The significance of respiration timing in the energetics estimates of free-ranging killer whales (Orcinus orca)

Abstract

Respiration rate has been used as an indicator of metabolic rate 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 10 adult Norwegian herring-feeding killer whales (Orcinus orca) recorded with high-resolution tags (DTAGs). We compared fixed O 2 uptake per respiration models with 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. In contrast to findings 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 increased and became less variable at higher swimming speeds, possibly to increase O 2 uptake efficiency per respiration. 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 expected to be 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.

Using Digital Tags With Integrated Video and Inertial Sensors to Study Moving Morphology and Associated Function in Large Aquatic Vertebrates

“…Whales are air‐breathing divers that incur significant oxygen debt while searching for, pursuing, and capturing prey at depth. After a dive, whales repay that oxygen debt through a series of breaths often referred to as a surface series (Roos et al, ). Typically, these breaths are taken as the whale is in motion, where the body arches and pitches to orient the dorsally positioned blowholes out of the water (Goldbogen et al, ).…”

“…During each breath, a large volume of air is expired and inspired in a very short amount of time (Brodie, ), thereby resulting in extremely high flow rates through the blowhole(s) (Kooyman et al, ). Although it is clear that the cetacean respiratory apparatus has undergone a suite of modifications for a fully aquatic life (Kooyman, ; Piscitelli et al, ), respiratory events in free‐ranging whales have only been inferred from animal‐borne sensor data (Goldbogen et al, ; Miller et al, ; Roos et al, ). By placing our movement‐video tags directly behind the blowhole, we can document the precise opening and closing of the blowholes after a range of different dives and behaviors (Fig.…”

Correlations of metabolic rate and body acceleration in three species of coastal sharks under contrasting temperature regimes

“…Elliott et al, 2012;Stothart et al, 2016;Roos et al, 2016). This type of concomitant validation in the field is unfortunately not possible for water-breathing taxa; instead, calibrations in the laboratory represent the most comprehensive validation possible for the method in fish.…”

“…Using respiratory frequency to estimate metabolic rates of air-breathing marine taxa such as cetaceans has also been successful (e.g. Roos et al, 2016), but again this method is difficult to apply to water-breathing taxa. Instead, respirometry has become the standard in measuring metabolic rate in fishes (Carlson et al, 2004).…”

Spatial behavior, swimming speed and surfacing rate of two captive harbor porpoises in ambient sound control conditions

“…Nile tilapia, Oreochromis niloticus (Barreto and Volpato, 2011)) and also varied in response to sound exposure in a study on a harbor porpoise (Kastelein et al, 2015). However, respiration rates and general activity levels may also vary independently, as O 2 uptake is not always maximal in odontocetes, especially not at moderate to low levels of arousal (Roos et al, 2016).…”