The significance of respiration timing in the energetics estimates of free-ranging killer whales ( Orcinus orca )
Respiration rate has been used as an indicator of metabolic rates and associated cost-of-transport (COT) of free-ranging cetaceans, discounting potential respiration-by-respiration variation in O 2 uptake. To investigate the influence of respiration timing on O 2 uptake we developed a dynamic model...
| Published in: | Journal of Experimental Biology |
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| Main Authors: | , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
2016
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| Subjects: | |
| Online Access: | https://risweb.st-andrews.ac.uk/portal/en/researchoutput/the-significance-of-respiration-timing-in-the-energetics-estimates-of-freeranging-killer-whales-orcinus-orca(afea3a48-5e13-458a-9a6f-007c0476abc5).html https://doi.org/10.1242/jeb.137513 https://research-repository.st-andrews.ac.uk/bitstream/10023/11163/1/Roos_2016_Significance_JEB_2066.pdf |
| Summary: | Respiration rate has been used as an indicator of metabolic rates and associated cost-of-transport (COT) of free-ranging cetaceans, discounting potential respiration-by-respiration variation in O 2 uptake. To investigate the influence of respiration timing on O 2 uptake we developed a dynamic model of O 2 exchange and storage. Individual respiration events were revealed from kinematic data from ten adult Norwegian herring-feeding killer whales ( Orcinus orca ) recorded with high-resolution tags (DTAGs). We compared fixed-O 2 -uptake-per-respiration models to O 2 uptake per respiration estimated through a simple 'broken-stick' O 2 -uptake function, in which O 2 uptake was assumed to be the maximum-possible O 2 uptake when stores are depleted or maximum total body O 2 store minus existing O 2 store when stores are close to saturated. Conversely to assuming fixed O 2 uptake per respiration, uptake from the broken-stick model yielded a high correlation (r 2 > 0.9) between O 2 uptake and activity level. Moreover, we found that respiration intervals became less variable and increased at higher swimming speeds, possibly to increase O 2 uptake efficiency per breath. As found in previous studies, COT decreased monotonically versus speed using the fixed-O 2 -uptake-per-respiration models. However, the broken-stick uptake model yielded a curvilinear COT-curve with a clear minimum at typical swimming speeds of 1.7-2.4 m s -1 . Our results showed that respiration-by-respiration variation in O 2 uptake is significant. And though O 2 consumption measurements of COT for free-ranging cetaceans remain impractical, accounting for the influence of respiration timing on O 2 uptake will lead to more consistent predictions of field metabolic rates than using respiration rate alone. |
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