American marten (Martes americana) COSEWIC assessment and status report: chapter 9

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Limiting Factors and Threats

The major limiting factors are accidental trapping and snaring and habitat loss due primarily to logging. Secondary limiting factors are habitat loss due to fire and insect damage and a limited prey base.

The Newfoundland marten’s habitat requirements are not limited to mature and overmature coniferous forests (Hearn et al. 2005); therefore it is questionable whether habitat loss from forest harvesting remains the most serious limiting factor as suggested by Forsey et al. (1995).

An outbreak of encephalitis, likely caused by distemper, killed 10 of 40 study animals at Little Grand Lake in 1986-87 (Bissonette et al. 1989, Fredrickson 1990). No other diseases or significant parasite problems have since been reported (J. Brazil, pers. comm., 2007). Catastrophic mortality, in addition to other limiting factors and risks, can greatly increase extinction risk (Thompson 2004).

The prey base is limited compared to other parts of the marten’s range in North America. Introductions of prey species, in particular snowshoe hares and, recently, southern red-backed voles (Hearn et al. 2005) may enhance the marten’s viability in Newfoundland. On the other hand, concurrent increases in predator populations may threaten marten.

The incidental capture of marten in snares set for snowshoe hares and, to a lesser degree snares and traps set for red fox, is a significant source of mortality for Newfoundland marten (Forsey et al. 1995). Newfoundlanders snare and hunt about 1.8 million snowshoe hares per year (Forsey et al. 1995). Hare snares are non-selective and capture marten incidentally (Proulx et al. 1994). An annual average of 5 accidentally snared marten is reported, but researchers documented 10 to 17 marten mortalities when actively seeking snared marten from persons snaring hares from 1984 to 1987 (Forsey et al. 1995). This source of mortality is considered a serious impediment to marten dispersing from refuges to unprotected vacant habitats (Forsey et al. 1995, Thompson and Curran 1995). The degree of compliance of trappers in no- and modified snaring zones has not been assessed.

Proulx et al. (1994) proposed a snare system that killed snowshoe hares, but from which marten could escape. Using differences in torque and tension exerted by marten and hare, snare wires which hold hares but release marten have been tested (Fisher and Twitchell 2003, 2004). Modified snares and traps are mandatory in zones in 5,235 km² of Newfoundland; Corner Brook-Grand Lake, Red Indian Lake, Gros Morne and Terra Nova areas.