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Pine Marten Habitat Project
140-001
Description: Marten (Martes americana) are small mammalian carnivores that inhabit forested areas throughout Canada. They have generally been thought to require large areas of old growth forest rather than landscapes dominated by younger stands (Buskirk and Powell 1994). However, some recent evidence suggests that marten may not use old forests exclusively, but may also be found, and possibly breed successfully, in younger second-growth forests (Chapin et al. 1994, Potvin 1998). This contention is supported by an abundance of anecdotal evidence from Ontario trappers, who regularly capture marten in young forests. Snow-tracking has also shown that marten occur in logged areas (Thompson et al. 1989, Bowman and Robitaille 1997). Despite intensive timber harvesting for 50 years in Ontario, there appears to have been no decline in the provincial commercial harvest of marten, or their harvest in most local districts. These observations raise legitimate doubts about the importance of old growth forest for conserving marten populations. Moreover, this issue has important financial implications for sustainable forest management in boreal and mixed forest ecosystems.
Contemporary ecological theory suggests three competing hypotheses that could explain why we might observe substantial numbers of marten in young, regenerating forest even though individuals may prefer mature forest. All of these hypotheses start with the same basic assumptions: that there is spatial heterogeneity in habitat quality due to intrinsic autecological factors augmented by forest harvesting practices (Thompson, 1994), that martens defend feeding territories (Francis and Stephenson 1972, Powell 1972, Taylor and Aubrey 1982), and that young animals disperse from their natal territories in the autumn of their first year.
Source-sink hypothesis. If landscapes consist of patches of high quality habitat (sources) interspersed in a matrix of poorer quality habitat (sinks), then dispersing individuals may be distributed widely across the landscape, even though sustainable recruitment of offspring is limited to source populations (Pulliam 1988, Pulliam and Danielson 1991). According to this hypothesis, martens may require old growth forest for sustainable recruitment of offspring, which in turn disperse into young forest blocks where they are subject to trapping and other sources of observation. Even though animals are found in these sink habitats, however, population sustainability depends on uncut blocks of mature forest, consistent with the specifications of the forest management guidelines.
Ideal-despotic distribution hypothesis. If animals space themselves across a heterogenous landscape to maximize their individual fitness, we might expect to find high densities of breeding individual preferentially occupying high quality habitats, whereas lower quality habitat is occupied by lower density populations of individuals (Fretwell and Lucas 1974). Within each habitat, we would expect to find individuals of different social status, with fitness variation within a habitat type associated with rank, but little difference in lowest fitness levels observed across habitat types. According to this hypothesis, martens might prefer old forest, but at sufficiently high population densities some individuals would be displaced into poorer habitats. Nonetheless, populations of martens would have sustainable recruitments in all habitats, but with considerable differences in mean fitness across habitats.
Equal-fitness hypothesis. The null hypothesis is no fitness differences associated with forest serial stage. This hypothesis predicts that martens have sustainable recruitment in all habitats, with equal levels of Malthusian fitness.
The objective of the study then is to determine the factors and mechanisms that underpin the primary hypothesis supported by our research. Such factors include the relationship between marten and their prey, habitat suitability, fitness (especially mortality factors in managed populations), and socio-behavioural factors.
The work will have significance at the provincial, national, and international level because of the importance of marten in current forest management planning. Understanding the role of dispersal in a wild population is particularly important because dispersal is a poorly estimated variable in population modeling (including in the Schneider and Yodzis [1994] model used here to develop the hypotheses). We will provide information on the ecological factors that influence marten population dynamics and provide key insights into marten demography in managed landscapes to assess the potential destabilizing effects that logging may play in their populations in the short or long-terms. Improvement in the parameters of the Schneider-Yodzis model will enable better modeling of marten populations in boreal habitats across North America. Results will be transferred to industry through improved marten habitat management guidelines, and an assessment of marten as an indicator of old forest condition. We will have the opportunity to address a key question in conservation biology: that of maintaining populations on landscapes in suboptimal habitat.
The Project Team: Ian Thompson, CFS, John Fryxell, University of Guelph, Jim Baker, OMNR, Gerry Racey, OMNR, Bob Watt, OMNR
Project Outputs:
Population Ecology of Marten (Martes americana) in the Boreal Forests of Northern Ontario
Quantifying genotyping errors in noninvasive population genetics
Genetic isolation by distance and landscape connectivity in the American marten
Dispersal and genetic structure in the American marte
Habit-mediated variation in predation risk by the American marten
Mammalian dispersal behaviour and its fitness correlates
Winter Resources selection by the American Maten. The effects of model resolution
Habitat seleaction by the red-backed vole. The boreal forest of northwen Ontario
Project Work Report (click here)
Special Issue of the Forestry Chronicle articles:
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