Abundance trends of American martens in Michigan based on statistical population reconstruction

Estimating the dynamics of furbearer populations is challenging because their elusive behavior and low densities make observations difficult. Statistical population reconstruction is a flexible approach to demographic assessment for harvested populations, but the technique has not been applied to furbearers. We extended this approach to furbearers and analyzed 8 yr of age-at-harvest data for American marten (Martes americana) in the Upper Peninsula of Michigan. Marten abundance estimates showed a general downward trend from an estimate of N̂ = 1,733.3 (SÊ = 861.3) animals in 2000 to N̂ = 1,163.9 (SÊ = 520.1) in 2007. The harvest probability of martens increased nearly 5-fold from 0.0542 (SÊ = 0.0250) in 2000 to 0.2637 (SÊ = 0.1154) in 2007, which corresponded to a 5-fold increase in trap-nights. Continued monitoring of martens in the Upper Peninsula, Michigan, and a reassessment of current harvest regulations are necessary given the estimated decreases. Moreover, we do not encourage the use of harvest indices as the sole technique to assess the status and trends of marten and fisher populations. Auxiliary studies in the Upper Peninsula, Michigan, will allow for continued use and improvement in the application of these models.