Applied investigations into grizzly and black bear ecology and management.

摘要

The following dissertation is composed of three stand-alone manuscripts. However all contribute to a working set of knowledge and techniques pertaining to the ecology and management of grizzly (Ursus arctos) and black (U. americanus) bears. In Chapter I, I studied the interaction of grizzly and black bear abundance with declining numbers of cutthroat trout along spawning stream reaches. We estimated numbers of grizzly bears and black bears visiting streams by (1) capturing hair from collection sites along 35 historically fished streams and (2) modeling individual DNA encounter histories. When compared to 1997–2000 levels, the number of spawning cutthroat trout per stream and the number of streams with cutthroat trout had decreased. We estimated that 48 (95% CI = 42–56) male and 23 (95% CI = 21–27) female grizzly bears visited the historically fished tributary streams during the 3-yr study. In any one year, 46 to 59 independent individuals (8–10% of estimated Greater Yellowstone Ecosystem [GYE] population) visited these streams. When compared with estimates from the 1997–2000 study and adjusted for equal effort, 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. Due to changing management philosophies and policies in Yellowstone National Park (YNP), large numbers of black bears were removed (13 to 30% of population per annum) from the core of the ecosystem between 1930 and 1970. Using ancient DNA (aDNA) extraction techniques on historic specimens, we investigated whether these removals influenced genetic diversity of black bears within the GYE. While Ne values were found to be historically low (Ne point estimates of 19–87) 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. However, the strength of genetic drift following removals may have been much more substantial without this outside introgression.;Chapter III introduces a novel combination of anesthetics shown to be quite effective in immobilizing captive and wild grizzly bears. Fast induction of anesthesia, maintenance of healthy vital rates, and predictable recoveries are essential when immobilizing bears for research and management. We investigated these attributes in both captive and wild grizzly bears anesthetized with a combination of a reversible &agr;2¬ agonist (dexmedetomidine) and a nonreversible glutamate agonist and tranquilizer (tiletamine and zolazepam, respectively). A smaller than expected dose of the combination (1.23 mg tiletamine, 1.23 mg zolazepam, and 6.04 µg dexmedetomidine per kg bear) produced reliable, fast ataxia (3.7 ± 0.5 min, ± SE) and workable anesthesia (8.1 ± 0.6 min) in captive adult grizzly bears. Contrary to previously published accounts of bear anesthesia with medetomidine, this combination produced less significant hypertension, hypoxemia, hypoventilation, or rectal temperatures, although mild bradycardia (< 50 beats per minute) occurred in most bears during the active season. With captive bears, effective dose rates during hibernation were approximately half those during the active season. The time 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). Field trials confirmed that the dexMTZ + atipamezole protocol is safe, reliable, and predictable when administered to wild grizzly bears during foothold snare, and helicopter capture operations.