Emergence of Ixodes scapularis (Acari: Ixodidae) in a Small Mammal Population in a Coastal Oak-Pine Forest, Maine, USA

In the United States, surveillance has been key to tracking spatiotemporal emergence of blacklegged ticks [Ixodes scapularis Say (Ixodida:Ixodidae)] and their pathogens such as Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner (Spirochaetales: Spirochaetaceae), the agent of Lyme disease. On the Holt Research Forest in midcoastal Maine, collection of feeding ticks from live-trapped small mammal hosts allowed us to track the emergence and establishment of I. scapularis, 1989–2019. From 1989–1995, we collected only I. angustus Neumann (Ixodida: Ixodidae)(vole tick), Dermacentor variabilis Say (Ixodida: Ixodidae) (American dog tick), and I. marxi Banks (Ixodida: Ixodidae) (squirrel tick) from seven species of small mammals. The most abundant tick host was the white-footed mouse [Peromyscus leucopus Rafinesque (Rodentia:Cricetidae)] followed by the red-backed vole (Myodes gapperi Vigors (Rodentia: Cricetidae)). Emergence of I. scapularis was signaled via the appearance of subadult I. scapularis in 1996. Emergence of B. burgdorferi was signaled through its appearance in I. scapularis feeding on mice in 2005. There was a substantial increase in I. scapularis prevalence (proportion of hosts parasitized) and burdens (ticks/host) on white-footed mice and red-backed voles in 2007. The ~11-yr time-to-establishment for I. scapularis was consistent with that seen in other studies. White-footed mice comprised 65.9% of all captures and hosted 94.1% of the total I. scapularis burden. The white-footed mouse population fluctuated interannually, but did not trend up as did I. scapularis prevalence and burdens. There were concurrent declines in I. angustus and D. variabilis. We discuss these results in the broader context of regional I. scapularis range expansion.

Effects of Brush Piles on Small Mammal Abundance and Survival in Central Pennsylvania

Brush piles have long been promoted as a means to enhance wildlife habitat, yet few studies have experimentally tested the perceived benefits of these structures for wildlife or evaluated the efficacy of different arrangements of these piles within landscapes. During summers 2005 and 2006, we used a mark–recapture study to compare small mammal abundance and survival in forested habitats provisioned with brush piles vs. similar habitats without, both at sites located adjacent to agricultural edges and within the interior of forests in central Pennsylvania. Northern short-tailed shrews Blarina brevicauda, mice Peromyscus, and eastern chipmunks Tamias striatus were all frequently captured within brush piles at edge and interior sites. Peromyscus were significantly more abundant at edge vs. interior sites. The presence of brush piles, however, seemed to have little effect on small mammal abundance or survival with the only potential effect being an increased overwinter survival rate experienced by Peromyscus at brush pile sites. We hypothesize that although brush piles provide cover and foraging sites for small mammals, the large quantities of coarse woody debris that exist naturally in many forested systems may already adequately provide these habitat features, minimizing the effects of brush piles on small mammal population dynamics.