Trailblazers in the Forest: Response of Endangered Mt. Graham Red Squirrels to Severe Insect Infestation

Abstract

I examined habitat selection of middens within insect-damaged forest and compared home range and survival for Mt. Graham red squirrels (Tamiasciurus hudsonicus grahamensis) in insect-damaged and healthy forest. Squirrels used habitat in areas with < 69% tree mortality. Basal area, canopy cover, and log volume were greater at middens than random locations. Within midden sites, only greater basal area of live trees distinguished occupied sites from unoccupied sites. Surface temperature at occupied middens tended to be cooler than unoccupied middens. Squirrels living in insect-damaged forest had larger home ranges than in healthy forest. Squirrel body mass and reproductive condition did not differ between forest types, suggesting that insectdamaged forest provided adequate resources. However, squirrels inhabiting insectdamaged forest experienced lower survivorship and 50% fewer potential reproductive events than squirrels in healthy forest, implicating presence of an ecological trap. Preservation of remaining healthy forest is a priority for management of this endangered species.