Harbor seals ( Phoca vitulina ) exhibit sex‐specific differences in diet and spatial distribution. Previous studies have documented consistent variation in sexual composition among haul‐out sites, but the proximate factors underlying this spatial segmentation remain poorly understood. We examined whether variation in haul‐out site sex composition is associated with proximity to anthropogenic disturbance or prey availability ac...

West Coast Transient (WCT) killer whales ( Orcinus orca rectipinnus ) hunt marine mammals along the west coast of North America from California to southeastern Alaska. However, little information is available on their seasonal use of nearshore areas and the relative importance of different parts of their range. Using sighting data from 2016 to 2023, we assessed their seasonal distribution and abundance in the inside waters of...

The American manatee ( Trichechus manatus ) requires freshwater mainly from rivers and springs to maintain osmoregulatory balance in saline environments. However, in Brazil's semi‐arid Potiguar Basin, manatees now rely solely on submarine freshwater springs because hypersaline estuaries have become unsuitable sources of freshwater. We applied MaxEnt modeling to presence‐only data (sightings and filtered telemetry records) to p...

Eastern North Pacific gray whales ( Eschrichtius robustus ) rely on energy obtained from Arctic feeding grounds to complete their 15,000–20,000 km annual round‐trip migration between feeding and breeding areas. However, quantitative estimates of their food requirements remain scarce. Using an age‐structured bioenergetics model incorporating life cycle stages and migration timings, we estimated daily energy needs across life st...

The world's smallest porpoise—the vaquita ( Phocoena sinus )—is on the brink of extinction. Endemic to the upper Gulf of California, it has dwindled to fewer than 19 individuals in 2023. The primary source of mortality is drowning in gillnets set for totoaba (a giant croaker fish). Our review of the past 50 years of efforts to simultaneously attain conservation goals for the vaquita and economic and social goals for the fisher...

High‐resolution tri‐axial accelerometry biologging tags have quantitatively described behaviors in baleen whale species that forage using lunges and continuous ram filtration. However, detailed quantitative descriptions of foraging behaviors do not exist for gray whales, a unique baleen whale species that primarily uses benthic suction feeding with a rolling component. We deployed suction cup biologging tags on Pacific Coast F...

The enlarged size of the aortic bulb is thought to enhance the ability of marine mammals to remain underwater for extended periods. However, a convincing link between aortic bulb size and diving capacity has not been established. Using new and existing data, we examined the relationships between body size, maximum and routine dive duration, and aortic bulb size of pinnipeds. Comparisons among seven species of pinnipeds showed...

The ecological impact of environmental changes at high latitudes (e.g., increasing temperature, and decreased sea ice cover) on low-trophic species, such as bowhead whales, are poorly understood. Key to understanding the vulnerability of zooplanktivorous predators to climatic shifts in prey is knowing whether they can make behavioural or distributional adjustments to maintain sufficient prey acquisition rates. However, little...

Availability of preferred salmonid prey and a sufficiently quiet acoustic environment in which to forage are critical to the survival of resident killer whales ( Orcinus orca ) in the northeastern Pacific. Although piscivorous killer whales rely on echolocation to locate and track prey, the relationship between echolocation, movement, and prey capture during foraging by wild individuals is poorly understood. We used acoustic b...

Knowing size‐at‐age is important for determining food requirements and making inferences about the nutritional status of individuals and their populations. Accurate growth curves are also needed to quantify drug dosages to treat wounded or entangled animals. However, body sizes are often based on small numbers of measured animals that must be improved as new data become available. We updated an existing body growth model for N...

Animal‐borne instruments have become a standard tool for collecting important data from marine mammals. However, few studies have examined whether placement of these data loggers affects the behavior and energetics of individual animals, potentially leading to biasing data. We measured the effect of two types of relatively small data loggers ( Callorhinus ursinus ) while swimming at depth. Swim speeds and rates of oxygen consu...

We reconstructed the foraging tracks of lactating northern fur seals ( Callorhinus ursinus ) from two eastern Bering Sea islands (St. Paul Island and Bogoslof Island) using linear interpolation between GPS locations recorded at a maximum of four times per hour and compared it to tri‐axial accelerometer and magnetometer data collected at 16 Hz to reconstruct pseudotracks between the GPS fixes. The high‐resolution data revealed...

A number of hypotheses have been proposed to explain the most recent decline (1977–2012) of S teller sea lions ( SSL ; E umetopias jubatus ) in the G ulf of A laska and A leutian I slands. We examined hypotheses about fisheries competition, environmental change, predation, anthropogenic effects and disease using observations of modern A leut and archaeological, ethnohistoric and ethnographic data from the western G ulf of A la...

Ecologists are increasingly interested in quantifying consumer diets based on food DNA in dietary samples and high‐throughput sequencing of marker genes. It is tempting to assume that food DNA sequence proportions recovered from diet samples are representative of consumer's diet proportions, despite the fact that captive feeding studies do not support that assumption. Here, we examine the idea of sequencing control materials o...

Thermoregulatory capacity may constrain the distribution of marine mammals despite having anatomical and physiological adaptations to compensate for the thermal challenges of an aquatic lifestyle. We tested whether subadult female northern fur seals ( Callorhinus ursinus ) experience increased thermoregulatory costs in water temperatures potentially encountered during their annual migration in the Bering Sea and North Pacific...

The thermoregulatory abilities of northern fur seals ( Callorhinus ursinus ) during their first two years in the frigid waters of the North Pacific Ocean may limit their geographic distribution and alter the costs for exploiting different species of prey. We determined the thermoneutral zone of six young northern fur seals by measuring their metabolism in ambient air and controlled water temperatures (0°C–12°C) from ages 8 to...