Year of Award
Doctor of Philosophy (PhD)
Department or School/College
College of Forestry and Conservation
Michael K. Schwartz
Mark Hebblewhite, L. Scott Mills, Michael Mitchell, William J. Zielinski
University of Montana
As a taxonomic group, carnivores are amongst those with the highest conservation concern due to the combination of wide-ranging behavior, typically slow reproductive rates, and low density. The Pacific marten (Martes caurina) is a carnivore species of conservation concern throughout much of its southern range in the U. S. The Pacific marten (marten hereafter) is considered a habitat-specialist, due to its association with late-successional forest habitat which provide specific elements, such as cavities in large-diameter trees for denning, to meet a variety of its life history needs. Across its range, threats to marten persistence range from timber harvest, wildfire and fuels management, and recreational development. Ski areas represent one form of recreation development that involves both the modification of habitat and high concentrations of human activity. My dissertation investigates the influence of landscape pattern from ski area development on population processes to provide insight on the marten’s compatibility with this form of recreational development and to develop a sound ecological basis for guiding management.
By comparing 3 pairs of ski and controls areas I found that martens exhibited avoidance behavior in response to winter recreation activities by both reducing the frequency of habitat use and occupancy at ski areas in winter. Females avoided ski areas in winter more strongly than males by also having lower densities at ski areas during winter compared to controls. After winter recreation activity ceased in the spring and summer, habitat use, occupancy rates, and female density at ski areas were no different than at control areas. Both sexes selectively moved iii between remnant forest patches with the shortest ski run crossing distances in all seasons at ski areas. Overall the fragmentation of habitat from ski runs reduced the functional connectivity by 41% at ski areas compared to controls.
I found that females were more selective than males for both resources during the denning season and for remnant habitat patches at ski areas. During the denning season females selected for mesic forest habitat in the largest trees size class available and for more of this habitat type than males. Selection for both the largest size class of forest habitat and larger quantities of that habitat types suggests that suitable denning habitat is composed of two resources: suitable denning sites in large-diameter live and dead trees and large amounts of habitat associated with the highest prey abundances. At ski areas females selected for the largest patch sizes of remnant forest while males did not.
Using capture-mark-recapture analysis I found that adult male apparent survival was reduced at ski areas compared to control areas but female survival was not affected. This reduced survival rate was consistent with skewed age structure for males at ski areas suggesting this was largely representative of reduced true survival. Estimates of seniority for sub-adults of both sexes were lower at ski areas, suggesting recruitment of this age class to the adult age class is reduced. Using genetic parentage analysis at 16 microsatellite loci for 53 yearling martens I found that more immigrants were captured at ski areas and the recruitment rate of yearling per adult female was > 4 times lower at ski areas compared to controls.
Overall, my research shows that, considering behavioral responses alone, martens appear compatible with developed ski areas. However, the demographic responses suggest otherwise as the combination of reduced survival of males and reduced recruitment of juveniles suggest martens are just able to maintain persistence at ski areas, but contribute little to the larger iv population. Collectively, this suggests ski areas represent ecological traps for martens, where typically reliable sex-specific cues—suitable remnant habitat for denning for females and presence of females for males—are mismatched in landscapes fragmented by ski runs that ultimately reduce individual fitness.
Slauson, Keith Michael, "LINKING LANDSCAPE PATTERN TO POPULATION PROCESSES FOR A CARNIVOROUS MAMMAL" (2017). Graduate Student Theses, Dissertations, & Professional Papers. 11055.
© Copyright 2017 Keith Michael Slauson