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Hide or die: use of cover decreases predation risk in juvenile North American porcupines

Abstract In many mammals, juveniles are vulnerable to predators because of their low mobility and small body size. Cover hides juveniles from predators and has been assumed to lower predation risk. However, among mammal species, studies relating use of cover to fitness remain infrequent and have been predominantly performed on ungulates. We measured habitat selection and survival of juvenile North American porcupines (Erethizon dorsatum). We tested whether juveniles selected for cover, use of cover depended on meteorological conditions (there could be a trade-off between predation risk and radiative heat gain during sunny days), and use of cover influenced survival. We also examined how sex, body mass, mobility of the juvenile, and distance to the mother affected survival. We found that juvenile porcupines (14 individuals observed on 299 occasions) selected high protective cover (microhabitat scale) within areas with low herb cover (local scale). Use of cover partly depended on weather, with use of dens decreasing on sunny and warm days but use of cover outside of the den being independent of meteorological conditions. Ten juveniles died during the study and 90% of deaths were due to predation. Use of microhabitats with high protective cover and use of sites with high shrub cover at the local scale enhanced survival. We found no effect on survival of sex, body mass, mobility, and distance to the mother. These results demonstrate that use of cover was crucial to survival in a system where predation was the main limiting factor, and that predation risk was modulated by habitat use of juveniles.