Basal metabolism of an adult male killer whale ( Orcinus orca )

Knowing how much energy an individual requires is fundamental to resolving a number of questions about the role an animal plays in its ecosystem. Various authors have used different approaches to assess energy needs of in situ (free-ranging) killer whales (Orcinus orca), including estimates based on observations of prey capture and consumption rates (e.g., Williams et al. 2004, Maniscalco et al. 2007) or extrapolations from bioenergetic models using data derived from ex situ (managed in zoological parks) individuals (e.g., Kastelein and Vaughan 1989, Kasting et al. 1989, Kriete 1995, Kastelein et al. 2003). The few measurements that have been made on ex situ killer whales include assessments of respiratory capabilities (e.g., Spencer et al. 1967, Kriete 1995), quantification of food/energy intake rates (e.g., Kastelein and Vaughan 1989, Kastelein et al. 2000a), or measures of metabolic rate (e.g., Kasting et al. 1989, Kriete 1995). These latter measurements have frequently not met the criteria of Kleiber (1975) due to whales being immature, pregnant, and/or active. The goals of the present study were to develop a functional methodology that could be employed to measure resting oxygen consumption rates of ex situ killer whales and obtain basal metabolic rate (BMR) measurements. The foundation of any bioenergetic model is an accurate assessment of BMR. They are not only used to estimate “resting” costs, but multiples of BMR are often used to estimate total field metabolic rates. Such models are important for estimating energy expenditures since it is difficult or impossible to acquire direct measures, especially for in situ whales, due to their large size and limited accessibility. Mass-balance simulation models have been used to estimate feeding requirements for some marine mammal species (e.g., Winship et al. 2002, Williams and Noren 2009), but because actual energetic measurements (including critical estimates of BMR) are impossible