Seasonal Changes in Food Consumption, Respiration Rate, and Body Condition of a Male Harbor Porpoise (Phocoena phocoena)

High field metabolic rates of wild harbour porpoises

“…Previous studies have speculated that captive porpoises overeat due to boredom, leading to an overestimation of the FMR of wild individuals if extrapolating from captive conspecifics (Yasui and Gaskin, 1986). However, the body composition and blubber thickness data do not support this notion; captive porpoises in our study had fat contents of 24-37% of body weight, and blubber thickness in the mid-dorsal area of 17-38 mm (Kastelein et al, 2018;, closely resembling measurements from wild individuals for the same seasons and body lengths (Lockyer, 1995;Lockyer and Kinze, 2003;McLellan et al, 2002). In principle, captive porpoises could still have an elevated food intake and a low FMR if their assimilation capacities were poor compared with wild conspecifics.…”

“…estimated precision of the DLW method, and much lower than the expected heat loss variation. Despite the rather stable FMR, we observed large fluctuations in the food intake of captive porpoises Kastelein et al, 1997aKastelein et al, , 2018, with energy acquisition increasing around mid-July, and peaking during mid-November (more than 50% increase relative to the minimum) after which it decreased again during late winter and spring . The increase in food intake was followed by a similar increase in blubber mass of up to 10 kg (Kastelein et al, 2018), while lean body mass remained stable (Table 1).…”

“…Direct and indirect respirometry measurements from sea otters and small pinnipeds have led to the notion that small marine mammals have elevated FMRs to counter a high mass-specific heat loss in water (Hurley and Costa, 2001;Sparling, 2004;Yeates et al, 2007). For one of the smallest cetaceans, the harbour porpoise, some studies suggest that FMRs are similar to those of similar-sized terrestrial mammals (Yasui and Gaskin, 1986;Otani et al, 2001;Gallagher et al, 2018), but this conflicts with the high food intakes (Andersen, 1965;Dudok Van Heel, 1962;Kastelein et al, 1990Kastelein et al, , 1997aKastelein et al, , 2018Myers et al, 1978) and high metabolic rates (Kanwisher and Sundnes, 1965) reported for captive porpoises, and the recent reports of high feeding rates in wild porpoises (Wisniewska et al, 2016). To address this knowledge gap, we here combine unique data from captive and wild harbour porpoises to test the hypothesis that harbour porpoises have elevated FMRs.…”

“…In an early study, Kanwisher and Sundnes (1965) reported that the BMR of two captive juveniles were two to three times higher than in similar-sized terrestrial mammals, and argued that the high BMR was due to the high cost of thermoregulation in water. The notion of high metabolic rates is also supported by high food intakes reported for captive individuals (Dudok Van Heel, 1962;Andersen, 1965;Myers et al, 1978;Kastelein et al, 1990Kastelein et al, , 1997aKastelein et al, , 2018. In a similar setting as Kanwisher and Sundnes (1965), Reed et al (2000) measured oxygen consumption rates in captive juvenile porpoises in a small tank that rendered values two times higher than the BMR predicted from similar-sized terrestrial mammals.…”

“…Kooyman (1989) presented a general equation describing the relationship between TLC and body mass for marine mammals, TLC=0.1×M b 0.96 . However, this equation may be problematic in harbour porpoises, whose body mass varies by more than 15% during the year as they alter their blubber layer (Lockyer, 1995;Kastelein et al, 2018). While lean body mass should be a more reliable measure, lean body mass estimates were not available for all the wild harbour porpoises in this study.…”