2014 Deer Browse and Pellet Survey Apostle Islands National Lakeshore

Sizer, Marc; Johnson, Lane

Long-term monitoring of white-tailed deer and associated browse related impacts are designed to provide park staff with critical information needed 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: Cat, Devils, Eagle, Gull, Ironwood, 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. 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 to have no more than 10 deer/mi2, which is 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.Canada yew (Taxus Canadensis) is of special concern because this species has been nearly extirpated on the mainland, yet islands within Zone 1 retain landscape level Canada yew in their understory. It is a highly preferred winter browsing species and appears poorly defended against deer browse, having fewer chemical and physical deterrents than other species (Windels and Flaspohler 2011). Where supply exceeds demand, deer can quickly reduce the local population to near extinction. Currently, island deer populations are limited to Sand, York, Oak, and Basswood. On Sand and York, two islands with a history of few to no deer, an overwintering population became established in the early 2000’s. The deer population 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 or has recently occurred, 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. 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 abundance; browse surveys to determine the impact of deer on browse sensitive species; presence/absence surveys 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. 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).