Spring 2025 Mule Deer Survey: Gardiner Basin

Spring 2025 Mule Deer Survey: Gardiner Basin Prepared by: Michael Yarnall, Livingston Area Wildlife Biologist 2025 Survey Survey Details Date: 9 May 2025 Pilot: Neil Cadwell (FWP) Observers: Michael Yarnall (FWP) and Noah Starling (FWP) Aircraft: A-star (helicopter) Objective: Obtain a total count and classify deer as adults or fawns in the Gardiner Trend Area as an index of total numbers and population trend. The age and sex structure are characterized relative to the number of adult deer. Flight Details: This survey was combined with bighorn sheep survey efforts. We took off from the Gardiner airport at 6:26 and surveyed mule deer in the Gardiner Basin Trend Area, beginning on the west side of the Yellowstone because the morning light hits that side of the basin earliest. We crossed the river near at the north end of the trend area and surveyed south to the vicinity of Little Trail Creek, when we returned to the airport to refuel (9:42-10:03). We continued working southward, finishing the mule deer survey near Deckard Flats at approximately 11:12. We then flew to the upper end of Tom Miner Basin to survey high elevation bighorn sheep winter range. Total flight time was 7.3 hours, including 5.1 hours of survey time and 2.2 hours of pilot ferry time. Survey Conditions: The temperature was 45 F at takeoff and 62 F at the end of our flight. Winds were light at takeoff (5-6 mph), and remained light throughout the survey (generally <10 mph). Lighting conditions were good with primarily bright sun. Because this survey was conducted later than normal, vegetation green up was substantially more advanced than it usually is. Deer were primarily up feeding at the beginning of the survey, but warm temperatures and advanced green up contributed to deer bedding down in the shade during the latter part of the survey. Overall survey quality was good. Survey Results We observed 869 total mule deer in 132 groups. We classified 612 adults and 247 fawns; 10 deer were unclassified (Figure 1). This resulted in 40.4 fawns per 100 adults. Observed recruitment was similar on both sides of the Yellowstone River (Table 1). We also observed 2golden eagles, 2bald eagles, 1black bear, and 121 bighorn sheep in addition to elk, pronghorn, and bison. 1 HD 317 HD 314 HD 313 YNP N8 km Figure 1: Flight path and locations of mule deer groups (red) and incidental observations of other species (blue) during the 2025 survey of the Gardiner Trend Area (outlined in purple). 2 Table 1: Mule deer distribuiton by herd unit as observed during the 2025 spring survey of the Gardiner Trend Area. Subunit Adults Fawn Unclassified Total Deer Slip and Slide Creek to Little Trail Creek 158 59 0 217 Little Trail Creek to Deckard Flats 224 89 10 323 West of Yellowstone River 187 78 0 265 Yellowstone National Park 43 21 0 64 Total 612 247 10 869 Population Trends This year’s total count (869) was a 16 percent decrease from the 2023 count of 1032 (Figure 2). The total count was 37 percent lower than the 10-year average (1386) and 53 percent lower than the long-term average of counts since 1986 (1832, SE = 73.4, Figure 2). However, the proportion of deer observed that were fawns was notably higher this year (Figure 3, Figure 4); the observed number of fawns per 100 adults (40.4) was 103 percent higher than the 2023 ratio of 19.9 and is 2 percent above the long-term average (39.7, SE = 2.1). Montana’s Adaptive Harvest Management (AHM) plan for mule deer designates the Gardiner Basin as part of the Southern Mountains Mule Deer Management Area, with a recruitment standard of 30-45 fawns per 100 adults. Ratios observed in the Gardiner Basin have fluctuated above and below this range; the observed ratio this spring is within the recruitment standard (Figure 4). The harsh winter of 2022-2023 likely contributed to low fawn:adult ratios observed in spring 2023. There was a cold and snowy period last winter (primarily mid January to mid February) which served to concentrate animals on the winter range. However, conditions prior to that were mild, and a warmer period in late February stripped some low elevation snow. On the whole, winter 2024-2025 was not extreme, which likely contributed to the good recruitment levels observed during spring 2025. It is possible that the reduced total number of deer observed during this survey was due in part to the lateness of the survey, which was caused by challenges associated with aircraft availability and maintenance. Because the survey was flown later than normal, spring green up was substantially more advanced. It is possible that some deer had already began to move away from their winter ranges (and outside the trend area). Future surveys will provide insight into whether the low number of deer observed this year was due to the late survey or if it represents an actual population decline. It is important to note that aerial surveys are subject to both population and sampling variability. Annual results should be interpreted with caution; inferences based on long term trends are more robust. 3 1000 1500 2000 2500 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016 2018 2020 2022 2024 Year Total Mule Deer Count Type Total Count 10−Year Average 20−Year Average Long Term Average Figure 2: Total mule deer numbers observed during spring surveys of the Gardiner Trend Area located in HD 313, 1986-Present. Note that the 10-year and 20-year averages are the average of all surveys spanning 10/20 years up to and including the current year; because surveys are usually conducted every year, this average typically includes about 10/20 surveys, but may include fewer during decades where an annual survey was not conducted. The long-term average includes all data through the current year. 4 0 1000 2000 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016 2018 2020 2022 2024 Year Total Mule Deer Count Type Total Count Adults Fawns Unclassified Deer Figure 3: Number of total mule deer, adults, and fawns observed during spring surveys of the Gardiner Trend Area located in HD 313, 1990-Present. 5 20 30 40 50 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 2007 2009 2011 2013 2015 2017 2019 2021 2023 2025 Year Fawns Observed Per 100 Adults Ratio Type Current Year 10−Year Average 20−Year Average Long Term Average Figure 4: Fawn:Adult ratios observed during spring surveys of the Gardiner Trend Area located in HD 313, 1987-Present. The grey ribbon indicates the recruitment standard of 30-45 fawns per 100 adults for southern mountain areas identified by Montana’s Adaptive Harvest Management Plan for mule deer. Note that the 10-year and 20-year averages are the average of all surveys spanning 10/20 years up to and including the current year; because surveys are usually conducted every year, this average typically includes about 10/20 surveys, but may include fewer during decades where an annual survey was not conducted. The long-term average includes all data through the current year. 6 Harvest and Management History The Gardiner trend area informs management in HD 313 and HD 314 where it is located. Additionally, the data from the Gardiner trend area also contributes to management of mule deer in HDs 316 and 317. HDs 313, 314, 316, and 317 are within the Southern Mountains Population Management Unit (as described in FWP’s 2021 Mule Deer Adaptive Harvest Management plan). Each hunting district is discussed separately below. HD 313 Harvest HD 313 is a mule deer special management district. Mule deer wintering in the Gardiner Basin are primarily migratory, some traveling long distances from many different summer ranges. Once deer arrive on winter range in the Gardiner Basin they are highly vulnerable to harvest due to the open terrain, large amounts of public land, and road systems that facilitate hunter access in areas of high mule deer use. A special management season has been in place since 1994 which allows a three week buck season and no buck harvest opportunity during the final two weeks of the general season. These changes were made in fall 1994 following three years of a “2-Point Mule Deer Season” during 1991-1993 which did not achieve objectives. These changes were made with the objectives of improving quantity and quality of bucks, specifically to: •Maintain a post season ratio of at least 15 bucks:100 does (previously 4-6 bucks/100 does) •Increase the percentage of older bucks ( ≥2.5 years) in the post season population to 35% or more (previously 25-29%). The buck:doe ratio observed during the post-2024 hunting season survey was very slightly above the minimum goal and the objectives of the 3-week buck season have been met most years since it was established (See Post-2024 Hunting Season Mule Deer Survey report for additional details). Antlerless harvest has been permitted with antlerless B licenses in varying numbers over the years (Table 2). In December 2023, the Fish and Wildlife Commission adopted a change to the boundary for HD 313, which impacted mule deer opportunity in 2024. The HD 313/314 boundary was adjusted to move the portion of HD 313 west of the Yellowstone River into HD 314. Beginning in 2024, this area between Sphinx Creek and Yellowstone National Park is now managed under the regulations for HD 314, including a 5-week season for buck mule deer. This change prevents direct comparisons of to prior harvest levels because the it is impossible to separate harvest that occurs in the southern end of new HD 314 (old HD 313 west of the Yellowstone) from harvest that occurs in the remainder of HD 314. In figures shown below, the dashed vertical line at 2024, indicates that data from 2024 and later is not directly comparable to data from prior years. Total harvest has trended down in recent years, though harvest increased notably in 2024 (Figure 5); this decline was driven by a decline in buck harvest, as antlerless harvest has been relatively stable (Figure 6) since 2018. The increase in 2024 is particularly notable in light of the boundary change described above, because the increased harvest occurred in a smaller area. The 2022 hunting season saw a moderate increase in mule deer harvest (Figure 5), but a decline was observed in 2023. The 2022 increase was likely caused in part by earlier winter conditions, which moved more deer into the Gardiner Basin before the mule deer season closed. Additionally, the early winter weather stimulated elk migration, which increased hunter interest and may have increased the number of hunters on the landscape that could harvest mule deer. A mild fall in 2023 may have contributed to limited harvest during that hunting season. Although buck harvest has trended down in recent years, the proportion of larger bucks harvested (≥4 antler points on one side) has remained relatively stable (Table 2). Mule deer buck harvest trends are shown in Figures 7 and 8; excepting 2024, buck harvest has been below the long-term average since 2019. Due to spring survey results indicating declining mule deer numbers (Figure 2) and declining harvest (Figures 5 and 6), antlerless opportunity was reduced for the 2012-2013 seasons. Mule deer antlerless licenses were largely eliminated statewide for the 2014-2015 seasons due to concerns over statewide mule deer numbers. 7 As the number of mule deer observed in the Gardiner Basin increased, antlerless B licenses were reinstituted with a limited quota of 50 in 2016. This quota was increased to 100 in 2018. When the population is within 30% of the long-term average, Montana’s Adaptive Harvest Management plan for mule deer recommends none-moderate numbers of anterless B licenses. When the population is substantially below the long term-average, the AHM plan recommends limiting antlerless harvest to B licenses issued to respond to localized game damage situations. In light of reduced deer numbers and low recruitment observed during the spring 2023 survey, a within-quota adjustment was made to lower the number of B licenses available for the 2023 hunting season. Realized antlerless harvest at the current quota level (Table 2) is low enough that the impact of antlerless harvest on population trend is likely negligible. Hunter effort, represented by the number of hunter days and by the number of days per harvested mule deer are shown in figures 9 and 10 (hunter effort data is not collected every year). Although FWP’s hunter effort estimates do not differentiate between whitetail and mule deer effort, the level of whitetail harvest in HD 313 is negligible and these figures represent mule deer hunter effort. 8 200 300 400 500 2004 2006 2008 2010 2012 2014 2016 2018 2020 2022 2024 Year Estimated Total Mule Deer Harvest in HD 313 Harvest Type Total Mule Deer Harvest 10−Year Average Long Term Average Figure 5: Estimated total mule deer harvest in HD 313, 2004-Present. The shaded red ribbon represents the 80 percent confidence interval for each annual total harvest estimate. Note that the 10-year average is the average of all surveys spanning 10 years up to and including the current year. The long-term average includes all data through the current year (i.e. the sample size increases in later years). Due to a boundary change prior to the 2024 hunting season, harvest data from 2024 onward is not directly comparable to prior years; this is indicated by the dashed vertical line. 9 (Figure 13, Table 3). Excepting 2024, buck harvest has been slightly below the long-term average since 2017 (Figure 14). Mule deer B licenses were reduced in 2012. In 2014, most antlerless harvest opportunity was eliminated statewide due to concerns over statewide mule deer numbers. In 2018, 100 B licenses were reintroduced in HD 314. Realized antlerless harvest at that quota level (Table 3) is low enough that the impact of antlerless harvest on population trend is likely negligible. Hunter effort, represented by the number of hunter days and by the number of days per harvested mule deer are shown in figures 15 and 16 (hunter effort data is not collected every year). It is important to note that FWP’s deer hunting effort estimates do not differentiate between whitetail and mule deer hunting effort; the figures below represent the combined deer hunting effort in HD 314. 16 200 300 400 500 2004 2006 2008 2010 2012 2014 2016 2018 2020 2022 2024 Year Estimated Total Mule Deer Harvest in HD 314 Harvest Type Total Mule Deer Harvest 10−Year Average Long Term Average Figure 11: Estimated total mule deer harvest in HD 314, 2004-Present. The shaded red ribbon represents the 80 percent confidence interval for each annual total harvest estimate. Note that the 10-year average is the average of all surveys spanning 10 years up to and including the current year. The long-term average includes all data through the current year (i.e. the sample size increases in later years). Due to a boundary change prior to the 2024 hunting season, harvest data from 2024 onward is not directly comparable to prior years; this is indicated by the dashed vertical line. 17 0 200 400 2004 2006 2008 2010 2012 2014 2016 2018 2020 2022 2024 Year Estimated Mule Deer Buck and Antlerless Harvest in HD 314 Harvest Type Total Harvest Buck Harvest Antlerless Harvest Figure 12: Estimated total, buck, and antlerless mule deer harvest in HD 314, 2004-Present. Due to a boundary change prior to the 2024 hunting season, harvest data from 2024 onward is not directly comparable to prior years; this is indicated by the dashed vertical line. 18 100 200 300 400 2004 2006 2008 2010 2012 2014 2016 2018 2020 2022 2024 Year Estimated Mule Deer Buck Harvest in HD 314 Harvest Type Total Buck Harvest ≤3 Antler Points ≥4 Antler Points Figure 13: Estimated mule deer buck harvest in HD 314, 2004-Present. Due to a boundary change prior to the 2024 hunting season, harvest data from 2024 onward is not directly comparable to prior years; this is indicated by the dashed vertical line. 19 200 250 300 350 400 2004 2006 2008 2010 2012 2014 2016 2018 2020 2022 2024 Year Estimated Mule Deer Buck Harvest in HD 314 Harvest Type Total Buck Harvest 10−Year Average Long Term Average Figure 14: Estimated mule deer buck harvest and long-term averages in HD 314, 2004-Present. Due to a boundary change prior to the 2024 hunting season, harvest data from 2024 onward is not directly comparable to prior years; this is indicated by the dashed vertical line. 20 6000 7000 8000 9000 2004 2006 2008 2010 2012 2014 2016 2018 2020 2022 Year Estimated Deer Hunter Days in HD 314 Figure 15: Estimated total deer hunter days in HD 314, 2004-Present (hunter effort estimates are not collected every year). The shaded red ribbon represents the 80 percent confidence interval for each year’s hunter day estimate. Note that FWP’s hunter effort estimates do not differentiate between mule deer and whitetail hunting days. This metric should be interpreted with caution, because changes in whitetail hunting effort could influence potential conclusions independent of any changes in mule deer hunting effort. 21 15 20 25 30 35 40 2004 2006 2008 2010 2012 2014 2016 2018 2020 2022 Year Estimated Hunter Days per Harvested Mule Deer in HD 314 Figure 16: The estimated number of hunter days per mule deer harvested in HD 314. Note that FWP’s hunter effort estimates do not differentiate between mule deer and whitetail hunting days. This is a very coarse metric that should be interpreted with caution, because changes in whitetail hunting effort could influence potential conclusions independent of any changes in mule deer hunting effort. 22 Table 3: Estimated harvest mule deer in HD 314, 2004-Present. License Year Total Harvesta Antlerless Harvest B License Quota Buck Harvest Proportion Bucks ≥4 Pointsb Hunter Days per Harvested Mule Deerc 2004 529 104 223 424 0.599 15 2005 380 91 225 290 0.529 16 2006 448 88 223 357 0.530 17 2007 370 118 225 252 0.597 18 2008 337 101 300 235 0.564 25 2009 303 131 300 173 0.625 25 2010 288 118 300 170 0.572 26 2011 312 115 300 198 0.561 23 2012 248 27 75 220 0.625 2013 231 46 75 185 0.542 34 2014 253 0 0 253 0.520 2015 186 0 0 186 0.661 2016 291 3 0 288 0.581 2017 218 3 0 215 0.602 32 2018 244 34 101 210 0.622 2019 231 36 100 195 0.526 30 2020 192 26 101 165 0.703 2021 233 24 100 208 0.638 39 2022 236 13 101 223 0.485 2023 234 23 100 212 0.546 38 2024d335 27 100 308 0.626 aRounding error may result in an estimated total that is different than the sum of the buck and antlerless harvest. bThe proportion of bucks harvested that had at least 4 antler points on one side. cThe estimated total hunter days divided by the estimated total number of mule deer harvested. Note that FWP’s effort estimates do not differentiate between mule deer and whitetail deer hunting effort. This is a very coarse metric that should be interpreted with caution, because changes in whitetail hunting effort could influence potential conclusions independent of any changes in mule deer hunting effort. dDue to a boundary change by the Fish and Wildlife Commission prior to the 2024 hunting season, harvest data from 2024 onward is not directly comparable to prior years. HD 317 Harvest HD 317 does not have a separate trend area; management is informed in part by the Gardiner Trend Area in adjacent HD 313, as well as by evaluating trends in harvest and other observations. The Adaptive Harvest Management Plan recommends an “antlered buck” season structure for both archery and general seasons with none to moderate numbers of antlerless B licenses under a standard regulation and B licenses restricted to localized game damage situations when a restrictive season type is warranted. Total mule deer harvest in HD 317 (Figure 17) has generally increased in the last decade, but has been subject to substantial annual fluctuations. Excepting limited harvest via B licenses, harvest is primarily of antler-buck mule deer (Figure 18). The proportion of bucks that are greater than 4 points on at least one side fluctuates annually, but in most years harvest estimates indicate that over half the bucks harvested are at least 4 points (Figure 19, Table 4). Excepting low harvest years in 2020 and 2024, buck harvest has been above the long-term average since 2012 (Figure 20). Mule deer B licenses were reduced in 2012. In 2014, most antlerless harvest opportunity was eliminated 23 statewide due to concerns over statewide mule deer numbers. In 2018, 85 B licenses were reintroduced in HD 317. Realized antlerless harvest at that quota level (Table 4) is low enough that the impact of antlerless harvest on population trend is likely negligible. Hunter effort, represented by the number of hunter days and by the number of days per harvested mule deer are shown in figures 21 and 22 (hunter effort data is not collected every year). It is important to note that FWP’s deer hunting effort estimates do not differentiate between whitetail and mule deer hunting effort; the figures below represent the combined deer hunting effort in HD 317. 150 200 250 300 2004 2006 2008 2010 2012 2014 2016 2018 2020 2022 2024 Year Estimated Total Mule Deer Harvest in HD 317 Harvest Type Total Mule Deer Harvest 10−Year Average Long Term Average Figure 17: Estimated total mule deer harvest in HD 317, 2004-Present. The shaded red ribbon represents the 80 percent confidence interval for each annual total harvest estimate. Note that the 10-year average is the average of all surveys spanning 10 years up to and including the current year. The long-term average includes all data through the current year (i.e. the sample size increases in later years). 24 0 100 200 300 2004 2006 2008 2010 2012 2014 2016 2018 2020 2022 2024 Year Estimated Mule Deer Buck and Antlerless Harvest in HD 317 Harvest Type Total Harvest Buck Harvest Antlerless Harvest Figure 18: Estimated total, buck, and antlerless mule deer harvest in HD 317, 2004-Present. 25 0 10 20 30 40 2004 2006 2008 2010 2012 2014 2016 2018 2020 2022 2024 Year Estimated Mule Deer Buck and Antlerless Harvest in HD 316 Harvest Type Total Harvest Buck Harvest Antlerless Harvest Figure 24: Estimated total, buck, and antlerless mule deer harvest in HD 316, 2004-Present. 32 0 10 20 30 40 2004 2006 2008 2010 2012 2014 2016 2018 2020 2022 2024 Year Estimated Mule Deer Buck Harvest in HD 316 Harvest Type Total Buck Harvest ≤3 Antler Points ≥4 Antler Points Figure 25: Estimated mule deer buck harvest in HD 316, 2004-Present. 33 10 20 30 40 2004 2006 2008 2010 2012 2014 2016 2018 2020 2022 2024 Year Estimated Mule Deer Buck Harvest in HD 316 Harvest Type Total Buck Harvest 10−Year Average Long Term Average Figure 26: Estimated mule deer buck harvest and long-term averages in HD 316, 2004-Present. 34 300 600 900 2004 2006 2008 2010 2012 2014 2016 2018 2020 2022 Year Estimated Deer Hunter Days in HD 316 Figure 27: Estimated total deer hunter days in HD 316, 2004-Present (hunter effort estimates are not collected every year). The shaded red ribbon represents the 80 percent confidence interval for each year’s hunter day estimate. Note that FWP’s hunter effort estimates do not differentiate between mule deer and whitetail hunting days. However, in HD 316 whitetail deer hunting is negligible. 35 10 20 30 40 50 2004 2006 2008 2010 2012 2014 2016 2018 2020 2022 Year Estimated Hunter Days per Harvested Mule Deer in HD 316 Figure 28: The estimated number of hunter days per mule deer harvested in HD 316. Note that FWP’s hunter effort estimates do not differentiate between mule deer and whitetail hunting days. However, in HD 316 whitetail deer hunting is negligible. 36 Table 5: Estimated harvest mule deer in HD 316, 2004-Present. License Year Total Harvesta Antlerless Harvest Buck Harvest Proportion Bucks ≥4 Pointsb Hunter Days per Harvested Mule Deerc 2004 27 0 27 0.659 35 2005 34 0 34 0.539 12 2006 22 0 22 0.332 33 2007 30 0 30 0.631 19 2008 24 0 24 0.872 16 2009 23 0 23 0.500 36 2010 11 0 11 1.000 23 2011 6 0 6 0.509 55 2012 17 0 17 0.667 2013 14 0 14 0.400 28 2014 17 0 17 0.503 2015 20 0 20 0.570 2016 21 0 21 0.570 2017 27 3 24 0.623 24 2018 27 0 27 0.569 2019 24 0 24 0.570 20 2021 11 0 11 0.649 56 2022 17 0 17 0.801 2023 23 0 23 0.724 38 2024 42 3 39 0.374 aRounding error may result in an estimated total that is different than the sum of the buck and antlerless harvest. bThe proportion of bucks harvested that had at least 4 antler points on one side. cThe estimated total hunter days divided by the estimated total number of mule deer harvested. Note that FWP’s effort estimates do not differentiate between mule deer and whitetail deer hunting effort. In HD 316, the whitetail hunting is negligible. 37