Prey switching as a coping strategy in subsistence coupled human-natural systems

Background/Question/Methods

Many rural Alaskans are part of northern coupled human-natural systems.  They rely on a suite of ecosystem services for subsistence, and as a result shape ecological processes around them.  There is qualitative evidence that Alaskan subsistence hunters substitute prey in the face of changing constraints (i.e., ecological concept of prey switching) to maximize the acquisition of a resource, or minimize the time needed to acquire the necessary amount of a resource. Our objective was to quantify the extent that four rural Alaskan communities employ prey switching tactics to cope with fluctuating levels in the annual availability of subsistence resources (i.e., salmon, moose, and caribou). We hypothesized that hunters would compensate for a decline in harvest of one resource by increasing harvest of another.  We developed a predictive framework and conducted a correlation analysis to demonstrate how currently available harvest data may be applied within the framework to assess the extent of prey switching in rural Alaskan communities.

Results/Conclusions

We found a significant negative association (β= -0.91; p= 0.04) between annual harvests in one community, a negative but insignificant trend in another (β= -0.55; p= 0.31), evidence for an integrated subsistence system when the previous community was considered in tandem with its sister community (β=-0.88; p=0.12), and no clear relationship in the fourth.  Although our approach provided strong statistical support for our hypothesis in one community, and to a lesser extent in others, currently available data may be inadequate to discount the use of prey switching in communities that lacked evidence for the process.  Potentially confounding factors accounted for in our predictive framework but not in the statistical exercise include the availability of store bought foods and small game resources.  Our findings imply that a single-resource wildlife management approach is inadequate to address the vulnerability of subsistence communities or facilitate adaptation to changes in the characteristics of coupled human-natural systems.  Managing ecosystem services individually rather than as an interrelated system may make the goals of conservation and subsistence mutually exclusive.  Managers should take into account the health of all individual components of the system and allow for subsistence compensation when viable if harvest closures of one species are necessary.