2015 Deer Pellet and Browse Report: Basswood, Cat, Oak, Sand, and York Islands, Apostle Islands National Lakeshore

Aldred, Tanya; Bartnick, Travis

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: Cat, Devils, Eagle, Gull, Ironwood, North Twin, Otter, 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 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, Oak, Basswood and Stockton Islands. 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. Currently, there is not a deer population on York and the numbers of deer on Sand Island have been greatly reduced. The need for monitoring differs, depending on the current status of the islands. On islands such as Sand and York, where culling has occurred, it is very important to determine whether or not culling efforts are needed 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 to 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. Monitoring includes: pellet surveys to determine relative changes in deer abundance; browse surveys to determine the impact of deer on browse sensitive species; and the use of trail cameras to determine presence/absence. Trial cameras have also been used on Sand Island 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). On Sand and York Islands, the level of deer browse on yew and other browse-sensitive tree and shrub species has declined steadily since 2011. In many areas throughout the island, Canada yew appears to have started recovering from the heavy browsing by deer that occurred from their first detection through 2010. 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. In 2015, browse surveys were conducted on Basswood, Cat, a