Habitat fragmentation is a major concern of conservation biology because its two primary components, habitat loss and the conversion of contiguous habitats into smaller isolated patches, threaten biodiversity worldwide. Dispersal, the main process connecting animal populations inhabiting isolated habitat patches, is hard to quantify for small to medium-size, wide-ranging species. This project is developing a novel, noninvasive method for quantifying dispersal rates of American martens (Martes americana), an obligate forest carnivore. Because the ratios of stable isotopes of hydrogen, carbon, and nitrogen of the diet are incorporated into the tissues of consumers, martens that have consumed isotopically enriched baits will have distinct isotopic label in their hairs. By applying unique combinations of artificially enriched isotopic markers to different forest stands, the isotopic signature of hair collected from hair traps, will reflect the forest patch where the individual originated. In feeding trials with five captive martens, consumption of one dose of isotopically enriched baits elicited a distinct label in hair. Validation of the use of isotopic labeling of martens in the field will allow the rigorous quantification of dispersal rates for this and a variety of other species.
This project is part of a larger study evaluating the relation between evolutionary history and responses of organisms to human-induced fragmentation. Martens from the two distinct lineages (M. a. americana and M. a. caurina) are habitat specialists and sensitive to forest fragmentation. During the Pleistocene, the two marten lineages evolved in a contiguous southeastern forest refugium (americana) and a glacially fragmented southwestern refugium (caurina). Currently, these animals occur on separate islands in the Alexander and Queen Charlotte (Haida-Gwaii) Archipelagos, which have varying levels of habitat fragmentation from industrial logging. Because old-growth reserves in the Tongass National Forest may not be large enough to maintain viable populations, dispersal among forest stands is vital for persistence of martens. Thus, the distribution of martens in the Tongass National Forest on fragmented and unfragmented islands creates a natural laboratory to test whether caurina martens have higher dispersal capabilities and are therefore better suited to persist in modern-day fragmented landscapes than americana. In addition, information gathered will be applied to the re-designing of the conservation strategy of the Tongass Land Management Plan. An important question to be addressed in the upcoming revision of the Forest Plan is whether different conservation measures for martens should be implemented on different islands of the Alexander Archipelago.
