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What happened to mule deer in Colorado and what does the future hold?

Are mature mule deer a thing of the past in Colorado

Are mature mule deer a thing of the past in Colorado? Photo credit: Brady Miller

If you hunted mule deer in Colorado during the 2019 season, then you’ve probably asked yourself a lot of questions since your hunt ended. With the 2020 Colorado application season already knocking on our doors, there’s no better time than now than to look at what might have caused the 2019 season to result in lower success across the entire western slope  — and what might be in store for the future of Colorado’s mule deer herds.

For those of you who had a great mule deer hunt in Colorado last year, I tip my hat to you as you most definitely earned your success and are definitely in the minority.

Unfortunately, the majority of the people I talked to experienced a season that was a little disheartening, considering they were hunting in the mule deer capital of the world. Keep in mind that everything in Colorado isn't doom and gloom, but I wanted to put together an article on some of my thoughts and do my best to figure out what could be happening.

So what happened to mule deer hunting during the 2019 season?

Frustrated look after hunting Colorado mule deer in 2019

This is an unstaged photo I took of Neville on our last day of hunting after pursuing mule deer for nine days straight and only turning up a tiny 4x4.

What created the perfect storm that resulted in decreased harvests across the Centennial State? Was it weather? Winterkill? Too many hunters? Were there too many deer taken in 2018? Did an influx of elk hunters impact the deer hunts? Did chronic wasting disease (CWD) mitigation efforts play a role? Did prior hard winters finally catch up with fewer bucks making it to maturity? Other impacts outside of hunting? Were there too many predators and not enough predator control? I believe a lot of factors contributed to the tough 2019 season. There isn't one answer to this question.

A lot of thoughts have gone through my head since the hunting season ended. What exactly happened?


Let’s put some numbers behind the 2019 season

Last week, Colorado published their 2019 harvest statistics. These numbers were not available as of March 12 when we published our Colorado mule deer application strategy article.

Because Colorado doesn’t require mandatory harvest reporting, their harvest reports do not account for every buck or doe killed by hunters. And the total hunter numbers could be higher as well. I've voiced my concern to states I hunt, but I do wish more states would go to mandatory harvest reporting. I felt like it was important to look at these values, even though they aren't the end-all solution.

Now, before we go further I do want to point out that while some of the percentages might not seem that significant to some people, but it's hard to not look at them and wonder what all the hype was about with reports from hunters that 2019 was the worst year of hunting they had seen. Even with a small decrease in harvest success, there is still a trend happening in Colorado when more hunters are in the field, harvest success is slowing decreasing.

Another aspect I think about is it's hard to say if some of these success rates were due to hunters shooting any buck on the last day as they didn't want to come home empty-handed. The reason I'm thinking this way is while visiting with hunters, the ones I talked to told me they hadn't seen anything all week so they just shot a buck since they were out there. I have also received plenty of emails and messages of similar reports. Keep in mind that it is definitely their right to take a deer and not go home empty. When I look at harvest success reported from a state, I really wish we had another report to see the age class of the deer being taken so we can see the percentage of young vs old bucks.

2019 statewide all weapons harvest numbers

During the 2019 season, 28,310 deer were taken statewide. This is a 5.99% decrease from 2018 when 30,114 were taken. Further, the 2019 season was the lowest harvest since 2015. Trends do happen (the up and down swings), but this is just something that I'm watching closely.

Also, the total number of deer hunters for all seasons has been on the rise since 2015. And you can also notice an interesting trend that the more hunters, the lower the harvest success. Another aspect I have touched on during other articles is the pressure put on by elk hunters during all the mule deer seasons. It's hard to quantify, but when you have unlimited elk hunters in a unit, they are going to impact other hunters. I'll save this for another day.

Third rifle season numbers

During the 2019 third rifle season, 9,531 bucks were taken. This is a 12.38% decrease from 2018 when 10,711 bucks were killed. Also, the lowest record number of bucks killed since 2015.

The total number of deer hunters during the third season in 2019 was 25,544. While the harvest numbers were lower, the number of deer hunters in the field was not. That number marks a 9.44% increase in the number of hunters for 2019.

Based upon the trends during the past few years in both hunter numbers and harvest success rates, it seems Colorado has possibly hit its tipping point: too many hunters in the field will now impact their harvest numbers.

As you can see from the above graphic, 2019 was the lowest recorded harvest success in the past 10 years. And harvest success is on a downward trend.

Second rifle season numbers

During the 2019 second rifle season, 9,400 bucks were taken. This is a 2.35% decrease from 2018 when 9,626 bucks were killed. This isn't an alarming trend, as I stated earlier, up and down swings do happen.

The total number of hunters for the second season in 2019 was up again when compared to 2018. 2019 found 27,417 hunters afield with a 3.58% increase overall. Again, 2019 had the lowest recorded harvest success rate in the past 10 years. And, again, you can see that harvest success is slowing going downhill.

It should be worth noting that since 2015, there has been a 21.28% increase in the number of second season deer hunters. And those hunters have taken a bunch of deer!

Muzzleloader season numbers

Did the muzzleloader hunters do any better? After all, they got to hunt the bucks before the popular rifle seasons kicked off. Unfortunately, the downward trend continued with muzzleloader hunts.

2019 was tied for the lowest recorded harvest success rate in the past 10 years! 

The graphic above paints a clear picture. Too many tags plus not enough deer equals a lower harvest success rate across the board.

The overall muzzleloader harvest for bucks is not too alarming. But it is still the lowest recorded kill count since 2015.

Fourth rifle season numbers

This is an interesting season to look at the data. While the 2019 buck harvest doesn't seem to be too far off the historic average, what is interesting is the 2018 harvest. You will see the giant spike in buck harvest. Now it might not seem like a big deal when we are talking 200 more bucks, but it is something I feel worth noting. So it seems that another theory of the 2018 season being the "perfect storm" compounded with all the other factors, might have made a slight impact on the deer herds. The big question remains, what will these numbers look like when the 2021 season dates arrive for the fourth season? Those mule deer hunters will be hunting bucks over Thanksgiving!

Calling out the above 2018 value might seem a little odd since 2018 was not that different than the norm (roughly 14% increase from 2017 to 2018, and almost a 15% decrease from 2018 to 2019), but I'm just trying to figure out trends in the data and this was just a thought that jumped in my head after I built this graphic and I figured it was worth sharing. Another way to look at this is to keep in mind that there are only 96 units that have a fourth season hunt in Colorado and all of them are west of the Continental Divide. So while 200 deer isn't a lot, it is still a slight outlier.

In looking at the total number of fourth season hunters, you will again see the giant trend of more hunters and decreased harvest success.

Again, the 2019 fourth season hunter numbers have jumped up to 3,231 which is a 7.7% change. An even crazier thing to look at is that since 2014, there has been a 46.33% increase in the number of fourth season hunters. And like all the other rifle seasons, harvest success is on a downward trend.


What do I think is happening to Colorado mule deer?

There are a few factors that could be contributing to the issue:

  • Too many predators/mismanagement of predators
  • Mule deer management
  • A harder winter in 2018/2019 than was previously thought (and prior winters)
  • Other factors (I'll try to touch on this area in another article as well)

It will be really telling how the 2020 season plays out, but since we can’t predict the future, we might as well look at hard evidence. 

Let's look at a few of those items. The predator section, that part of my research has gotten long-winded fast. So I will save that for a followup article that will be published next week. This is always a touchy subject, so I'm trying to do my best with the research.

Mule deer management

While mule deer populations are decreasing across the West. Colorado has seen a slight increase in deer populations.

Since 2013, the deer population has increased from 390,660 to 433,130, based upon the last available report in 2018. Before that, Colorado was on a drastic eight-year decline. I'm interested to see what the 2019 post-hunt deer population estimates will look like.

It’s hard to look at the harvest data and future season dates and understand that the population trend isn’t going to continue. (The 2019 post-hunt statewide deer population wasn’t available as of the date that this article was written.)

With the season dates getting pushed back even further, I believe mule deer are going to plummet after a few more years. If you want a recap of those changes, you can check out an article I wrote in July 2019. Along those same lines, maybe for the management of mule deer, the state needs to look at other items like other outdoor recreation activities. I wouldn't touch on it much here since I don't live in Colorado, but goHUNT has put out several news articles about this in the past.

2021 approved season dates:

  • Second season rifle will now be Oct. 30 to Nov. 7.
  • Third season rifle will now be Nov. 13 to 19.
  • Fourth season rifle will now be Nov. 24 to 28.

Colorado pushed third season dates back into what could be considered prime mule deer rut dates. Those dates had typically been your premium fourth season dates. They also shortened third season dates, which could create crowding issues since that season is already loaded with tons of OTC elk hunters. Further, the tag numbers are not changing. And, on top of that, you now have a ton of second season hunters (a rifle season that typically has higher tag holders) hunting season dates that were previously third season dates.

In my mind, these later system dates will really benefit elk hunters as the increase of snowpack will push elk lower; however, these dates are going to have a huge impact on mule deer — especially on mature bucks. I won't touch on it here, but I do know Colorado is looking to do more to prevent CWD, so these later hunts will be a tool to take out more deer. I need to do some more research about this, because personally, it's hard to hear that and understand that it will help in the long run.

Keep in mind that if you are an archery or muzzleloader hunter, these later season dates are going to impact you as well because some of the better bucks that might have slipped through the rifle seasons will not be there during the following year for archery and muzzleloader hunters.

In my opinion, all of these factors seem to indicate that Colorado wants to take a different approach when it comes to managing mule deer and I can't see these season dates helping the herds.

The 2018/2019 winter was harder than previously thought

This is something that I keep coming back to. Last year, for the most part, we never heard reports that Colorado had bad winterkill. Was the winter harder on deer than we thought even though it didn’t seem to be particularly impactful in other ways?

As most know by now, due to my biology background, I love data and graphics. So, below, we will take a look at some data I continually compile in Colorado each year for my hunting research.

Just because spring might seem to have arrived in March, the danger zone is far from over for mule deer. April, May and parts of June are critical times in the life cycle of mule deer. Warm weather might be on the way, but remember that all of that can change if we get a historic late spring storm.

Remember that mule deer just can’t put on fat stores overnight after coming off a long winter. Stress during these “danger months” can potentially be fatal to mule deer.

March 2019

Colorado snow water equivalent percent of normal as of March 2019

March 11, 2019 snow water equivalent. Source: NRCS

Here is a look at the tail end of the winter in Colorado on March 11, 2019. You can see that the majority of the state was continuing to experience elevated levels of snowpack. Based upon this timeframe, these numbers don’t seem too far out of the ordinary.

April 2019

Colorado snow water equivalent April 2019

April 1, 2019 snow water equivalent. Source: NRCS

Once again, these values are slightly above the 30-year average, but not overly alarming. In certain areas of the state there was an increase in the average snowpack and, in other areas, there was a slight decrease when compared to March.

May 2019

Colorado snow water equivalent May 2019

May 1, 2019 snow water equivalent. Source: NRCS

Now on to May. The alarming part of the above graphic is that even though it’s May, snow water equivalent values are still increasing. These values could start to impact mule deer trying to put on fat after a hard winter.

June 2019

Colorado snow water equivalent map June 2019

June 1, 2019 snow water equivalent. Source: NRCS

We have finally arrived at the month I want to discuss. One look at the image above and it should be alarming. The scary thing is that there are other data sources from the NRCS that reported even higher values later in June.

First, snowpack values this high could severely impact fawn recruitment and thus will impact future years mule deer populations. Winter weather conditions this late in the year could make it tough on a newborn fawn. At the same time, that much snowpack still in the mountains is going to impact the high country from greening up. All of this snowpack could cause mule deer to postpone their spring migrations to their summer range and, in doing so, could face more highway mortalities. These snowpack levels mean there was a ton of snow still in the highcountry and the spring melt has been delayed. Along with all this, parts of Colorado saw over two feet of new snow in June! Maybe all this late spring and new snow conditions impacted mature bucks that were already depleted from the winter?

Other factors

Personally I want to dive into some research efforts on other areas of concern for mule deer. And not just in Colorado, but in other states that are experiencing a decline in mule deer populations. I'll try to collect my thoughts and findings with a supplemental article. But in the meantime, I'd love to hear from everyone on possible areas to look at.


Warmer weather wasn’t the real reason the later rifle seasons were so tough. Here’s why:

I’m not going to blame the difficult 2019 season on the slightly warmer weather. I said it on a podcast right before the second season kicked off. I mentioned that I predicted a second season tag was going to be a phenomenal tag. Those hunters got the snow and cold temperatures. If people are basing things off weather, 2019 still had snow and some cold temperatures that pushed deer down. In fact, there was more snow in 2019 than 2018 in some areas. In 2016, during another warm weather third season, I located an absolutely crazy number of mature bucks. Everywhere I looked I saw a mature deer and tons of smaller bucks. Plus they were rutting during the earlier third season dates and warm weather.

Here is the proof

Colorado snow water equivalent November 2019

November 1, 2019 snow water equivalent. Source: NRCS

The graphic above is showcasing Colorado’s snow water equivalent as a percent of normal. This is essentially known as snowpack. As of November 1, 2019 you can see that Colorado actually had a ton of snowpack for that time of year. 

During my hunt with Neville in 2019, we hunted as high as we could in the unit and as low as we could. When we hunted deep in the snow, we found deer, but only does. We pushed higher and still only located does. Not a buck around. We even resorted to still hunting in the timber following tracks. We didn’t see our first 4x4 buck until the second to the last day of the season and this buck was barely over 120”.

It was a tough year and I have been thinking about what we could have done differently ever since. If we had shot a few giant deer, you better believe that I'd still be writing this article due to so many people who I heard from who thought this past year was the worst season in Colorado ever.

It maybe seems that, since the 2016 winterkill year in the West, Colorado hasn’t recovered and currently can’t take the pressure from the current number of tag holders, especially when hunter numbers are increasing for deer. Further, those hunters are taking more bucks on average than what used to be the case, resulting in overall lower hunter numbers.

In conclusion

So where did all the mature bucks go in Colorado? Did they just disappear? Or were they never there to begin with? I think this is a serious question to consider.

In 2019, I saw far fewer fawns than I have ever seen in Colorado — maybe only two to three fawns during the entirety of a nine-day hunt. This isn't a good thing for the future of deer in this great state.

I’ve talked to Colorado residents who have said that based upon where they live, 2019 was the worst year they have seen. In their area where deer typically winter — and some deer live year-round there — in 2019, there were barely any deer at all. In some cases, there were none.

Are the bucks outsmarting hunters and hunters not adapting to the conditions? Maybe, but when looking at the bigger picture, everyone I talked to who hunted during the third and fourth season across different areas of the state experienced the same thing. While driving around during the day and evening to move hunting spots, I only saw two dead deer in all of the hunting camps I passed.

Overall, like many, I’m very concerned about the direction of Colorado mule deer and what managers are doing to fix the current situation. With extremely later season dates on the horizon in 2021, I wonder if things are only going to get worse.

At the rate Colorado is headed, I know people will still apply, but I seriously think people ahead of the curve will start looking elsewhere for a while. And maybe they should.

Stay tuned for my follow-up article on the topic of predators. Like I stated earlier, I wrote out the predator portion for this article... but it got very long and detailed fast. The next article will add some great value to the overall picture.

I'd love to hear your thoughts.

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