Despite its essential role in bioenergetic modeling, reliable measures of energy expenditure (i.e., oxygen consumption) associated with the different activities of wild animals have remained elusive. Oxygen consumption rate (VO₂) associated with activity can be estimated as a function of heart rate (fh), and the empirical relationship between the two has been determined for several aquatic vertebrates while fasting and resting. However, the simplified fh:VO₂ relationships established from such studies may differ under more complex physiological circumstances, such as when animals are foraging at depth or feeding on prey. I assessed the efficacy of using fh to predict VO₂ in 7 captive Steller sea lions, Eumetopias jubatus, while fasting and feeding at rest (on land or in water) and while diving (up to 40 m in the open ocean). Linear mixed-effects models revealed that environment, amount of food fed, and type of diving activity all altered the fh:VO₂ relationship. They also showed that different linear equations are needed to predict VO₂ from fh for sea lions fasted while on land or in water, but that a single equation can predict VO₂ on land regardless of whether fasted or feeding. When in water, feeding animals a 4, 6, or 12 kg meal changed the fh:VO₂ relationship compared to fasted animals. While fh can reliably be used to predict VO₂ in diving sea lions, the relationship differed between single dive cycles (one dive +surface interval) and dive bout cycles (multiple dives+surface intervals). However, the equation that predicted VO₂ for single dive cycles did not differ from that for sea lions resting on the surface. Neither dive duration, dive depth, nor food consumed significantly affected the fh:VO₂ relationships. Heart rate could be used to predict VO₂ in diving sea lions, but only over complete dive cycles or dive bouts where animals recovered fully from the O₂ debt incurred underwater. Based on these results, separate equations that distinguish among environmental, digestive, and diving states can be employed to accurately predict VO₂ from heart rate in wild Steller sea lions.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU.2429/23511 |
| Date | 05 1900 |
| Creators | Young, Beth Lyn |
| Publisher | University of British Columbia |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
Page generated in 0.0242 seconds