Wildlife visitation at abandoned mines

Abstract

AbstractAbandoned mines provide habitat for bats, but their importance to other wildlife is less understood. This descriptive study was designed to answer the following questions with an emphasis on carnivores: are wildlife species other than bats visiting abandoned mines, is wildlife entering abandoned mines, does wildlife visitation at abandoned mines differ seasonally, and does wildlife visitation differ at individual mines? To address these questions, we monitored 50 abandoned mines using remote cameras in the northern Sangre de Cristo Mountains, Colorado, USA, for 25,201 camera days from May 2017 to August 2020. We monitored mines in 2 phases. During phase 1 (May 2017–May 2019), we monitored 30 randomly selected mines to gather baseline data on carnivore visitation and to model carnivore visitation. During phase 2 (May 2019–August 2020), we monitored 27 mines to test the visitation model and to determine if carnivores visited multiple mines as they traveled across the landscape. We observed >48 species of vertebrates at mines, including 11 of 14 carnivore species known to occur in the Sangre de Cristo Mountains. Carnivores ranged in size from ringtails (Bassariscus astutus) to American black bears (Ursus americanus). Pumas (Puma concolor) visited mines most frequently and we observed pairs of adult pumas entering mines, presumably during courtship and mating. We also observed American black bears, pumas, and common gray foxes (Urocyon cinereoargenteus) visiting and entering mines with young. Carnivores visited mines at low levels throughout the year and visitation differed by season, temperature, and carnivore species, size, and family. Our most parsimonious generalized linear models identified mine elevation, entrance (portal) size, land cover type, tree cover, and aspect as significant predictors of visitation. Our top models explained ≥78% of the variation in carnivore visits and indicated that carnivores in the Sangre de Cristo Mountains were most likely to visit small horizontal mines at lower elevations in dense piñon (Pinus edulis)—juniper (Juniperus sp.) woodlands. We encourage resource managers to monitor abandoned mines for ≥1 year prior to closing or gating mines to understand which wildlife species might be affected by closures.