Habitat use patterns in relation to escape terrain:: are alpine ungulate females trading off better foraging sites for safety?

Predation risk often forces prey to trade off good foraging sites for safety, and compromises are expected to be greater in females with vulnerable offspring than in barren females. To determine whether adult females of large herbivores traded off forage for safety, we assessed habitat use and estimated vegetation abundance and quality in relation to distance to escape terrain in marked mountain goats (Oreamnos americanus de Blainville, 1816). We found that all females spent more time foraging near escape terrain than away from them. Females with young foraged on average 20 m closer to escape terrain than barren females in June, a time when offspring were particularly vulnerable to predation. Plant biomass did not vary with distance to escape terrain in June, but was lower closer than away from escape terrain during all other months. The abundance of forbs and shrubs increased with distance to escape terrain, but their quality did not vary. For grasses and sedges, plant digestible content decreased closer to escape terrain, but interestingly proteins increased. Our results suggest that females traded off forage abundance, and to a lesser extent forage quality, for safety. Compared with barren females, females with offspring may face a trade-off in plant digestible content by foraging in safer areas than barren females.