Behavioural Culture in Orca (Orcinus orca) as a Criterion for Conservation Prioritisation

Behavioural Culture in Orca (Orcinus orca) as a Criterion for Conservation Prioritisation is my postgraduate dissertation research project, undertaken at Birkbeck University of London. Evidence of culture within orca (killer whales) is well documented. Focusing on often complex foraging and social behaviours exhibited by orca, which are socially learned and transmitted within families and communities, my research aimed to establish the importance of this ‘behavioural’ culture in the prioritisation of orca communities for conservation attention. 

Multiple themes emerged during the course of my research, including the issues surrounding orca classification as a single species, despite the myriad differences between orca populations around the globe, and also the complexities of orca categorisation into so-called ‘ecotypes’ – categories which are used to define distinct orca populations based on morphological, ecological and regional differences. This extract from my dissertation presents a section of Chapter 5, entitled ‘Taxonomic classification and ecotype categorisation’ and deals with the confusion which may arise when attempting to categorise orca communities into rigid categories which may not serve to accurately, or adequately, describe them, and the implications this has for conservation. 

Download this paper or scroll down to read an extract.

Excerpt

(pg. 9-10)

The North Pacific Residents and Bigg’s are the most widely studied orca in the world from whom much of what is known about orca has been established. Orca ecotype categorisation was developed from the very clear differences between these populations which, though sympatric, exist completely independently of one another. (Interviewee 4 commented “they’re literally seen bashing each other to get away from each other”). But these ecotypes are very extreme examples of differentiation between orca communities. One participant in particular provided detailed points on the issue of ecotype classification and the inherent inability to accurately categorise all populations into the rigid ecotype structure detailed in Table 1, describing it as a “topic of confusion” (Interviewee 4).

However this point was picked up by five additional participants in varying ways. “...these North Pacific populations really are the oddball... they’re the exception and everything else seems to be what’s normal.”

“...we've [researchers] relied really heavily on this standard in the North Pacific of these two populations that are really genetically divergent, ecologically divergent. And they've kind of come up... with this idea of what an ecotype... should be.”

Interviewee 4

As research develops, it is becoming clearer that orca in other areas do not fall into such neatly divided categories as the Residents and Bigg’s (e.g. Best et al, 2004, Baird et al, 2006 and Lauriano et al, 2020). For instance, with the return of large baleen whales and the opportunity for other significant prey resources including seals, orca have returned to Australia and are found in both tropical and temperate regions. Populations existing around Australia are not detailed in Figure 3. It is unclear what ecotype these may belong to, or – importantly – if any (Lauriano et al, 2020). Some populations are relatively distinct, some however were described to me as “soup” – “...offshoot populations that are a... mix of everything” (Interviewee 4). Referring to the morphology of certain orca, Interviewee detailed “...we do have Antarctic-looking ones”, showing the confusion and difficulty in categorising a population that may visually resemble Antarctic orca but which, by regional definition would not fit into the ecotype.