Importance:  The 35 km long Mary Mountain Trail penetrates the heart of the Central Yellowstone Plateau as it extends to the east along Nez Perce Creek from the Firehole River drainage, up Mary Mountain, and over to the Hayden Valley.  This trail forms the major migratory corridor that allows the central bison herd to travel from its summer ranges in the Hayden Valley and Pelican Valley to its winter range in the Madison-Firehole-Gibbon area. 

Primary wildlife:  Bison (Bison bison) are the prominent ungulate species of interest along the Mary Mountain Trail as they migrate seasonally from their summer ranges in the Hayden Valley and Pelican Valley to their winter range in the Firehole, Madison, and Gibbon drainages during fall and early winter.  Between 250 and 1,300 bison have occupied the Madison-Firehole-Gibbon area throughout the winters during the years of this long-term study.  The area also provides important gray wolf (Canis lupus) habitat year-round as well as elk (Cervus elaphus) and grizzly bear (Ursus arctos) habitat during the spring and summer.

Description:  The study area consists of the 35 km long Mary Mountain trail that connects the Lower Geyser Basin of the Firehole Valley to the Hayden Valley.  Elevations range from 2,200 m in the Lower Geyser Basin to 2,400 m in the Hayden Valley.  The maximum elevation along the trail is 2,500 m at Mary Mountain--located roughly in the middle of the length of the trail.  The entire area along the Mary Mountain Trail is roadless.

Habitat:  Lodgepole pine (Pinus contortus) dominates the forested area with stands of Engelman spruce (Picea engelmanni), subalpine fir (Abies lasiocarpa), and Douglas fir (Pseudotsuga mensiesii) interspersed.  More than 50% of the forested area was burned during the summer of 1988. Burned areas are characterized by snags and downed trees, Ross' sedge (Carex rosii), elk sedge (Carex geyeri), leafy aster (Aster foliaceus), and regenerating lodgepole pine.  Wet meadows, which occur in the unforested areas along the rivers, are characterized by standing water or saturated soils and grasses, sedges (Carex spp.), and marsh reedgrass (Calamagrostis spp.). Drier meadows are dominated by grasses (Festuca idahoensis, Poa spp.), and sagebrush (Artemesia spp.). The study area contains small areas of geothermal influence where snow accumulation is retarded or prevented.  

Weather:  Winter conditions along the Mary Mountain Trail are typically severe.  Snow pack begins accumulating in October and averaged 117 days > 40 cm and 36 days > 70 cm at the Madison Junction ranger station (elevation 2,075 m) from 1992 to 1998.  The average start of melt at the Madison Junction ranger station between 1992 and 1998 was early March.  At higher elevations in the study area snow continues to accumulate after snow melt starts in the valleys.  The average start of melt at the National Resources Conservation Service Madison Plateau SNOTEL site at 2,362 m was early-mid April from 1992 to 1998.  Using averaged daily high and low temperatures, winter mean monthly temperatures in the valleys range from 2.5° C in October to -11.0° C in December and January, increasing to -4.2° C in March and 6.5° C in May.

Nez Perce Creek

Mary Lake Ranger Patrol Cabin along the Mary Mountain trail

Bison herd foraging in Highland Hot Springs area

Spacious Spruce Creek meadows