Related Experiment Video
Updated: Mar 1, 2026
10:20
Linking Predation Risk, Herbivore Physiological Stress and Microbial Decomposition of Plant Litter
Published on: March 12, 2013
14.0K
Constraints on herbivory by grizzly bears
Karyn D Rode1, Charles T Robbins1, Lisa A Shipley2
1Department of Zoology, Washington State University, Pullman, WA, 99164-4236, USA.
Oecologia
|May 27, 2017
Summary
Grizzly bears, often carnivores, can thrive on plants. Smaller bears gain weight on vegetation, but larger bears struggle due to foraging constraints. Managing nutritious forbs can improve grizzly bear nutrition.
Area of Science:
- Ecology
- Animal Nutrition
- Wildlife Biology
Background:
- Grizzly bears (Ursus arctos horribilis) are known carnivores but consume over 200 plant species, acting as herbivores in some ecosystems.
- Herbaceous vegetation is a crucial seasonal food source for grizzly bears, even where meat is abundant.
Purpose of the Study:
- To examine the morphological, physiological, and environmental factors influencing the nutritional value of herbaceous plants for grizzly bears.
- To understand the constraints on intake rate, including plant and bear characteristics, during foraging.
Main Methods:
- Short-term foraging trials with captive grizzly bears to assess intake rate constraints (bite size, rate, bear size, plant traits, distribution).
- Feeding trials to determine the impact of protein levels (12-35%) and digestible dry matter intake on weight gain.
- 12-day trials measuring maximum daily intake, foraging time, and weight change on abundant forbs and grasses.
Main Results:
- Short-term trials overestimated free-ranging intake by 2-7 times.
- Smaller bears (<120 kg) gained more weight than larger bears due to larger bite sizes, lower energy needs, and higher intake capacity.
- Forbs are preferred over grasses due to higher protein and digestibility, benefiting smaller, herbivorous bear populations.
Conclusions:
- Nutritional well-being of wild grizzly bears can be enhanced by managing for nutritious forbs, especially in herbivorous populations.
- Foraging efficiency and weight gain on herbaceous vegetation are significantly influenced by bear size and plant characteristics.
- Targeted management of palatable forbs can improve grizzly bear nutrition in herbivorous ecosystems.
Related Concept Videos
02:39Predator-Prey Interactions
21.9K
Predators consume prey for energy. Predators that acquire prey and prey that avoid predation both increase their chances of survival and reproduction (i.e., fitness). Routine predator-prey interactions elicit mutual adaptations that improve predator offenses, such as claws, teeth, and speed, as well as prey defenses, including crypsis, aposematism, and mimicry. Thus, predator-prey interactions resemble an evolutionary arms race.
21.9K
00:48Optimal Foraging
14.1K
How animals obtain and eat their food is called foraging behavior. Foraging can include searching for plants and hunting for prey and depends on the species and environment.
14.1K
02:26Defenses Against Pathogens and Herbivores
29.7K
Plants present a rich source of nutrients for many organisms, making it a target for herbivores and infectious agents. Plants, though lacking a proper immune system, have developed an array of constitutive and inducible defenses to fend off these attacks.
29.7K
01:50Threats to Biodiversity
27.5K
There have been five major extinction events throughout geological history, resulting in the elimination of biodiversity, followed by a rebound of species that adapted to the new conditions. In the current geological epoch, the Holocene, there is a sixth extinction event in progress. This mass extinction has been attributed to human activities and is thus provisionally called the Anthropocene. In 2019 the human population reached 7.7 billion people and is projected to comprise 10 billion by...
27.5K
02:31Habitat Fragmentation
21.7K
Habitat fragmentation describes the division of a more extensive, continuous habitat into smaller, discontinuous areas. Human activities such as land conversion, as well as slower geological processes leading to changes in the physical environment, are the two leading causes of habitat fragmentation. The fragmentation process typically follows the same steps: perforation, dissection, fragmentation, shrinkage, and attrition.
21.7K
01:38Limits to Natural Selection
35.6K
Organisms that are well-adapted to their environment are more likely to survive and reproduce. However, natural selection does not lead to perfectly adapted organisms. Several factors constrain natural selection.
35.6K