Recovery Plan for the Northern Spotted Owl - DRAFT

AmphibiansHome range size of martens varies with population density, food abundanceand sex (Buskirk et al. 1989, Clark et al. 1987). Martens are opportunisticforagers that will feed on a wide variety of small mammals, birds, reptiles,invertebrates, and plants depending on availability. In Oregon, red-backedvoles, flying squirrels, and Douglas' squirrels are important winter prey (Irwin1987, Marshall 1991). Fruits, insects, and birds, mostly absent from thewinter diet, may comprise a significant proportion of the summer diet (Irwin1987). The close association of martens with mature and old-growth coniferousforests has been confirmed in numerous investigations (Irwin 1987, Jonesand Raphael 1991, Hargis 1981, Koehler et al. 1975). High canopy closure andabundant coarse woody debris are the two most important components ofmarten habitat provided by old-growth forests. Forest cover and large woodydebris are critical in winter, when they provide cover from predators andinsulation from harsh winter conditions. Loss of habitat and timber harvestare the primary limiting factors for marten populations in the Pacific Northwest(Irwin 1987, Marshall 1991, Washington Department of Wildlife 199 lb). Clearcuttingand stand-replacing fires significantly have reduced the amount ofmature and old-growth habitat available. Over-harvesting by commercialtrapping is a major concern for martens in California (Grinnell et al. 1937, G.Gould, Klamath National Forest, California, pers. comm.) and also may be aproblem in Washington, where martens are concurrently listed as "game" andas 'sensitive." Marten trapping continues in Oregon, but to a limited degree(Irwin 1987).The committee solicited an account of the ecology of amphibians and reptiles(Beatty et al. 1991) in the course of its examination of other species. Thefollowing treatment is extracted from that report.Twenty-three species or species groups of amphibians and reptiles wereidentified whose ranges overlap with the distribution of the northern spottedowl and whose ecological requirements appear to be linked with the remainingdistribution of older forest ecosystems in the Pacific Northwest. These speciesrepresent approximately 40 percent of the extant amphibians and reptiles inthe region (Nussbaum et al. 1983, Stebbins 1985). Within this group ofanimals, eight were designated as priority species by the committee. They arethe Olympic salamander (four species), the Oregon slender salamander, Pacificgiant salamander, Cope's giant salamander, Del Nortesalamander, the LarchMountain salamander, the Siskiyou Mountain salamander, and the tailed frog.The reasons for selecting these animals as a subset of the 23 species or speciesgroups center on at least two characteristics they share. One is their relativelylimited distribution. (Figures D.2 - D.4) The other is with their apparentlynarrow ecological requirements in comparison with close relatives. Distributionsare fairly well worked out for most of these animals, but more field workmay reveal new populations in what most herpetologists would consider novelhabitats. Examples of this finding include the discovery of Larch Mountainsalamanders in the central Cascades of Washington (Aubry et al. 1987) and theOregon slender salamander east of the Cascade crest (Kirk and Forbes 1991).A related point is that not much is known about the precise ecological requirementsof many of these species. Research indicates that amphibian populationsmay be a significant component, and may play an important functionalrole in ecosystems, especially with respect to energy flow through the systems.One of the important characteristics of these animals' biology is the geneticstructure of their populations. Evidence indicates that, at least for salamanders,there is considerable genetic differentiation among populations(Wake and Yanev 1986; Good 1989). The results of these studies indicate that391