Unit of Study:
The Bears of Yellowstone

Subject:
Science (Biology)

Grade Level:
5^th - 8^th

Objectives:
The student will . . .

• Define carrying capacity.

• Describe some of the factors that determine carrying capacities.

• Explain why carrying capacity is important for wildlife.

• Explain why carrying capacity is important for people.

Background

Carrying Capacity Defined

The number of animals that can live in an area is determined by the area's "carrying capacity". Generally, we define it as the number of animals of a given type (species) that can be supported within a given area. Certain habitat requirements of a given species may limit carrying capacity. Such requirements include the quantity of and quality of available food, water, shelter, and space. Both natural and human causes affect carrying capacity. Effects may be short or long term.

The Greater Yellowstone Ecosystem (GYE), though large in area, is just so big. As a gallon bucket will hold only one gallon of liquid, the GYE can only support a specific number of bears. As with all habitats, for whatever species, the GYE varies seasonally and/or yearly in its carrying capacity. Any habitat can only support the numbers that can be carried at the lowest ebb of the season or year. Those surplus animals, born during richer seasons, are lost to some limiting factor prior to or during the harsher season.

Results of Artificially Increasing Carrying Capacity

At one time, the carrying capacity for wildlife in Yellowstone National Park was artificially increased with a "dump". In the earlier years of the park, administrators had the garbage from the park facilities and hotels dumped in one place. Bears and other wildlife found the dump to be an easy source of food. It became a great tourist attraction. Where else could one view up close such a large number of grizzly and black bears feeding together?

Bears had become so dependent on the dump for food that its sudden closure by park officials led to higher bear death rates. Park visitors had some readjusting to do as well. Not only did visitors have to learn how to keep human food away from bears, they had to remember to always APPLY their knowledge. The old habits of bears and people were hard to break. For sometime to come, bears sought food in developed areas and were, at times, quite aggressive in their efforts. So bear-inflicted human injuries did not go away instantly with the closure of the dump.

Management of Grizzly Bears in the Greater Yellowstone Ecosystem

The grizzly bear cannot be confined to Yellowstone National Park because it knows no legal boundaries. GYE is a complex habitat that includes two national parks, portions of six national forests, three national wildlife refuges, private and state lands, tribal lands, and Bureau of Land Management holdings.

Bear management policies within the park eliminates human entry and disturbance in specific areas, in order to prevent human/bear conflict and to provide areas where bears can pursue natural behavioral patterns and other social activities free from human disturbance. Types of restrictions include area and trail closures, no off-trail travel, a recommended party size of four or more people, and travel limited to daylight hours or established trails.

Bears are very large creatures, requiring a lot of food from diverse sources. Whenever carrying capacity is exceeded within the boundaries of Yellowstone National Park, bears are more likely to "come down from the mountain" and into the rest of the GYE where they are more likely to conflict with humans.

Procedure:
Following the Electronic Field Trip, the teacher will . . .

• Share the background section with the students.

• Facilitate a discussion that allows students to reach the objectives stated previously.

Extension:
Invite older students to research a local animal species and all aspects of its current habitat. Then, challenge the students to determine the carrying capacity for the species. There are numerous activities published on the worldwide web that contain instructions and formulas for determining carrying capacity.

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