Killer whales (Orcinus orca) recovery strategy: chapter 4

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4. Knowledge gaps

While resident killer whales are among the best studied cetaceans in the world, it is clear that key information is still needed to assist their recovery. In part this is due to the fact that although studies of killer whales have been ongoing over the last 30 years, killer whales spend the majority of time underwater, and their whereabouts are unknown during much of the year. As well, opportunities to learn from killer whale carcasses occur relatively infrequently. Only seven to eight carcasses are recovered around the world each year (Raverty and Gaydos 2004). In a 30 year period, only 14 resident carcasses have been found and necropsies in British Columbia (Ford et al. 1998), a recovery rate of 6%.

Listed below are the key areas where further knowledge is needed:

• The year-round distribution and behaviour of resident killer whales
• Critical and important habitat for resident killer whales, in addition to the areas identified in this strategy
• The historical abundance of resident killer whales
• The year-round diet and energetic requirements of resident killer whales
• The consequences of changes in key prey populations on resident killer whales, as well as their historic trends
• The population level consequences of low population size and its effects on the sustainability and viability of resident killer whales
• The population size that is needed to maintain the cultural and genetic diversity of resident killer whales
• The long- and short-term effects of physical disturbance (shipping, whale watching, aircraft, researchers and film makers) on resident killer whales
• The long- and short-term effects of acoustic disturbance (whale watching, seismic surveys, military sonar, researchers and film makers) on resident killer whales
• The full range of anthropogenic environmental contaminants to which killer whales and their prey are exposed, over time and in space, with special attention paid to the identification of sources and the resulting effects of environmental contaminants on resident killer whales, their prey and their habitat
• Diseases, pathogens, parasites and pathologies of resident killer whales
• The effects of climate or environmental change on resident killer whale prey and their habitat