Size‐Related Effects of Predation on Habitat Use and Behavior of Porcupines (Erethizon Dorsatum)

Ecological and behavioral strategies that reduce predation were examined in North American porcupines (Erethizon dorsatum) by testing two hypotheses: (1) habitat use varies with activity level and age class of animals, and (2) with increasing nutritional stress, individuals accept increased predation risk to avoid starvation. Observational and experimental data were gathered over a 2—yr period for a Great Basin Desert porcupine population during winter. Field experiments included manipulations of perceived risk using predator urines and simulated predator encounters with a dog (Canis familiaris). Compared to foraging animals, sleeping porcupines of all age classes avoided high risk (i.e., open) areas. Mass loss varied by habitat with individuals foraging in open areas (high risk) experiencing less mass loss than those foraging in groves (low risk). Age class also affected habitat use by foraging porcupines. Juveniles invariably remained in low—risk areas, even when more risky habitats contained potentially better quality forage. Two—year—old porcupines shifted to high risk areas as body condition deteriorated, but condition exerted little influence on habitat use by adults, as this age class utilized habitat similarly throughout winter. These data reveal how a species with formidable antipredator morphology uses habitats in risk—sensitive ways.