Wolves and bears don't normally get along, but new research shows that they can have a positive impact on each other's lives. Specifically, wolves are helping bears get fat.
Bears rely on berries to help them fatten up for hibernation, the only problem is that elk herds do too. The reintroduction of wolves, which prey on elk, into Yellowstone National Park has freed up more berries for bears to eat. Berries also provide nutrion for smaller critters such as hummingbirds.
The findings can be found online in the Journal of Animal Ecology.
"Wild fruit is typically an important part of grizzly bear diet, especially in late summer when they are trying to gain weight as rapidly as possible before winter hibernation," said lead author of the study William Ripple, a professor at the Oregon State University (OSU) Department of Forest Ecosystems and Society. "Berries are one part of a diverse food source that aids bear survival and reproduction, and at certain times of the year can be more than half their diet in many places in North America."
The removal of wolves from Yellowstone allowed their natural prey, such as elk, to roam freer and gorge themselves, wreaking havoc not only on other animals' diets, but also on the actual foliage itself. The population of plants such as young aspen and willow trees, elk favorites, have also shown considerable improvement after the reintroduction of wolves.
"Studies like this also point to the need for an ecologically effective number of wolves," said co-author Robert Beschta, a professor emeritus from OSU. "As we learn more about the cascading effects they have on ecosystems, the issue may be more than having just enough individual wolves so they can survive as a species. In some situations, we may wish to consider the numbers necessary to help control overbrowsing, allow tree and shrub recovery, and restore ecosystem health."