Bears: Unlikely Guardians of Plants
Ants: A Double-Edged Sword
Ants are often seen as pests, but they can also play a beneficial role in ecosystems. In the alpine meadows of Colorado, ants provide shelter for sage grouse and other insects. However, ants can also become a problem when they swarm plants, deterring other insects from landing on their leaves. This can create an “enemy-free space” for herbivores like treehoppers, which can then damage the plants.
Enter the Black Bear
Black bears are known for their fondness for ants. And as it turns out, their ant-eating habits have a positive impact on plants. By removing ants from the vicinity, bears reduce the number of herbivores that can damage the plants.
A Closer Look at the Relationship
Joshua Grinath, a graduate student in ecology at Florida State University, conducted a study to investigate the relationship between bears, ants, and rabbitbrush, a yellow-flecked shrub that serves as a popular shelter for sage grouse.
Grinath found that hungry bears destroyed up to 86 percent of ant nests in the vicinity. While this was bad news for the ants, it was great news for the rabbitbrush shrubs. Without the ants to deter them, other insects were able to land on the leaves and eat the treehoppers, which are herbivores that can damage the plants.
Benefits for Plants
Grinath’s study showed that plants that had their ants removed were better able to grow and produce seeds. This suggests that bears play an important role in maintaining the health of plant communities in the alpine meadows of Colorado.
Mutualism: Ants and Treehoppers
In his study, Grinath also noted that ants and treehoppers have a mutualistic relationship. Ants provide shelter for treehoppers, while treehoppers help to disperse ant seeds. However, this mutualism can become a problem for plants when ants swarm their leaves, creating an enemy-free space for treehoppers and other herbivores.
The Role of Black Bears
Black bears help to break this cycle by removing ants from the vicinity of plants. This reduces the number of herbivores that can damage the plants, allowing them to grow and thrive.
Implications for Ecosystem Management
Grinath’s study highlights the importance of considering the indirect effects of species interactions when managing ecosystems. By understanding the complex relationships between plants, animals, and insects, we can better protect and manage these ecosystems for the benefit of all species.
