[PDF] Distribution Of Beaver In Yellowstone National Park 1994 eBook

Author : Douglas W. Smith
Publisher :
Page : 12 pages
File Size : 49,20 MB
Release : 2012
Category : Aspen
ISBN :

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Despite Yellowstone National Park's (YNP) long history and well studied large mammals and vegetation, beavers (Castor canadensis), an important ecosystem driver, have received relatively little study. We summarize population surveys of beavers that began in 1921 and continued up to the present. The first surveys (1921 and 1923) were from the ground and conducted in a limited area in the northern portion (northern range; NR) of the park. Twenty-five colonies were found and beavers were considered abundant and using aspen (Populus tremuloides) and willow (Salix spp.) as a food source and building material. A follow up survey in 1953 found 6 NR sites, but none of the earlier sites from the 1920s were active and no aspen use was reported. Some locations were reported from the park interior. A limited ground survey was conducted in 1979-80. In 1988-89 and 1994 two incomplete, mostly ground surveys were conducted and estimated 71 and 44 colonies, respectively, in YNP. In 1996, 1998, 1999, 2001, 2003, 2005, 2007 and 2009 complete, park-wide aerial surveys were conducted and active colonies ranged from 44 (1996) to 127 (2007) with an increasing trend. Therefore, in a period of about 90 years (1920s?2000s) the beaver population in the northern portion of the park appears to have declined then increased probably because of a willow recovery.

Author : Lyman Persico
Publisher :
Page : 87 pages
File Size : 12,14 MB
Release : 2006
Category : Beavers
ISBN :

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Studies how the beavers in Yellowstone have affected stream geomorphology in the park.

Author : Matthew Allan Scrafford
Publisher :
Page : 8 pages
File Size : 27,61 MB
Release : 2018
Category : Beavers
ISBN :

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Beavers (Castor canadensis) disappeared from drainages north of Yellowstone National Park in the mid-1900s because of trapping, a potential tularemia outbreak, and willow (Salix spp.) stand degradation by ungulates. Beavers were reintroduced in 1986 after a 40?yr absence with inventories of active-beaver structures completed each fall after reintroduction for 24 consecutive yr. We used this inventory to evaluate the expansion of beaver populations in a riparian environment recovering from past overuse by ungulates. Specifically, we investigated the density of active-beaver colonies and dams, the change in willow cover, and habitats associated with beaver expansion since reintroduction. Successful establishment and expansion of beavers indicate that sufficient resources were available to the population despite the suboptimal condition of riparian vegetation. Carrying capacity on third-order streams was reached approximately 14 yr after reintroduction (2000) with an average annual density of 1.33 (95th percentile = 1.23 ? 1.44 active colonies/stream km) between 2000 and 2010. The average annual density of beaver dams during this time was 2.37 (2.04 ? 2.71 active dams/stream km). Despite the beaver population being at carrying capacity in meadows since 2000, willow cover increased by 16% between 1981 and 2011. We speculate that beaver activities, together with reduced ungulate browsing from predation and habitat loss, combined to increase willow cover. Willow cover and height were positively associated with colony longevity, but numerous other influencing variables included secondary channels, sinuosity, stream depth, and sandbar width. Our results provide evidence that beaver reintroduction can be successful in riparian areas where willow stand condition is less than optimal and that beavers might ultimately improve willow condition. We suggest that reducing ungulate use of overgrazed riparian environments will facilitate the reestablishment of beaver populations. We also provide managers with habitats that should be identified in an environment targeted for reintroduction.

Author : Douglas W. Smith
Publisher :
Page : 8 pages
File Size : 15,94 MB
Release : 1997
Category : Beavers
ISBN :

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"The number of active beaver (Castor canadensis) colonies in Yellowstone National Park was determined by aerial survey in late October and early November 1996. This was the first near-complete autumn aerial count of beavers in park history. Flying time for the survey was 14.9 house, plus 4 hours ferry time from Bozeman, Montana, for a total of 18.9 hours. Total number of beaver colonies with food caches was 49; three other sites had beaver sign (beaver dam or cutting) indicating that beavers were probably present, but no lodge or food cache was sighted. Ninety percent of the park's beavers were located in three areas: 1) the Yellowstone River southeast of Yellowstone Lake, 2) the Beechler area, and 3) creeks and rivers in the northwest corner of the park which included the Madison and Gallatin rivers, and Cougar, Campanula, and Gneiss creeks. There was only one beaver colony on Yellowstone's Northern Range. All colonies were associated with willow (Salix spp.)."--Page 1.