CAN SHRUB COVER INCREASE PREDATION RISK FOR A DESERT RODENT

Previous research indicates that predation risk may influence activity patterns, habitat partitioning, and community structure of nocturnal desert rodents. Shrub microhabitat is typically considered safer than open microhabitat for these small mammals. We investigated predation r isk for Townsend's ground squirrels (Spermophilus townsendii), which a re diurnal desert rodents that detect predators visually and use burro ws for refuge. Our results suggested that shrub cover may increase ris k for these squirrels by decreasing their ability to escape from preda tors. Our field experiment indicated that running speeds of juvenile s quirrels were lower in shrub (Ceratoides lanata) habitat than in open areas. Shrub cover was also associated with shorter predator-detection distances (mammalian and avian) and fewer refuges (burrow entrances p er hectare) than in open areas in one year but not in another. Our stu dy demonstrated that the visual and locomotive obstruction of vegetati ve cover may increase predation risk for diurnal desert rodents and th at elements of habitat-dependent risk may be temporally dynamic.