Factors affecting harvests of fishers and American martens in northern michigan

Harvest data (e.g., number of animals harvested, trapper effort) are an important source of information for state wildlife agencies to manage harvested furbearers. These data provide evidence to support adapting harvest regulations when necessary. Setting appropriate harvest regulations for fishers (Martes pennanti) and American martens (Martes americana) is critical, as these species often exist at low densities, are sensitive to timber-management practices and trapper-harvest, and experience some level of interspecific predation and competition in sympatric populations. We estimated effects of management (e.g., number of fishers or martens harvested per trapper per season [harvest limit], season length) and extrinsic (e.g., weather, pelt prices) factors on regulated harvests of fishers and martens in the Upper Peninsula of Michigan during 1996–2007. We used generalized linear mixed models in an information-theoretic approach (quasi-likelihood adjusted Akaike Information Criterion [QAIC]) to discern which factors most strongly influenced fisher and marten harvests. For harvest of fishers, the 3 QAIC-best models included harvest limit, season length, and number of trappers, suggesting that regulatory changes within the ranges tested may be implemented to influence harvest. The QAIC-best model (harvest limit) contained 26% of the weight of evidence, and using an independent subset of data, showed no difference between model predictions and harvest data. In contrast, harvest of martens was not strongly influenced by any factors we tested. Possible reasons for a lack of measurable effects while modeling harvest of martens include a low harvest limit (i.e., 1 marten) or incidental harvest of martens by fisher or bobcat (Lynx rufus) trappers. Knowledge of influences on harvest will lead to informed decision-making when managers are setting harvest regulations, particularly for low-density furbearers. © 2011 The Wildlife Society.     

Windows of opportunity: white-tailed deer and the dynamics of northern hardwood forests of the northeastern US

Herbivory, lighting regimes, and site conditions are among the most important determinants of forest regeneration success, but these are affected by a host of other factors such as weather, predation, human exploitation, pathogens, wind and fire. We draw together >50 years of research on the Huntington Wildlife Forest in the central Adirondack Mountains of New York to explore regeneration of northern hardwoods. A series of studies each of which focused on a single factor failed to identify the cause of regeneration failure. However, integration of these studies led to broader understanding of the process of forest stand development and identified at least three interacting factors: lighting regime, competing vegetation and selective browsing by white-tailed deer (Odocoileus virginianus). The diverse 100–200 year-old hardwood stands present today probably reflect regeneration during periods of low deer density (<2.0 deer/km²) and significant forest disturbance. If this hypothesis is correct, forest managers can mimic these “natural windows of opportunity” through manipulation of a few sensitive variables in the system. Further, these manipulations can be conducted on a relatively small geographic scale. Control of deer densities on a scale of 500 ha and understory American beech (Fagus grandifolia) on a scale of <100 ha in conjunction with an even-aged regeneration system consistently resulted in successful establishment of desirable hardwood regeneration.     

Marten space use and habitat selection in managed coniferous boreal forests of eastern Canada

Effects of habitat loss and fragmentation on the behavior of individual organisms may have direct consequences on population viability in altered forest ecosystems. The American marten (Martes americana) is a forest specialist considered as one of the most sensitive species to human-induced disturbances. As some studies have shown that martens cannot tolerate >30–40% clear-cuts within their home range, we investigated marten space use (home range size and overlap) and habitat selection in landscapes fragmented by 2 different patterns of timber harvesting in the black spruce boreal forest: dispersed-cut landscapes (10–80 ha cut-blocks) and clustered-cut landscapes (50–200 ha cut-blocks). We installed radio-collars on female martens and determined 20 winter home ranges (100% minimum convex polygons and 60–90% kernels) in dispersed-cut (n = 8) and clustered-cut (n = 12) landscapes. Home range size was not related to the proportion of clear-cuts (i.e., habitat loss), but rather to the proportion of mixedwood stands 70–120 years old. However, female body condition was correlated to habitat condition inside their home ranges (i.e., amount of residual forest and recent clear-cuts). At the home range scale, we determined that mixedwood forests were also among the most used forest stands and the least used were recent clear-cuts and forested bogs, using resource selection functions. At the landscape scale, home ranges included more mixedwood forests than random polygons and marten high activity zones were composed of more residual forest and less human-induced disturbances (clear-cuts, edges, and roads). These results suggest that mixedwood forests, which occupy approximately 10% of the study area, play a critical role for martens in this conifer-dominated boreal landscape. We recommend permanent retention or special management considerations for these isolated stands, as harvesting mixedwood often leads to forest composition conversion that would reduce the availability of this highly used habitat. © The Wildlife Society, 2013