2011 Deer Pellet and Browse Report: Sand and York Islands, Apostle Islands National Lakeshore

Bartnick, Travis; Duerkop, Peter

Long-term monitoring of white-tailed deer and associated browse related impacts are designed to provide park staff with critical information used to effectively manage deer populations. The monitoring includes quantitative information on the impacts of deer browse to vegetation and estimates of population density. From these two types of data, changes in vegetative communities corresponding to fluctuations in deer populations can be traced over time. The park’s Wildlife Management Plan for Harvestable Species establishes two management zones. One zone includes those islands without a historic population of deer that have abundant Canada yew in their forest understory. Islands within this zone are: Devils, Eagle, Gull, North Twin, Outer, and Raspberry Islands, Sand and York Islands. The goal for these islands is to keep the deer population as low as possible, preferably deer-free. The other zone includes the rest of the islands which have a diverse history of deer occurrence and abundance. The goal for this zone is no more than 10 deer/mi2, the estimated pre-logging abundance of deer in northern Wisconsin. For a summary of the history of deer in the Apostle Islands, see Appendix A. Currently, island deer populations are limited to Sand, York, Oak, and Basswood. On Sand Island, overwintering deer were documented in 2001 and on York in 2005. Populations rapidly increased on both islands, resulting in heavy impacts on Canada yew. The park began efforts to reduce deer numbers in 2004 and, with the help of Great Lakes Restoration Initiative funding, greatly increased efforts beginning in 2009. The need for monitoring differs, depending on the current status of the islands. On islands, such as Sand and York, where active culling is occurring, it is very important to determine the effectiveness of culling efforts and, hopefully, to document recovery. On Islands, such as Oak and Basswood, where deer populations have occurred for decades at low levels, occasional monitoring is needed to determine if numbers start rapidly increasing and unacceptable impacts begin to occur on browse sensitive vegetation. On other islands, especially those that have not had a history of deer and have abundant Canada yew, it is important to monitor for presence/absence. This is most effectively done through winter aerial surveys. It is critically important to take action early if deer become established on high priority islands. One of these is Raspberry Island, which not only has an absence of deer and lush Canada yew, but is also almost completely covered in old-growth forest. Raspberry is especially at risk since its location is very close to both the mainland and York Island. Monitoring includes: pellet surveys to determine relative changes in deer numbers; browse surveys to determine the impact of deer on browse sensitive species; aerial surveys to determine presence/absence and deer concentrations areas; and, most recently, the use of trail cameras to obtain population estimates with a mark-recapture technique through the identification of individual bucks using their unique antler characteristics. The use of trail cameras is still in the experimental stage, but shows great promise. Annual browse surveys and pellet counts have been conducted on Sand Island since 2003 and on York since 2005. In 2005-2006, more intensive surveys were conducted as part of a research project that included pellet counts and browse surveys on Sand, York, Basswood, the Mainland, Raspberry, and Oak Islands (Smith 2007). On Sand and York Islands, high levels of browse continue to be found, with browsing found in nearly all of the plots with Canada yew. Browse surveys have been conducted less frequently on Oak and Basswood Islands (Meeker 2001; Smith 2007; Fraker 2010). The populations on these islands appear to remain small, with minimal impact on browse sensitive species.