MISSOULA, Mont. (AP) -- Dogs are being blamed for the deaths of two sheep that were part of a small herd that is sent to Missoula's North Hills hiking area to graze on noxious weeds.

Morgan Valliant, conservation lands manager for Missoula Parks and Recreation, tells the Missoulian the herd began grazing in the area Sunday and is asking dog owners to keep their pets on a leash when hiking.

The grazing sheep control weeds on more than 1,000 acres very economically and without the use of chemicals.

Valliant says he is "asking for the public's help in this very narrow time frame -- three to four weeks -- to control their dogs and let the sheep do their work."

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Information from: Missoulian, http://www.missoulian.com

Copyright 2011 The AP.