Subsurface swimming and stationary diving are metabolically cheap in adult Pacific walruses (Odobenus rosmarus divergens).

Walruses rely on sea-ice to efficiently forage and rest between diving bouts while maintaining proximity to prime foraging habitat. Recent declines in summer sea ice have resulted in walruses hauling out on land where they have to travel farther to access productive benthic habitat while potentially increasing energetic costs. Despite the need to better understand the impact of sea ice loss on energy expenditure, knowledge about metabolic demands of specific behaviours in walruses is scarce.

Lung function assessment in the Pacific walrus () while resting on land and submerged in water.

In the present study, we examined lung function in healthy resting adult (born in 2003) Pacific walruses () by measuring respiratory flow ([Formula: see text]) using a custom-made pneumotachometer. Three female walruses (670-1025 kg) voluntarily participated in spirometry trials while spontaneously breathing on land (sitting and lying down in sternal recumbency) and floating in water. While sitting, two walruses performed active respiratory efforts, and one animal participated in lung compliance measurements.

Comparative Respiratory Physiology in Cetaceans.

In the current study, we used breath-by-breath respirometry to evaluate respiratory physiology under voluntary control in a male beluga calf [, body mass range ( ): 151-175 kg], an adult female (estimated = 500-550 kg) and a juvenile male ( = 279 kg) false killer whale () housed in managed care. Our results suggest that the measured breathing frequency ( ) is lower, while tidal volume ( ) is significantly greater as compared with allometric predictions from terrestrial mammals. Including previously published data from adult bottlenose dolphin () beluga, harbor porpoise (), killer whale (), pilot whale (), and gray whale () show that the allometric mass-exponents for and are similar to that for terrestrial mammals ( : 1.

Whistling is metabolically cheap for communicating bottlenose dolphins ().

Toothed whales depend on sound for communication and foraging, making them potentially vulnerable to acoustic masking from increasing anthropogenic noise. Masking effects may be ameliorated by higher amplitudes or rates of calling, but such acoustic compensation mechanisms may incur energetic costs if sound production is expensive. The costs of whistling in bottlenose dolphins () have been reported to be much higher (20% of resting metabolic rate, RMR) than theoretical predictions (0.

Ventilation and gas exchange before and after voluntary static surface breath-holds in clinically healthy bottlenose dolphins, .

We measured respiratory flow (), breathing frequency (), tidal volume (), breath duration and end-expired O content in bottlenose dolphins () before and after static surface breath-holds ranging from 34 to 292 s. There was considerable variation in the end-expired O, and following a breath-hold. The analysis suggests that the dolphins attempt to minimize recovery following a dive by altering and to rapidly replenish the O stores.

Impact of gas emboli and hyperbaric treatment on respiratory function of loggerhead sea turtles (.

Fisheries interactions are the most serious threats for sea turtle populations. Despite the existence of some rescue centres providing post-traumatic care and rehabilitation, adequate treatment is hampered by the lack of understanding of the problems incurred while turtles remain entrapped in fishing gears. Recently it was shown that bycaught loggerhead sea turtles () could experience formation of gas emboli (GE) and develop decompression sickness (DCS) after trawl and gillnet interaction.