Applied investigations into grizzly and black bear ecology and management

Teisberg, Justin

The manuscripts herein contribute to a working set of knowledge and techniques pertaining to the ecology and management of grizzly (Ursus arctos) and black bears (U. americanus). In chapter one, I focus on responses of numbers of grizzly and black bears to declining numbers of spawning Cutthroat trout along streams within Yellowstone National Park. When compared to 1997–2000 levels, the number of spawning cutthroat trout per stream and the number of streams with cutthroat trout had decreased. In any one year, 46 to 59 independent individuals (8–10% of estimated Greater Yellowstone Ecosystem population) visited these streams. When compared with estimates from a previous study, the number of grizzly bears using the stream corridors had decreased by 63%. In the second Chapter, I investigated the genetic consequences of management actions and genetic introgression on black bears by using ancient DNA techniques on historic specimens. Due to changing management philosophies and policies in Yellowstone National Park (YNP), large numbers of black bears were removed from the core of the ecosystem between 1930 and 1970. While effective population sizes (Ne) were found to be historically low since the early years of the Park, we observed only slight decreases in all diversity measures before and after the large-scale removal of black bears, likely due to gene flow from outside demes. To add, the strength of genetic drift following removals may have been much more substantial without this outside introgression. Chapter III introduces the immobilization of grizzly bears with a novel combination of anesthetics (dexmedetomidine, tiletamine, and zolazepam [dexMTZ]). Smaller than expected doses of the combination produced reliable, fast induction of anesthesia in captive and wild bears. When compared to other drug regimes, this combination produced lesser degrees of hypertension, hypoxemia, hypoventilation, or rectal temperatures. Time (min) to first signs of recovery after the initial injection of dexMTZ was influenced by heart rate (P < 0.001) and drug dose (P < 0.001), offering a modest degree of predictability. Field trials confirmed that our dexMTZ protocol provides degrees of safety and reliability that surpass previous drug combinations, especially with helicopter captures.