Subjects

• Examine seven models and maps of the Mary Mountain bison migration corridor.
• Correlate at least two separate bits of information between at least two different models or maps.
• Reference at least two geographical features on the shaded relief map.
• Identify the Mary Mountain bison migration corridor on at least two different maps or models.
• Express in writing a thoughtful inference on how hydrothermal activity influences bison migration, including at least one specific reference to information obtained from the maps and models.

Materials
Pencil, markers or colored pencil
Attachment A—Map of Yellowstone National Park (1.4MB pdf)
Attachment B—Six Models or Maps of the Mary Mountain Bison Migration Corridor, Yellowstone National Park (662KB pdf)

Background
Thermally influenced areas facilitate ungulate migration to extended destinations in the winter by modifying the depth of the snow along portions of the migration route. Although capable of navigating through deep snow, bison have found that the thermal areas provide refuges of warmth and plentiful forage. This “hopscotch” between thermal areas allows the animal to recoup before tackling the next stage of the journey. Once ungulates are familiar with such destinations, ungulate range expansion continues as a function of population size.

Extensive snow sampling and modeling of the central portion of the park has allowed researchers to produce GIS images that incorporate effects of thermal influence on snow depths along the Mary Mountain bison migration route. Representations of thermal areas in the same area are based on radioactive heat flux.

Procedure
Note: The instructor may prefer to do this activity as a class and layer transparencies of the various maps and models.
The instructor will:

1. Explain to students that many bison in the central part of Yellowstone migrate considerable distances in the winter, even though it is not unusual for the ground to be covered by more than two feet of snow.

2. Give each student a copy of Attachment A. Explain that Attachment A is a map of Yellowstone National Park. The Mary Mountain bison migration corridor is in the central part of the park, stretching between Hayden Valley, across the Central Plateau, to the Lower and Midway Geyser Basins on the Firehole River. Have students locate this area on their maps.

3. Give each student a copy of Attachment B. Explain that Attachment B contains a series of models and maps of the area of the Mary Mountain bison migration corridor.

4. Ask students to examine the Colored Relief Map of Yellowstone National Park and once more locate Hayden Valley, the Central Plateau, and the geyser basins on the Firehole River. Ask students to study the elevation and topographic changes shown on the map in this part of Yellowstone.

5. Direct students to proceed to the Shaded Relief Map of the Mary Mountain bison migration corridor. Be sure students realize this is an enlarged view of the specific area they just located on the other two maps. Have students identify the Madison/Firehole Rivers, Yellowstone Lake, the Grand Canyon of the Yellowstone, the Yellowstone River, and Hayden Valley on the Shaded Relief Map by correlating between the previous two maps and the Shaded Relief Map. Students should write in these place names on the Shaded Relief Map.

6. Direct students to examine the Digital Elevation Model in Attachment B. Be sure they can once again identify important geographic features for reference such as the Madison/Firehole Rivers and the Yellowstone River. Now ask students to observe how the colors of the elevation model reflect the elevation changes depicted on the two relief maps.

7. Direct students to create an elevation key on the Digital Elevation Model. They should describe the order in which colors reflect elevation changes from low to high. (white, blue, green, yellow, red, pink, purple)

8. Direct students to examine the Thermal Ground Heat Model and then place it beneath the Shaded Relief Map, holding both papers before a lighted window. They should mark areas of thermal ground heat on their Shaded Relief Map with a pencil.

9. Direct students to place the Thermal Ground Heat Model beneath the Snow Depth Model. Ask students if they observe similarities between the two models. On the basis of these similarities, what would they infer the darkest areas on the Snow Depth Model indicate?

10. Direct the students to place the Mary Mountain Bison Migration Corridor and Home Range map beneath the Shaded Relief map and hold it against a lighted window. Instruct students to trace the Migration Map onto the Shaded Relief Map.

11. Ask students how the bison migration route corresponds with the geothermal ground heat areas they drew on their map. Ask if the snow depths would vary along this route and why. Ask students to indicate areas where the bison would “hopscotch” between areas of deeper snow.

12. Direct students to express, in writing, an inference on how thermal activity influences bison migration in the central part of Yellowstone, using at least one specific reference to information obtained by using the models and maps.