Efficiency of different spatial and temporal strategies for reducing vertebrate pest populations

Abstract

Understanding effectiveness of control strategies of pest species is fundamental for planning efficient and cost-effective management programs. In addition to culling rates, there are many potential factors that can determine efficiency of different management strategies, including demographic processes such as immigration rates, birth dynamics, and spatial ecology. We developed a stochastic, data-based simulation model of feral swine population dynamics which accounted for social dynamics in space. We tested the impacts of different spatio-temporal management strategies (i.e., culling rates, timing of culling during the year, spatial pattern of culling and strength of a barrier to immigration) on population response and efficiency. The spatial culling strategy dramatically impacted efficiency of control-using zonation required removal of fewer pigs (up to 46% less) to achieve similar reductions compared with other spatial strategies. Also, our spatially-explicit model predicted that lower culling intensities could be used to achieve population reductions when zonation was applied relative to predictions from harvesting theory based on simple logistic models. As culling intensity increased (≥50% of target population annually) and the target population reached low density (<5% of original density), effects of spatial strategy became less pronounced relative to immigration barrier effects. Lastly, for the same level of moderate culling effort, prioritization of culling during the low-birthing period generally resulted in faster population reduction to near zero abundance relative to prioritization during the high-birthing period, or spreading the work over a year period, but the significance of this effect depended on the spatial culling strategy and culling intensity. Our results imply that continually updating knowledge of current abundance during management may not only be important for determining culling quotas, but also for updating and optimizing management strategies. When the management goal is maximum population control, consideration of birth and spatial dynamics can increase return on management effort and bring to light management inefficiencies.

Pest control at a regional scale: Identifying key criteria using a spatially explicit, agent‐based model

“…For example, Pepin et al. () studied wild pig populations following pest control in the USA. They showed that prioritizing culling during the low‐birthing period generally resulted in faster population reduction than other temporal strategies, but this effect was small compared to the effects of spatial prioritization.…”

Accounting for heterogeneous invasion rates reveals management impacts on the spatial expansion of an invasive species

“…) and fertility control (see Pepin et al. , b for theoretical evaluation). These are investments that have not yet been realized in terms of feral swine removals.…”

“…In addition, previous work has shown that prioritizing removals during non‐birthing periods can improve the efficiency of control (Pepin et al. , b), suggesting that further optimization of timing could be helpful. However, our results are national‐scale averages and previous work has indicated that forage availability can greatly impact feral swine population growth and establishment (Tabak et al.…”

Effectiveness of signs of activity as relative abundance indices for wild boar

“…In most cases, the resources (funds, materials and labor) available for these measures are limited; thus, efficient strategies are needed to meet management goals. In particular, spatial culling quotas according to local densities are effective in wildlife management, including wild boar management (McMahon et al 2010, Pepin et al 2017). Therefore, reliable estimates of population abundance and trends are important for the adaptive management of wildlife (Nichols and Williams 2006).…”