Fig 1.
Map of the study area and GPS locations of 33 Mongolian gazelles within the Eastern Steppe of Mongolia.
The inset map shows the portion of the Eastern Steppe that is east of the fenced railroad that goes from Ulaanbaatar to Beijing. Note how the fences along the border prevent Mongolian gazelles from entering into Russia and China.
Fig 2.
Selection by Mongolian gazelles for A) snow cover during winter and B) NDVI during the growing season. RSFs show Mongolian gazelles select for intermediate snow cover in winter (Aug. 30 –May 8) (A). During the growing season (May 8 –Aug. 29), gazelles select for above average NDVI (B). Selection is quantified as relative selection strength (RSS). Curves were plotted based on the best fit RSF for the population as determined by AIC. The vertical line indicates the mean NDVI (fraction snow cover), which was used as the reference point to create the curves. Dots indicate the NDVI (fraction snow cover) value at which RSS peaks. The curve is only plotted for the range of NDVI (fraction snow cover) observed at the used and available points over the study period (Oct. 2014—May 2018), where the upper and lower 5% of values have been removed. Means are also based on this subset.
Table 1.
AIC values for the different growing season (May 9 –Aug. 29) and winter (Aug. 30 –May 8) RSF models examining how Mongolian gazelles select for NDVI and snow cover.
Fig 3.
Differences among Mongolian gazelles in selection for NDVI during the growing season and for snow cover in winter at different scales (A– 1 day, B– 5 day, C– 10 day step scale) based on individual SSFs. Blue, yellow, and orange sections of the bar plots show the percent of individuals selecting for NDVI during the growing season or for snow cover during winter, grey sections shows the percent of individuals that did not show selection. For those individuals showing selection, dark blue indicates selection for the highest NDVI (or snow cover) available, light blue indicates selection for the lowest NDVI (or snow cover) available, yellow selection for intermediate values, and orange selection for both high and low NDVI (or snow cover). Above each bar are the number of individuals which had sufficient data (minimum of 20 steps) to run step-selection functions. The data show no evidence for selection for the majority of individuals and this trend holds across all scales tested.
Fig 4.
Selection for NDVI at the 1 day step scale shown by individual Mongolian gazelles during the growing season (May 9 –Aug. 29).
Selection is quantified as relative selection strength (RSS). Curves were plotted based on the results of the individual SSFs and show the best fit model for an individual. Only those individuals who showed significant selection at the 1 day step-scale are shown. The vertical line indicates the mean NDVI (as described in the methods), which was used as the reference point to create the curves. Dots indicate the NDVI values at which RSS peaks. The curve is only plotted for the range of NDVI available to the individual gazelle as defined in the methods. Positive log(RSS) values indicate selection for that NDVI value over the mean NDVI value, negative log(RSS) values indicate avoidance of that NDVI value when compared to mean NDVI. Results for the 5 and 10 day scales can be found in the (S5 and S6 Figs).
Fig 5.
Selection for snow cover at the 1 day step scale shown by individual Mongolian gazelles in a given year during winter (Aug. 30 –May 8).
Selection was quantified as relative selection strength (RSS). Curves were plotted based on the results of the individual SSFs and show the best fit model for an individual. Only those individuals who showed significant selection at the 1 day step-scale are shown. The vertical lines indicate mean snow cover for a specific year (as described in the methods) and were used as the reference points to create the curves. Dots indicate the snow cover values at which RSS peaks. The curve is only plotted for the range of snow cover available to the individual gazelle as defined in the methods. Positive log(RSS) values indicate selection for that snow cover value over the mean snow cover value, negative log(RSS) values indicate avoidance of that snow cover value when compared to the mean snow cover value. Results for the 5 and 10 day scales can be found in the (S7 and S8 Figs).
Fig 6.
Percent of Mongolian gazelles that showed different selection strategies for snow cover in different years according to SSFs.
Not all Mongolian gazelles show consistent selection strategies for snow cover across years. For all individual gazelles for which we had more than one year of data during the winter season the percent that switched their selection strategy at least once was calculated. This could be a switch from one type of selection to another (e.g. high snow cover vs. intermediate snow cover) or from selecting to not showing selection. We did not have sufficient data to run individual-year models at all scales during the growing season.