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

• Published in: The Journal of animal ecology Vol. 90; no. 5; pp. 1264 - 1275
• Main Authors: Rayl, Nathaniel D., Merkle, Jerod A., Proffitt, Kelly M., Almberg, Emily S., Jones, Jennifer D., Gude, Justin A., Cross, Paul C.
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01-05-2021; John Wiley and Sons Inc
• Subjects: Allotments; Animal diseases; Animal migration; Applied Ecology; Behavioural Ecology; Bison bison; Bos taurus; Brucellosis; Brucellosis Brucella abortus; Buffalo; Cervus canadensis; Community Ecology; cross‐species pathogen spillover; Demography; Disease Ecology; Disease transmission; Ecosystem Ecology; Ecosystem services; Ecosystems; Elk; elk Cervus canadensis; Fetuses; Health risks; human–wildlife conflict; Landscape Ecology; Livestock; Migrants; Migration; Movement Ecology; partial migration; Pathogens; resource selection function; Risk; Risk assessment; Risk taking; Snowpack; Spatial Ecology; Weather; Wildlife; wildlife disease; Brucellosis Brucella abortus; wildlife disease; cross-species pathogen spillover; elk Cervus canadensis; resource selection function; partial migration; human-wildlife conflict
• ISSN: 0021-8790; 1365-2656
• DOI: 10.1111/1365-2656.13452

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.
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 foetuses) from migrant and resident elk to livestock.
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.
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.
Our results demonstrate links between migration behaviour, 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. Furthermore, 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. They 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.
The authors examined the influence of elk migration in the risk of disease spillover. Their findings demonstrate links between migration, spillover risk, and environmental variability, highlighting the utility of integrating disease transmission and movement models to generate novel insights about the influence of migration in spillover risk.