Abstract:Fishers (Pekania pennanti) in the west coast states of Washington, Oregon, and California, USA have not recovered from population declines and the United States Fish and Wildlife Service has proposed options for listing them as threatened. Our objectives were to evaluate differences in survival and mortality risk from natural (e.g., predation, disease, injuries, starvation) and human‐linked causes (e.g., rodenticide exposure [toxicants], vehicle strikes). We monitored survival of 232 radio‐collared fishers at … Show more
“…This is at odds with findings from other fisher populations (Krohn et al 1994) and other populations of mustelids exposed to fur harvest (Krebs et al 2004) where males, particularly subadults, are generally more at risk to trapping mortalities (Koen et al 2007). By comparison, in populations that are not exposed to commercial fur harvest, predation is the primary source of mortality (e.g., California; Sweitzer et al 2016 a ), which was the second‐most common mortality source in the populations that we studied.…”
Fishers (Pekania pennanti) are a forest-dependent carnivore of conservation concern in British Columbia, Canada. Ecological, spatial, and genetic evidence suggests that there are 2 distinct populations (Boreal and Columbian) that occur in forests at low to moderate elevations in the boreal and central interior regions of the province. In British Columbia, fishers occur at low densities relative to other parts of their range in North America, are trapped for their fur, and are sensitive to habitat change. Despite these factors, little demographic information exists to assist with management decisions for these populations. We collated and analyzed survival and reproductive data from 100 radio-tagged fishers from 5 independent studies conducted between 1990 and 2012 in British Columbia: 2 in the Boreal population, and 3 in the Columbian population. We also collated litter size data from 1 den box study and a translocation project of fishers from the Columbian population. Annual survival rates were not significantly different between the populations or between males and females; however, adult survival rates were higher than subadults (0.79 and 0.63, respectively). Subadult females had significantly lower survival rates than other sex or age classes. Reproductive rates were significantly different between the 2 populations (denning rate = 0.54 [Columbian], 0.82 [Boreal]; x ¯litter size = 1.7 [Columbian], 2.6 [Boreal]). These differences resulted in net reproductive rates in the Columbian population that were less than half of those in the Boreal population (0.92 kits/reproductive season compared to 2.13, respectively). Population growth rates suggest that the
“…This is at odds with findings from other fisher populations (Krohn et al 1994) and other populations of mustelids exposed to fur harvest (Krebs et al 2004) where males, particularly subadults, are generally more at risk to trapping mortalities (Koen et al 2007). By comparison, in populations that are not exposed to commercial fur harvest, predation is the primary source of mortality (e.g., California; Sweitzer et al 2016 a ), which was the second‐most common mortality source in the populations that we studied.…”
Fishers (Pekania pennanti) are a forest-dependent carnivore of conservation concern in British Columbia, Canada. Ecological, spatial, and genetic evidence suggests that there are 2 distinct populations (Boreal and Columbian) that occur in forests at low to moderate elevations in the boreal and central interior regions of the province. In British Columbia, fishers occur at low densities relative to other parts of their range in North America, are trapped for their fur, and are sensitive to habitat change. Despite these factors, little demographic information exists to assist with management decisions for these populations. We collated and analyzed survival and reproductive data from 100 radio-tagged fishers from 5 independent studies conducted between 1990 and 2012 in British Columbia: 2 in the Boreal population, and 3 in the Columbian population. We also collated litter size data from 1 den box study and a translocation project of fishers from the Columbian population. Annual survival rates were not significantly different between the populations or between males and females; however, adult survival rates were higher than subadults (0.79 and 0.63, respectively). Subadult females had significantly lower survival rates than other sex or age classes. Reproductive rates were significantly different between the 2 populations (denning rate = 0.54 [Columbian], 0.82 [Boreal]; x ¯litter size = 1.7 [Columbian], 2.6 [Boreal]). These differences resulted in net reproductive rates in the Columbian population that were less than half of those in the Boreal population (0.92 kits/reproductive season compared to 2.13, respectively). Population growth rates suggest that the
“…Maximum age in this population was 9 years for both sexes ( n = 18 males, n = 32 females; M. Gabriel, Integral Ecology Research Center, personal communication; Gabriel et al ). The population was unexploited, with some anthropogenic mortality noted from road traffic collisions and toxicant poisoning (Sweitzer et al ).…”
Section: Methodsmentioning
confidence: 99%
“…Mean annual adult survival rate in the fisher population was estimated across sexes as 0.69, or for females as 0.72 (Sweitzer et al ). Sweitzer et al () estimated survival rate using the Kaplan–Meier estimator modified by Pollock et al (). The female‐only survival rate estimate enabled us to compare model predictions for a sexually dimorphic species using female‐specific mass and maximum age data.…”
“…The study area was centered in the California Wildlife Habitat Relations (CWHR) Sierran mixed-conifer forest habitat type ( http://www.dfg.ca.gov/biogeodata/cwhr/wildlife_habitats.asp ). Additional details on the diversity of trees and shrubs, and historic and current land use within the study area were provided elsewhere [9] , [10] , [11] .…”
Section: Experimental Design Materials and Methodsmentioning
These data provide additional information relevant to the frequency of fisher detections by camera traps, and single-season occupancy and local persistence of fishers in small patches of forest habitats detailed elsewhere, “Landscape Fuel Reduction, Forest Fire, and Biophysical Linkages to Local Habitat Use and Local Persistence of Fishers (Pekania pennanti) in Sierra Nevada Mixed-conifer Forests” [10]. The data provides insight on camera trap detections of 3 fisher predators (bobcat [Lynx rufus]). Coyote [Canis latrans], mountain lion [Puma concolor], 5 mesocarnivores in the same foraging guild as fishers (gray fox [Urocyon cinereoargenteus]) ringtail [Bassariscus astutus], marten [Martes americana], striped skunk [Mephitis mephitis] spotted skunk [Spilogale gracilis], and 5 Sciuridae rodents that fishers consume as prey (Douglas squirrel [Tamiasciurus douglasii]), gray squirrel [Sciurus griseus], northern flying squirrel [Glaucomys sabrinus], long-eared chipmunk [Neotamias quadrimaculatus], California ground squirrel [Spermophilus beecheyi]. We used these data to identify basic patterns of co-occurrence with fishers, and to evaluate the relative importance of presence of competing mesocarnivores, rodent prey, and predators for fisher occupancy of small, 1 km2 grid cells of forest habitat.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.