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Report: Invasive Plant Management on Bighorn Sheep Winter Ranges: Bull River and Wigwam Flats Year 4 COL-F21-W-3286

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Rocky Mountain bighorn sheep (Ovis canadensis) are blue listed (vulnerable) within BC due to threats such as loss of habitat, predators and disease. Some bighorn sheep populations within the Kootenay Boundary Region have decreased since 2010. Possible causes of decline are increased winter severity, increased predator populations, and reduced winter range habitat condition.

Author:  Irene Teske

Old Reference Number:  COL-F21-W-3286

Old Reference System:  FWCP - Fish Wildlife Compensation Program Columbia

Date Published:  Apr 2021

Report ID:  59356

Audience:  Government and Public

In the Forest Practices Board Report (2016) on rangelands, invasive plants were identified as an issue that threatens the sustainability of rangelands over the long term. Invasive plants are capable to alter habitats and disrupt essential ecosystem functions by displacing native vegetation. Invasive plants reduce soil productivity, impact water quality and quantity, degrade range resources and wildlife habitat, threaten biodiversity, and alter natural fire regimes. With declining effectiveness of biocontrol for St. Johns Wort (Hypericum perforatum) in the East Kootenay and rapid invasion of new invasive plant species such as yellow hawkweed (Hieracium spp), intensified invasive plant management is required to restore bighorn sheep winter ranges. This project aligns with the Upland & Dryland Action Plan: Action #11 Terrestrial Invasive Species. This report discusses results of Year 4: 2020-21 management of invasive plants at Bull River and Wigwam Flats. In Year 1, Treatment units were created and mapped, vegetation sampling plots were installed and sampled, selected units were treated with herbicide in the spring and selected sites with resulting low vegetation cover were seeded in the fall (fall rye), and vegetation sampling data was collated, analyzed and summarized. In Year 2, additional vegetation plots were installed, a subsample of vegetation plots were sampled, selected units were treated with herbicide in the spring, seeding of sites with low vegetation cover (agronomic mix) occurred in the fall and vegetation sampling data summarized. In Year 3, in addition to Year 2 activities we sampled most of the vegetation plots and conducted fertilizer trials. In Year 4, we sampled fertilizer trial areas. Bighorn sheep inventories were conducted during winters of 2016-17, 2017-18 and 2018-19 and 2020-21 with funding from the Ministry. In 2018-19, 65 sheep were observed in Bull River. In 2020-21, 59 sheep were observed in Bull River. Previous inventories occurred in 2012 and 2014 with observed results of 100 and 97, respectively. Sheep population estimate has reduced from 120 in 2012 to 80 in 2019. The population appears to have declined 40% since 2012. Cause of decline is unknown but appears to be predation driven. In Wigwam Flats, a total of 184 bighorn sheep were observed in February 2019 and 184 in March 2021. Bighorn sheep inventories were not conducted in this area in 2019-20. The population estimate has remained stable at approximately 230 sheep. Six treatment units were delineated at Bull River covering a total of 166.1 hectares. At Bull River, 39 plots were established, 23 in 2017, 5 in 2018 and 11 in 2019. The 11 plots established in 2019 were to attempt to monitor fertilizer trials. Seven treatment units were established at Wigwam Flats covering 227 hectares. At Wigwam Flats, 25 plots were established, 18 in 2017 and 6 in 2018 and 1 in 2019. All plots were sampled prior to herbicide treatments.

Report Type
  Mammals - Bighorn Sheep: Ovis canadensis
  Region - Kootenay
  Vegetation - Plant Ecology
  Vegetation - Vegetation (VRI)

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