History of Deer Herd Reduction for Tick Control on Maine’s Offshore Islands

Abstract

The incidence of Lyme disease in Maine is associated with high abundance of blacklegged (deer) ticks, which in turn has been partly attributed to local overabundance of white-tailed deer. With evidence from Monhegan Island that the complete removal of deer reduced ticks and risk of contracting Lyme disease, nine other offshore communities initiated efforts to cull deer. We reviewed and summarized available histories of deer management on Maine’s offshore islands. Concern about Lyme disease provided the overarching impetus for deer culls. Culls mostly occurred on islands that have no regular firearms hunting season, island communities have been challenged to control deer numbers, and social acceptance of deer culls varied. Integrated tick management (ITM) is the key to controlling ticks, but statewide ITM policy is lacking. Formation of vector control districts with statewide ITM policy would support all communities in Maine. In the Northeast including Maine, blacklegged ticks feed on birds, rodents, and deer (Eisen et al. 2016). Migratory birds disperse tick larvae and nymphs over long distances (e.g., Smith et al. 1996). Locally, white-footed mice (Peromyscus leucopus) and some other rodent species are reservoirs of B. burgdorferi and transmit this pathogen to feeding blacklegged tick larvae and nymphs (e.g., Mather et al. 1989). However, blacklegged tick adults do not feed on mice. Indeed, the white-tailed deer (Odocoileus virginianus) is the most important host of adult blacklegged ticks by providing a mating site to adults and providing roughly 90 percent of female blacklegged tick blood meals (Wilson et al. 1990). A blood-fed, female blacklegged tick may lay approximately 2,000 eggs (Mount et al. 1997). Given the importance of white-tailed deer for completion of the blacklegged tick life cycle, and correlations between deer and tick numbers (e.g., Rand et al. 2003), high blacklegged tick density on New England’s offshore islands has been attributed to overabundant white-tailed deer. Accordingly, over the past three decades, New England island communities including several of Maine’s—such as Monhegan and Islesboro—have debated and in some cases implemented the controversial task of reducing their deer herds in an attempt to lower risk of tick bites and tickborne illnesses. Monhegan’s history of deer removal is the best known example of community management of a deer herd on an offshore island in Maine. In the 1990s, concern about Lyme disease led the community to remove all deer, which resulted in a substantial decline in blacklegged tick density (Rand et al. 2004). Other Maine offshore island communities, facing locally burgeoning deer densities, began to cull (reduce) deer. Maine has 15 unbridged, offshore islands with year-round populations (Figure 1). The formation of town tick or deer control committees in some of these communities reflects the broader concept that betterment of public health sometimes hinges on community-initiated policies that improve environmental conditions (Deprez and Thomas 2016). To suppress blacklegged ticks and Lyme disease, Telford (2017) suggested lowering the density of whitetailed deer to approximately 8–13 per square mile. The Maine Department of Inland Fisheries and Wildlife’s 2017 Big Game Management Plan (MDIFW 2017) stated that maintaining deer at or below 11 per square mile may lower tick abundance and subsequently decrease risk of tick-borne pathogens. Our intent is not to debate whether Lyme disease can be measurably reduced by lowering and maintaining deer density to 8–13 per square mile. Rather, we will summarize the efforts that Maine’s offshore communities have made to control deer, while also assessing islanders’ motivations. White-tailed deer are valued by Maine people for viewing, hunting, and the species’ contribution to the economy, but overabundant deer have negative consequences beyond tick-borne disease, including vehicle collisions, orchard and landscaping damage, and reduced deer and forest health (e.g., Beguin et al. 2009; McShea 2012). The history of efforts to reduce deer populations on Maine’s offshore islands has been documented in a piecemeal fashion over time. To consolidate this history, we drew from scientific articles, Maine Department of Inland Fisheries and Wildlife (MDIFW) reports and biologists, and print and online news articles. Maine’s news outlets have followed deer herd management across the decades, and reporters have solicited expert opinions from special permit hunters, MDIFW biologists, public health officials, and municipal personnel. Our aims were (1) to determine whether deer culls reduced and maintained deer density in the range of 8–13 per square mile; (2) to qualitatively assess motivations for and methods of deer herd reduction; and (3) to discuss the efficacy of deer herd management in the larger context of integrated tick management (ITM), social acceptance, and gaps in policy. We hope this article will serve as a reference for island and mainland communities and state agencies. These entities will benefit by understanding the motivations, magnitude, and effects of efforts to reduce deer herds and can use this knowledge to initiate or broaden ITM policies. HISTORY OF DEER HERD MANAGEMENT ON OFFSHORE ISLANDS I Maine, white-tailed deer ranged from scarce around the turn of the 20th century to locally overabundant around the turn of the 21st century. Due to this scarcity, Maine’s eight southern counties, which include all the offshore islands in our study, were closed to hunting from 1894 through 1902 (MDIFW 2017). Islesboro, North Haven, and Vinalhaven reinstituted the regular firearms season in the 1950s (Moore 2002). Given safety concerns, other islands maintained hunting bans. In 2000, MAINE POLICY REVIEW • Vol. 30, No. 1 • 2021 o.2 DEER HERD REDUCTION