Modeling localized deer removal strategies for managing chronic wasting disease
We used a published individual-based model to evaluate localized deer removal strategies for managing chronic wasting disease (CWD) in a free-ranging white-tailed deer population in central Michigan, USA. We simulated fine-scale (23.3 km 2 ) deer culling using ring, land parcel-based, and habitat quality-based removal methods. Ring culling consisted of highly concentrated culling in a focal area (e.g., CWD detection area), with effort diminishing as distance away from that location increased. Land parcel-based culling represented a scenario where land access permissions varied across space. Habitat quality-based culling represented intense culling in areas thought to be high-quality deer habitat (thereby likely containing more targets). We also assessed male-targeted strategies for ring and parcel-based methods. We used cost estimates from 2016–2021 in Michigan to calculate total annual localized deer culling expenditures for each removal method. Lastly, we investigated how local conditions, including initial deer density and study area context, affected management outcomes. Chronic wasting disease was less likely to persist in our projections, and prevalence rate was lower, for deer inhabiting a suburban study area compared to an exurban area. All culling methods reduced the probability that CWD would persist and lowered 15-year prevalence in the population compared to no culling. Ring culling near the site of detection (1.6-km instead of 2.4-km radii ring) was most effective at minimizing CWD persistence at medium and high deer densities. However, the ring size most effective at reducing 15-year CWD prevalence depended on study area context and deer densities, with the 2.4-km cull resulting in the lowest prevalence at medium and high deer densities in the suburban study area. At low deer density, parcel-based culling performed best in both study area contexts. Targeting male deer only was consistently less effective at reducing CWD persistence and prevalence and more costly than non-selective deer culling. All culling methods that did not target males had similar total costs for one year of culling in the 23.3-km 2 area, but costs varied considerably based on study area ($5,500–22,100 USD) and deer density ($14,300–25,700). Our model simulations indicated that male-focused culling strategies are less effective and more expensive than non-selective strategies, that ring-based culling is most effective at medium and high deer densities, and that CWD persistence and prevalence in exurban locales are greater compared to suburban locales, regardless of culling strategy.