AURORA WILDLIFE RESEARCH

Transcription

1 AURORA WILDLIFE RESEARCH Kim Poole 2305 Annable Rd. Nelson, BC, V1L 6K4 Canada Tel: (250) ; Fax: (250) April 2005 Mike Gall Conservation Specialist and Glenn Campbell Southern Rockies Area Supervisor Parks and Protected Areas, Ecosystem Section Environmental Stewardship Division 205 Industrial Road G. Cranbrook, BC V1C 7G5 Re: Bighorn sheep survey of Mt. Assiniboine Provincial Park, April 2005 Following is a brief summary of the survey methodology and results for an aerial survey for Rocky Mountain bighorn sheep on wintering range in Mt. Assiniboine Provincial Park near Citadel Pass. Also included are recommendations to enhance data return for future surveys. Introduction Surveys of known core wintering areas for Rocky Mountain bighorn sheep were conducted in 2001 and 2002 in most of the East Kootenay of southeastern British Columbia (Teske and Forbes 2002). Population trends have fluctuated among areas over the past several decades, but severe winters in the mid-1990s, and forest ingrowth and associated predation appear to have negatively affected many populations. BC Parks has been monitoring sheep numbers on the Mt. Assiniboine Provincial Park winter range since the early 1990s. This survey is a continuation of that monitoring program. Methods Survey timing has generally occurred during March each year (M. Gall, personal communication), but the 2005 survey took place on 22 April. We used a Bell 206 Long Ranger, flown by John Christensen from Airspan Helicopters, Invermere. Kim Poole was the front seat navigator and recorder, and Glenn Campbell and Mike Gall were rear seat observers. Study design and methodology generally followed RISC standards (RISC 2002), and consisted of a total count survey. We surveyed all alpine and open subalpine habitat down to the valley bottom, and flew roughly m ( foot) contour lines at km/hr, m out from the hillsides. Flight lines occurred both up and down-slope. Animal locations and flight track were recorded with a hand-held global positioning system (GPS) unit, which was later downloaded to a computer. We recorded elevation from the helicopter s altimeter (to the nearest 100 feet), and classified sheep to Level 4 classification (RISC 2002), which consisted of lambs, juveniles (yearlings) by sex if possible, adult females, and Class I, Class II, Class III, and Class IV rams.

2 2 We initially surveyed from the Sunshine Meadows to Citadel Pass, which is the standard known core winter range covered during previous years. We subsequently surveyed a hillside of potentially suitable winter range south of Citadel Pass. Results Survey conditions were good with excellent visibility; air temperature on survey was 2 4 C, with clear skies and light winds. Snow cover was gone from most open southwest-facing slopes, but present in treed areas and on cooler slopes. We spent 67 minutes surveying the core winter range of 12.8 km 2, an average survey intensity of 5.2 minutes/km 2. We spent an additional 10 minutes surveying the hillside south of Citadel Pass (3.3 km 2 ; 3.0 minutes/km 2 ). We observed 65 sheep in 13 groups; all but 1 animal was on the core winter range (Fig. 1). Group size ranged from 1 12 animals. We attempted to classify all but 1 group of 5 sheep, and counted 9 lambs, 8 juveniles (2 of which were identified as males), 21 ewes, 7 Class I rams, 5 Class II rams, 8 Class III rams, and 2 Class IV rams. Age and sex ratios were 43 lambs:100 ewes and 105 rams:100 ewes. These ratios would be affected by the unclassified group, which was a mixed ewe/lamb group not classified because of the stirring of sheep from other groups in the same vicinity. Elevation of sheep groups ranged from 5,700 to 7,900 feet. Fourteen mountain goats in 6 groups were also observed during the survey (Fig. 1). No kids were observed, and only single goats were observed on the core sheep winter range. All goats were at moderately high elevation (7,200 8,000 feet). Figure 1. Location of bighorn sheep (red dots) and mountain goats (purple dots) on the Mt. Assiniboine sheep winter range, 22 April Dots are scaled to group size (1 to 12 for sheep; 1 to 4 for mountain goats). The census zone is represented by the polygons; the larger polygon to the left is considered the core sheep winter range.

3 3 Discussion BC Parks has been surveying for sheep wintering in Mt. Assiniboine Provincial Park since 1992 (Table 1). Population levels have fluctuated over time, with slightly higher total counts in the early to mid- 1990s, and lower counts in the late 1990s to early 2000s (Fig. 2). Table 1. Summary of surveys for bighorn sheep on the Mt. Assiniboine Provincial Park winter range, 1992 to Data from 1992 to 2002 from BC Parks, Cranbrook. Year Total Lambs Juveniles Ewes Cl 1&2 Cl 3&4 Lamb:100 ewes a a Five sheep in 1 ewe/lamb group were not classified. Mt. Assiniboine sheep surveys Total no. of sheep Figure 2. Total counts (uncorrected) of bighorn sheep on the Mt. Assiniboine sheep winter range, 1992 to The black lines represents a 4 th order polynomial line fitted to the data using Excel.

4 4 This survey represents a total count on the wintering range, but it is unlikely that all sheep present were observed. Teske and Forbes (2002) reported 80 85% sightability from 4 tests conducted with marked animals in the East Kootenay, and suggested sightability would be even less in forested habitats. Given stable survey conditions (timing, snow conditions, survey effort, observer experience, etc.), annual counts should be a rough but reliable index to wintering sheep numbers, and should be indicative of broad trends in population size. Survey data since 1992 suggest either the origin of sheep within the core winter range fluctuates among years, age and sex classification are inconsistent and inaccurate, or sightability is far lower than anticipated (thus, missed sheep from year to year are affecting classification). Dramatic changes in the proportion of Class I/II and Class III/IV rams among years, insufficient yearlings to account for population increases the following year, and on one occasion more juveniles than lambs the previous year cannot occur within a closed population when survey sightability is high. Recommendations The following recommendations are suggested: 1. Surveys should be conducted when snow is present in sufficient depth to limit sheep mobility. During late April, the disturbed sheep were able to run far and fast, making it difficult to classify sheep and keep groups straight. Surveys during mid-february to March would likely reduce this problem. 2. A quieter helicopter should be used to minimize disturbance to sheep. I believe a Bell 206B is quieter than a Long Ranger, acknowledging that this is a relative term. You might want to also consider using an R-44 piston helicopter, currently available from near Cranbrook. Although the R-44 is restricted to 2 passengers, the lower noise levels may make counting and classification more accurate, since the sheep should react less to the disturbance. 3. All survey participants, including the pilot, should have direct and extensive experience at sheep classification. Ideally, at least 2 of the participants (pilot included) should have extensive experience at sheep classification. At a minimum, all participants should review aging and sexing criteria prior to the flight. 4. When disturbed, sheep tend to move down-slope (personal observation; P. Davidson, personal communication), thus to minimize mixing and disturbance with other groups, sections of winter range should be flown from lower elevations upwards. 5. Since this is essentially a minimum count survey over time to establish population trend, as many factors as possible should be kept constant from year to year. These include seasonal and daily timing, aircraft type, observers, observer experience, weather conditions, survey effort, and coverage. 6. I suggest that sheep classification be modified from the Level 4 provided in the RISC (2002) manual. Teske and Forbes (2002) identified the following classes during winter surveys in 2001 and 2002: juveniles (lambs ~9 10 months of age), adult females, Class I, Class II, Class III, and Class IV rams. This classification was used due to the difficulty of distinguishing between yearling rams and Class I rams; yearling rams were included with the Class I ram classification (<½ curl). However, to the experience observer, yearling and Class I rams should be distinguishable from other age and sex categories, and yearling females would be lumped in with the adult ewe category (P. Davidson, personal communication). Aerial survey conditions with rapidly moving animals make it difficult to accurately classify these younger and small categories, thus it might be prudent to lump categories to provide more accurate estimates.

5 5 Literature cited 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 Information Standards Committee, B.C. Ministry of Sustainable Resource Management, Victoria, British Columbia. Teske, I., and B. Forbes East Kootenay Rocky Mountain sheep inventory: winter 2001 and Unpublished report, Ministry of Water, Land and Air Protection, Environmental Stewardship Division, Cranbrook, B.C. Kim Poole Wildlife Research Biologist Attachment: Excel spreadsheet