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Grantee Research Project Results

Grantee Research Project Results

Movement Behavior of Forest-Dependent Squirrels in Fragmented Landscapes

EPA Grant Number: U915341
Title: Movement Behavior of Forest-Dependent Squirrels in Fragmented Landscapes
Investigators: Bakker, Victoria J.
Institution: University of California - Davis
EPA Project Officer: Broadway, Virginia
Project Period: August 1, 1998 through July 1, 2000
Project Amount: $79,373
RFA: STAR Graduate Fellowships (1998)
Research Category: Academic Fellowships , Ecological Indicators/Assessment/Restoration , Fellowship - Ecology and Ecosystems



The objectives of this research project are to: (1) determine how forest fragmentation influences the movement behavior of two forest-dependent tree squirrels; and (2) identify specific habitat features that facilitate squirrel movement.


Working in logged landscapes in southeast Alaska, I am using translocations to induce squirrel movement, transporting individuals from their home ranges in intact forest on one side of a clearcut to the other side, and releasing them. For each translocated squirrel, the shortest return route to its home range is directly across the clearcut. Consequently, translocations force the individual to make movement decisions at "hard" habitat edges formed by forest-clearcut boundaries as well as along "softer" edges formed by the mosaic of macro- and microhabitats along their entire homing path. The beginning of the squirrel's homing path is documented using tracking spools, fine inversely wound spools of thread affixed to the rump that unwind and leave an exact trace of the movement path. The remainder of the path is documented using radiotelemetry. I am assessing path selection by comparing the habitat characteristics of the paths that squirrels chose relative to the characteristics of the land available to them for homing movements. I have hypothesized that path selection is governed by behaviors that decrease susceptibility to predation, reduce encounters with territorial conspecifics, and increase speed of movement. I also am measuring variables linked to these behaviors.

Because animals with spatial memories may move differently on and off their home ranges, I have assumed that removing squirrels from their home ranges is the best way to simulate dispersal-type movements, and specifically, to force animals to select specific macro- and microhabitat types on unfamiliar ground. I also have also assumed that selection of travel routes through forest rather than across clearcuts or second-growth forests is analogous to finding and using corridors. Unless a corridor is narrow enough that squirrels can perceive both edges, it is likely that corridors and continuous forest are indistinguishable to squirrels. Because translocated squirrels are highly motivated to travel in the homeward direction, my results regarding preferential travel in forest are likely to be conservative. Because translocated squirrels are highly motivated to travel in the homeward direction, my results regarding preferential travel in forest are likely to be conservative.

Supplemental Keywords:

fellowship, animal movement paths, squirrels, fragmented landscapes, corridors, dispersal, forest fragmentation, Tamiasciurus hudsonicus., RFA, Scientific Discipline, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Ecology, exploratory research environmental biology, wildlife, Ecosystem/Assessment/Indicators, Chemical Mixtures - Environmental Exposure & Risk, Ecosystem Protection, State, Zoology, Ecological Effects - Environmental Exposure & Risk, Ecological Effects - Human Health, Habitat, Ecology and Ecosystems, Ecological Indicators, landscapes, logging, landscape indicator, red squirrels, animal responses, conservation, habitat fragmentation, forests, Alaska (AK), movement behavior, spatically-explicit conservation theory, forest fragmentation, glaucomys sabrinaus, tamiascuirus hudsonicus

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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

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