Human and wildlife use of mountain glacier habitat in western North America

The global recession of glaciers and perennial snowfields is reshaping mountain ecosystems. However, beyond physical changes to the landscape and altered downstream hydrology, the implications of glacier decline are poorly known. Before predictions can be made about how climate change may affect wildlife in glacier-associated ecosystems, a more thorough accounting of the role that glaciers play in species’ life histories is needed. In this study, we deployed an elevational transect of wildlife cameras along the western margin of the Paradise Glacier, a rapidly receding mountain glacier on the south side of Mount Rainier, WA, USA. From June to September 2021, we detected at least 16 vertebrate species (seven birds, nine mammals) using glacier-associated habitats. While humans, and primarily skiers, were the most common species detected, we recorded 99 observations of wildlife (birds and mammals). These included three species of conservation concern in Washington: wolverine (Gulo gulo), Cascade red fox (Vulpes vulpes cascadensis), and White-tailed ptarmigan (Lagopus leucura). Collectively, our results reveal a rich diversity of wildlife using a single mountain glacier and adjacent habitat in the Pacific Northwest, emphasizing a largely overlooked risk of climate change to mountain biodiversity. We highlight the global need for similar studies to better understand the true scale of biodiversity that will be impacted by glacier recession in mountain ecosystems.


INTRODUCTION 38
As climate change proceeds and mountain glaciers are lost, there is a pressing need to 39 understand how the loss of glacier ice will impact habitats and ecosystems ( (Figures 1b,c). 102 However, we only analyzed data through 25 September 2021 because variable but often 103 persistent snowpack either buried or obscured cameras during the final five weeks of the field 104 season (25 September -31 October 2021). We placed six cameras along an elevational 105 transect from 2,164 to 2,469 m (7,100 -8,100 feet). We re-visited the cameras every 3-5 weeks. 106 We focused our cameras to target the margins of the glacier where talus and boulders give way 107 to ice. Because the Paradise Glacier is such a dynamic environment during summer, with a 108 dramatically shifting physical surface (both in area and elevation), we moved the cameras as 109 needed to maintain close proximity (generally 0-10 m) to the ice surface. Due to the variable 110 terrain and goals of the study, we made no attempts to control for the amount of area each 111 camera could "see" which likely affected the comparability of our results across cameras. 112

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To account for the need to move the cameras throughout the melt season and to minimize their 6 2a,b). Cameras were mounted to 5-gallon (18.9 liter) cylindrical Igloo coolers that were covered 116 in camouflage duct tape with small, camouflage ratchet straps. The coolers were filled with 117 snow and loose rocks from the trapping area and sealed with ⅛" coated steel cable and a small into the landscape, we added a small label to the top of each trap noting its purpose with 120 contact information. When triggered, cameras took bursts of five photos in quick succession 121 with a 30-second rest period between triggers. While our camera traps were largely reliable and 122 stayed in working order throughout the study, we did experience a memory card failure at C5 123 from 20 August -25 September. 124 125 Animal identification and data analysis 126 Images were visually inspected for any evidence of vertebrate detection (see example images in 127 Figure 3). When humans or wildlife (birds and mammals) were detected, they were identified to 128 the lowest taxonomic level possible by consulting guides for Mount Rainier National Park and 129 the Pacific Northwest as well as our own research team's expertise in mammals (A.A. and L.W., 130 specifically) and birds (J.B., N.A.P., and P.W., specifically).Given the proximity of our cameras 131 7 above. Photos of the research team were also excluded from all analyses. Observations were 142 totaled and analyzed for each of the 14 weeks of the study. We note that the final "week" (week 143 14) contained two extra days due to where the study endpoint fell (25 September) relative to the 144 end of that particular week (23 September). 145

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To test for a relationship between human and wildlife occurrences in our data set, we performed 147 a series of statistical analyses in R (R Core Team 2021). First, we grouped all human and 148 wildlife observations separately for each camera on a week-by-week basis. Then, we tested for 149 normality of the human and wildlife data sets using a Shapiro-Wilk normality test ("shapiro.test"). 150 Because both data sets were significantly different from normal (P, Shapiro-Wilk < 0.001), we 151 performed correlation analyses with a Spearman's rank correlation. We tested for a correlation 152 between the number of human versus wildlife detections across all cameras and weeks in the 153 study. 154

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Across 307 detections in the Mount Rainier alpine, we identified at least 16 vertebrate species 157 (seven birds, nine mammals) using glacier-associated habitats (Table 1). Humans were the 158 most frequently observed taxon (N = 208), followed by American pipits (N = 18), mountain goats 159 (N = 13), marmot (N = 13), and wolverines (N = 8; Table 1, Figure 4). Just under one-fifth of 160 birds could not be identified to species but for those that were identified, American pipits and 161 White-tailed ptarmigan accounted for more than half of the observations. However, a number of 162 nondescript brown and gray "blurs" were also recorded, of which many were likely small birds, 163 and thus our results for birds are likely underestimations. 164 165 We observed the most humans at the third-highest camera, C3 (N = 59), and the most wildlife at 166 the lowest camera, C6 (N = 36; Figure 4). Interestingly, C6 also recorded the fewest humans (N comparisons across cameras (and detection periods since cameras were adjusted throughout 172 the study), should be interpreted with caution. 173

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We observed the highest number of detections during the first week of the study (18-24 June 175 2021) but this pattern was overwhelmingly driven by humans ( Figure 4). Indeed, ~54% of all 176 human observations were within this period. For wildlife (mammals and birds), no clear temporal 177 pattern was present. At cameras where humans and wildlife were regularly observed (e.g., C4, 178 C5), we observed a temporal separation with humans being seen early in the season from mid-179 June to mid-July and other taxa appearing later (after mid-July; Figure 4). However, we did not 180 observe a correlation between the presence of humans and wildlife across all cameras and 181 weeks of the study (P, Spearman's rho = 0.106). 182 183 During the study, we observed three taxa of conservation concern in Washington state: 184 wolverines (including two kits playing on the glacier), a Cascade red fox, and White-tailed 185 ptarmigan (Figures 3e-g). We observed wolverines at the three lowest cameras (C4-C6) in late 186 July/early August, a Cascade red fox at our C4 camera in mid-August, and White-tailed 187 ptarmigans at the two highest cameras (C1-C2) and the lowest camera (C6), including a pair of 188 ptarmigans together in mid-July at C2. mesocarnivores (e.g., wolverines) where we also observed common prey species (e.g., 226 marmots; Table 1). 227 228 While our camera trap design and array in the Mount Rainier alpine was successful, it was not 229 without difficulties. Indeed, the challenging nature of camera trapping in a high-alpine landscape 230 should not be overlooked. In addition to highly variable, and often difficult, weather conditions, 231 the landscape does not lend itself well to traditional camera trapping approaches for three 232 reasons. (1) The physical landscape dramatically changes during summer due to snowmelt. 233 During 2021, seasonal snow depth at a substantially lower elevation than our study area peaked 234 in early summer at 5.33 m (210 inches). This seasonal snow completely melted by mid-July, 235 effectively lowering the habitat surface by several meters during the first month of our study 236 (mid-June to mid-July). Thus, camera trap locations were limited to areas that were snow-free 237 and had to be moved small distances throughout the season to track shifting ice margins. 238 Changing snow depth also meant that framing the view, and controlling for the field of vision 239 across cameras, was nearly impossible. For instance, one view that was completely snow-240 covered in early July was entirely rock and talus within a matter of days. The end of the season 241 offers another complication as seasonal snow can accumulate rapidly, particularly in "sheltered" 242 areas that are ideal for obscuring camera traps. Thus, we recommend that similar future studies 243 in the PNW or comparable areas conclude by the end of September or that researchers devise 244 a strategy for finding snow-covered cameras and/or keeping them free of snow. (2) Hiking 245 and/or game trails are minimal or non-existent above treeline. Thus, an exceptionally large and 246 consistent survey area exists with little to no mechanism for targeting areas where wildlife may 247 be more abundant. To this end, a denser camera array would have certainly yielded better 248 quantifications of vertebrate presence and interactions (e.g., links between carnivores and prey 249 or humans and wildlife). Finally, (3) we did not observe many songbirds on the glacier and in 250 surrounding habitats despite well-known connections between the two (e.g., Hotaling et al. 251 2020). This was likely due to a combination of our cameras not being sensitive enough to detect 252 them and images with potential birds in-flight being too blurry for identification. Indeed, a 253 number of photographs included unidentifiable brown or gray blurs that we could not confidently 254 categorize as a bird or something else (e.g., a flying insect). One way to overcome this, or at 255 least improve the detection rate of small birds, would be to pair cameras with acoustic recorders 256 at each site so song could be used in combination with (or in lieu of) imagery.     to unique sightings and the total observations for a given taxonomic group are given at the top 371