Hostile winters; are changes in Arctic/Boreal North America seasonal snow conditions causing Dall Sheep population decline?

Authors: Christopher Cosgrove*, Oregon State University
Topics: Cryosphere, Remote Sensing, Mountain Environments
Keywords: Remote Sensing, Passive Microwave, Rain-on-snow, Arctic Change, Alaska, Mountain Ecosystems, Snow/Wildlife Interactions
Session Type: Paper
Day: 4/12/2018
Start / End Time: 3:20 PM / 5:00 PM
Room: Regent, Marriott, River Tower Elevators, 4th Floor
Presentation File: No File Uploaded

Dall sheep are an emblematic species of alpine northwestern N. America, their ranges contained entirely within the Arctic/Boreal region. A large ungulate, reliant on year-round access to forage in open-alpine terrain, Dall sheep population decline, 20% range-wide since 1990, may be a description of broad-scale alpine ecosystem change in Alaska and northwestern Canada. Trophy-hunting, subsistence and tourism opportunities mean that Dall Sheep are an important ecosystem service to remote communities; their successful management hence a critical and contentious issue at local to regional scales. Changing seasonal snow cover is believed to be a principal cause of Dall Sheep population decline, with increasing harsh spring weather, icing and rain-on-snow (RoS) events thought to be obstacles to forage. This study explores the relationships between observations of Dall Sheep recruitment - summer ewe to lamb ratios - and metrics of snow and climate conditions derived from a spatially-explicit snow-evolution model and a remotely-sensed RoS and icing event dataset. Noting that Fall mean air temperature positively correlates with recruitment, whereas Winter mean snow depth and Spring mean snow density does so negatively, long-term trends in the frequency and periodicity of hostile versus friendly winters are examined from 1980 to 2017.

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