Kinship, Cultural Traditions and the Resilience of Killer Whale Populations in the North Pacific

Long-term studies of killer whales in the North Pacific have documented populations characterized by a highly philopatric, matrilineally organized social structure. These populations are often small and both gene flow and dispersal are restricted. Moreover, prey preferences and seasonal ranging patterns appear to be extremely persistent, and are largely shaped by the vertical transmission of cultural traditions among related individuals within matrilines and populations. These characteristics make killer whales unique among marine mammals in many respects, but do they also contribute to the vulnerability of the population to anthropogenic impacts and environmental change? As highly mobile apex predators, killer whales theoretically have the ability to exploit a wide variety of prey resources, thereby adapting to changes in the abundance and distribution of prey. However, behavioral observations and multiple supporting data sets indicate that this assumption based on a biological ability to adapt is not fully realized in some local populations. Recent decades have seen dramatic changes in the population demographics of a number of small killer whale populations in the eastern North Pacific. Both demographic changes and changes in social cohesion have been linked to prey dynamics, suggesting that behavioral specializations and cultural traditions may restrict a population’s ability to adapt to ecological changes. Here we consider the unique characteristics associated with killer whale populations and discuss the conservation and evolutionary implications in terms of the long-term resilience of local populations.