Joseph Jacquot

Mechanical thinning to restore oak savanna promoted predator assemblages of gypsy moth pupae in Michigan

The United States Forest Service conducted an oak savanna restoration using thinning and prescribed burning in the Manistee National Forest in Michigan to provide additional habitat for species dependent on this rare community type, including the Karner blue butterfly (Lycaeides melissa samuelis). Because the Karner blue butterfly is a federally endangered species, managers cannot spray Bt‐k (Bacillus thurigiensis var kurstaki) in areas undergoing restoration to control exotic invasive defoliators, such as European gypsy moths (Lymantria dispar). Although gypsy moths are invasive in North America, several native predators, such as white‐footed mice (Peromyscus leucopus), other small mammals and invertebrates, help keep gypsy moth populations at nondestructive levels. The present study investigated whether the small mammal community and gypsy moth predation rates were affected by the type of mechanical forest thinning method (bulldozer, masticator, shear cutter) used during an oak savanna restoration at two sites in Michigan within the suppression zone in 2010 and 2011. Predation rates on gypsy moth pupae were higher in bulldozer and shear cutter thinned compared with control plots at both sites in 2010. White‐footed mice relative abundance was significantly higher in thinned compared with control plots at one site in 2010 and 2011. Thinning maintained or promoted white‐footed mice abundance, which will maintain or enhance predation on gypsy moth pupae during oak savanna restoration.

Genetic diversity of reintroduced American martens in Michigan’s Lower Peninsula

Reintroductions are an important conservation and management technique used to restore extirpated populations. Negative genetic consequences (e.g., diversity loss, bottlenecks, inbreeding) are often an unintentional result of reintroductions, due to a small number of founders or suboptimal habitat at release sites. American martens (Martes americana) were extirpated from Michigans Lower Peninsula in 1911 due to habitat loss and unregulated trapping. Martens were reintroduced into 2 areas of the Lower Peninsula in 1985–1986. The Lower Peninsula reintroduction was characterized by a relatively small number of founders (85 individuals) released into 2 geographically disparate, fragmented sites. We genotyped martens sampled at the 2 release sites approximately 20–25 years since reintroduction, using 11 microsatellite loci. We detected low average allelic richness (3.92 alleles per locus), moderate levels of inbreeding (mean FIS = 0.106), and multiple loci with significant heterozygote deficiencies. Effective population size estimates were small, ranging between 6 and 27 individuals depending on the estimator and the sample group. We also detected significant population structuring between the release sites (FST = 0.093 using the most recent sample). With small population size and limited to no gene flow, we predict the 2 Lower Peninsula marten populations will continue to diverge and potentially further lose genetic diversity. This study highlights the importance of long-term genetic monitoring of reintroduced populations.

Resting Site Characteristics of American Marten in the Northern Lower Peninsula of Michigan

Abstract American marten are associated with forests that are characteristically late successional, closed canopy, and diverse in structure; these attributes meet their habitat requirements and provide resting sites. However, the small populations of marten in Michigans Northern Lower Peninsula face modern habitat conditions that are fragmented and considerably altered from presettlement environments. Resting site structures are required habitat components that are used daily and provide protection from predation and inclement weather but may be limiting and require active management to preserve. We identified resting site characteristics of American marten in the Manistee National Forest from May 2011 to December 2013. Twenty-five marten (15 male and 10 female) were monitored to identify resting sites. We identified 522 unique resting site structures; tree cavities (n = 255, 48.9%), branches (n = 162, 31%), and nests (n = 90, 17.2%) were most commonly observed. During the summer (April–September) marten used more exposed tree branches (41.8%); while in the winter (October–March) they used more cavities (64.5%). Marten used structures that were associated with high percent canopy closure (≥67%). Resting sites were found in live trees 86% of the time, and the three predominant species included oak (Quercus spp.), maple (Acer spp.), and red pine (Pinus resinosa). Trees used as resting sites had significantly larger mean diameter at breast height (DBH) than the average DBH of nonresting site trees found at resting site locations (U′ = 268721, P = < 0.001). The average stand basal area (x¯ = 33.92 ± 9.04 m2 ha) found in resting site plots was significantly larger than that found at control plots (x¯ = 31.10 ± 8.69 m2 ha, P = 0.007). Maintaining complex forest structure, abundant CWD, high percent canopy closure and high basal area should be considered when managing for marten. Silvicultural techniques that promote tree species diversity, older tree age classes, and retention of CWD are all important factors to consider when managing for marten.