Journal of Comparative Physiology B

, Volume 160, Issue 6, pp 637–644 | Cite as

The effect of submergence on heart rate and oxygen consumption of swimming seals and sea lions

  • T. M. Williams
  • G. L. Kooyman
  • D. A. Croll
Article

Summary

Respiratory, metabolic, and cardiovascular responses to swimming were examined in two species of pinniped, the harbor seal (Phoca vitulina) and the California sea lion(Zalophus californianus).

  1. 1.

    Harbor seals remained submerged for 82–92% of the time at swimming speeds below 1.2 m·s-1. At higher speeds, including simulated speeds above 1.4 m·s-1, the percentage of time spent submerged decreased, and was inversely related to body weight. In contrast, the percentage of time spent submerged did not change with speed for sea lions swimming from 0.5 m·s-1 to 4.0 m·s-1.

     
  2. 2.

    During swimming, harbor seals showed a distinct breathhold bradycardia and ventilatory tachycardia that were independent of swimming speed. Average heart rate was 137 beats·min-1 when swimming on the water surface and 50 beats·min-1 when submerged. A bimodal pattern of heart rate also occurred in sea lions, but was not as pronounced as in the seals.

     
  3. 3.

    The weighted average heart rate (WAHR), calculated from measured heart rate and the percentage time spent on the water surface or submerged, increased linearly with swimming speed for both species. The graded increase in heart rate with exercise load is similar to the response observed for terrestrial mammals.

     
  4. 4.

    The rate of oxygen consumption increased exponentially with swimming speed in both seals and sea lions. The minimum cost of transport calculated from these rates ranged from 2.3 to 3.6 J · m-1 · kg-1, and was 2.5–4.0 times the level predicted for similarly-sized salmonids. Despite different modes of propulsion and physiological responses to swimming, these pinnipeds demonstrate similar transport costs.

     

Key words

Heart rate Oxygen consumption Harbor seal Sea lion 

Abbreviations

ECG

electrocardiogram

HR

heart rate measured during steady swimming (beats·min-1)

Tsub or surface

fraction on time spent submerged or on the water surface

Vsim

simulated swimming speed (m · s-1)

Vw

towing speed for animals with drag cups (m·s-1)

O2

rate of oxygen consumption (ml O2·kg-1·min-1)

W AHR

weighted average heart rate (beats·min-1)

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Copyright information

© Springer-Verlag 1991

Authors and Affiliations

  • T. M. Williams
    • 1
  • G. L. Kooyman
    • 1
  • D. A. Croll
    • 2
  1. 1.Physiological Research LaboratorySeripps Institution of OceanographyLa JollaUSA
  2. 2.National Marine Fisheries ServiceNE SeattleUSA

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