Center for
WHALE RESEARCH

To understand the drivers and consequences of natural processes, scientists need to observe and record that process over relevant timescales. For researchers studying animal populations, this means collecting data on those animals throughout a lifespan or, ideally, over multiple lifespans. When these animals are long-lived, like many large mammals, this can mean several decades of research are needed. That has been the goal of the Center for Whale Research (CWR) for the last 46 years: to understand and conserve the Southern Resident killer whale (SRKW) population through long-term, individual-based scientific research.

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Through the ORCA SURVEY program, the primary goal of the Center for Whale Research has been to provide an up-to-date census of the Southern Resident killer whale community. This data is ultimately what scientists and managers use to assess the status and trends of this endangered population over time. The information has been crucial for establishing conservation planning in this population. CWR’s census provided the data to identify the SRKW’s small population size and their decline in the 1990s, ultimately leading to the whales being listed as endangered. This same data revealed key correlations between the Southern Residents’ survival, reproduction, and social cohesion and the abundance of Chinook salmon, which identified salmon recovery as the key conservation action for the SRKWs.

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In the last decade, the Center for Whale Research’s long-term data has revealed even more factors driving killer whale survival and identified risk factors in the population. CWR research has shown that even adult killer whales are dependent on their mothers and grandmothers and suffer increased mortality risk when they lose these key family members. Further analysis showed that male killer whales are dependent on their wider social circle: socially integrated males have greater survival probabilities than more peripheral individuals. These social effects, especially the effect of grandmothers and social integration, interact with salmon abundance: social relationships are more important when times are hard. The critical role of social relationships in determining killer whale fitness may have important implications for this population’s trajectories. If the population begins losing mothers and grandmothers during periods when salmon is sparse, we could see a rapid population decline.

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While the last several decades have taught us many things about the Southern Residents, there is still much to learn. And what we don’t know may be crucial. While we know that social relationships and prey abundance influence orca survival, we don’t yet fully understand the interplay between ecology, demography, and social structure.

 

• How do deaths and births change social relationships?

• What are the health consequences for the orcas that remain?

• How does the dependence of individuals on their mothers influence the trajectory of the population?

• What are the long-term effects of reduced social cohesion for the population?

 

These questions are crucial for fully understanding the state of the SRKW population and setting conservation goals—and will take many more years of data collection and analysis. One of the key tasks right now is to determine which salmon runs have the most influence on killer whale vital rates, which is challenging in a small population with a slow life history. We need to continue the long-term census of the Southern Residents to eventually determine the fine-scale correlates of survival and fecundity in this population.

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In addition to continued long-term monitoring, the Center for Whale Research is utilizing new methods to piece together a better picture of killer whale society and its consequences on individuals and populations. Using aerial observations, CWR measures and analyzes fine-scale social interactions, including affiliative social contact, aggression, and prey sharing. This data will be used to determine what drives social relationships and the consequences of particular kinds of social relationships for individual survival and reproduction. Supplementing this, CWR has used intensive image analysis to determine what drives differences in injuries received from conspecifics (“rake marks”) in these killer whales.