In March, the U.S. Fish and Wildlife Service (USFWS) officially proposed to delist the Greater Yellowstone Ecosystem (GYE) grizzly bear population from the Endangered Species Act (ESA), for the second time. The population stands at about 700 bears and its recovery is being hailed as one of America’s great conservation successes. However, the future of one tree, the whitebark pine, could stand in the way of GYE grizzlies delisting.
Since its initial listing in 1975, the GYE grizzly bear population has been intensely monitored, with the ultimate goal being to recover the GYE bears to a self-sustaining population. In 1993, a recovery plan was drafted that laid out specific recovery goals. By all accounts, the recovery criteria have been met for more than a decade, and the GYE grizzly population was first proposed for delisting in 2005. However, legal action put the bears back on the list when concerns were raised over the potential impacts from the loss of whitebark pine seeds as a food source.
The whitebark pine tree is a conifer that is generally found in cold, windy, high elevation or high latitude sites in western North America. Like most conifers, they create cones filled with their seeds. Whitebark pine trees produce large, dense seeds that lack wings and depend upon birds and squirrels to disperse them across the landscape. Cone production is variable from year to year, but trees produce large amounts of cones during periodic masting events; with a good crop of cones every 1 to 4 years. But the future of whitbark pine is uncertain. Due to climate change, beetle outbreaks and a rust fungus, these pines are experiencing long-term decline.
Throughout the early 1990s, it was thought that whitebark pine seeds were an essential part of the grizzly bear’s diet in the GYE population. Bears typically raid seed caches, known as middens, collected by red squirrels rather than collecting individual pine cones themselves. If whitebark pine seeds are essential for bear survival, then fewer seeds would mean fewer bears. However, more recent studies suggest that whitebark seeds are consumed opportunistically as part of a diverse diet, rather than an essential fall staple. Moreover, as omnivores, GYE grizzly bears consume hundreds of types of foods, but are also highly carnivorous, even compared with other grizzly bear populations in the Rocky Mountains. Animal matter accounts for 40–50% of GYE grizzly bear’s annual diet.
Researchers have also been following GYE bears fitted with GPS collars since the early 2000s. Using bear movement information, scientists were able to evaluate bear-whitebark pine relationships before, during, and after the peak of the recent beetle irruption. They found that in the GYE about 1/3 of grizzly bears do not use whitebark pine seeds at all, as the seeds are not available in their territory. For bears with pines in their territory, selection of the whitebark pine areas declined over time; which suggests that as availability of seeds declined, bears sought them less frequently. Researchers also looked at the bears’ movement patterns and found that the bears do not roam further from their ranges in search of alternate food sources.
Additional concern was raised that the decline of whitebark pine may be slowing the growth of the GYE population. However, this does not appear to be the case. A population-level assessment suggests that the slowdown in population growth is associated with the GYE bears reaching carrying capacity. Increasing bear density, rather than a decline in food resources, may also be associated with this slowdown in population growth. Researchers are currently working on long term studies that will further investigate these questions.
The USFWS should make a final decision about delisting the GYE bears in the next several months, but with science on their side, the whitebark pine issue should not be the reason to keep them on the list. Further, delisting the bears will not remove all protection from the population, but would return management authority to state and tribal agencies. State and Tribal authorities will closely regulate and manage the populations in their areas to ensure that a sustainable population of grizzlies continues to exist. SCI Foundation will continue to work closely with state and tribal authorities to ensure scientific management occurs.
SCI Foundation continues to support the delisting of this recovered population, and filed comments in partnership with SCI to address several substantive legal and scientific issues, including the FWS’s delisting authority, hunting, food sources, genetics, and social tolerance. To review these recent comments, please click here.
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