Predation or starvation: Consequences of foraging decisions by porcupines (Erethizon dorsatum)

Data on starvation and predation in porcupines (Erethizon dorsatum) were gathered over a 5-year period to examine hypotheses about foraging. I predicted that predation would be greater in open habitats than in closed habitats, small porcupines would be more vulnerable to predation than large ones, and nutritionally stressed porcupines would trade-off increased risk of predation for decreased risk of starvation. Over 90% of predator-killed porcupines were located in open grasslands or juniper shrublands, suggesting that open areas were higher in risk than wooded, riparian areas. High rates of predation in open areas in late winter supported the hypothesis of a trade-off between nutrition and predation risk. Mountain lions (Puma concolor) preyed on porcupines at a higher rate than did coyotes (Canis latrans), but predation by mountain lions was independent of body size of porcupines (small samples precluded analysis of predation by coyotes). These data reveal how predation and starvation influence populations of porcupines. Further, data indicate that poor nutritional status can drive animals to forage in risky habitats where predation is high.