BILLINGS – Wildlife biologists with Montana Fish, Wildlife & Parks conduct aerial surveys for mule deer every spring to assess population trends and fawn recruitment. In south-central Montana—FWP’s Region 5—biologists recorded above-average fawn recruitment in some areas but low populations in most of the region during surveys this spring.  

Survey overview  

Biologists typically conduct 15 aerial surveys for mule deer across Region 5 in designated trend or census areas. Aerial surveys, conducted in small planes or helicopters flown by FWP pilots, are highly dependent on weather and habitat conditions to prioritize staff safety and effective sampling. Information collected from these and other annual surveys help FWP develop hunting season structures and adjust license numbers, in accordance with the Adaptive Harvest Management Plan.  

Aerial mule deer surveys occur post hunting season, usually in December and January, to assess buck to doe ratios and again in the spring. The following information focuses on spring survey results.   

Spring surveys have two primary goals: to count the total number of deer in a trend area to compare with long-term averages, and to determine fawn to adult ratios to determine winter fawn survival. Fawns that survive their first winter, typically the hardest period in an animal’s lifecycle, are considered recruited into the population. Biologists record the number of fawns per 100 adults to generate recruitment ratios. These ratios can help inform FWP on overall winter survival, how the population is faring as it enters the summer season, and what the potential for growth might be in the upcoming year. Note that the trend areas surveyed are meant to be a sample of the total land area, and deer populations may vary across the region and in individual hunting districts. 

What impacts mule deer survival?  

Annual variation in weather conditions can have dramatic impacts on mule deer survival and population numbers. Harsh winters are harder for fawns, and mule deer of all ages, to survive, often leading to poor recruitment. The winter of 2025-2026 was very mild, with low snowpack and warmer temperatures. High fawn recruitment in many trend areas within the region reflects this.  

Spring and summer moisture also impacts mule deer populations. Wetter summers lead to more forage for mule deer to eat, which allows them to build more fat reserves for winter survival. Larger fawns have a higher probability of surviving the winter than smaller fawns, and does with better body conditions for winter may have higher fawn production the following spring.  

Billings district  

The Billings district includes 6 subunits that are analyzed as a single trend area within Hunting District (HD) 590. These subunits were designed to compare fawn to adult ratios in the spring surveys and buck to doe ratios in the post hunting season surveys. Below-average fawn recruitment was recorded during 2026 surveys. Fawn recruitment this year was 31% below the long-term average. 

Roundup district  

The Roundup district includes the only trend areas where an increase in mule deer was observed during 2026 surveys. Fawn recruitment for the Big Coulee trend area within HD 515 has been above average for several years and surveys this year showed mule deer numbers 150% above the long-term average. Deadmans trend area, within HD 535, also had above average mule deer numbers and fawn recruitment.  

The Big Snowy Mountains trend area was not surveyed in 2026 due to staff and aircraft availability, but 2025 surveys showed below average mule deer numbers and average fawn recruitment. Similar trends were observed in the eastern portion of HD 535 on the Adolph census area and the HD 535 subunits for 2026.  

Big Timber district  

The Big Timber district includes five trend areas. In three trend areas within HDs 525 and 580, mule deer numbers ranged from 53% to 60% below the long-term average. Fawn recruitment on these trend areas was above average, indicating a possible population increase in the future.  

Two trend areas within HD 515—Cherry Creek and Yellowstone Breaks—were not surveyed this year due to staff and aircraft availability. During 2025 spring surveys, mule deer numbers differed widely between the two trend areas. Biologists observed mule deer numbers that were 25% above average in the Cherry Creek area, which is similar to 2024 survey results. Fawn recruitment was also above average for this area. Mule deer counts in the Yellowstone Breaks trend area between Greycliff and Reed Point, however, were 61% below average, despite high fawn recruitment. The strong fawn recruitment should contribute to increasing total deer numbers in the coming years.   

Red Lodge district 

The Red Lodge area includes two trend areas and one census area and includes portions of HD 502, 525 and 575.  

Mule deer numbers in all Red Lodge district areas were below average, and two had the lowest number on record. Fawn recruitment was also below average in two trend areas. In accordance with FWP’s Chronic Wasting Disease (CWD) Management Plan, mule deer in this area are managed for lower deer densities to maintain a low CWD prevalence rate across the landscape.  

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