Models to assess ability to achieve localized areas of reduced white-tailed deer density
Van Buskirk, Amanda et al. (2020), Models to assess ability to achieve localized areas of reduced white-tailed deer density, Dryad, Dataset, https://doi.org/10.5061/dryad.m37pvmd18
Localized management of white-tailed deer (Odocoileus virginianus) involves the removal of matriarchal family units with the intent to create areas of reduced deer density. However, application of this approach has not always been successful, possibly because of female dispersal and high deer densities. We developed a spatially explicit, agent-based model to investigate the intensity of deer removal required to locally reduce deer density depending on the surrounding deer density, dispersal behavior, and size and shape of the area of localized reduction. Application of this model is illustrated using the example of abundant deer populations in Pennsylvania, USA. Most scenarios required at least 5 years before substantial deer density reductions occurred. Our model indicated that a localized reduction was successful for scenarios in which the surrounding deer density was lowest (30 deer/mi²), localized antlerless harvest rates were ≥ 30%, and the removal area was 5 mi² or larger. When the size of the removal area was < 5 mi2, end population density was highly variable and, in some scenarios, exceeded the initial density. The shape of the area of localized reduction had less influence on the ability to reduce deer density than the size. There were no differences in mean deer density in the same size circle or square removal areas. Similarly, increasing the ratio of sides (length : width) in rectangular removal areas had little influence on the ability to locally reduce deer densities. Situations in which deer density was higher (40 or 50 deer/mi2) required antlerless removal rates to exceed 30% and took more than 5 years to considerably reduce density in the localized area regardless of its size. These results indicate that the size of the area of reduction, surrounding deer density, and antlerless harvest rate are the most influential factors in locally reducing deer density. Therefore, localized management likely can be an effective strategy for lower density herds, especially in larger removal areas. For high density herds, the success of this strategy would depend most on the ability of resource managers to achieve consistently high antlerless harvest rates.
There are two Netlogo models that accompany the manuscript. The first model "Deer Stable" is a Netlogo model that is used to simulate a realistic model deer population. The second model "Deer Reduction"is a Netlogo model that runs various scenarios to explore the effect of different variables on the ability to locally reduce deer density. Both models are parameterized using data from peer-reviewed literature and from local data on deer populations in Pennsylvania, USA.
The user can click on the "Info" tab within both models to see a description of how the models are run.
Pennsylvania Game Commission, Award: 1434-03HQRU1548
Pennsylvania Department of Conservation and Natural Resources, Award: 4400015622