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The science behind the mule deer rut

Mule deer buck sniffing estrus doe during the rut

This article was a collaborative effort by Dave Loescher and Brady Miller. Photo credit: Shutterstock

Note: This article was originally published in November of 2015. Some of the data has been updated to reflect more years of data.

Every year it seems that mule deer hunters are divided into two camps: the early season high country velvet enthusiasts and the late-season hunters with hopes of capturing the excitement of the peak rut. Each hunting extreme has its distinct advantages and disadvantages. Although the early season high country craze is hitting its stride in popularity (thanks to growing swarms of ambitious hunters wanting to become known as backcountry experts), the late season rut hunts will always be the most coveted of mule deer seasons.

Hunt while their defenses are down

Mule deer buck chasing does in the rut

Photo credit: Shutterstock

Late season rut hunts find otherwise cagey bucks letting down their defensive instincts. This is the time when bucks are clearly most vulnerable as well as most active in daylight hours. This short period of intensive rut activity averages roughly ten days and has become the reason for many hunters to amass double-digit bonus points in an effort to get one chance to hunt large, swollen necked bucks void of their wits.

The myth of cold weather

10 degree morning on a November mule deer hunt

Cold weather increases deer movement, but it's not the pure driver of the rut. Photo credit: Brady Miller

“If the weather is cold, then the rut will be on fire!” This is the statement heard over and over every year. Most hunters do not realize that the cold temperatures are not what starts or drives the mule deer rut. Cold weather is beneficial to keeping deer on their feet and on the move, making them easier to spot. Hunting active deer is always more exciting than lethargic deer hidden in shady, cool places. Yet, contrary to popular belief, the cold weather is not what kicks off the rut.

What really starts the rut?

The truth is that photoperiod is the driver of the rut. Photoperiodism is defined as the physiological reaction of organisms to the length of day or night. In other words, the length of daylight experienced over a 24 hour period. This is the primary factor in determining the breeding season at a given latitude. Near the equator, where the length of day doesn't vary much, fawns can be dropped in any month of the year. At latitudes like ours in the West, photoperiod follows the same pattern year after year and the rut is triggered at about the same time. A great tool for determining the amount of daylight per day based on latitude can be found here.

Amount of daylight in 24 hour period

State Month
11.1 10.6 10.1 9.7 9.5 9.6 9.8
11.3 10.8 10.4 10.1 10.0 10.0 10.2
Colorado 11.1 10.4 9.9 9.5 9.3 9.4 9.6
Idaho 10.8 10.0 9.4 8.9 8.6 8.6 9.0
Montana 10.7 9.8 9.1 8.5 8.2 8.2 8.6
Nevada 11.1 10.5 10.0 9.6 9.4 9.4 9.7
11.1 10.5 10.1 9.7 9.5 9.6 9.8
Oregon 10.9 10.1 9.4 9.0 8.7 8.8 9.1
Utah 11.0 10.4 9.9 9.5 9.3 9.3 9.6
Washington 10.7 9.9 9.1 8.6 8.3 8.3 8.7
Wyoming 10.8 10.1 9.4 8.9 8.7 8.7 9.0
11.4 11.0 10.6 10.4 10.2 10.3 10.4

Based on the chart above, you can see the variance in peak rut dates based on the photoperiod.

Below is a graph of the table above to show the differences based on latitude.

Other factors affecting the timing of the rut

Nutrition can also affect the timing of the rut. The condition of the habitat in terms of feed and water will greatly impact not only the timing of the rut, but the intensity of the rut as well. Poor nutrition and intense drought can cause the rut to begin later. Conversely, a good feed year can push the rut earlier. In times of severe drought, it is not uncommon for does to shorten or miss their cycle and focus on finding feed to stay alive. This is a rare situation but can happen on occasion. 

The magical days of the rut

Large mule deer buck with does

Photo credit: Shutterstock

When the stars align and you find yourself in the field during the peak of the rut, the anticipation is high. Bucks are easily found either with does or moving from group to group. Bucks abandon their wits and put on one of the most awesome behavioral displays of the year. Bucks chase away bucks, spar with other bucks for dominance, run after does and stand with their noses held high with the occasional lip curl while smelling the surrounding air. It is an awesome behavior to observe, especially with a tag in your pocket.

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Determining the peak days of the rut in your area

Mule deer average 202 to 210 days for gestation. Gestation is defined as the length of time a bred doe carries a fawn before giving birth. 

Touch or click on the state in the graphic above for peak rut dates.

In the mountain states of Wyoming, Montana, Idaho, northern Utah, northern Colorado and northern Nevada, the Rocky Mountain mule deer generally have the peak fawning period during the first week of June. If you start with June 7 and count backwards 205 days for gestation, that would place the peak rut dates in the mountain states during the week surrounding November 14. As a general rule, the mule deer fawning period is later as you travel south. The desert mule deer of Sonora and southern Arizona generally have a peak fawning period of around August 7. Subtracting 205 days would suggest that the average peak rut for these extreme southern desert mule deer would take place the week of January 14. The mule deer in the areas between these two examples will rut at a time between these two extremes. If a doe is not bred, she will be receptive again roughly 30 days later.
Peak mule deer rut calculator

What about the pre-rut?

Some avid mule deer hunters will argue and say that they would rather hunt the beginning stages of the rut rather than the peak rut — and for good reason. These early stages of the rut are often referred to as the pre-rut among hunters. The pre-rut is usually the two-week period that is prior to the peak of the rut. During pre-rut, we find bucks cruising in search of does and moving carelessly about at otherwise inactive hours. This behavior makes bucks vulnerable. The other major advantage of the pre-rut is that bucks are rarely carrying broken racks because aggressive fighting has not yet started. The major risk to targeting the pre-rut is that not all bucks will be on the move. Some of the oldest bucks will continue to move very little until the first does actually begin to cycle into estrus.

Selecting your season to fit the rut

The first step is to identify the typical rut week for the state/area you are considering. State agencies across the West have different approaches when it comes to setting season dates. Some states offer season dates that coincide with the peak of the rut.

Montana is the overwhelming king when it comes to providing peak rut opportunity to rifle hunters. Nearly every hunt district in Montana will allow hunting during mid to late November. Another opportunity — and one of the most coveted — is with a Colorado fourth season rifle tag in a unit in the northern half of the state. The caution with the Colorado fourth rifle season is the short number of hunting days. At only five days in length, one severe storm can quickly cut your hunt in half. The mule deer in the southern units of Colorado rut later than the rest of the state and typically will not capture peak rut activity like the central and northern Colorado units. Idaho also provides some great rifle and muzzleloader peak rut opportunities. Peak rut rifle opportunities for mule deer are very limited in Arizona, NevadaNew Mexico, Oregon and Wyoming.

Archery opens doors

One of the most overlooked and hidden peak rut opportunities is buried in the archery seasons. Arguably, some of the best mule deer hunting in New Mexico is offered as a January archery season. Although this season opens on January 1, it can still capture some late rut action and is capable of offering some of New Mexico’s best mule deer hunting. Nevada also has some very good rut seasons offered exclusively to archery hunters. Utah also has a limited number of peak rut archery seasons offered. The extended archery seasons in Utah offer seasons that include the entire month of November. Arizona and Idaho both have over-the-counter archery tags available that offer season dates that will allow you to hunt during the rut.

What about migration?

Most units across the West have migratory mule deer herds. In many locations, this migration will coincide with some phase of the rut. The pre-rut is the most commonly found behavior among bucks as the migration is taking place. Regardless of the phase of the mule deer rut, when you combine migrating deer with bucks chasing does, you could be in for the time of your life. This scenario is exactly what most western hunters are trying to find.

November is king!

Across the West, the large majority of mule deer hunters take to the field in the month of October. Although some states like Montana have their general rifle mule deer seasons scheduled in November, most states (Utah, Colorado second rifle, Wyoming rifle, Nevada) have their high tag quota seasons scheduled for the month of October. According to Boone and Crockett, the month of November stands supreme for producing the highest scoring bucks since 1990. Taking this into consideration, it is evident that the majority of B&C qualifying bucks are harvested during pre-rut and rut behavior patterns. 

Top 200 B&C typical and nontypical mule deer since 1990

Month Typical Nontypical TOTAL
July 0 1 1
August 2 3 5
September 23 17 40
October 69 58 127
November 56 76 132
December 16 13 29
January 12 2 14
February 0 1* 1
Unknown** 22 29 51

* February buck was picked up.
**Boone & Crockett lists unknown months
**Data updated October 23, 2019

In summary

Large mule deer buck lockdown with doe

Photo credit: Shutterstock

If an exciting hunt and a chance for a long-haired cape on a hard horned muley is what you are after, then hunting the rut is your answer. Truly understanding the rut will help you to make this dream a reality. Use our Unit Profiles and Filtering 2.0 to search out areas that will provide the terrain and habitat that should provide rut action. The profiles will also help you find the units with the trophy quality you seek. Do your homework and go make a memory!

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Tim H. - posted 4 months ago on 11-18-2019 02:07:50 pm

Great article, love the deep dive into the science behind it vs. "my grandpa told me once..." myths.
When I was younger, the prevailing opinion around weather kicking the rut into gear was pretty strong, and while it can definitely help or hinder deer movement, it isn't the silver bullet for when the rut starts.

On a recent bowhunt in Idaho for mule deer (last week) the rut was coming on, but the 60° days with bright sun kept the deer in the shade and brush, and they headed for it within about 2 hrs. of sunrise. However, it was encouraging to see deer on their feet in north facing areas by 2pm until dark feeding and acting more rutty. The daylight charts are very helpful.

SCOTT R. - posted 4 months ago on 11-11-2019 01:03:32 pm
Reno, NV

Just hunted the 2019 coveted unit 44 Colorado 3rd season Nov 2nd-10th. OUCH! I ate tag soup. Probably will not hunt that one again in this lifetime.
Timing.....I probably saw over 200 bucks. Problem is they were the young bucks and the 170-180 class bucks. I was looking for the mega giant. The dream buck. And why not. A tag that takes 20+ years to draw. Never did one giant show himself. Reading the article it makes sense. Pre-Rut. A lot of does grouped, a lot of younger bucks sniffing does, just no giants. It was also extremely hot. That led to deer not on their feet very long each day. Well I still would have hunted the unit but just a bummer it wasn't later this year, and a bummer it was sunny with highs in the mid 60's every single day.

Charles G. - posted 3 years ago on 11-24-2016 10:08:07 am
Little Rock, AR

Great article Dave. Any thoughts on why the December numbers for non-typicals are so high compared to typicals?

Michelle T. - posted 3 years ago on 11-18-2016 01:20:46 pm

I personally don't know what could have helped my recent 3rd season Colorado rifle hunt! The weather definitely had an impact on this hunt, it was 60 degrees at 11,00 ft. The bucks just wouldn't come down from the high country and had no interest in the doe's whatsoever. The only bucks I saw with the gals were a few little two points. No matter how many times we rattled, called, hiked into the dark timber, open hill sides or the low sage areas, they weren't budging! In fact, the doe's would answer and come to our calls without a buck insight. I've never seen anything like it. We talked with several other hunters, both local and from out of state like us, and they were all having the same problem. Strange and frustrating season to say the least, but still a blast! I'm just grateful I got to go, and like my hubby said...."there's no crying in hunting":)

Erik E. - posted 3 years ago on 11-13-2016 09:24:27 pm

Great article I always get an otc archery tag in Az when I hunt Javelina in January. I have yet to take a rutting Muley, but patience will pay off

Kevin C. - posted 3 years ago on 11-13-2016 06:58:59 pm
Flagstaff, AZ

Dave the article was great and right on. Heading to the North Kaibab for the late hunt this week. Your article was great reading as I am getting ready to roll. Nothing better than the late Kaibab for rutting bucks as you know well. Keep this good stuff coming.

Dave Loescher
Dave L. - posted 4 years ago on 11-25-2015 12:21:11 pm
Cedar City, UT
goHUNT Team

@Jared P. Thank you for sharing that first hand local experience. Hopefully you have a successful rut season this year. Please send in any photos when you harvest. Good luck!

Jared P. - posted 4 years ago on 11-25-2015 07:01:18 am
Piedmont, SD

I live in Southern New Mexico and the first two weeks of January are the prime time for the rut. I have a blast every January chasing bucks with a bow. Enjoy!

Dave Loescher
Dave L. - posted 4 years ago on 11-24-2015 02:25:30 pm
Cedar City, UT
goHUNT Team

@Sheldon A. I actually think you are going to hit things just about perfect! The first two weeks of January are primetime when hunting south of the US/Mexico border. Good luck to you guys and please keep us posted on how you do!
Thanks for the comment.

Sheldon A. - posted 4 years ago on 11-24-2015 08:54:11 am

Good write. I will be in southern New Mexico right off Mexican border second week of Jan. on my sons first out of state archery hunt. Was worried I would miss the rut but we could hit it perfect. Should be fun!!!

Dave Loescher
Dave L. - posted 4 years ago on 11-18-2015 07:38:40 pm
Cedar City, UT
goHUNT Team

@Robert H. You are accumulating an impressive pile of points in your awesome home state of CO! It sure sounds like you have a solid plan in place to make the most of those precious points too. I look forward to seeing a picture of you with a big buck in 2017! Good luck and we are glad you found the article helpful.

Robert H. - posted 4 years ago on 11-18-2015 07:20:50 pm

Very informative in a fact based article. Next year I will get my 15th preference point at home here in Colorado so I am looking at an area that has produced many Boone and Crockett bucks. 2017 I believe I will have enough to draw for sure because I have to pick my vacation dates in the November before the year I will be hunting. Even though the season here is only 5 days ..Wednesday through Sunday I will have 4 days to do some late scouting. In fact next year I will be out there doing the same thing. But without a tag,

Dave Loescher
Dave L. - posted 4 years ago on 11-18-2015 06:37:21 am
Cedar City, UT
goHUNT Team

@Brian D. We think alike!! Some of my favorite hunting memories are from late season bowhunts in Arizona. It is really tough to beat the weather, action, and options that are offered there. Good luck to you and thanks for being an INSIDER!

Brian D. - posted 4 years ago on 11-17-2015 07:02:05 pm

Great article! Chasing late season, rutting muleys in Arizona is a great time to be had! Again, fantastic, informative article.

Dave Loescher
Dave L. - posted 4 years ago on 11-15-2015 08:37:53 pm
Cedar City, UT
goHUNT Team

@ Stefan W. Appreciate your comment. I hope this information helps you in making your decision as you research the areas of AZ and NM. The AZ OTC archery seasons really offer a great chance to find some rut action. Best of luck to you!

Stefan Wilson
Stefan W. - posted 4 years ago on 11-14-2015 06:59:28 am
Gilbert, AZ

Such a great and informative article. I'm hoping to hunt the mule deer rut in New Mexico or Arizona next year. This article really helped me understand when/where to go.

Dave Loescher
Dave L. - posted 4 years ago on 11-13-2015 07:30:36 pm
Cedar City, UT
goHUNT Team

@Kellen G. Thanks for the comment and I am glad you enjoyed the information. Your timing sure sounds about perfect for your upcoming MT hunt. The bucks are really getting going in many parts of Colorado right now. Good luck and thank you for being an INSIDER! Let us know how you do on the MT hunt.

Kellen G. - posted 4 years ago on 11-13-2015 08:32:52 am

Wonderful article, thanks for the great info. Hitting an archery only unit in West Central Montana this weekend, seen lots of younger Muleys moving trhough the area the last two weeks but hopefully the big boys are on the move. Keep up the great work!