Impacts of white-tailed deer removal on a Canada yew plant community on Sand and York Islands, Apostle Islands National Lakeshore

Ruid, David; Van Stappen, Julie; Willging, Robert

High levels of white-tailed deer (Odocoileus virginianus) herbivory on Sand (2,949 acres, 11.93 km²) and York (321 acres, 1.29 km²) Islands in the Apostle Islands National Lakeshore (APIS) on Lake Superior in Wisconsin have negatively impacted sensitive understory plant communities, threatening natural diversity. Deer densities may have reached a peak of approximately 13/ km² and 19/ km² on Sand and York Islands, respectively. Canada yew (Taxus canadensis), an evergreen understory shrub highly susceptible to browsing by deer, has been nearly extirpated on the mainland. However, landscape scale Canada yew populations still exist on Apostle Islands that historically had few to no deer, including Sand and York Islands. In the early 2000’s, deer became established on Sand and York Islands and their populations very rapidly expanded. Severe impact to Canada yew and other sensitive species occurred at a very rapid pace. A 2007 APIS Wildlife Management Plan designated two deer management zones. Management objectives for Zone 1 (includes Sand and York), are to keep the deer population as low as possible. In accordance with the plan, deer population reduction efforts were implemented in 2007 utilizing a variety of methods, including public hunting, culling by APIS staff and volunteers, and trapping using clover traps. In 2009 APIS partnered with the United States Department of Agriculture, Wildlife Services (USDA-WS) to remove deer through sharpshooting. During a pilot removal effort in May 2009, 13 deer were removed on Sand Island in two nights. In total, 214 deer were culled from both Islands (Sand 178, York 36) from spring, 2007–2013. Biological samples from nearly all culled deer were collected in order to evaluate health status. Culling efforts were successful in eliminating deer from York Island and reducing the population on Sand Island to approximately 0.67 /km². Canada yew recovery on both islands is evident. Annual monitoring indicates a very large decrease in the number of plots with yew browse and a slow, but steady increase in the average percent cover of Canada yew. Challenges to the removal effort included extreme weather, boat logistics, and lack of road or trail networks on the islands. While the project was conducted on islands without easy public access, it was of great interest to local tribes, sportsmen, media and the general public.