PARENT SESSION
Oral Session # 78: Predator - Prey Ecology II: Terrestrial II.
Presiding: M Wolf
Thursday, August 7. 1:30 PM to 5:00 PM, SITCC Meeting Room 103.
Prey abundance, availability, and anxiety in logged and unlogged boreal forest.
Andruskiw, Mark*,1, Fryxell, John1, Thompson, Ian2, 1 University of Guelph, Guelph, Ontario, Canada2 Canadian Forest Service, Sault Ste. Marie, Ontario, Canada
ABSTRACT- Most studies of prey vulnerability come from laboratory aquatic systems. The common result is reduced vulnerability in structurally complex environments due to impeded predator search and physical refuge for prey. Here we present a terrestrial predator-prey system with the opposite result. We tested the hypothesis that American marten suffer reduced foraging efficiency in structurally simpler forests generated by clearcut logging. From fall 2001 to spring 2002 marten foraging dynamics were studied in logged and unlogged boreal forest of northwestern Ontario. Coarse woody debris and availability of subnivean access were censused along linear transects. Small mammals were censused by live trapping. Marten hunting behavior was examined from snowtracking 34 marten over 100km, and diets were quantified by scat analysis. Behavioral response of voles to predation risk was measured with giving-up densities. While coarse woody debris levels were higher in unlogged forest, marten selected subnivean access in both forest types. Despite equal small mammal densities, marten encountered and killed prey twice as often in unlogged forest. Giving-up densities of voles were higher in unlogged forest indicating greater fear of predation risk. We conclude that, rather than providing refuge for small mammals, forest structure creates an aggregated and predictably located resource for marten. Second-growth forest therefore represents reduced hunting efficiency. We are calculating prey preferences to test the hypothesis that marten use alternate prey in logged forest where small mammals are less vulnerable.
Key words: prey preference, boreal forest, prey vulnerability, foraging efficiency