Conservation
[edit]
Because apex predators have powerful effects on other predators, herbivores, and plants, they can be important in nature conservation.[21] Humans have hunted many apex predators close to extinction, but in some parts of the world, these predators are now returning.[22] They are increasingly threatened by climate change. For example, the polar bear requires extensive areas of sea ice to hunt its prey, typically seals, but climate change is shrinking the sea ice of the Arctic, forcing polar bears to fast on land for increasingly long periods.[23]
Dramatic changes in the Greater Yellowstone Ecosystem were recorded after the gray wolf, both an apex predator and a keystone species (one with a large effect on its ecosystem), was reintroduced to Yellowstone National Park in 1995 as a conservation measure. Elk, the wolves' primary prey, became less abundant and changed their behavior, freeing riparian zones from constant grazing and allowing willows, aspens, and cottonwoods to flourish, creating habitats for beaver, moose, and scores of other species.[24] In addition to their effect on prey species, the wolves' presence also affected one of the park's vulnerable species, the grizzly bear: emerging from hibernation, having fasted for months, the bears chose to scavenge wolf kills,[25] especially during the autumn as they prepared to hibernate once again.[26] The grizzly bear gives birth during hibernation, so the increased food supply is expected to produce an increase in the number of cubs observed.[27] Dozens of other species, including eagles, ravens, magpies, coyotes, and black bears have also been documented as scavenging from wolf kills within the park.[28]