Evelyn L. Bull

SURVIVAL, CAUSES OF MORTALITY, AND REPRODUCTION IN THE AMERICAN MARTEN IN NORTHEASTERN OREGON

Survival rates, causes of mortality, and reproduction in the American marten (Martes americana) were determined in northeastern Oregon from 1994 until 1997 with radiocollared martens. The probability of survival of martens >9 mo old was 0.55 for 1 yr, 0.37 for 2 yr, 0.22 for 3 yr, and 0.15 for 4 yr. The mean annual probability of survival was 0.63 for 4 yr. Twenty-two of 35 radiocollared martens died. Of the 18 martens killed by predators, 8 were killed by bobcats (Lynx rufus), 4 by raptors, 4 by martens, and 2 by coyotes (Canis latrans), based on necropsies and circumstantial evidence at kills. Three martens died of exposure and 1 of collar entrapment. Of 13 reproductive efforts, 4 females weaned 21 kit, 8 efforts failed, and the outcome of 1 was unknown. Predation of adult females prior to weaning was the source of reproductive failure for some efforts.

HOME RANGE AND DISPERSAL OF THE AMERICAN MARTEN IN NORTHEASTERN OREGON

Home ranges and dispersal of American martens (Martes americana) were determined in northeastern Oregon between 1993 and 1997 to provide managers with information necessary for developing management options to maintain habitat for viable populations. The average home range for males (2717 ha; SD = 1092.9; n = 10) was about twice that of females (1416 ha; SD = 744.3; n = 9). Home ranges were largely mutually exclusive for same-sex martens. Correlation analyses showed no significant linear relationships between the percentage of unharvested forest and home range size. Three juvenile martens (2 males, 1 female) that established home ranges outside the study area dispersed a mean of 33.3 km (range = 28 to 43.2 km).

Characteristics of Black Bear Dens in Trees and Logs in Northeastern Oregon

Forty-one percent of 165 black bear (Ursus americanus) dens were in hollow trees or logs in northeastern Oregon from 1993 tol999. The remainder of the dens were in ground excavations (37%) and in caves or rock structures (22%). Hollow trees with the den entrance in the broken-off trunk were typically large-diameter grand fir (Abies grandis; x = 114 cm dbh) with Indian paint fungus (Echinodotium tinctorium) decaying the heartwood. Hollow trees with a base-entry were large-diameter grand fir and western larch (Larix occidentalis; (x = 108 cm dbh) with basal decay. Hollow logs in grand fir and western larch made up 11% of the 165 dens. Although a wide variety of habitat types were used, the majority of trees used for denning (88%) were in moist, late-seral stands of grand fir. Retaining large-diameter grand fir and western larch with evidence of decay will increase den site options for black bears in northeastern Oregon.

Intraspecific Predation on American Marten

Acknawledgements. The senior author thanks the Rob & Bessie Welder Wildlife Foundation for support making this and other research efforts possible. Both authors extend their thanks for assistance and samples provided by personnel at Hart Mountain National Antelope Refuge and for critical comments provided by B. Coblentz, G. Matson, D. Olson, and an anonymous reviewer. Oregon Agricultural Experiment Station technical paper no. 10,843.