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Post by grrraaahhh on Jun 20, 2013 20:29:07 GMT -9
With an emphasis but not exclusive focus on morphometrics, this thread examines the interior grizzly bear populations residing in the U.S. Lower 48 states.
To be continued....
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Post by grrraaahhh on Jul 14, 2013 20:05:11 GMT -9
Copied from the Distribution & density of U. arctos in N. America thread:The lower 48 states, USA: Background: When Lewis and Clark explored the West in the early 1800s, an estimated 50,000 grizzly bears roamed between the Pacific Ocean and the Great Plains, across vast stretches of open and unpopulated land. But when pioneers moved in, bears were persecuted and their numbers and range drastically declined. As European settlement expanded over the next hundred years, towns and cities sprung up, and habitat for these large omnivores--along with their numbers--shrunk drastically. Today, with the western United States inhabited by millions of Americans, only a few small corners of grizzly country remain, supporting about 1,200 - 1,400 wild grizzly bears. Of 37 grizzly populations present in 1922, 31 were extirpated by 1975. In 1975, the U.S. Fish and Wildlife Service listed the grizzly bear as a threatened species in the Lower 48 States under the Endangered Species Act, placing the species under federal protection. Locations: Today, grizzly bear distribution is primarily within but not limited to the areas identified as Recovery Zones including--the Yellowstone area in northwest Wyoming, eastern Idaho, and southwest Montana (9,200 square miles (sq mi)) at more than 580 bears; the Northern Continental Divide Ecosystem of north central Montana (9,600 sq mi) at more than 400 bears; the North Cascades area of north central Washington (9,500 sq mi) at less than 20 bears; the Selkirk Mountains area of northern Idaho, northeast Washington, and southeast British Columbia (2,200 sq mi) at approximately 40 to 50 bears; and the Cabinet Yaak area of northwest Montana and northern Idaho (2,600 sq mi) at approximately 30 to 40 bears. There is an additional Recovery Zone known as the Bitterroot Recovery Zone in the Bitterroot Mountains of east central Idaho and western Montana (5,600 sq mi) but this area does not contain any grizzly bears at this time. The San Juan Mountains of Colorado also were identified as an area of possible grizzly bear occurrence, but no evidence of grizzly bears has been found in the San Juan Mountains since a bear was killed there in 1979. Source: Dr. Chris Servheen, U.S. Fish and Wildlife Service (online).  Source: Servheen, C. 1999. Status and management of the grizzly bear in the lower 48 United States. Pages 50-54 in C. Servheen, S. Herrero, and 8. Peyton, comps. Bears: Status survey and conservationaction plan. IUCN/SSC Bear and Polar Bear Specialist Groups, IUCN, Gland, Switzerland, and Cambridge, UK.
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Post by grrraaahhh on Jul 18, 2013 22:37:38 GMT -9
The Grizzly Bears of Yellowstone National Park (Quick Recap) History A heated debate began in the 1960s and 1970s and grew to a national scope concerning the grizzly bears in the GYE. For decades, grizzly bears were allowed to rummage through garbage dumps searching for food. As early as the 1940s, some researchers suggested closing the open-pit dumps within Yellowstone National Park. In 1963, the Advisory Board on Wildlife Management in the National Parks released the “Leopold Report” which recommended that natural ecosystems should be recreated, including predator/prey relationships.  By 1967, Yellowstone National Park’s Superintendent Anderson began to implement recommendations of the Leopold Report. The Park began closing the open-pit dumps and bears were to be weaned off garbage. Some researchers suggested gradually phasing out the dumps, but the Park staff closed everything, rationalizing that there were enough backcountry bears that did not use dumps to sustain the mortality. The controversy continued because grizzly bear mortality increased substantially as dumps were closed. Between 1967 and 1972, a minimum of 229 Yellowstone ecosystem grizzlies died. The IGBST was formed by the Department of Interior in 1973 as a direct result of this controversy. The high mortality that followed dump closure and concerns for the population’s future led to its listing as threatened under the Endangered Species Act in 1975. Early research by the team indicated that following listing, the population continued to decline into the 1980s. This information was the foundation and impetus for the formation of the Interagency Grizzly Bear Committee (IGBC) in 1983. The IGBC, represented by administrators from federal and state agencies, implemented several regulations on federal lands designed to reduce human-caused grizzly bear mortality. These management policies, in concert with favorable environmental conditions, halted the population’s decline. Grizzly bear numbers have increased since the mid-1980s and today bears again occupy historical range well beyond Yellowstone National Park. USGS SOURCE LINK: www.nrmsc.usgs.gov/research/igbst-home.htm#HistoryTo be continued.....
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Post by grrraaahhh on Jul 18, 2013 22:39:00 GMT -9
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Post by grrraaahhh on Jul 18, 2013 22:41:03 GMT -9
Yellowstone National Park (continued)Weight & MeasurementsI. 1959-1970 Text Extract: "Reliable data on measurements of grizzly bears exist for populations in the Brooks Range of Alaska (Rausch 1963), the Yukon Territory (Pearson 1975), and the Yellowstone ecosystem (Craighead and Craighead 1973b). Weights of large adult animals from the Yellowstone ecosystem ranged from 158 to 204 kg for females, and from 363 to 500 kg for males. Average weights and physical dimensions by age classes of Yellowstone grizzly bears are given in table 25.1 (J. J. Craighead unpublished data)." Craighead, J. J., and J. A. Mitchell. 1982. Grizzly Bear. Pp. 515-556 in J. A. Chapman and G. A. Feldhamer (eds.). Wild Mammals of North America: biology, management and economics. John Hopkins Univ. Press, Baltimore, MD. II."Blanchard (in press) found that in Yellowstone National Park, male grizzlies were consistently heavier than females for all age classes except cubs and yearlings. Sexual dimorphism beginning at age 2 was also apparent in other study areas (Troyer and Hensel 1969, Pearson 1975). Males in Yellowstone steadily gained weight until at least 15 years, but the mean annual rate of weight increase for males aged 4-15 (5.6%) was much less than the rate for cubs through 3 years (42.1%). The mean weight of adult males was 29% greater than for females and body measurements were 8-17% greater. Males attained full size in 7 of 11 body measurements by age 6 and in all 11 by age 9." SOURCE: Grizzly Bear Compendium (1987) by the Inter agency Grizzly Bear Committee.     Blanchard, B. 1987. Size and growth patterns of the Yellowstone grizzly bear. International Conference on Bear Research and Management 7:99-107. PDF LINK: www.google.com/url?q=http://www.bearbiology.com/fileadmin/tpl/Downloads/URSUS/Vol_7/Blanchard_Vol_7.pdf&sa=U&ei=-tapTeOSH47EsAOus8j5DA&ved=0CBYQFjAA&usg=AFQjCNEX0N4nRyQtzC8ZznyXgIlw9pIIlA
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Post by grrraaahhh on Jul 19, 2013 4:44:19 GMT -9
YNP Weight & Measurements (continued)Yellowstone National Park (continued) Text Extract:
"Reliable data on measurements of grizzly bears exist for populations in the Brooks Range of Alaska (Rausch 1963), the Yukon Territory (Pearson 1975), and the Yellowstone ecosystem (Craighead and Craighead 1973b). Weights of large adult animals from the Yellowstone ecosystem ranged from 158 to 204 kg for females, and from 363 to 500 kg for males. Average weights and physical dimensions by age classes of Yellowstone grizzly bears are given in table 25.1 (J. J. Craighead unpublished data)."Craighead, J. J., and J. A. Mitchell. 1982. Grizzly Bear. Pp. 515-556 in J. A. Chapman and G. A. Feldhamer (eds.). Wild Mammals of North America: biology, management and economics. John Hopkins Univ. Press, Baltimore, MD.   Dental impressions are used, top, to determine the ages of the bears. An electrocardoigram, above, shows the bear's
heart action. A spring scale, right, is used to weigh young grizzlies.Source: Craighead, Frank Cooper; Craighead, John Johnson, Tuning in on the grizzly, 1973, Science Year/Worldbook Science Annual, 35-49.
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Post by grrraaahhh on Oct 23, 2013 6:08:22 GMT -9
YNP Weight & Measurements (continued)Yellowstone National Park (continued) Text Extract:
"Reliable data on measurements of grizzly bears exist for populations in the Brooks Range of Alaska (Rausch 1963), the Yukon Territory (Pearson 1975), and the Yellowstone ecosystem (Craighead and Craighead 1973b). Weights of large adult animals from the Yellowstone ecosystem ranged from 158 to 204 kg for females, and from 363 to 500 kg for males. Average weights and physical dimensions by age classes of Yellowstone grizzly bears are given in table 25.1 (J. J. Craighead unpublished data)."Craighead, J. J., and J. A. Mitchell. 1982. Grizzly Bear. Pp. 515-556 in J. A. Chapman and G. A. Feldhamer (eds.). Wild Mammals of North America: biology, management and economics. John Hopkins Univ. Press, Baltimore, MD.
heart action. A spring scale, right, is used to weigh young grizzlies.Source: Craighead, Frank Cooper; Craighead, John Johnson, Tuning in on the grizzly, 1973, Science Year/Worldbook Science Annual, 35-49. This post is a follow up to a PM I recently received. It's about the largest grizzly bear weighed at YNP (1,120 lbs) and is more or less on topic. If you read the quoted material there is some reference or indirect mention made about this bear. Also, the following Craighead book scan might look familiar to some of you as it was originally made by me in 2009 in another forum and has since been re posted by other people.  I was asked if there is a photo of this record specimen and as far as I know I am unaware of any published photo. I also have collected a good amount of the Craighead literature but regrettably there is little detail/information about this bear. Also, staying on topic, there is the author comment of weight averages provided. As it relates to morphometrics, this subject is of great interest to me especially on the topic of mature older bears regardless of population. It is possible to examine the published morphometric Craighead literature in this thread in juxtaposition to the earlier Craighead weight average statement from the book, Track of the Grizzly. FWIW, I suggest a careful review of the material. Moreover, as it relates to detailed data on YNP mature bears, it is clear there is more 'Craighead' data but it is not published. On a final point regarding morphometric data on YNP bears; keep in mind the following historical factors: the dump years, the post dump years, the reintroduction of wolves to YNP, and the changes to YNP fisheries. |
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