, multi-organ congestion, and disseminated gas bubbles detected grossly during the necropsy and histologically. In contrast, froth in the trachea or primary bronchi, and lung changes (i.e. wet, heavy, froth, edema, congestion, and hemorrhage) were poor indicators of PUE. This is the first study that provides insight into the different published parameters for PUE in bycatch. For regions frequently confronted by stranded marine mammals with non-specific lesions, this could potentially aid in the investigation and quantification of marine fisheries interactions.

The effective size of a population (Ne), which determines its level of neutral variability, is a key evolutionary parameter. Ne can substantially depart from census sizes of present-day breeding populations (NC) as a result of past demographic changes, variation in life-history traits and selection at linked sites. Using genome-wide data we estimated the long-term coalescent Ne for 17 pinniped species represented by 36 population samples (total n = 458 individuals). Ne estimates ranged from 8,936 to 91,178, were highly consistent within (sub)species and showed a strong positive correlation with NC ( $${R}_{\mathrm{adj}}^2$$ = 0.59; P = 0.0002). Ne/NC ratios were low (mean, 0.31; median, 0.13) and co-varied strongly with demographic history and, to a lesser degree, with species’ ecological and life-history variables such as breeding habitat. Residual variation in Ne/NC, after controlling for past demographic fluctuations, contained information about recent population size changes during the Anthropocene. Specifically, species of conservation concern typically had positive residuals indicative of a smaller contemporary NC than would be expected from their long-term Ne. This study highlights the value of comparative population genomic analyses for gauging the evolutionary processes governing genetic variation in natural populations, and provides a framework for identifying populations deserving closer conservation attention. Using comparative population genomics across pinnipeds, this study explores how demographic change and life-history traits are correlated to the effective size of a population and conservation status.

The protozoans Toxoplasma gondii and Sarcocystis spp. (Sarcocystidae: Apicomplexa) affect a wide variety of vertebrates. Both have been reported to infect pinnipeds, with impacts on health ranging from inapparent to fulminant disease and death. However, little is known regarding their infections and associated pathology in South American pinnipeds. We used histological techniques to survey for the presence of T. gondii and Sarcocystis spp. in 51 stranded pinnipeds from Brazil. Immunohistochemical and molecular assays were employed in those cases consistent with Sarcocystidae infection. T. gondii cysts were detected in the central nervous system and heart of a South American fur seal Arctocephalus australis, associated with meningoencephalitis, myocarditis and endocarditis, and confirmed by immunohistochemistry. Additionally, this animal presented Sarcocystis sp. cysts in brain and heart tissues. Four additional specimens-2 Subantarctic fur seals A. tropicalis, an Antarctic fur seal A. gazella and another South American fur seal-presented intrasarcoplasmic cysts compatible with Sarcocystis spp. in muscle samples. There was no inflammation associated with the Sarcocystis spp. tissue cysts and all cysts were negative for S. neurona immunohistochemistry. The B1 gene of T. gondii was amplified in the 5 pinnipeds infected by Sarcocystidae protozoans. To our knowledge, this is the first report of toxoplasmosis in wild South American pinnipeds and of Sarcocystis spp. in South American fur seals. Detection of terrestrial parasites in aquatic mammals could be an indicator of their presence in the marine environment.

Pinnipeds are aquatic predators feeding on a vast range of prey, and their social behaviour differs greatly between species (from extreme polygyny in some sea lions to monogamy in some true seals). It has been hypothesised that the foraging and social complexity of their lifestyle should drive the evolution of their cognitive abilities. To investigate how aware pinnipeds are of their own behaviour, a grey seal (Halichoerus grypus), two harbour seals (Phoca vitulina) and four South American sea lions (Otaria flavescens) were trained to repeat their own behaviour on command. Three already trained behaviours were used, and the animal was asked to repeat the behaviour twice to ensure that the animal recalled its own behaviour and not the command given for the previous behaviour. All three species could recall their own behaviour significantly better than by chance. The duration for which the animals could recall their behaviour was tested using a staircase paradigm. A delay was implemented between the completion of the behaviour and the command to repeat it. The delay was increased after correct responses and decreased after incorrect responses. The performance of all species fell towards chance level after 12–18 s, with no significant difference between species. These results indicate that sea lions and true seals are aware of their own behaviour and that true seals have similar short-term memory abilities. It also shows that pinnipeds have less developed short-term memory abilities compared to other aquatic predators, such as the bottlenose dolphin. The complexity of pinniped foraging and social behaviour does not seem to have driven the evolution of short-term memory abilities in these animals but might have contributed to their ability to recall their own behaviour.

Mammal species have made the transition to the marine environment several times, and their lineages represent one of the classical examples of convergent evolution in morphological and physiological traits. Nevertheless, the genetic mechanisms of their phenotypic transition are poorly understood, and investigations into convergence at the molecular level have been inconclusive. While past studies have searched for convergent changes at specific amino acid sites, we propose an alternative strategy to identify those genes that experienced convergent changes in their selective pressures, visible as changes in evolutionary rate specifically in the marine lineages. We present evidence of widespread convergence at the gene level by identifying parallel shifts in evolutionary rate during three independent episodes of mammalian adaptation to the marine environment. Hundreds of genes accelerated their evolutionary rates in all three marine mammal lineages during their transition to aquatic life. These marine-accelerated genes are highly enriched for pathways that control recognized functional adaptations in marine mammals, including muscle physiology, lipid-metabolism, sensory systems, and skin and connective tissue. The accelerations resulted from both adaptive evolution as seen in skin and lung genes, and loss of function as in gustatory and olfactory genes. In regard to sensory systems, this finding provides further evidence that reduced senses of taste and smell are ubiquitous in marine mammals. Our analysis demonstrates the feasibility of identifying genes underlying convergent organism-level characteristics on a genome-wide scale and without prior knowledge of adaptations, and provides a powerful approach for investigating the physiological functions of mammalian genes.

A sphincter on the inferior vena cava can protect the heart of a diving mammal from overload when elevated abdominal pressures increase venous return, yet sphincters are reported incompetent or absent in some cetacean species. We previously hypothesized that abdominal pressures are elevated and pulsatile in fluking cetaceans, and that collagen is deposited on the diaphragm according to pressure levels to resist deformation. Here we tested the hypothesis that cetaceans generating high abdominal pressures need a more robust sphincter than those generating low pressures. We examined diaphragm morphology in seven cetacean and five pinniped species. All odontocetes had morphologically similar sphincters despite large differences in collagen content, and mysticetes had muscle that could modulate caval flow. These findings do not support the hypothesis that sphincter structure correlates with abdominal pressures. To understand why a sphincter is needed, we simulated the impact of oscillating abdominal pressures on caval flow. Under low abdominal pressures, simulated flow oscillated with each downstroke. Under elevated pressures, a vascular waterfall formed, greatly smoothing flow. We hypothesize cetaceans maintain high abdominal pressures to moderate venous return and protect the heart while fluking, and use their sphincters only during low-fluking periods when abdominal pressures are low. We suggest pinnipeds, which do not fluke, maintain low abdominal pressures. Simulations also showed retrograde oscillations could be transmitted upstream from the cetacean abdomen and into the extradural veins, with potentially adverse repercussions for the cerebral circulation. We propose that locomotion-generated pressures have influenced multiple aspects of the cetacean vascular system.

Noninvasive sampling can provide an efficient means of genetically monitoring mammals. Due to the fragmented quality of DNA derived from such samples, few methods span taxonomic groups beyond species. Here, we describe a more universal protocol for the molecular sex identification of order Carnivora. PCR amplification of a 176 bp segment of the SRY gene indicates a male, whereas no amplification indicates a female. A 245 bp segment of the ZFX gene serves as a positive control. This method is internally consistent, and multiple trials confer confidence in results. It applies to at least three families (Canidae, Felidae, and Phocidae) in both carnivore suborders (Feliformia and Caniformia), rendering this protocol the first sex identification method with amplicon sizes appropriate for noninvasive samples suitable for multiple families within order Carnivora.

Internal pressures change throughout a cetacean's body during swimming or diving, and uneven pressures between the thoracic and abdominal compartments can affect the cardiovascular system. Pressure differentials could arise from ventral compression on each fluke downstroke or by a faster equilibration of the abdominal compartment with changing ambient ocean pressures compared with the thoracic compartment. If significant pressure differentials do develop, we would expect the morphology of the diaphragm to adapt to its in vivo loading. Here, we tested the hypothesis that significant pressure differentials develop between the thoracic and abdominal cavities in diving cetaceans by examining diaphragms from several cetacean and pinniped species. We found that: (1) regions of cetacean diaphragms possess subserosal collagen fibres that would stabilize the diaphragm against craniocaudal stretch; (2) subserosal collagen covers 5–60% of the thoracic diaphragm surface, and area correlates strongly with published values for swimming speed of each cetacean species (P

We characterize Brucella infection in a wild southern sea otter ( Enhydra lutris nereis) with osteolytic lesions similar to those reported in other marine mammals and humans. This otter stranded twice along the central California coast, US over a 1-yr period and was handled extensively at two wildlife rehabilitation facilities, undergoing multiple surgeries and months of postsurgical care. Ultimately the otter was euthanized due to severe, progressive neurologic disease. Necropsy and postmortem radiographs revealed chronic, severe osteoarthritis spanning the proximal interphalangeal joint of the left hind fifth digit. Numerous coccobacilli within the joint were strongly positive on Brucella immunohistochemical labelling, and Brucella sp. was isolated in pure culture from this lesion. Sparse Brucella-immunopositive bacteria were also observed in the cytoplasm of a pulmonary vascular monocyte, and multifocal granulomas were observed in the spinal cord and liver on histopathology. Findings from biochemical characterization, 16S ribosomal DNA, and bp26 gene sequencing of the bacterial isolate were identical to those from marine-origin brucellae isolated from cetaceans and phocids. Although omp2a gene sequencing revealed 100% homology with marine Brucella spp. infecting pinnipeds, whales, and humans, omp2b gene sequences were identical only to pinniped-origin isolates. Multilocus sequence typing classified the sea otter isolate as ST26, a sequence type previously associated only with cetaceans. Our data suggest that the sea otter Brucella strain represents a novel marine lineage that is distinct from both Brucella pinnipedialis and Brucella ceti. Prior reports document the zoonotic potential of the marine brucellae. Isolation of Brucella sp. from a stranded sea otter highlights the importance of wearing personal protective equipment when handling sea otters and other marine mammals as part of wildlife conservation and rehabilitation efforts.

During independent diagnostic screenings of otariid seals in California (USA) and phocid seals in Scotland (UK), Campylobacter-like isolates, which differed from the established taxa of the genus Campylobacter, were cultured from abscesses and internal organs of different seal species. A polyphasic study was undertaken to determine the taxonomic position of these six isolates. The isolates were characterized by 16S rRNA gene and AtpA sequence analysis and by conventional phenotypic testing. The whole-genome sequences were determined for all isolates, and the average nucleotide identity (ANI) was determined. The isolates formed a separate phylogenetic clade, divergent from all other taxa of the genus Campylobacter and most closely related to Campylobactermucosalis. Although all isolates showed 100 % 16S rRNA gene sequence homology, AtpA and ANI analyses indicated divergence between the otariid isolates from California and the phocid isolates from Scotland, which warrants subspecies status for each clade. The two subspecies could also be distinguished phenotypically on the basis of catalase activity. This study shows clearly that the isolates obtained from pinnipeds represent a novel species within the genus Campylobacter, for which the name Campylobacter pinnipediorum sp. nov. is proposed. Within this novel species, the Californian isolates represent a separate subspecies, for which the name C. pinnipediorum subsp. pinnipediorum subsp. nov. is proposed. The type strain for both this novel species and subspecies is RM17260T (=LMG 29472T=CCUG 69570T). The Scottish isolates represent another subspecies, for which the name C. pinnipediorum subsp. caledonicus subsp. nov. is proposed. The type strain of this subspecies is M302/10/6T (=LMG 29473T=CCUG 68650T).

In this study we examine the auditory capabili- ties of the sea otter (Enhydra lutris), an amphibious marine mammal that remains virtually unstudied with respect to its sensory biology. We trained an adult male sea otter to perform a psychophysical task in an acoustic chamber and at an underwater apparatus. Aerial and underwater audio- grams were constructed from detection thresholds for nar- rowband signals measured in quiet conditions at frequen- cies from 0.125-40 kHz. Aerial hearing thresholds were also measured in the presence of octave-band masking noise centered at eight signal frequencies (0.25-22.6 kHz) so that critical ratios could be determined. The aerial audiogram of the sea otter resembled that of sea lions and showed a reduction in low-frequency sensitivity relative to terrestrial mustelids. Best sensitivity was −1 dB re 20 µPa at 8 kHz. Under water, hearing sensitivity was significantly reduced when compared to sea lions and other pinniped species, demonstrating that sea otter hearing is primarily adapted to receive airborne sounds. Critical ratios were more than 10 dB higher than those measured for pinni- peds, suggesting that sea otters are less efficient than other marine carnivores at extracting acoustic signals from back- ground noise, especially at frequencies below 2 kHz.

The threatened Himalayan brown bear has a fragmented range in the Himalayas. However, its habitat has never been documented, which hinders conservation efforts. The Deosai Plateau in northern Pakistan has long been recognized as the core area for this subspecies in the country. To provide knowledge to help conserve the remnant populations in the Himalayan region, and especially in protected areas, we investigated habitat selection of brown bears and the influence of human presence on brown bear distribution in Deosai National Park, Pakistan. We used an Ecological Niche Factor Analysis to assess brown bear habitat selection, using scats sampled along transect routes throughout the park as location data. Habitat use based on 137 observations of brown bears during monitoring confirmed that differential scat detectability did not bias our results. Only 65% of the park area had productive vegetation. Our analyses indicated that brown bears avoided higher elevations and steeper slopes and selected more productive parts of the park (marshy, grassy, and stony vegetation types). The marshy vegetation was the most preferred habitat, probably because it had the highest forage production and density of golden marmots. Brown bears tolerated human infrastructures, like roads and camps, but strongly avoided grazing areas with high livestock density. The habitat suitability map generally followed the biomass productivity patterns of the park. It indicated the central part as suitable, and classified half of the park, mainly peripheral areas, as unsuitable for brown bears. The vegetation and habitat suitability maps also provide an objective criterion for evaluating present and future developments in the park. Until recently, communities seem to have used the park’s resources without significantly affecting the brown bear population. However, in recent years a large influx of nomadic communities with their livestock has become a challenge, which needs urgent attention to continue the present brown bear population recovery and to secure its habitat. We recommend monitoring the livestock and conducting a detailed inventory of the rangeland to understand grazing dynamics in the park and to maintain sustainable stocking rates.

The remote measurement of data from free-ranging animals has been termed ‘biologging’ and in recent years this relatively small set of tools has been instrumental in addressing remarkably diverse questions – from ‘how will tuna respond to climate change?’ to ‘why are whales big?’. While a single biologging dataset can have the potential to test hypotheses spanning physiology, ecology, evolution and theoretical physics, explicit illustrations of this flexibility are scarce and this has arguably hindered the full realization of the power of biologging tools. Here we present a small set of examples from studies that have collected data on two parameters widespread in biologging research (depth and acceleration), but that have interpreted their data in the context of extremely diverse phenomena: from tests of biomechanical and diving-optimality models to identifications of feeding events, Lévy flight foraging strategies and expanding oxygen minimum zones. We use these examples to highlight the remarkable flexibility of biologging tools, and identify several mechanisms that may enhance the scope and dissemination of future biologging research programs.

The extirpation of black-footed ferrets ( Mustela nigripes ) from the wild resulted from the rangewide decline of prairie dogs ( Cynomys spp.) brought about by poisoning campaigns, the arrival of an exotic disease, and habitat loss. It is widely accepted that ferrets are an obligate, near monophagous, dietary specialist of prairie dogs and that high-density prairie dog colonies are necessary for effective recovery. To test the extent to which ferrets are dietary specialists, we measured the stable isotopic values of 321 ferrets of known age and sex as well as of their potential prey (e.g., prairie dogs, mice, ground squirrels, and rabbits). Our results confirmed that prairie dogs are the most common diet item for ferrets, although ferrets possessed greater foraging plasticity than previously reported, consuming substantial quantities of other species. The degree to which ferrets were specialized on prairie dogs differed between age–sex groups. Adult male and juvenile ferrets had equivalent diets, with prairie dogs constituting nearly 75% of their assimilated diet. In contrast, adult females obtained over one third of their diet from other species, notably mice. However, female ferrets appeared to have provisioned prairie dogs to their dependent offspring. Conservation of ferrets, one of North America’s most endangered mammals, will require prairie dogs, not just as prey, but also for the prey-rich habitat that their colonies provide.

Ecologists often use transect surveys to estimate the density and abundance of animal populations. Errors in species classification are often evident in such surveys, yet few statistical methods exist to properly account for them. In this paper, we examine biases that result from species misidentification when ignored, and we develop statistical models to provide unbiased estimates of density in the face of such errors. Our approach treats true species identity as a latent variable and requires auxiliary information on the misclassification process (such as informative priors, experiments using known species, or a double-observer protocol). We illustrate our approach with simulated census data and with double-observer survey data for ice-associated seals in the Bering Sea. For the seal analysis, we integrated misclassification into a model-based framework for distance-sampling data. The simulated data analysis demonstrated reliable estimation of animal density when there are experimental data to inform misclassification rates; double-observer protocols provided robust inference when there were "unknown" species observations but no outright misclassification, or when misclassification probabilities were symmetric and a symmetry constraint was imposed during estimation. Under our modeling framework, we obtained reasonable apparent densities of seal species even under considerable imprecision in species identification. We obtained more reliable inferences when modeling variation in density among transects. We argue that ecologists should often use spatially explicit models to account for differences in species distributions when trying to account for species misidentification. Our results support using double-observer sampling protocols that guard against species misclassification (i.e., by recording uncertain observations as "unknown").

A species’ occurrence can be influenced by natural and anthropogenic factors; disentangling these is a precursor to understanding the mechanisms of distribution. Anthropogenic factors may be especially important at contracting range edges. We test this premise for wolverines (Gulo gulo luscus L., 1758) at the edge of their Rocky Mountain range in Alberta, Canada, a mosaic of natural heterogeneity and extensive landscape development. As wolverines have a suspected negative response to human activity, we hypothesized their occurrence on the Rockies’ slopes is predicted by a combination of natural and anthropogenic features. We surveyed wolverines at 120 sites along a natural and anthropogenic gradient using hair trapping and noninvasive genetic tagging. We used abundance estimation, generalized linear, and hierarchical models to determine whether abundance and occurrence was best predicted by natural land cover, topography, footprint, or a combination. Wolverines were more abundant in rugged areas protected from anthropogenic development. Wolverines were less likely to occur at sites with oil and gas exploration, forest harvest, or burned areas, even after accounting for the effect of topography. The relative paucity of wolverines in human-impacted portions of this range edge suggests that effective conservation requires managing landscape development, and research on the proximal mechanisms behind this relationship.

We document the first associations of two recently described species of Pasteurellaceae bacteria with lesions in wild pinnipeds in rehabilitation. Samples were collected from nine lesions in four California sea lions (Zalophus californianus) and two Pacific harbor seals (Phoca vitulina) during necropsy or admission examinations at a rehabilitation facility in northern California. Seven Pasteurellaceae isolates were identified using phenotypic tests and partial rpoB gene sequencing. Six strains of Otariodibacter oris were isolated from California sea lions. Otariodibacter oris was isolated in pure culture from four abscesses, an affected lymph node, and a bone lesion consistent with osteomyelitis. Otariodibacter oris was also cultured with Arcanobacterium phocae and β-hemolytic streptococci. A pure culture of Bisgaardia genomospecies 1 was obtained from an abscess in a harbor seal. This is the first time, to our knowledge, that O. oris has been associated with infection. Isolation of these bacteria in pure culture from abscesses and osteomyelitis strongly indicates a pathogenic potential of this organism. Likewise, the isolation of Bisgaardia genomospecies 1 in pure culture from an abscess in a harbor seal implies causality.

Although black bears (Ursus americanus) were believed to be extirpated from the Interior Highlands of North America by the early 1900s, populations have recently recovered, aided in part by reintroductions in Arkansas. Today black bears can be found in the Ozark and Ouachita National Forests of northern and western Arkansas, the White River National Wildlife Refuge in eastern Arkansas, and the Ozark region of southern Missouri. Previous genetic studies have investigated the effects of translocating black bears from Minnesota and Manitoba, Canada, into the Ozark and Ouachita National Forests between 1958 and 1968, with differing results. We used nuclear microsatellite loci to infer the genetic structure of black bears across the Interior Highlands and to investigate the sources of bears found today in southern Missouri. Our results suggest that the Ozark population was strongly influenced by the reintroductions, whereas the Ouachita population was influenced to a lesser degree. Although the majority of bears in the Ozark region of Arkansas and Missouri represent a single genetic unit, bears in Webster County, Missouri, may represent a remnant of the historical population of the region. Our results confirm that the bear population in the White River National Wildlife Refuge is strongly differentiated genetically from other Arkansas populations and support previous reports that the Ouachita bear population may have resulted from an admixture of a remnant population and reintroduced bears.

Post-mortem examination of dead and live stranded beach-cast pinnipeds and cetaceans for determination of a cause of death provides valuable information for the management, mitigation and prosecution of unintentional and sometimes malicious human impacts, such as vessel collision, fishing gear entanglement and gunshot. Delayed discovery, inaccessibility, logistics, human safety concerns, and weather make these events challenging. Over the past 3 decades, in response to public concern and federal and state or provincial regulations mandating such investigations to inform mitigation efforts, there has been an increasing effort to objectively and systematically investigate these strandings from a diagnostic and forensic perspective. This Theme Section provides basic investigative methods, and case definitions for each of the more commonly recognized case presentations of human interactions in pinnipeds and cetaceans. Wild animals are often adversely affected by factors such as parasitism, anthropogenic contaminants, biotoxins, subclinical microbial infections and competing habitat uses, such as prey depletion and elevated background and episodic noise. Understanding the potential contribution of these subclinical factors in predisposing or contributing to a particular case of trauma of human origin is hampered, especially where putrefaction is significant and resources as well as expertise are limited. These case criteria descriptions attempt to acknowledge those confounding factors to enable an appreciation of the significance of the observed human-derived trauma in that broader context where possible.

Auditory sensitivity in pinnipeds is influenced by the need to balance efficient sound detection in two vastly different physical environments. Previous comparisons between aerial and underwater hearing capabilities have considered media-dependent differences relative to auditory anatomy, acoustic communication, ecology, and amphibious life history. New data for several species, including recently published audiograms and previously unreported measurements obtained in quiet conditions, necessitate a re-evaluation of amphibious hearing in pinnipeds. Several findings related to underwater hearing are consistent with earlier assessments, including an expanded frequency range of best hearing in true seals that spans at least six octaves. The most notable new results indicate markedly better aerial sensitivity in two seals (Phoca vitulina and Mirounga angustirostris) and one sea lion (Zalophus californianus), likely attributable to improved ambient noise control in test enclosures. An updated comparative analysis alters conventional views and demonstrates that these amphibious pinnipeds have not necessarily sacrificed aerial hearing capabilities in favor of enhanced underwater sound reception. Despite possessing underwater hearing that is nearly as sensitive as fully aquatic cetaceans and sirenians, many seals and sea lions have retained acute aerial hearing capabilities rivaling those of terrestrial carnivores.

Understanding individual attitudes and how these predict overt opposition to predator conservation or direct, covert action against predators will help to recover and maintain them. Studies of attitudes toward wild animals rely primarily on samples of individuals at a single time point. We examined longitudinal change in individuals' attitudes toward gray wolves (Canis lupus). In the contiguous United States, amidst persistent controversy and opposition, abundances of gray wolves are at their highest in 60 years. We used mailed surveys to sample 1892 residents of Wisconsin in 2001 or 2004 and then resampled 656 of these individuals who resided in wolf range in 2009. Our study spanned a period of policy shifts and increasing wolf abundance. Over time, the 656 respondents increased agreement with statements reflecting fear of wolves, the belief that wolves compete with hunters for deer (Odocoileus virginianus), and inclination to poach a wolf. Endorsement of lethal control of wolves by the state and public hunting of wolves also increased. Neither the time span over which respondents reported exposure to wolves locally nor self-reported losses of domestic animals to wolves correlated with changes in attitude. We predict future increases in legal and illegal killing of wolves that may reduce their abundance in Wisconsin unless interventions are implemented to improve attitudes and behavior toward wolves. To assess whether interventions change attitudes, longitudinal studies like ours are needed. Analisis Longitudinal de las Actitudes Hacia Lobos.

Food limitation may be one of the causes of declines in northern fur seal populations on the Pribilof Islands. This hypothesis could be tested by comparing foraging behavior from decreasing Pribilof fur seal populations and an increasing population, such as on the Lovushki Islands, Russia, but factors other than prey availability that differ between sites may also influence behavior. Therefore, we evaluated such factors, including lunar cycle, weather, seal body size, and size of recording instruments, by studying 41 lactating northern fur seals on Lovushki Island over 4 summer breeding seasons using instrument packages of various sizes. With greater moon- light, seals increased foraging trip duration, dive depth, dive duration, and time spent on the bot- tom of dives but decreased descent rate and diving bout duration. Larger females made shorter shore visits, spent a greater proportion of time at sea diving, and had longer dive bouts than smaller females. Tags with larger frontal surface areas and higher drag caused seals to dive longer and to descend and ascend faster during dives but did not affect foraging trip durations or mass change rates. Seals, therefore, appeared capable of compensating for instrument effects on the scale of indi vidual dives. Although lactating seals from Lovushki Island appeared to spend less foraging effort than seals from the Pribilofs, future studies should control for methodological fac- tors and local environmental conditions before concluding whether food limitation could explain differences in population trajectories.

Within the nasal cavity of mammals is a complex scaffold of paper-thin bones that function in respiration and olfaction. Known as turbinals, the bones greatly enlarge the surface area available for conditioning inspired air, reducing water loss, and improving olfaction. Given their functional significance, the relative development of turbinal bones might be expected to differ among species with distinct olfactory, thermoregulatory and/or water conservation requirements. Here we explore the surface area of olfactory and respiratory turbinals relative to latitude and diet in terrestrial Caniformia, a group that includes the canid and arctoid carnivorans (mustelids, ursids, procyonids, mephitids, ailurids). Using high-resolution computed tomography x-ray scans, we estimated respiratory and olfactory turbinal surface area and nasal chamber volume from three-dimensional virtual models of skulls. Across the Caniformia, respiratory surface area scaled isometrically with estimates of body size and there was no significant association with climate, as estimated by latitude. Nevertheless, one-on-one comparisons of sister taxa suggest that arctic species may have expanded respiratory turbinals. Olfactory surface area scaled isometrically among arctoids, but showed positive allometry in canids, reflecting the fact that larger canids, all of which are carnivorous, had relatively greater olfactory surface areas. In addition, among the arctoids, large carnivorous species such as the polar bear (Ursus maritimus) and wolverine (Gulo gulo) also displayed enlarged olfactory turbinals. More omnivorous caniform species that feed on substantial quantities of non-vertebrate foods had less expansive olfactory turbinals. Because large carnivorous species hunt widely dispersed prey, an expanded olfactory turbinal surface area may improve a carnivore's ability to detect prey over great distances using olfactory cues.

This study aimed to assess the enamel ultrastructure in modern otariid pinnipeds and in the extinct walrus Pelagiarctos. Teeth of the New Zealand fur seal (Arctocephalus forsteri), sea lion (Phocarctos hookeri), and fossil walrus Pelagiarctos thomasi were embedded, sectioned, etched, and analyzed via scanning electron microscopy. The enamel of NZ otariids and Pelagiarctos was prismatic and moderately thick, measuring 150-450 μm on average. It consisted of transversely oriented Hunter-Schreger bands (HSBs) from the enamel-dentine junction (EDJ) to near the outer surface, where it faded into prismless enamel less than 10 μm thick. The width of HSB was variable and averaged between 6 and 10 prisms, and they presented an undulating course both in longitudinal and cross sections. The overall organization of the enamel was similar in all teeth sampled; however, the enamel was thicker in canines and postcanines than in incisors. The crowns of all teeth sampled were uniformly covered by enamel; however, the grooved incisors lacked an enamel cover on the posterior side of the buccal face. Large tubules and tuft-like structures were seen at the EDJ. HSB enamel as well as tubules and tufts at the EDJ suggest increased occlusal loads during feeding, a biomechanical adaptation to avoid enamel cracking and failure. Despite overall simplification in tooth morphology and reduced mastication, the fossil and modern pinnipeds analyzed here retained the complex undulating HSB structure of other fossils and living Carnivora, while other marine mammals such as cetaceans developed simplified radial enamel.

Background Models that predict changes in the abundance and distribution of fauna under future climate change scenarios often assume that ecological niche and habitat availability are the major determinants of species’ responses to climate change. However, individual species may have very different capacities to adapt to environmental change, as determined by intrinsic factors such as their dispersal ability, genetic diversity, generation time and rate of evolution. These intrinsic factors are usually excluded from forecasts of species’ abundance and distribution changes. We aimed to determine the importance of these factors by comparing the impact of the most recent climate regime change, the late Pleistocene glacial-interglacial transition, on two sympatric, ice-dependent meso-predators, the emperor penguin (Aptenodytes forsteri) and Weddell seal (Leptonychotes weddellii). Methods We reconstructed the population trend of emperor penguins and Weddell seals in East Antarctica over the past 75,000 years using mitochondrial DNA sequences and an extended Bayesian skyline plot method. We also assessed patterns of contemporary population structure and genetic diversity. Results Despite their overlapping distributions and shared dependence on sea ice, our genetic data revealed very different responses to climate warming between these species. The emperor penguin population grew rapidly following the glacial-interglacial transition, but the size of the Weddell seal population did not change. The expansion of emperor penguin numbers during the warm Holocene may have been facilitated by their higher dispersal ability and gene flow among colonies, and fine-scale differences in preferred foraging locations. Conclusions The vastly different climate change responses of two sympatric ice-dependent predators suggests that differing adaptive capacities and/or fine-scale niche differences can play a major role in species’ climate change responses, and that adaptive capacity should be considered alongside niche and distribution in future species forecasts. Electronic supplementary material The online version of this article (doi:10.1186/s12862-016-0630-3) contains supplementary material, which is available to authorized users.

When aquatically adapted mammals and birds swim submerged, they exhibit a dive response in which breathing ceases, heart rate slows, and blood flow to peripheral tissues and organs is reduced. The most intense dive response occurs during forced submersion which conserves blood oxygen for the brain and heart, thereby preventing asphyxiation. In free-diving animals, the dive response is less profound, and energy metabolism remains aerobic. However, even this relatively moderate bradycardia seems diametrically opposed to the normal cardiovascular response (i.e., tachycardia and peripheral vasodilation) during physical exertion. As a result, there has been a long-standing paradox regarding how aquatic mammals and birds exercise while submerged. We hypothesized based on cardiovascular modeling that heart rate must increase to ensure adequate oxygen delivery to active muscles. Here, we show that heart rate (HR) does indeed increase with flipper or fluke stroke frequency (SF) during voluntary, aerobic dives in Weddell seals (HR = 1.48SF - 8.87) and bottlenose dolphins (HR = 0.99SF + 2.46), respectively, two marine mammal species with different evolutionary lineages. These results support our hypothesis that marine mammals maintain aerobic muscle metabolism while swimming submerged by combining elements of both dive and exercise responses, with one or the other predominating depending on the level of exertion.

Rensch’s rule, which states that the magnitude of sexual size dimorphism tends to increase with increasing body size, has evolved independently in three lineages of large herbivorous mammals: bovids (antelopes), cervids (deer), and macropodids (kangaroos). This pattern can be explained by a model that combines allometry, life-history theory, and energetics. The key features are that female group size increases with increasing body size and that males have evolved under sexual selection to grow large enough to control these groups of females. The model predicts relationships among body size and female group size, male and female age at first breeding, death and growth rates, and energy allocation of males to produce body mass and weapons. Model predictions are well supported by data for these megaherbivores. The model suggests hypotheses for why some other sexually dimorphic taxa, such as primates and pinnipeds (seals and sea lions), do or do not conform to Rensh’s rule.