Human-Caused Mortality and Population Trends of American Marten and Fisher in a U.S. National Park

Abstract

American marten (Martes americana) and fisher (M. pennanti) are susceptible to overharvest. National Park Service policies require managers to ensure long-term population viability of native wildlife while concurrently provide recreation opportunities, which can include harvest of wildlife. I investigated human-caused mortality factors of American martens and fishers in Pictured Rocks National Lakeshore (PRNL), Michigan, from May-December 2001-2005. Thirty-five martens and 14 fishers were captured and survival was monitored using radio telemetry. Four martens were legally trapped, one marten was killed by a vehicle collision within PRNL, and three martens died of natural causes. The only fisher mortality was through legal trapping within PRNL. In addition, vehicles in the study area killed an uncollared marten and fisher. Greatest marten mortality occurred during the harvest season in December, with only males reportedly harvested. Overall, marten and fisher survival from June-December was 0.803 (95% confidence interval [CI]: 0.689 to 0.882) and 0.812 (95% CI: 0.374 to 0.977), respectively. Using survival rates from this study and reported rates of fecundity, I estimated that current marten mortality rates are sustainable and that the population was increasing at a rate of 16%/year. Survival data and harvest records suggest that the fisher population is stable or increasing. Human-caused mortality appears to be the greatest source of mortality for martens and fishers at PRNL. Although current harvest rates are comparatively low, continued monitoring of harvest within and adjacent to PRNL, in addition to monitoring vehicle collisions, is warranted to ensure viable populations are maintained.