Fig 1.
The study region spans portions of the Great Basin, Colorado Plateau, and Chihuahuan Desert ecoregions in southwestern North America (ca. 34–42° N).
White polygons represent sampling units for all demographic and plant phenology data. Sampling units are based on the intersection of state-defined wildlife management units and high elevation summer mule deer habitat.
Fig 2.
Panel A. Polygons symbolize high elevation summer mule deer habitats in southwestern North America (ca. 34–42° N). Map illustrates the latitudinal shift in the seasonality of moisture across the mountains of the Great Basin, Colorado Plateau, and northern Chihuahuan Desert ecoregions. Colors represent the percentage of total annual precipitation that comes in the form of thunderstorms during July-September (color key: blue ≤ 17%; beige = 18–49%; green ≥ 50%). Panel B. Growing season phenological curves for high elevation mule deer summer ranges in southwestern North America (2004–2011; 33–42° N). From top to bottom, curves represent a transition from ecosystems where plant phenology is driven by spring snowmelt and dry summers, to those in which phenology is timed to the onset of summer (monsoonal) rains. Thick bands represent approximate mule deer parturition dates at select latitudes.
Fig 3.
Estimated mule deer fawning dates (Birthdate), start of growing season (Start), and peak of growing season (Peak) as a function of latitude in southwestern North America, 2004–2011.
Fig 4.
The proportion of annual precipitation occurring from July-September (monsoonal moisture) and the associated standard deviation (SD) in the start (Start) and peak (Peak) of season as a function of latitude in southwestern North America.
Fig 5.
Values for Spearman’s rank correlation coefficient (r) between fawn counts and monthly NDVI values among migratory mule deer populations (2004–2011; 34–42° N).
June and July are the primary months of parturition in this region. Asterisks indicate a statistically significant relationship between fawn counts and NDVI for that month.
Table 1.
Relationship between the mean and CV (square root transformed) in mule deer fawn counts and mean NDVI, by growing season month, across a latitudinal gradient in southwestern North America (34°-42° N).
Fig 6.
Mean autumn fawn counts and associated coefficient of variation (CV) for migratory mule deer populations in southwestern North America, 2004–2011.