Low-frequency hearing and masking parameters in representative seals and sea lionsa).

Despite the prevalence of low-frequency natural and human-generated noise, there are relatively few biological data describing hearing and masking in non-human mammals at frequencies below 100 Hz. Information about the auditory capabilities of mammals with high sensitivity to low-frequency sounds is needed to understand and quantify masking effects. In this study, behavioral methods were used to investigate low-frequency underwater hearing in two trained bearded seals (Erignathus barbatus) and a California sea lion (Zalophus californianus) in quiet conditions and in the presence of controlled background noise.

Temporary threshold shifts from mid-frequency airborne noise exposures in sealsa).

To evaluate the residual effects of airborne noise, hearing thresholds were obtained before and after noise exposure using behavioral psychophysics for two phocid carnivores: a northern elephant seal (Mirounga angustirostris) and a harbor seal (Phoca vitulina). The seals were trained to position calmly during exposure to octave-band white noise centered at 1 or 2.5 kHz with varying level (65 to 125 dB sensation level, SL) and duration (1.

Sensorimotor synchronization to rhythm in an experienced sea lion rivals that of humans.

Is human beat keeping unique among vertebrates? The only non-human data showing consistent and lagless beat matching to novel stimuli, including music, come from Ronan, a trained sea lion [Cook et al., J. Comp.

Nonlinear phenomena in pinnipeds: a preliminary investigation in the contact calls of northern elephant seal pups.

As acoustic markers of emotional state, nonlinear phenomena (NLP) are commonly found in the calls that young mammals produce to solicit attention from their parents. However, data are lacking to assess the ontogeny of these NLP during early development, including the extent to which these acoustic cues vary with the age and sex of the emitter. In the present study, we evaluated the occurrence of NLP in the contact calls that northern elephant seal () pups emit to solicit maternal care during the three-week period of maternal dependence.

SEASONAL VARIATION OF BLOOD ANALYTES ASSOCIATED WITH SKIN HEALTH IN ALASKAN ICE SEALS.

Recent unusual mortality events involving skin pathology in bearded (), ringed (), and spotted seals () in Alaska highlight the potential sensitivity of ice-associated species to the complex effects of climate change. The regulation of thyroid hormones, cortisol, and vitamin A have been shown to play essential roles in skin health and seasonal molt in some pinnipeds. Unfortunately, the lack of available reference data for healthy Alaskan ice seals has prevented the adequate evaluation of these factors in cases associated with mortality events.

Vocal tract dynamics shape the formant structure of conditioned vocalizations in a harbor seal.

Formants, or resonance frequencies of the upper vocal tract, are an essential part of acoustic communication. Articulatory gestures-such as jaw, tongue, lip, and soft palate movements-shape formant structure in human vocalizations, but little is known about how nonhuman mammals use those gestures to modify formant frequencies. Here, we report a case study with an adult male harbor seal trained to produce an arbitrary vocalization composed of multiple repetitions of the sound wa.

An Ecological and Neural Argument for Developing Pursuit-Based Cognitive Enrichment for Sea Lions in Human Care.

While general enrichment strategies for captive animals attempt to elicit variable and species-typical behaviors, approaches to cognitive enrichment have been disappointingly one-size-fits-all. In this commentary, we address the potential benefit of tailoring cognitive enrichment to the "cognitive niche" of the species, with a particular focus on a reasonably well-studied marine carnivore, the sea lion. Sea lions likely share some cognitive evolutionary pressures with primates, including complex social behavior.

Auditory masking in odobenid and otariid carnivoresa).

As the only living species within the odobenid lineage of carnivores, walruses (Odobenus rosmarus) have no close relatives from which auditory information can be extrapolated. Sea lions and fur seals in the otariid lineage are the nearest evolutionary outgroup. To advance understanding of odobenid and otariid hearing, we conducted behavioral testing with two walruses and one California sea lion (Zalophus californianus).

Maintaining control: metabolism of molting Arctic seals in water and when hauled out.

Seals haul out of water for extended periods during the annual molt, when they shed and regrow their pelage. This behavior is believed to limit heat loss to the environment given increased peripheral blood flow to support tissue regeneration. The degree to which time in water, particularly during the molt, may affect thermoregulatory costs is poorly understood.

In-situ observations of the sensory hairs of Antarctic minke whales (Balaenoptera bonaerensis).

The sense of touch in the largest marine mammals is poorly understood. While mysticetes possess specialized sensory hairs that are present through adulthood, descriptions of these structures are based almost entirely on examination of tissues in post-mortem individuals. Sensory hairs have rarely been observed and described in living whales.

Walruses produce intense impulse sounds by clap-induced cavitation during breeding displays.

Male walruses produce some of the longest continuous reproductive displays known among mammals to convey their physical fitness to potential rivals and possibly to potential mates. Here, we document the ability of a captive walrus to produce intense, rhythmic sounds through a non-vocal pathway involving deliberate, regular collision of the fore flippers. High-speed videography linked to an acoustic onset marker revealed sound production through cavitation, with the acoustic impulse generated by each forceful clap exceeding a peak-to-peak sound level of 200 dB re.

In-air hearing in Hawaiian monk seals: implications for understanding the auditory biology of Monachinae seals.

The auditory biology of Monachinae seals is poorly understood. Limited audiometric data and certain anatomical features suggest that these seals may have reduced sensitivity to airborne sounds compared to related species. Here, we describe the in-air hearing abilities of a Hawaiian monk seal (Neomonachus schauinslandi) trained to participate in a psychophysical paradigm.

Molting strategies of Arctic seals drive annual patterns in metabolism.

Arctic seals, including spotted (), ringed () and bearded () seals, are directly affected by sea ice loss. These species use sea ice as a haul-out substrate for various critical functions, including their annual molt. Continued environmental warming will inevitably alter the routine behavior and overall energy budgets of Arctic seals, but it is difficult to quantify these impacts as their metabolic requirements are not well known-due in part to the difficulty of studying wild individuals.

An MRI protocol for anatomical and functional evaluation of the California sea lion brain.

Background: Domoic acid (DOM) is a neurotoxin produced by some harmful algae blooms in coastal waters. California sea lions (Zalophus californianus) exposed to DOM often strand on beaches where they exhibit a variety of symptoms, including seizures. These animals typically show hippocampal atrophy on MRI scans.

measurement of lung volume in ringed seals: insights from biomedical imaging.

Marine mammals rely on oxygen stored in blood, muscle and lungs to support breath-hold diving and foraging at sea. Here, we used biomedical imaging to examine lung oxygen stores and other key respiratory parameters in living ringed seals (). Three-dimensional models created from computed tomography (CT) images were used to quantify total lung capacity (TLC), respiratory dead space, minimum air volume and total body volume to improve assessment of lung oxygen storage capacity, scaling relationships and buoyant force estimates.

Evaluating temporary threshold shift onset levels for impulsive noise in seals.

The auditory effects of single- and multiple-shot impulsive noise exposures were evaluated in a bearded seal (Erignathus barbatus). This study replicated and expanded upon recent work with related species [Reichmuth, Ghoul, Sills, Rouse, and Southall (2016). J.

Adaptations for amphibious vision in sea otters (Enhydra lutris): structural and functional observations.

Sea otters (Enhydra lutris) are amphibious mammals that maintain equal in-air and underwater visual acuity. However, their lens-based underwater accommodative mechanism presumably requires a small pupil that may limit sensitivity across light levels. In this study, we consider adaptations for amphibious living by assessing the tapetum lucidum, retina, and pupil dynamics in sea otters.

High-amplitude vocalizations of male northern elephant seals and associated ambient noise on a breeding rookery.

Northern elephant seals (Mirounga angustirostris) are massive, land-breeding marine mammals that produce loud, stereotyped calls during annual breeding seasons. To determine vocalization source levels emitted by competing males on a mainland breeding rookery, aerial calls were measured on-axis at 1 m from adult males using three different sound pressure level metrics. Time-averaged (1 min) ambient noise was also measured under variable environmental and social conditions.

In Vivo Measurements of Lung Volumes in Ringed Seals: Insights from Biomedical Imaging.

Marine mammals rely on oxygen stored in blood, muscle, and lungs to support breath-hold diving and foraging at sea. Here, we used biomedical imaging to examine lung oxygen stores and other key respiratory parameters in living ringed seals (Pusa hispida). Three-dimensional models created from computed tomography (CT) images were used to quantify total lung capacity (TLC), respiratory dead space, minimum air volume, and total body volume to improve assessments of lung oxygen storage capacity, scaling relationships, and buoyant force estimates.

Long-term evidence of noise-induced permanent threshold shift in a harbor seal (Phoca vitulina).

In psychophysical studies of noise-induced hearing loss with marine mammals, exposure conditions are often titrated from levels of no effect to those that induce significant but recoverable loss of auditory sensitivity [temporary threshold shift (TTS)]. To examine TTS from mid-frequency noise, a harbor seal was exposed to a 4.1-kHz underwater tone that was incrementally increased in sound pressure level (SPL) and duration.

Comparative Health Assessments of Alaskan Ice Seals.

Bearded (), ringed (), spotted (), and ribbon () seals rely on seasonal sea-ice in Arctic and sub-Arctic regions. Many aspects of the biology and physiology of these seals are poorly known, and species-typical health parameters are not available for all species. Such information has proven difficult to obtain due to the challenges of studying Arctic seals in the wild and their minimal historic representation in aquaria.