HD 401 CWD Update

By Ryan Rauscher, MFWP

25 Mule deer in Hunting District 401, also known as the Sweet Grass Hills area, were collared with satellite collars that record a single location once every 23 hours.   This photo shows approximately  5393 daily locations. Currently of the 25 collared deer 3 are residing just north of the border and the furthest any have gone north is  roughly 5 miles. Interestingly, no deer have moved between any of the three buttes that make up the Sweet Grass Hills. 


As described in the May 2016 edition of the Post Rider, HD 401 has been identified as a high risk area for Chronic Wasting Disease (CWD) because of the presence of the disease in Alberta.  CWD is a contagious neurological disease that attacks the brain of members of the deer family.  Mule deer are susceptible to the disease in HD 410.  To assess the risk to HD 401 mule deer and to improve our understanding of mule deer movement patterns, movement corridors, and connectivity to CWD positive populations in Canada,  Montana Fish, Wildlife & Park, (MFWP) captured 25 mule deer, 20 bucks and 5 does, near the Canadian border in HD 401.  The collars are satellite collars that record a single location daily.  Through a service, MFWP can monitor deer locations without physically relocating the animal.  This is a brief update on deer movements since capture.


Surprisingly, only a couple of the collared deer have been reported seen, yet all of the collared deer have survived since capture.  The collars have worked relatively well, providing locations once every 23 hours the majority of the time.  Occasionally, a few locations will be missed due to terrain, satellite position, etc.  As of the writing of this article, 5393 locations have been recorded, or approximately 215 locations per deer.  Compare that to previous studies of collared elk in HD 401 where most animals were relocated once a month or only 12 locations per year if they could be found.


Most of the collared deer are relatively sedentary, moving on short distance around the capture location.  A relatively few deer have moved back and forth into Alberta.  Currently, 3 of the deer are residing just north of the border.  The furthest movement north of the border is roughly 5 miles.  A few deer have displayed minor movements between winter range where they were captured to summer range a short distance away.  Interestingly, no deer have moved between any of the three buttes.  One deer moved southward about 8 miles for a few weeks and then moved back northward.


This is all good news.  None of the collared deer have moved close to the infected area in Alberta or from capture area to the Marias River.  However, the study is in its infancy.  Over time these collars will provide more movement information as the collars are expected to last for 4 years.


These data are important  and will be used to develop better risk assessment models to predict transmission risk both into Montana and within Montana once CWD is detected.   Along with other efforts, these data will be used to inform management decisions aimed at early detection of CWD and reducing the spread of the disease.


Given the amount of resources required to collar these deer and the value of the data, MFWP encourages hunters to avoid harvesting radio-collared deer in HD 401 even though it is legal.  Again, this research would not be possible without the cooperation of local landowners allowing access to their lands.  Thank you.




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