Kootenay Mule Deer Composition Surveys:

Transcription

1 : Winter Patrick Stent and Tara Szkorupa Ministry of Forests, Lands and Natural Resource Operations Cranbrook BC December 2012

2 Executive Summary The Ministry of Forests, Lands and Natural Operations (FLNRO) conducted mule deer composition surveys in portions of Management Units (MUs) 4 06, 4 07 (Creston area) and 4 02, 4 03, 4 21, 4 22 and 4 26 (East Kootenay) to monitor buck ratios after a region wide any buck hunting season was introduced in 2010, preceded and followed by a 4 point or greater regulation. Low buck ratios measured in the Cranbrook Game Management Zone (GMZ) in winter 2010/11 and 2011/12 prompted the closure of the any buck season in the Cranbrook GMZ and a region wide shortening of the 4 point and greater season from November 15 th to November 10 th. Buck ratios were monitored in the Cranbrook, Fernie and Nelson GMZs in 2009 (pre regulation change), 2010 (1 year post regulation change) and 2011 (2 years post regulation change). All surveys followed general standards for aerial inventories (RISC 2002). We observed 812 mule deer, including 491 does, 185 fawns, 81 <4 point bucks and 36 4 point bucks. Target sample sizes of 100 deer per MU (> 5% of the estimated population) were achieved in all areas except MU 4 22 in Buck:doe ratios varied from 11:100 (90% CI: 6 18) in MU 4 03 to 39:100 (CI: 29 51) in MU Fawn to doe ratios were highest in MU 4 26 (50:100 [CI: 38 62]) and lowest in MU 4 02 (28:100 [CI: 21 37]). Buck ratios increased in the Cranbrook GMZ, following cancellation of the any buck season in 2012, but were still below the management target of 20 bucks:100 does post hunt. Buck ratios were stable and above target in the Fernie and Nelson GMZs, suggesting the any buck regulation is sustainable in these GMZs. Research across North America has failed to show a relationship between buck ratios and fawn production, even at buck to doe ratios below 20:100. We also found stable and relatively high fawn ratios in MU 4 03 despite low buck ratios in 2010 and 2011, and hence believe the current buck harvest is not threatening the viability of mule deer. Composition surveys are designed to measure changes in population demographics in response to hunting regulations but cannot detect changes in population size. Research into factors limiting population growth is needed to address mule deer population declines in the region. Ministry of Forests, Lands and Natural Resource Operations 2012 ii

3 Acknowledgements We thank W. Maki of Kootenay Helicopters for his exceptional piloting skills. We would also like to thank the enthusiastic observers who helped out with the surveys: B. Phillips, M. Gall and M. Neufeld. Funding for the survey was provided by the Habitat Conservation Trust Foundation (HCTF) and FLNRO. Ministry of Forests, Lands and Natural Resource Operations 2012 iii

4 Table of Contents Executive Summary... ii Acknowledgements... iii List of Figures... iv List of Tables... v Introduction... 1 Study Area... 1 Methods... 4 Survey Area Selection... 4 Survey Procedures... 4 Classification... 5 Data Analysis... 5 Results... 5 Sampling Effort... 5 Observations... 6 Population Ratios Other Species Discussion Key Findings ( ) Literature Cited List of Figures Figure 1: Map showing areas surveyed for mule deer (green polygons)... 3 Figure 2: Mule deer observations scaled to group size and flight lines in the Creston area... 7 Figure 3: Mule deer observations scaled to group size and flight lines in MUs 4 02 and Figure 4: Mule deer observations scaled to group size and flight lines in MU Figure 5: Mule deer observations scaled to group size and flight lines in MU Figure 6: Mule deer buck ratios measured from fall/winter composition surveys, Ministry of Forests, Lands and Natural Resource Operations 2012 iv

5 List of Tables Table 1: Survey effort by Management Unit for mule deer composition surveys Table 2: Mule deer observations by Management Unit for composition surveys Table 3: Mule deer population ratios for Kootenay MUs surveyed November and December Ministry of Forests, Lands and Natural Resource Operations 2012 v

6 Introduction Composition surveys for mule deer (Odocoileus hemionus) were conducted annually between 2009 and 2012 to monitor population ratios after an October any buck general open season (GOS) was introduced in the East Kootenay and extended in the West Kootenay in fall The any buck season was preceded and followed by a 4 point or greater season. Low buck ratios measured in the Cranbrook Game Management Zone (GMZ) in winter 2010/11 and 2011/12 prompted the closure of the any buck season in that area and a region wide shortening of the 4 point and greater season from November 1 15 th to November 1 10 th. Prior to 2010, mule deer were managed under 3 different hunting regimes in the Kootenay Region. The East Kootenay had a 65 day 4 point or greater season, the West Kootenay had a 60 day 4 point or greater season and a 10 day any buck season, and the Revelstoke area had a 90 day any buck season. Objectives of mule deer composition surveys were to collect sex and age class data to assess the impact of current hunting regulations on mule deer demographics. FLNRO s management objectives are to increase hunting opportunity for mule deer, offer a diversity of hunting opportunities and maintain ratios of at least 20 bucks:100 does (MoE 2010). Study Area The areas surveyed in the East Kootenay included portions of the Fernie GMZ (MUs 4 21, 4 22, 4 02) and the Cranbrook GMZ (MUs 4 03 and 4 26; Figure 1). In MU 4 21 we surveyed Premier Ridge and the base of the Rocky Mountains to the Wild Horse River. In MU 4 22 we surveyed Iron Creek, Burton Creek, the lower Bull River and several hillsides southwest of Elko. The MU 4 02 survey included the hillsides southeast of Elko, the lower Wigwam River up to Lodgepole Creek and several drainages in the Galton Range. In MU 4 03, the banks of the Kootenay River and hillsides north of Newgate were surveyed as well as a portion of Tokay Hills, Plumbob Mountain and Gold Mountain. The MU 4 26 survey focused on winter ranges along the base of the Purcell Mountains, including Dutch Creek, Findlay River, Toby Creek and Horsethief Creek. Areas surveyed in the East Kootenay occur within the dry climatic region and included the Kootenay Dry Mild Interior Douglas Fir variant (IDF dm2) and the Dry Cool Montane Spruce (MS dk) biogeoclimatic (BEC) subzones. The IDF dm2 subzone occurs along the slopes of the Rocky Mountains, typically between 800 and 1200 m elevation. Douglas fir is the climax tree species; however due to past fire activity, mixed seral stands of Douglas fir (Pseudotsuga menziesii), lodgepole pine (Pinus contorta), western larch (Larix occidentalis) and trembling aspen (Populus tremuloides) were common. We also encountered open, bunchgrass dominated hillsides at low elevations in the Pickering Hills, Newgate and Premier Ridge areas within this subzone. The MS dk subzone occurs above the IDF dm2 zone, typically between 1200 and 1650 m. Dominant Ministry of Forests, Lands and Natural Resource Operations

7 tree species include hybrid white spruce (Picea engelmannii x glauca), balsam fir (Abies lasiocarpa) and lodgepole pine. On occasion we also surveyed into the Engelmann Spruce Subalpine Fir (ESSF dk) subzone, which occurs above the MS dk subzone (typically m on south aspects). Tree species adapted to short growing seasons (i.e., Engelmann spruce [P. engelmannii] and Balsam fir) occur in this subzone. In the Creston area we surveyed portions of MU 4 06 and 4 07, which are both within the Nelson GMZ. In MU 4 07, Corn Creek, Dodge Creek and Topaz Face (located above Summit Creek) were surveyed, while the MU 4 06 survey area included Kitchener Mountain, Leadville Creek, Sanca Creek and hillsides above Kuskanook (Figure 1). The surveyed portions of MU 4 06 and 4 07 occur in the moist climatic region and include the Interior Cedar Hemlock (ICH) very warm (xw) and dry warm (dw) subzones (Braumandl and Curran 2002). The ICH xw occurs at low elevations ( m) on warm aspects in this area and is characterized by mixed seral stands of Douglas fir and Ponderosa pine (P. ponderosa), and climax stands of western red cedar (Thuja plicata) and western hemlock (Tsuga heterophylla). The ICH dw subzone also occurs at low elevations ( m) in the area but on cooler sites than the ICH xw and stands typically includes a greater diversity of tree species in mixed seral stands (Douglas fir, paper birch [Betula papyrifera], western larch and western white pine [P. monticola]). Shrub dominated hillsides created from past fire events (especially ungulate enhancement burns) were common on south facing hillsides throughout the areas surveyed. Other ungulates occurring in survey areas include Rocky Mountain elk (Cervus canadensis), white tailed deer (O. virginianus), moose (Alces americanus), bighorn sheep (Ovis canadensis) and mountain goats (Oreamnos americanus). Potential predators of mule deer in these areas include cougars (Felis concolor), wolves (Canis lupus), coyotes (C. latrans), grizzly bears (Ursus arctos) and black bears (U. americanus). Ministry of Forests, Lands and Natural Resource Operations

8 Kootenay Mule Deer Composition Surveys Figure 1: Map showing areas surveyed for mule deer (green polygons) during composition surveys, November and December Ministry of Forests, Lands and Natural Resource Operations

9 Methods Survey Area Selection Mule deer observations from earlier composition surveys were used to identify survey areas where mule deer were expected to occur in early winter (Stent 2011 and 2012). We used survey units (i.e., blocks) established in the previous survey to guide us to potential high use areas but we frequently surveyed outside blocks if we saw other areas that looked like suitable mule deer habitat from the air. We preferentially selected open areas (i.e., shrub dominated hillsides and open forest), where mule deer would be most easily detected. Survey Procedures Surveys were conducted in a Bell 206B Jet Ranger helicopter equipped with front and rear bubble windows. Surveys followed general standards for aerial inventories (RISC 2002), although this manual does not provide specific guidance for composition surveys. We flew contours (i.e., transects) along winter ranges (usually steep hillsides), m above tree tops at km/hr. We avoided flying flat terrain at the base of hillsides and usually started our first transect along the lowest portion of the hillside and then moved upslope, spacing transects m apart. We repeated transects up the hillside until we no longer saw deer tracks or suitable deer habitat. Surveys were conducted with 3 observers (plus the pilot). The data recorder sat behind the pilot, which allowed 2 observers to classify animals from the same side of the machine. The observer in the front of the machine was also responsible for navigating, which was assisted using ArcPad mobile GPS (Version U; Environmental Systems Research Institute) on a laptop computer. The ArcPad program was connected to a Garmin Bluetooth Global Positioning System (GPS) so we could track our position in realtime. Flight paths were recorded on the digital map using the tracklog function. Most mule deer groups observed in open cover were classified by completing a single tight circle back over the group. However small groups encountered in forested habitat were often circled multiple times, as deer had a tendency to disperse into heavy cover and hide under trees. Large groups of deer (>15 animals) observed in heavy cover were typically hazed into openings so they could be classified with greater accuracy. Numerous deer encountered in heavy cover could not be classified to sex or age and were recorded as unclassified. We attempted to photograph all bucks larger than 2 points so buck classifications recorded from the air could be verified. Photographs were taken with a Nikon D 80 camera equipped with a mm Vibration Resistant lens. Photographs were also used to verify fawn numbers and total counts for large groups of deer. We photographed bucks at a close distance with a longer focal length so small antler points could be detected, while group photos for total counts and fawn numbers were usually taken at a further distance with a shorter focal length so all animals in the group would be in the picture. Ministry of Forests, Lands and Natural Resource Operations

10 Classification Mule deer bucks were classified as either 4 points or greater or less than 4 points, as defined in the BC Hunting Regulations (i.e., any buck having at least 4 points [ 1 inch], excluding the brow tine [point on main beam closest to head] on one antler; We defined 4 point as any buck having fewer than 4 points on both antlers, excluding the brow tine. Antlerless deer were classified as either does (females 1.5 years old) or fawns (young of the year). We also recorded a tally of moose, elk, white tailed deer and bighorn sheep observations on data sheets but did not attempt to classify these species to sex or age. Data Analysis Raw population ratios were calculated for bucks and fawns and expressed as the number per 100 does for each MU. No sightability correction was applied to observation data as the only mule deer model available was developed in Southern Idaho and is poorly suited to habitats found in the Kootenays (Stent 2010). Population ratio data were compared to raw ratios from pre GOs and post GOS composition data. We bootstrapped buck and fawn ratios (1000 iterations) to determine 90% confidence intervals using the PopTools program in Microsoft Excel. Results Sampling Effort Surveys occurred from November 24 th to December 8 th, Snow conditions were good in the Creston area but marginal in the East Kootenay survey, where coverage was patchy below 1200 m. The high elevation snowpack measured at Moyie Mountain (1830 m) indicated the high elevation snowpack was 10 20% below the 41 year average in late November (Ministry of Environment River Forecast Centre: Total survey time was 19 hours and 44 minutes (Table 1). Ministry of Forests, Lands and Natural Resource Operations

11 Table 1: Survey effort by Management Unit for mule deer composition surveys, November and December, Survey Areas MU Survey Date Survey Time Plumbob, Gold Mtn 4 03 Nov. 24th 1:20 Galton Range 4 02 Nov. 24th/25th 2:59 Wigwam River 4 02 Nov. 25th 0:45 Galton Range 4 02 Nov. 25th 0:43 Tokay Hills 4 03 Nov. 25th 0:25 Newgate 4 03 Nov. 25th 0:48 Sheep Mountain 4 22 Nov. 25th 0:29 Colvali 4 22 Nov. 25th 0:39 Burton Creek 4 22 Nov. 25th 0:50 Bull River, Iron Creek 4 22 Nov. 25th 1:12 Wild Horse River 4 21 Nov. 27th 0:48 Premier Ridge 4 21 Nov. 27th 1:28 Hofert, Dutch, Findlay, Wilmer 4 26 Nov. 27th 2:30 Kuskonook/Sanca Creek 4 06 Dec. 8th 1:29 Kitchener Mountain/Leadville Creek 4 06 Dec. 8th 0:53 Corn/Topaz/Dodge Creeks 4 07 Dec. 8th 2:26 Total 19:44 Observations We observed 812 mule deer, including 491 does, 185 fawns, 81 <4 point bucks and 36 4 point bucks (Table 2). There were 3 bucks that could not be classified by their antlers and 16 deer that could not be classified to sex or age class. Target sample sizes of 100 deer per MU were achieved in all units except MU Mule deer observations and flight lines are mapped in Figures 2 5. Table 2: Mule deer observations by Management Unit for composition surveys, November and December MU Total Does Fawns <4 point 4 point Unclassified Bucks Unclassified Deer / Total Ministry of Forests, Lands and Natural Resource Operations

12 Figure 2: Mule deer observations scaled to group size and flight lines in the Creston area from composition surveys, November and December Ministry of Forests, Lands and Natural Resource Operations

13 Figure 3: Mule deer observations scaled to group size and flight lines in MUs 4 02 and 4 03 from composition surveys, November and December Ministry of Forests, Lands and Natural Resource Operations

14 Figure 4: Mule deer observations scaled to group size and flight lines in MU 4 21 from composition surveys, November and December Ministry of Forests, Lands and Natural Resource Operations

15 Figure 5: Mule deer observations scaled to group size and flight lines in MU 4 26 from mule deer composition surveys, November and December Ministry of Forests, Lands and Natural Resource Operations

16 Population Ratios Buck ratios ranged from 11:100 does (90% CI: 6 18) in MU 4 03 to 39:100 does (CI: 29 51) in MU 4 02 (Table 3). Fawn ratios were highest in MU 4 26 (50:100 does [CI: 38 62]) and lowest in MU 4 02 (28:100 does [CI: 21 37]). We detected 88% of bucks with one or more does, suggesting rutting activity was still underway during surveys. Table 3: Mule deer population ratios for Kootenay MUs surveyed November and December MU Bucks:100 Does 90% Confidence Interval Fawns:100 Does 90% Confidence Interval / Other Species We also observed 706 elk, 150 white tailed deer, 66 sheep, and 16 moose. These species were tallied when detected on transects but not numerated outside of survey areas. Predators observed during surveys included 4 coyotes, 4 wolves and one cougar. Discussion Buck ratios remained below management objectives in MU 4 03 (11:100 does) despite the cancellation of the any buck season in the Cranbrook GMZ in The increase in the buck ratios in this unit from 2010 and 2011 surveys is largely due to the inclusion of Plumbob Mountain and Gold Mountain survey areas, where buck ratios were much higher (35 bucks:100 does) than lower elevation Newgate and Tokay Hills winter ranges. Buck ratios in the Newgate and Tokay Hills averaged 6:100 does and were similar to ratios measured from previous surveys of this area (2 5 bucks:100 does; Figure 6), prior to the closure of the any buck season. Behavioural differences between bucks and does could explain the lack of bucks observed amongst large doe and fawn herds, given 4 point bucks were not hunted in the Cranbrook GMZ but were largely absent from the low elevation groups. It is plausible that breeding bucks occur on the periphery of these herds and are more difficult to detect during surveys. Fawn ratios did not decline the year after low buck ratios were detected, suggesting buck ratios are not limiting recruitment to this population. Ministry of Forests, Lands and Natural Resource Operations

17 / / / /13 Additional areas surveyed with more bucks in 2012/ / Figure 6: Mule deer buck ratios measured from fall/winter composition surveys, Error bars are 90% confidence intervals. The any buck season was introduced to East Kootenay MUs in fall 2010 but cancelled in the Cranbrook GMZ (includes MUs 4 03 and 4 26) in fall After combining composition data for East Kootenay MUs sampled in all three survey years (4 21, 4 22 and 4 02), the buck ratio was 27:100 does in 2012 (CI 20 33), 28:100 does in 2011 (CI: 23 36), 37:100 does in 2010 (CI: 26 33) and 30:100 does in 2009/10 (CI: 14 44), suggesting no significant change in buck ratios in the Fernie GMZ since implementation of the any buck GOS. Adding the Cranbrook GMZ data to the sample dropped the East Kootenay buck ratio to 23:100 (CI: 19 27) does for the East Kootenay, an increase from 2011 ratios (19 bucks:100 does [CI: 16 23]). There appears to be little change in buck ratios in MUs 4 06 and 4 07 since the GOS was implemented (Figure 6). In 2012/13, buck ratios in MU 4 26 (30:100 does) were significantly higher than 2011/12 ratios (8:100 does); however the accuracy of the 2011/12 ratio is questionable as a result of the low sample size and late timing of the survey. Buck ratios were above management targets in remaining MUs surveyed that kept the any buck GOS in 2012, with the exception of MU 4 21, where buck ratios have been slightly below this target since Our data suggest relatively stable trends in buck ratios in the Cranbrook and Nelson GMZ, despite concerns that closure of the any buck season in the Cranbrook GMZ in 2012 would shift hunting pressure to neighbouring areas. Composition surveys are designed to measure effects of buck seasons on herd demographics and cannot be used to identify changes in mule deer population size over time. There is much concern with declining mule deer population trends in the Kootenay Region (and much of western North America); however research suggests buck only harvest will not affect reproductive rates even at buck ratios below 20:100 does (Gill 1999, Erickson et al. 2003). Our results support this notion as fawn ratios were similarly high in MU 4 03 and 4 21 in 2011 and 2012, despite the low buck ratio measured the previous Ministry of Forests, Lands and Natural Resource Operations

18 fall. To address mule deer population declines in the Kootenay Region, we recommend research be directed toward other factors that may be limiting growth of mule deer populations such as interspecific competition, predation and habitat change. Proportions of 4 point bucks were relatively low in most areas, which could be attributed to high harvest in the 4 point or greater or any buck season. Research has shown non hunting mortality (i.e., predation, accidental death, etc.) may be a more important factor than hunter harvest in limiting recruitment of bucks to adulthood, even when antler point regulations are in place to promote recruitment of adult bucks (Pac and White 2007). This study found populations with a restrictive private land hunt targeting trophy bucks had similarly low proportions of 4.5+ year old bucks to populations exposed to a more liberal any buck season, followed by a 2 point or less restriction during the rut. No sightability correction was applied to observation data as the only mule deer model available was developed in Southern Idaho and is poorly suited to habitats found in the Kootenays (Stent 2010). Analysis of variables affecting sightability was conducted with the 2010 data and there were no consistent differences in sightability between bucks and does. However low buck ratios reported from the 2009/10 surveys suggest a large number of bucks can be missed and buck ratios can be biased low if surveys occur post rut (Stent 2010). Given the high percentage of bucks observed with does (Table 6), we expect similar sightability of bucks and does in all MUs surveyed in late November and early December. Key Findings ( ) Changing the any buck GOS to a 4 point or greater season in the Cranbrook GMZ increased the overall buck ratio; however this could be attributed to greater survey effort of high elevation habitats in 2012/13, where buck ratios were higher. Surveying only low elevation winter ranges will likely result in a low buck ratio, given large congregations of doe and fawn groups are common but few bucks occur with these groups (or bucks have much lower detectability). When surveying during the rut, buck ratios were relatively consistent in MUs surveyed multiple years. Buck ratios were probably underestimated in MU 4 02 due to late survey timing in 2009/10, when we believe bucks had segregated from doe groups. Approximately 90% of bucks were observed with doe groups when surveys occurred before the second week of December, which likely enhances detectability of bucks. Photographs were effective in identifying antler points missed during classification from the helicopter when the photographer was able to get a side or angled profile of the antlers (i.e., not head on). Buck ratios were consistently above management targets in the Fernie and Nelson GMZs after introducing or lengthening the any buck GOS, suggesting the season is biologically sustainable in these areas. Ministry of Forests, Lands and Natural Resource Operations

19 Literature Cited Braumandl, T. F., and M. P. Curran A field guide for site identification for the Nelson Forest Region. British Columbia Ministry of Forests, Victoria, British Columbia, Canada. Erickson, G. L., J. R. Heffelfinger and J. H. Ellenberger Potential effects of hunting and hunt structure on mule deer abundance and demographics. In devos, J. C., M. R. Conover and N. E. Headrick (editors). Mule Deer Conservation: Issues and Management Strategies. Berryman, Institute Press, Utah State University, Logan. Gill, R. B. Mule deer populations in Colorado: Reasons and responses: A report to the Colorado legislature. Colorado Division of Wildlife, 54 pp. Ministry of Environment (MoE) Southern Interior Mule Deer Harvest Management Procedure Manual. Volume 4, Section 7, Subsection Effective on March 1, Ministry of Environment, Victoria, BC. Pac, D. and G. White Survival and cause specific mortality of male mule deer under different hunting regulations in the Bridger Mountains, Montana. J. Wild. Manage. 71 (3): Reid, A Shuswap and Boundary Mule Deer Composition Surveys: December Report prepared for the BC Ministry of Natural Resource Operations, Thompson/Okanagan Region. Penticton, B.C. RISC (Resources Information Standards Committee) Aerial based inventory methods for selected ungulates: bison, mountain goat, mountain sheep, moose, elk, deer and caribou. Standards for components of British Columbia s biodiversity No. 32. Version 2.0. Resources Inventory Committee, B.C. Ministry of Sustainable Resource Management, Victoria, British Columbia. Stent, P Kootenay mule deer composition surveys: Winter 2001/12. Report prepared for the Ministry of Forests, Lands and Natural Resource Operations, 15 pp. Stent, P Kootenay mule deer composition surveys: Winter Report prepared for the Ministry of Environment, Nelson B.C., 26 pp. Stent, P Kootenay mule deer composition surveys: Winter 2009/10. Report prepared for the Ministry of Environment, Nelson B.C., 26 pp. Unsworth, J. W., F. A. Leboan, E. O. Garton, D. J. Leptich, and P. Zager Aerial survey: user s manual. Electronic edition. Idaho Department of Fish and Game, Boise, Idaho. Ministry of Forests, Lands and Natural Resource Operations