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Elk migration influences the risk of disease spillover in the Greater Yellowstone Ecosystem

February 25, 2021
  1. Wildlife migrations provide important ecosystem services, but they are declining. Within the Greater Yellowstone Ecosystem (GYE) some elk (Cervus canadensis) herds are losing migratory tendencies, which may increase spatiotemporal overlap between elk and livestock (domestic bison [Bison bison] and cattle [Bos taurus]), potentially exacerbating pathogen transmission risk.
  2. We combined disease, movement, demographic, and environmental data from eight elk herds in the GYE to examine the differential risk of brucellosis transmission (through aborted fetuses) from migrant and resident elk to livestock.
  3. For both migrants and residents, we found that transmission risk from elk to livestock occurred almost exclusively on private ranchlands as opposed to state or federal grazing allotments. Weather variability affected the estimated distribution of spillover risk from migrant elk to livestock, with a 7‐12% increase in migrant abortions on private ranchlands during years with heavier snowfall. In contrast, weather variability did not affect spillover risk from resident elk.
  4. Migrant elk were responsible for the majority (68%) of disease spillover risk to livestock because they occurred in greater numbers than resident elk. On a per‐capita basis, however, our analyses suggested that resident elk disproportionately contributed to spillover risk. In five of seven herds, we estimated that the per‐capita spillover risk was greater from residents than from migrants. Averaged across herds, an individual resident elk was 23% more likely than an individual migrant elk to abort on private ranchlands.
  5. Our results demonstrate links between migration behavior, spillover risk, and environmental variability, and highlight the utility of integrating models of pathogen transmission and host movement to generate new insights about the role of migration in disease spillover risk. Further, they add to the accumulating body of evidence across taxa that suggests that migrants and residents should be considered separately during investigations of wildlife disease ecology. Finally, our findings have applied implications for elk and brucellosis in the GYE, and suggest that managers should prioritize actions that maintain spatial separation of elk and livestock on private ranchlands during years when snowpack persists into the risk period.
Publication Year 2021
Title Elk migration influences the risk of disease spillover in the Greater Yellowstone Ecosystem
DOI 10.1111/1365-2656.13452
Authors Nathaniel D. Rayl, Jerod Merkle, Kelly Proffitt, E. S. Almberg, Jennifer D. Jones, Justin Gude, Paul C. Cross
Publication Type Article
Publication Subtype Journal Article
Series Title Journal of Animal Ecology
Index ID 70218652
Record Source USGS Publications Warehouse
USGS Organization Northern Rocky Mountain Science Center