| 1. |
- Svärd, C., et al.
(författare)
-
Fasting affects the surface and diving metabolic rates of Steller sea lions Eumetopias jubatus
- 2009
-
Ingår i: Aquatic Biology. - Oldenorf/Luhe : Inter-Research. - 1864-7782 .- 1864-7790. ; 8:1, s. 71-82
-
Tidskriftsartikel (refereegranskat)abstract
- Changes in metabolic rates were measured in 3 captive female Steller sea lions Eumetopias jubatus that experienced fasts during summer and winter. We measured metabolic rates (via O2 consumption) before (MRs, surface) and after (DMR, dive + surface interval) the sea lions dove to 10–50 m depths. Measurements were obtained prior to and immediately after 9 to 10 d fasts, and during a 14 d recovery period. The sea lions lost significantly more body mass (Mb) during the winter fast (10.6%), compared with the summer (9.5%). Mass-corrected dive metabolic rate (cDMR = DMR × Mb–0.714) was not affected by dive depth or duration, but increased significantly following the winter fasts (13.5 ± 8.1%), but did not change during summer (–1.1 ± 3.2%). However, mass-corrected surface metabolic rate (cMRs) decreased significantly after both the summer (–16.4 ± 4.7%) and winter (–8.0 ± 9.0%) fasts. Consequently, the ratio between cDMR and cMRs was significantly higher in winter, suggestive of an increased thermal challenge and convective heat loss while diving. Increased cMRs following the fast indicated that digestion began during foraging and was not deferred, implying that access to ingested energy was of higher priority than optimizing diving ability. cDMR was elevated throughout the recovery period, independent of season, resulting in a 12% increase in foraging cost in winter and a 3% increase in summer. Our data suggest that Steller sea lions are more sensitive to changes in body condition due to food shortages in the winter compared with the summer.
|
|
| 2. |
- Fahlman, Andreas, et al.
(författare)
-
Metabolic costs of foraging and the management of O2 and CO2 stores in Steller sea lions
- 2008
-
Ingår i: The Journal of Experimental Biology. - Cambridge : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 211, s. 3573-3580
-
Tidskriftsartikel (refereegranskat)abstract
- The metabolic costs of foraging and the management of O2 and CO2 stores during breath-hold diving was investigated in three female Steller sea lions (Eumetopias jubatus) trained to dive between 10 and 50 m (N=1142 dives). Each trial consisted of two to eight dives separated by surface intervals that were determined by the sea lion (spontaneous trials) or by the researcher (conditioned trials). During conditioned trials, surface intervals were long enough for O2 to return to pre-dive levels between each dive. The metabolic cost of each dive event (dive+surface interval; DMR) was measured using flow-through respirometry. The respiratory exchange ratio (O2/CO2) was significantly lower during spontaneous trials compared with conditioned trials. DMR was significantly higher during spontaneous trials and decreased exponentially with dive duration. A similar decrease in DMR was not as evident during conditioned trials. DMR could not be accurately estimated from the surface interval (SI) following individual dives that had short SIs (<50 s), but could be estimated on a dive by dive basis for longer SIs (>50 s). DMR decreased by 15%, but did not differ significantly from surface metabolic rates (MRS) when dive duration increased from 1 to 7 min. Overall, these data suggest that DMR is almost the same as MRS, and that Steller sea lions incur an O2 debt during spontaneous diving that is not repaid until the end of the dive bout. This has important consequences in differentiating between the actual and `apparent' metabolic rate during diving, and may explain some of the differences in metabolic rates reported in pinniped species.
|
|
