How effective are buffer zones in managing invasive beavers in Patagonia? A simulation study

In an age of invasions, it is critical to design and test management strategies to more efficiently control foreign species. Spatially explicit individual based models (SEIBMs) are a powerful tool to explore different management scenarios to control invaders, but we rarely have enough data to parameterize these models, particularly for relatively long-lived species. Here we take advantage of our previous work estimating demographic rates of invasive beavers in Patagonia, and develop an SEIBM to model the spread of beavers in Patagonia. We used our SEIBM both to estimate dispersal distances by fitting their observed rate of spread and to test how placing a buffer zone (a longitudinal strip of land perpendicular to the direction of spread within which a fraction of beavers are culled) beyond the invasion front would work as a control strategy. Specifically, we explored six different scenarios with two different culling rates and two buffer zone widths. We found that beavers in Patagonia must disperse long distances on average to account for the observed rate of spread, and thus our model predicts that a 100 km buffer zone will be needed to slow (but likely not halt) the spread of beavers. Interestingly, culling a higher proportion of beavers within a 100 km buffer zone (90 vs. 60%) did not improve buffer zone performance. Our study shows that wide buffer zones can slow (but likely not halt) continental spread of beavers in Patagonia and potentially pave the way for beaver eradication.