Seasonal Habitat Selection by Marten in an Untrapped Forest Preserve

Abstract

American marten (Martes americana) are often associated with mature conifer-dominated forests; however, marten may require complex vertical and horizontal woody structure, rather than a coniferous overstory. To evaluate whether marten prefer forests with a mature conifer overstory, we investigated landscape-and stand-scale habitat selection of 38 (20 M, 18 F) resident (≥25 locations collected during ≥3 months), nonjuvenile (≥1 year [YR]) marten in a forest preserve in northcentral Maine where trapping and timber harvesting had been excluded for >35 years. At the landscape scale, nearly all of the available habitat was used by marten. Further, composition of forest types within home ranges of radiocollared resident marten was similar to areas outside of home ranges. At the stand scale, marten used forest types disproportionately (P = 0.03) from availability within their home ranges during summer (1 May-31 Oct), but exhibited no apparent selection (P = 0.83) during winter. During summer, stands with substantial spruce-budworm (Choristoneura fumiferana)-caused mortality (<50% overstory canopy closure) had the highest selection index. No significant difference in stand-scale selection was detected among mature, well-stocked coniferous, deciduous, or mixed forest types during summer or winter. Mature, well-stocked coniferous forest was the least abundant forest type in home ranges of both sexes in both seasons, whereas mature, well-stocked deciduous forest was the most abundant. Further, much variability was observed in the amount of coniferous (range 0.8-36.3%) and deciduous (range 6.3-66.1%) habitat occurring in marten home ranges. Nine of 10 adult females captured in late spring were lactating, despite that their home ranges composed only 3-36% (median = 10.5%) mature coniferous forest. Our results suggest that marten do not require a dense or coniferous forest overstory and are consistent with the hypothesis that vertical and horizontal structure may be more important habitat components than age or species composition of the forest overstory. Thus, forest practices, such as on-site delimbing, cull-tree retention, and slash management may provide opportunities to maintain use of regenerating forest habitat by marten after harvesting. Structural complexity often may be associated with age and species composition of forests; however, conservation practices should consider structural attributes that functionally, influence the quality of forested habitats for marten, rather than merely age, species composition, and canopy closure of the forest overstory.