Ecotype Divergence

Biggs and Northern Residents of British Columbia

The complex dynamics of potential speciation among orca ecotypes have been a hot topic in 2024, specifically in relation to the Resident and Biggs communities in British Columbia. But is their reproductive isolation biological or is it a matter of choice, behavior and cultural tradition? According to the Biological Species Concept, for speciation to occur, reproductive isolation is the key. For divergence of populations to occur there needs to be a mechanism—whether it is allopatric (geographic separation) or sympatric (same location but different behaviors or resources). In the case of these two communities, there is not geographic isolation but they do have different ecological niches. 

The suggestion that orcas may have evolved through cultural or behavioral choice rather than environmental pressures is intriguing. Loyalty to traditions, such as prey preferences, could have played a role in divergence. The fact that captured orcas initially refuse food outside their cultural norm highlights the strength of these behavioral barriers. Even in captivity, it is noted that some orcas will not eat unfamiliar prey until they have gone days without food, reinforcing how deeply ingrained these differences are.

I wonder if food competition might have driven divergence between these two groups. Biggs orcas, characterized by their morphological differences—such as larger size, elongated rostrum, and silent hunting strategies—are seen to have adapted to hunting larger prey like whales. These differences could explain why they evolved separately from Resident orcas, who focus on fish and possess different hunting tactics and social structures. The physical and behavioral distinctions between these groups might be connected to their ecological roles.

However, reflections on the limitations of genetic data reveal a greater interest in the cultural and ecological factors driving the potential speciation of orcas. Whether these differences are enough to classify them as separate species, as suggested with the names Orcinus ater and Orcinus rectippinus (Morin et al., 2024), remains up for debate among scientists, especially since hybrid orcas have been bred in captivity. This suggests some level of reproductive compatibility, even if it is not common in the wild. I continue to wonder if hybrid orcas are reproductively viable, but it seems the research on this is scarce and there are nuances. Here is Corky as an example: she is a Northern Resident being held captive at SeaWorld San Diego and she has experienced 7 births in captivity with the longest living calf only being 46 days old. Reproductive success in captivity already seems low. I would also not like to use captivity as a proxy in my research.

Regardless of whether orca ecotypes are distinguished as distinct species, their cultural richness and traditions make them intriguing and beloved. I have known that my love for orcas is ingrained deeply within me and I can tell that other scientists here at OrcaLab feel the same. With orca research, it cannot just be cut and dry science. To study and understand orcas, we are commanded by them to be creative. Because they are so intriguing, our minds cannot help but run wild trying to understand them. While the scientific details may be complex and filled with nuances, appreciation and respect for orca's mysterious lives will continue among anyone who has an appreciation for nature. 

References

https://royalsocietypublishing.org/doi/10.1098/rsos.231368

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