Lung function assessment in the Pacific walrus (Odobenus rosmarus divergens) 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 (Odobenus rosmarus divergens) by measuring respiratory flow (V̇) 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. For spontaneous breaths, V̇ was lower when lying down (e.g. expiration: 7.1±1.2 l · s−1) as compared to when in water (9.9±1.4 l · s−1), while tidal volume (VT, 11.5±4.6 l), breath duration (4.6±1.4 s), and respiratory frequency (7.6±2.2 breaths · min−1) remained the same. The measured VT and specific dynamic lung compliance (0.32±0.07 cmH2O−1) for spontaneous breaths, were higher than those estimated for similarly sized terrestrial mammals. The VT increased with body mass (allometric mass-exponent=1.29) and ranged from 3 to 43% of the estimated total lung capacity (TLCest) for spontaneous breaths. When normalized for TLCest, the maximal expiratory V̇ (V̇exp) was higher than that estimated in phocids, but lower than that reported in cetaceans and the California sea lion. The V̇exp was maintained over all lung volumes during spontaneous and active respiratory manoeuvres. We conclude that location (water or land) affects lung function in the walrus and should be considered when studying respiratory physiology in semi-aquatic marine mammals.

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Observations of Annual Walrus (Odobenus rosmarus divergens) Migrations in the Nearshore Waters of the Chukotka Peninsula from 1990 to 2012

ARCTIC ◽

10.14430/arctic70035 ◽

2020 ◽

Vol 73 (1) ◽

pp. 99-113

Author(s):

Vladimir V. Melnikov

Keyword(s):

Marine Mammals ◽

Chukchi Sea ◽

Relative Number ◽

Bering Strait ◽

Pacific Walrus ◽

Odobenus Rosmarus Divergens ◽

Odobenus Rosmarus ◽

Commercial Harvest ◽

The Pacific ◽

Pass Through

After the end of the commercial harvest, research regarding the Pacific walrus (Odobenus rosmarus divergens) in Russia was reduced and focused on the observation of animals at land-based haul-outs. This paper presents the long-term observations of the distribution, relative abundance, and direction of seasonal movements of walruses in the offshore waters of the Chukotka Peninsula, based on data obtained in 1990 – 2012. Observations of Pacific walruses and other marine mammals were conducted mainly from April through November, but some were conducted all year round. In some years up to 30 Native Chukotkan observers were employed at this task. Some watched from observation posts in Native villages onshore, and others from motorboats during hunting trips. These observations have shown that walruses are rare in January and February in the nearshore waters of the Chukotka Peninsula. Their numbers begin to increase in March. The northward movement of walruses begins in April, and walruses migrate from the Bering Sea to the Chukchi Sea throughout the summer months and early autumn. Based on observations from posts located directly in front of the southern Bering Strait, I conclude that 106 – 1055 walruses pass through the Bering Strait from July to September, to the northwest and north. At the haul-outs in the Gulf of Anadyr, the relative number of walruses remains stable during the summer (up to 11 000 individuals at all haul-outs in total based on observers’ estimates) and decreases only with the appearance of ice in October – November.

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