Yellowstone Grizzlies Under Threat
Yellowstone's Grizzly bears are facing multiple threats, writes Anna Taylor - from proposals to remove their protection under the US Endangered Species Act, and shortages of key foods caused by climate change.
Grizzly bear trophy hunting in Yellowstone National Park may resume in 2014 if the proposal to remove the bears from the protection of the Endangered Species Act is approved later this year.
The Yellowstone Ecosystem Subcommittee of the Inter-agency Grizzly Bear Committee recently recommended to the US Fish and Wildlife Service that the bears be de-listed.
The advice followed the publication of a controversial report by the Inter-Agency Grizzly Bear Study Team on 2nd December: Response of Yellowstone's Grizzly bears to changes in food resources - a synthesis.
In summary, the Synthesis report argues that the Park's grizzlies are doing just fine, indeed that they are now limited in numbers only by the Park's "carrying capacity".
However other scientists contest the Synthesis Report's findings and criticise it as incomplete, flawed and "politically motivated".
Mountain pine beetle
Key to the debate is the grizzlies most important food: the fatty, nutritious seeds of Whitebark pines.
Whitebark pine trees are increasingly falling victim to mountain pine beetle, which kills the trees when it lays its eggs under the bark. Whitebark pines are found at high elevations, typically over 2,500m, but climate change is making them more accessible to the pests.
A study conducted last year discovered that 16 of the 22 major mountain ranges in Yellowstone have experienced widespread moderate-to-severe mortality of whitebark pine - 82% of its total distribution.
The reason why whitebark pines are so important for Grizzly bears is that their seeds are a rich source of dietary fat (30-50%).
The fat is not only a great source of daily energy - it's also efficiently converted to body fat. And that promotes the survival and reproduction of female grizzlies, for hibernation and also to support lactation.
While acknowledging the importance of the pine seeds, the Synthesis Report controversially claims that the Grizzly bears have suffered "no profound negative effects" from the loss of whitebark pine seeds and demonstrated "notable resilience" by moving to other food sources.
Continue reading at ENN affiliate, The Ecologist.
Grizzly bear image via Shutterstock.