CWD management in Idaho: Here's what we're working toward

If you’ve hunted big game in Idaho, odds are good you’ve heard about chronic wasting disease, and hopefully, you know the basics of this incurable, fatal disease that infects deer, elk and moose. 

But you may be wondering “What is Fish and Game doing about it?” 

The answer is fairly simple. Idaho Fish and Game is working to protect the future of deer and elk hunting, and CWD is a threat to it. Biologists will continue testing, responding, and adapting to CWD. Fish and Game’s CWD management priority is keeping the percentage of animals infected – or prevalence – low in deer and elk herds to reduce and/or slow the spread of the disease. CWD can’t be eradicated because it remains in the environment for decades. 

But Fish and Game can’t do it alone. It’s going to take a long-term commitment and partnership with hunters. With a little luck and a lot of diligence, together we can minimize CWD’s effects on Idaho’s deer and elk and our hunting opportunities. 

Why cooperation from hunters is critical

We all want the same thing: healthy and abundant herds. The most effective way to get there is for Fish and Game and hunters to be partners in the fight against CWD. Even if there are disagreements on specific management actions, hopefully, there can be agreement on that goal. 

There is currently no reliable way to test live wild animals for CWD, so Fish and Game relies on hunters to monitor for the disease by having their harvested animals tested. In some units testing is mandatory (and free of charge) for all harvested deer because deer are most susceptible to CWD and where it is most likely to be detected. 

Fish and Game also offers free testing for hunters who voluntarily have animals tested in units where it is not mandatory. Hunters can check the results online. The Center for Disease Control recommends that people don’t consume CWD positive game. 

Hunters are also crucial in helping Fish and Game manage the disease in infected herds. Depending on the situation, reducing the total number of deer or changing the age structure of the herd may be the most effective method of combating the disease, but eradicating herds is never the goal. If additional animals need to be harvested to manage the disease, public hunting is the preferred tool Fish and Game uses.

CWD spreads slower when a small portion of the herd (less than 5 percent) is infected. Conversely, research has shown when prevalence is higher, the disease spreads much faster and to more animals. When a large portion of animals get infected, it eventually leads to a smaller deer herd.

Idaho’s recent history with CWD

A total of 100 deer and elk (mostly deer) have tested positive for CWD in Idaho since it was first detected in 2021. That’s a relatively small number considering hunters in 2024 alone killed about 21,000 elk and 45,000 deer.

CWD was first detected in Unit 14 in the Slate Creek area north of Riggins. Since then, it’s been detected in Unit 18 (just west of Unit 14), in Unit 23 (south of Unit 14), Unit 1 (in extreme north Idaho), and most recently, in private domestic elk operations in Unit 63A (north of Idaho Falls).

Each area where the disease was detected has been handled differently depending on the species, the number of detections, the migration patterns of deer and elk in the area, and other factors. 

Fish and Game has managed each scenario adaptively, instituting what they believe will be the most effective strategies to minimize prevalence and spread while simultaneously trying to minimize the burden on hunters.  

Adaptive CWD management

Units 14 and 18

When CWD was first detected in Slate Creek of Unit 14 in fall 2021, the Fish and Game Commission held emergency surveillance hunts in Units 13, 14, 18, and 23 to get a better idea of how prevalent the disease was and its distribution. Fish and Game found there was a hot spot in and around the Slate Creek area of Unit 14, with only a few other positive cases in other portions of Unit 14 and no positive cases in the other units. 

A CWD Management Zone was instituted in Units 14 and 15, which restricted the transportation of specific parts of deer, elk, and moose carcasses outside of the units. Unit 15 was initially included in the CWD Management Zone, even though no disease had been detected there, based on Fish and Game’s understanding of the seasonal movements of elk between the two units. 

Fish and Game subsequently increased deer hunting opportunities in Unit 14 to reduce densities, particularly of white-tailed deer, which have tested positive at a higher rate than mule deer or elk. 

The Slate Creek area has a large portion of private land, and while the Fish and Game Commission can expand hunting seasons and offer more tags, it’s largely landowners who determine how much hunting is allowed to take place in this area. The department has worked closely with landowners in the Slate Creek area for its CWD management. 

Because of the identified hot spot of disease, Fish and Game also used a series of “control actions” in late winter of 2023 and 2024 to reduce deer density in that area and minimize the spread. During these actions, Fish and Game and U.S.D.A. Wildlife Services (a federal agency that specializes in removing wildlife) used methods not typically used for hunting, including baiting and shooting at night, to reduce the deer herd in and around Slate Creek. 

When there was no disease detected in Unit 15 after extensive testing, it was removed from the CWD Management Zone and mandatory sampling requirements in that unit were lifted to minimize the burden on hunters. When CWD was detected across the river from Slate Creek in Unit 18, that unit was added to the CWD Management Zone and mandatory testing of harvested deer was implemented.

Fish and Game will continue to closely monitor this area and continue working with hunters and landowners to manage prevalence and spread of the disease. 

Unit 23

A single mule deer buck tested positive for CWD in Unit 23 in late-fall 2023. This case was managed significantly differently than the situation in Unit 14. Most mule deer migrate out of Unit 23 in early November and disperse into lower-elevation winter ranges in the surrounding units.     

Rather than immediately have a surveillance hunt, like in Unit 14, Fish and Game worked to get CWD samples from animals harvested in all remaining hunts that year, then the Fish and Game Commission required CWD testing of deer harvested from Units 23, 24, and 32A for the 2024 hunting season to evaluate disease prevalence and distribution in this area. 

To date, no additional animals have tested positive. Mandatory testing requirements have been continued in these units so Fish and Game gets enough samples to ensure there isn’t disease present. Aside from mandatory testing, there have been no changes to hunting seasons due to this single case of CWD. 

Unit 1

The first CWD detection in Unit 1 was in July 2024 when a white-tailed deer found dead tested positive. Fish and Game held an emergency CWD surveillance hunt in August 2024 to better understand prevalence and distribution of the disease in this portion of Unit 1, and two more white-tailed deer tested positive within a mile of the first detection.

The Fish and Game Commission established a CWD Management Zone and mandatory CWD testing requirements in the portion of Unit 1 east of the Selkirk Mountain crest. In total, 6 total white-tailed deer have tested positive in Unit 1 to date.

Unit 1 already had relatively long, either-sex general-season whitetail hunting opportunity, and Fish and Game also added CWD-focused controlled hunts for 2025 and 2026 to help monitor and manage the disease. CWD prevalence is currently low and biologists will continue to monitor prevalence and spread relative to the existing hunt structure, with the goal of effectively managing the disease while minimizing burden to hunters as much as possible.

What’s happening in other states with CWD

Idaho is not unique because within the last five years, a growing number of states have discovered CWD in their herds. To date, it has spread to 36 states, and only three western states have not detected it: Oregon, Nevada and Arizona. 

Some states have had CWD for decades longer than Idaho. Prevalence rates are high enough in many areas that hunters no longer want to hunt deer because of the high likelihood they will harvest an infected animal, or because deer herds have plummeted because CWD mortality exceeds birth rates. 

Fish and Game is trying to prevent those things from happening in Idaho by managing CWD at low prevalence levels with the long-term herd health and hunter opportunity in mind. 

Idaho’s current deer management may help reduce the risk of CWD spread

Hunters concerned about the threat of CWD to Idaho’s mule deer herds may rest a little easier knowing that current deer management may provide good hunting opportunity while also reducing the likelihood of CWD getting established at a high level in Idaho herds.

CWD research in other states has shown that fairly high harvest rates of mule deer bucks can keep CWD prevalence low. Mule deer bucks move around more than does and range over a broader area. If there is CWD in a herd, those wandering bucks are the most likely sources of transmission to nearby herds.

Idaho’s general season hunts typically lead to a fairly high harvest of bucks. It’s common that 25 to 40 percent of bucks are taken annually in many units. While that may seem high, those rates are sustainable while still maintaining adequate buck/doe ratios, typically around 15 to 25 bucks per 100 does. 

How to stay informed about CWD

Fish and Game has a webpage devoted to all current CWD information, as well as lists of places to get your animal tested, how to remove lymph nodes for testing, and other information.