Bears making comeback to Nevada's Great Basin

Conservation efforts are seeing the return of black bears into the Great Basin of Nevada, an area that hasn't seen the mammal for over 80 years according to a study released this week by the Wildlife Conservation Society (WCS), the Nevada Department of Wildlife (NDOW), and the University of Nevada-Reno (UNR).

Prior to this study, most of the state's black bears could be found around Lake Tahoe and the Pine Nut Mountains after being forced from the Great Basin by unregulated hunting and conflicts with domestic livestock.

The study's authors attribute the successful recolonization to conservation efforts conducted by WCS and NDOW over the course of more than 20 years. These included public education, investing in bear-proofing communities, reducing conflict rates between carnivores and people, and reduced human-caused carnivore mortality rates.

As a result of the efforts, a once negative population growth rate for bears in urban-interface areas became an average annual growth rate of 16 percent for more than a decade, and re-colonization of historic ranges in the mountains of the Great Basin ensued. Once extirpated from their former range, more than 500 black bears have now recolonized these areas.

In addition to the demographics of the recovery the scientists studied the impacts of this loss and subsequent recovery on the genetic makeup of the population.

Genetic analysis demonstrated that the population has indeed undergone an extirpation followed by a re-expansion. The re-colonizing bears originated from a source population in the Sierra-Nevada Mountains (refugia for bears during the last 100 years) and expanded in a west-to-east pattern back into the Great Basin.

“This study represents a great partnership between wildlife management and geneticists,” said Jason Malaney, lead author of the genetic study. “Wildlife managers deploy long-term field-surveys of black bears, collect tissue samples along the way,that are then used to better understand the complexities of re-colonization. This resuts in improved management outcomes.”

The authors of the study conclude that based on their results, black bears in the western Great Basin appear to currently maintain levels of connectivity between various mountain ranges that are sufficient to prevent genetic bottlenecks following recolonization. Further, black bears in the western Great Basin best represent a genetic metapopulation (a group of populations separated but of the same species with individuals that interact with other populations).

Finally, they note that as the human-footprint expands over time in the region, this level of genetic connection among various mountain ranges may not last without conservation efforts to maintain connectivity.

”The recovery of large carnivores is relatively rare globally yet this is the goal of conservation," said WCS Conservation Scientist Jon Beckmann. “Understanding the mode of recolonization and its genetic consequences is of broad interest in ecology and critical to successful conservation programs.”

Co-authors include: Jason L. Malaney of University of Nevada, Reno; Carl W. Lackey of Nevada Department of Wildlife; Jon P. Beckmann of the Wildlife Conservation Society; and Marjorie D. Matocq of University of Nevada, Reno. Their study is titled the "Natural rewilding of the Great Basin: genetic consequences of colonization by black bears (Ursus americanus)."