Date of Award
Master of Science
Mule deer (Odocoileus hemionus) populations have declined throughout their range in the western United States since the 1980s. Habitat loss, overgrazing, disease, and predation contribute to the decline of mule deer populations. Navajo Nation, the largest federally recognized Indian tribe in the United States, encompassing 71,000 km2 in New Mexico, Arizona, and Utah, has experienced a 49% decline in mule deer over the past decade. Given knowledge of space use is an important component to recovery plans, my objectives were to (1) classify each deer as a migrant, resident, disperser, or nomad; (2) determine dates and durations of deer classified as migrants including means and ranges of spring and fall migration; (3) quantify distances traveled during spring and fall migration; (4) estimate sizes of seasonal home ranges and core ranges for migratory mule deer; and (5) develop resource selection functions. GPS collars were placed on 99 mule deer (79 F, 20 M) during 2018-2020. Movements were analyzed using net-squared displacement for individuals with >6 mo of data. Movement trajectories (n=108) from 67 unique mule deer were analyzed to determine whether they were migrants or non-migrants. An ANOVA was performed to determine whether sex, season (i.e., spring or fall), strategy (i.e., short-distance or long-distance migrant), or an interaction between migration duration and migration distance. Seasonal home ranges were defined using 95% kernel density estimates (KDE), and core ranges with 50% KDE. An ANOVA was performed to determine whether sex, migration strategy (i.e., short-distance or long-distance), or season (i.e., winter or summer) affected seasonal home range and core range size. I modeled third-order resource selection functions (RSF) following a use-availability design. Seventy-four percent (n=50) of mule deer were long-distance migrants, 18% (n=12) were short-distance migrants, and 6% (n=5) were non-migrants. Minimum, maximum, and mean distances traveled during migration were 2.6 km, 68.3 km, and 17.7 ± 1.1 km, respectively. Seasonal home ranges, core range, and resource selection were quantified for 84 (15 M, 69 F) trajectories from 63 mule deer. Mean female and male summer home ranges were 9.1 ± 11.1 km2 and 7.4 ± 6.6 km2, respectively, and mean female and male winter home ranges were 15.6 ± 21.5 km2 and 16.1 ± 7.5 km2, respectively. Season had a significant effect on home range size (F1,158=28.02, P<0.001), such that winter home ranges were larger than summer home ranges for both males and females. As with seasonal home ranges, season affected core range size (F1,158=22.784, P<0.001). During the summer, mule deer selected for distance to water and forest landcover, while avoiding “other” landcover types and east, south, and west aspects. In winter seasonal home ranges, mule deer selected for forest landcover while avoiding tribal roads, county roads, and “other” landcover types. My research provides information to support mule deer conservation on Navajo Nation lands and the southern portion of mule deer range.
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