In a previous post, I pointed out that a proper understanding of "population" is central for claims about the endangered status of gray wolves under the U.S. Endangered Species Act (ESA).* The same is true for a recent ruling reaffirming the endangered status of southern resident orcas. Endangered "distinct population segments" are recognized under the ESA, but even the Fish and Wildlife Service (FWS) seems to acknowledge that their interpretation of this term may be faulty, having explicitly called for comment on it in their wolf delisting proposal. The National Marine Fisheries Service (NMFS), who issued the ruling on orcas, uses a more bare-bones interpretation of "distinct population segment" than the FWS does, considering only whether the population is "discrete" and "significant."
It is time for the FWS and the NMFS to recognize a more robust concept of population, based on the interactions among organisms. As I have argued elsewhere, populations ought to be characterized in terms of survival and reproductive interactions among organisms, with the boundaries of the population as the largest grouping for which the rates of interaction are much higher within the grouping than outside. The Pacific Legal Foundation, on behalf of the Orwellian-named "Center for Environmental Science Accuracy and Reliability" and two farms in central California,** argued that the southern resident orcas were not genetically distinct from other orcas. The NMFS found that the scientific evidence did not support this claim, and that, moreover, there are significant behavioral differences between the southern resident orcas and the other orcas: "differences in morphology, behavior, diet and feeding ecology, acoustical dialects and practices." In particular, the practice that orcas are most well known for, i.e., killing other whales (a practice that gives rise to the name "killer whale"), is not one that that the southern resident orcas engage in; rather, the southern resident orcas eat salmon. These differences are sometimes, perhaps with good reason, described as differences in culture.
If the FWS and the NMFS were to use an interactionist concept of population, it would be clearer that groups like the southern resident orcas are a distinct population because they interact amongst themselves in ways that they do not interact with other orcas. It thus would be harder for farmers, ranchers, hunters, etc., to raise legal challenges on genetic bases alone, which are clearly insufficient. An interactionist concept of population would be more general, covering the different kinds of species interactions that can cause differentiation of groups within the species; newly discovered behaviors would be covered by definition without having to stipulate them ahead of time. Furthermore, an interactionist concept would be more sensitive to evolutionary processes; even if it had turned out that the southern resident orcas were not genetically distinct, recognition of their interaction patterns would suggest that the group would likely become distinct in the future. Our ESA should not lock our preservation efforts into the present-day configurations of populations.
The NMFS made the right decision this time, but future ones may not go as well (and it remains to see what the FWS will do for wolves). They ought to adopt an interactionist concept of "population."
Notes
* Note that the comment period for the proposed removed of gray wolves from the endangered species list has been extended until October 28. Comments can be submitted here.
** The farms are worried that they will received reduced amounts of water in order to maintain salmon stocks for the orcas.
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