UBC Theses and Dissertations
Bioenergetics in the killer whale, orcinus orca Kriete, Birgit
A series of three papers is presented, each one related to the bioenergetics of killer whales, Orcinus orca. The first chapter describes how standard and realized metabolic rates were determined in captive killer whales by collecting respirations at different apneas and different activity states by training the animals to exhale into a funnel onto which a meteorological balloon was attached. These exhalations were analyzed for tidal volumes and respiratory gases; estimates of realized metabolic rates were based on activity budgets observed in the individual animals. Tidal volumes at rest were 2.7 to 4.2 times higher than those predicted by allometric equations, while estimated vital capacities are estimated to lie between 68% and 94% of the values predicted by allometric equations. Standard metabolic rates for the adult animals were similar to Kleiber’s estimates (1.2 to 1.3 times Kleiber). Realized metabolic rates were between 2.7 and 2.9 times those of the whales’ SMR, which are values similar to those of terrestrial mammals. In the second chapter, food consumption and the influence of other factors such as pregnancy, lactation and water temperature on the food intake of captive killer whales, were examined. Food data were collected from the aquaria at which the animals were held and analyzed for caloric values on a daily basis. While food intake increased with age, differences in water temperature ranging between 7 and 23 °C had little or no effect on food intake. Pregnancy caused an increase in food consumption of 25% only during the last month of gestation, but food intake increased up to 100% with lactation. The best fit for feeding rate as a function of body weight was determined as: food intake (kg/d) = 0.277 M⁰⁶⁶³, where M = body mass in kg. A mean net assimilation efficiency of 0.73 was calculated by comparing food intake to energy expenditure measured by respiration analysis. In the third chapter, realized metabolic rates were estimated in free-ranging killer whales along the Pacific West Coast of British Columbia and Washington. Swimming velocities and respiration rates were determined by tracking movements of whales using a theodolite and a loran. The relationship between swimming velocities and respiration rates showed an increase in respiration rate with increasing swimming speed for different age and sex classes of killer whales. These data were combined with metabolic rates determined by respiration analysis in captive killer whales during different activity states to estimate metabolic rates of wild killer whales during swimming (males: metabolic rate (kcal/kg/d) = 29.32 + 1.11V²⁵ females: metabolic rate (kcal/kg/d) = 32.29 + 1.26V²⁵). The minimum cost of transport for male and female killer whales occurred at 3.1 rn/sec which corresponded to 0.18 and 0.20 kcal/kg/km. The drag that killer whales experience at different swimming velocities was calculated based on theoretical assumptions and suggests that drag is mainly laminar (males: 88% of the flow was laminar and 12% were turbulent; females: 89% of the flow was laminar and 11% turbulent).