Assessing the success of American marten reintroduction to northern Wisconsin


The American marten (Martes americana) is the only state endangered mammal in Wisconsin. Martens were extirpated from the state in the 1920s due to unregulated trapping and extensive habitat loss from logging. In 1953 and 1956 the first reintroduction occurred in the state with a release of 10 individuals to Stockton Island of the Apostle Islands. The last reported observation occurred in 1969 and the reintroduction was considered a failure. Since 1975 reintroductions have occurred in the Chequamegon and Nicolet National Forest of Wisconsin with the release of 139 and 172 martens respectively, but population viability and connectivity has remained uncertain.

Previous research: Reintroduced mainland populations

Following multiple reintroduction attempts over the last 4 decades, there are recovering populations of martens in both the Chequamegon National Forest (CNF) and the Nicolet National Forest (NNF). To assess the potential role of competition in the delayed recovery of martens to the CNF, we used occupancy models and stable isotope analysis to explore niche partitioning between martens and a primary competitor, the fisher (Pekania pennanti). We observed significant niche overlap between the two species and concluded that competition may be contributing to the delayed recovery of martens in the CNF. Concurrently, we also non-invasively sampled marten DNA from the CNF and used genetic mark-recpature and parentage analyses to estimate marten abundance, density, survivorship, and recruitment. Many of these population processes and attributes were previously unknown for CNF martens and sound estimates of these parameters have helped gauge reintroduction success and guided future management.

To compare these vital rates and gain an understanding of mechanisms limiting marten recovery, we followed up the CNF project by initiating a project in the NNF where track surveys and anecdotal evidence suggest a potentially stable population. Similar to CNF, we estimated marten demographic parameters to conduct various population projections and found the importance of low levels of immigration on population viability. Following the work done in the CNF and NNF, we assessed genetic structure between populations within the Great Lakes region using Bayesian clustering approaches. We found distinct clustering of reintroduced populations with limited admixture between populations. The martens of CNF and NNF genetic makeup still predominately reflects that of the individual source populations used for reintroductions. The results suggest that reintroductions can create novel patterns of genetic structure across small spatial scales.

This work is funded by the US Department of Agriculture, Great Lakes Indian Fish & Wildlife Commission, US Forest Service, and the Wisconsin Department of Natural Resources.


Current research: Apostle Islands population

Surprisingly in 2010, martens were observed on the Apostle Islands after a nearly 50 year absence. We will first determine the origin and colonization history of martens to the Apostle Islands using genetic methods that will help inform management on dispersal and connectivity of this sensitive species in the state. In addition, we will use genetic mark-recapture techniques to estimate abundance, density, survivorship, and recruitment for this unique island population. We will quantify prey availability and use stable isotope analysis to understand the proportional diet of martens on the Apostle Islands. Such an approach will enable us to not only determine how marten colonized these islands, their overall population viability and the mechanism for their persistence, but also explore potential differences between the islands and mainland, identify the mechanisms for the different recovery trajectories, and ultimately explore the Apostle Islands as a potential habitat refugia for marten recovery to the state and region.

This work is funded by the US Department of Agriculture, Great Lakes Indian Fish & Wildlife Commission, National Park Service and the Wisconsin Department of Natural Resources.