POPULATION CENSUSES OF CARIBOU IN THE NORTH COLUMBIA MOUNTAINS- COLUMBIA SOUTH SUBPOPULATION. April, Kelsey Furk, John Flaa

Transcription

1 POPULATION CENSUSES OF CARIBOU IN THE NORTH COLUMBIA MOUNTAINS- COLUMBIA SOUTH SUBPOPULATION For Mt. Revelstoke and Glacier National Parks, Parks Canada April, 2009 Kelsey Furk, John Flaa Executive Summary Mountain caribou in the Columbia Forest District were studied using radiotelemetry from 1992 to Censuses conducted between 1994 and 1997 indicated a relatively stable population of between 290 and 375 animals in the area of the upper Columbia River. These censuses had jurisdictional, not ecological boundaries and changes in numbers in the mid-1990s likely reflected caribou movements in and out of the census areas among years more than actual changes in numbers. In 2002 the entire range of mountain caribou in British Columbia was censused so biological subpopulations could be enumerated. Even with the expanded census areas, the sum of the 4 subpopulations (Columbia North, Columbia South, Frisby/Queest, and Kinbasket South) that included the earlier census area was only 212 animals or 57% of the 1997 estimate for an annual decline of 10%. This downward trend occurred in all mountain caribou populations in southern B.C. Overall, numbers in the Columbia Forest District appeared to have stabilized in 2006 and However, trends within individual subpopulations vary. Only the Columbia South subpopulation (CS) was surveyed in 2009, and results of the survey are outlined in this report. Surveys of the CS in 2004, 2006 and 2007 indicated fluctuating but overall stable population numbers (estimate of 26-40). The population began to decline again in A census of the CS conducted on April 5 th and 6 th, 2009 indicates the population is now estimated at 13 animals, down from an estimated 20 in Calf recruitment has been very low over the past 2 years, with none of the 20 animals seen with calves in 2008 and only two of 13 animals seen with a

2 2 calf in This population is aging and, as predicted, is declining precipitously. Immediate action is required to avoid extirpation of caribou from the area. Introduction Woodland caribou (Rangifer tarandus caribou) in southeastern British Columbia are commonly referred to as mountain caribou. They are a unique ecotype of caribou distinguished from others by their use of the deep wet-belt snowpack (>2m) as a platform to access arboreal lichens in the canopy of subalpine forests during late winter. Because of their low numbers, decreasing population trend, and shrinking and fragmented distribution, these caribou are considered threatened by COSEWIC (Committee on the Status of Endangered Wildlife in Canada) and were added to the red-list (species at risk of extinction or extirpation) by the British Columbia Conservation Data Centre in Mountain caribou sub-populations are relatively contiguous in British Columbia from north of Prince George to the Columbia Forest District (CFD). Several small, isolated populations are found south of the CFD with one extending below the international border. Population characteristics of caribou on the Revelstoke Reservoir portion (former Revelstoke Forest District) of the CFD were examined from 1981 to 1985 by Simpson and Woods (1987) and from 1992 to 2008 by McLellan et al. (1994), Flaa and McLellan (2000), and Hooge et al. (2004), McLellan et al. (2006), Mclellan et al. (2008). Wittmer et al.(2005a) used a substantial province-wide dataset of telemetry data to establish biologically relevant sub-population boundaries. This report updates only the CS inventory to April Census Area This report covers the 2009 survey of the CS (as described in Wittmer et al Figure 1). The subpopulation is bound roughly to the west by Lake Revelstoke, to the south by the Trans-Canada Highway, to the East by Mountain Creek and to the north by the Goldstream River (excluding Brewster Creek and Caribou Basin).

3 3 Methods Between 1992 and 2009, 37 caribou in the CS were captured by net-gunning from a helicopter in subalpine habitat. All caribou were fitted with mortality/motion sensitive GPS or VHF radiocollars. Caribou were censused during late winter when they were in open subalpine parkland (Simpson and Woods 1987, McLellan et al. 1994, Seip 1992). In 2009, a Bell Long Ranger and an A Star were used for the majority of the survey area and a Cessna 337 was used to cover the area between St. Cyr Creek and Mars Creek. A contour near treeline ( m) was flown including all suitable habitat within the study area, and tracks were followed until animals were sighted unless the tracks descended into mature timber and were lost from view. An estimate of the number of caribou in these unsighted groups was based on separate tracks and/or beds. The location of each group was marked and numbered on a 1:250,000 map and recorded with a GPS. Although all male groups were easily identifiable, discrimination of young males from adult females in mixed groups was difficult and would have required additional harassment. We therefore limited our classes to calves and adults in these larger mixed groups. As in earlier censuses, animals with collars were used as marks for mark-resight estimates of the population size. However, there were only 3 radio-collared animals in the entire census area in 2009, which is less than required to use this method. We now must rely more on the total number of animals seen as well as tracks of groups that were followed but not found (usually, they moved into mature forests at lower elevations) than we did in the past.

4 4 Prince George HR GM NL NC British Columbia BV WG GH FQB AC CN KS CS Subpopulation census described in this report (Columbia south) Alberta Revelstoke DU 100 km Kamloops MS NA Pacific Ocean Vancouver Nelson USA SS PC Cranbrook PS Figure 1. Mountain caribou subpopulations in British Columbia as described by Wittmer et al. (2005). Subpopulations in the CFD include CN Columbia North, KS Kinbasket South, FQ = Frisby/Queest, CS = Columbia South, MS = Monashee South.

5 5 Results Based on this survey, the total estimated number of caribou in the CS was 14 in April On April 5 th, 6 th and 9 th caribou were seen in 6 groups and one set of tracks was followed unsuccesfully in the CS subpopulation (Figure 2). Eight hours total were spent searching from a helicopter on April 5 th and 6 th and one hour was spent searching from a Cessna 337 on April 9 th. Light and snow conditions were generally good. The snowpack at the Fidelity snow station was just below average at approximately 290cm on April 5 th, All three collared caribou were located during the survey. Four of six groups (and 8 of 13 caribou) were located within the boundaries of Mount Revelstoke or Glacier National Parks. The remaining groups were located in the Downie Creek drainage. In addition, the tracks of one caribou were followed but the caribou was not located at Standard Creek. A set of tracks of 2-3 animals were found at the head of West Woolsey Creek. However, these were very likely from a group of three located a short distance away (also in West Woolsey Creek). Two calves were observed during the survey, one at Mt. Shaugnessy, and one on the north side of Downie Creek. Group size varied from 1-4, with a mean of 2.2 and a median of 2. Census data is summarized in the appendix.

6 6 N Downie River Sorcerer Cr e ek % 1 Sta ndard C r. 1 4 M ountain C r e ek 2 2 Beaver River Lake Revelstoke Carnes Creek Fang Cr. Glacier National Park Laforme Cr. % 3 Mt. Revelstoke NP Woolsey Cre ek Illiciliwaet River Tangier River 1 caribou (labelled with number observed) % caribou tracks (labelled with estimated number) 5-April-09 flightpath 6-April-09 flightpath National Parks 9-April-09 flightpath 1: Figure 2. Groups of caribou or caribou tracks sighted during the 2009 caribou census of the Columbia South subpopulation.

7 7 Discussion Complete surveys of the CS have been conducted since the early 1990s (Table 1). Mountain caribou populations province wide declined dramatically in The CS declined sharply when compared to other subpopulations in the area (CN and FB). Since then, the CS appeared to have stabilized from 2002 to 2007 but continued to decline after The decline continues in 2009, with only 13 animals seen compared to 20 in 2008 and 32 in Sightability of collared animals was % during surveys in 1994, 1996 and 1997, when there were 9-12 collared animals in the CS (summarized in Mclellan et al. 2008). This in combination with a longer than average search time for this census area, a near-average snowpack, experienced observers and sighting 3 of 3 radio-collared caribou provide evidence for a high level of confidence in the estimated number of caribou (14). Calf recruitment (as percent observed) was slightly higher this year, but continues to be low overall, with 1 of 35, 1 of 32, 0 of 20, and 2 of 13 animals being calves in 2006, 2007, 2008 and 2009 respectively. In general 15% of the population must be calves for stable population growth (Bergerud 1992). Four years of low calf recruitment implies the subpopulation is aging (caribou live to a max of 15 years in this area) and is likely heading for extirpation in the near future. The subpopulation is becoming fragmented; with animals in the north (around Downie Creek) isolated from animals to the south in Mount Revelstoke and Glacier National Parks based on telemetry data (Figure 3). The cause of calf mortality in mountain caribou is largely unknown, but may be linked through a common agent (predation) with adult mortality (Seip 1992, Wittmer et al. 2005). In other woodland caribou populations predation has been identified as the primary cause of neonate mortality (Gustine et al. 2007). Substantial habitat alteration, primarily due to forestry, has resulted in an increase in forage for moose and deer, predator numbers have subsequently increased and presumably resulted in higher predation rates on mountain caribou (Wittmer et al. 2005). A substantial amount of the early winter habitat (including that for animals residing in the national parks) exists on

8 8 BC Provincial crown land and has been substantially altered by harvesting. Outside of the national parks, heli-skiing is active in most of the range of this sub-population and snowmobiling is popular in the Laforme Creek/Sale Mt. and Keystone/Standard creek area. Limited closures to snowmobiling provide minimal protection from disturbance in these areas. Within Mount Revelstoke and Glacier National Parks, ski touring is expanding in popularity and range. A closure was implemented at Mt. Klotz in 2009, in order to minimize disturbance. Increased ski touring activity in caribou winter range should prompt further closures. Recovering this small population will likely require augmentation and/or maternity pens in conjunction with enhanced predator management in order to increase the survival of adults (Seip 1992, Wittmer et al. 2005). In the long term, habitat recovery will be required in order to sustain the population at viable levels without perpetual management of alternate prey and predator populations. Management of human disturbance is also required. Table 1. Total number of caribou observed, estimates from tracks, and percent calves of the subpopulations of Wittmer et al. (2005) overlapping the Columbia Forest District. Includes NOREMARK estimates for populations with sufficient numbers of collared animals, 1994 to Table from Mclellan et al Columbia Observed Calves Number Collars Calculated 90% CL North (+ Tracks) (%) Collared Observed Estimate (209) (193) (204) (152) (136) (131) (142)

9 9 Columbia Observed Calves Number Collars Calculated 90% CL South (+ Tracks) (%) Collared Observed Estimate (117) (94) (93) (34) NA NA (40) NA NA (29) NA NA a (20) NA NA (14) NA NA a 9 animals were missed during the census but observed during telemetry flights Frisby/ Observed Calves Number Collars Calculated 90% CL Queest (+ Tracks) (%) Collared Observed Estimate NA NA NA NA NA NA NA NA NA NA NA NA NA NA Kinbasket Observed (+ Tracks) Calves (%) Number Collared Collars Observed Calculated Estimate 90% CL (25) NA NA (21) NA NA (5) NA NA a NA NA NA (2) NA NA NA NA NA a A small group ( 4 animals) were seen 2 weeks prior but missed during census Monashee Observed (+ Tracks) Calves (%) Number Collared Collars Observed Calculated Estimate 90% CL

10 Downie River Sorcerer Cr e ek N Downie River Sorcerer Cr e ek N Standard Cr. M ountain Cr eek Beaver River Standard Cr. M ountain Cr eek Beaver River Lake Revelstoke Carnes Creek Lake Revelstoke Carnes Creek Fang Cr. Glacier National Park Fang Cr. Glacier National Park Laforme Cr. Mt. Revelstoke NP Woolsey Creek Illiciliwaet River Tangier River Laforme Cr. Mt. Revelstoke NP Woolsey Creek Illiciliwaet River Tangier River 2006 Downie River Standard Cr. Sorcerer Cr e ek M ountain Cr eek Beaver River N 2004 Downie River Standard Cr. Sorcerer Cr e ek M ountain Cr e ek Beaver River N Lake Revelstoke Carnes Creek Lake Revelstoke Carnes Creek Fang Cr. Glacier National Park Fang Cr. Glacier National Park Laforme Cr. Mt. Revelstoke NP Woolsey Creek Illiciliwaet River Tangier River Laforme Cr. Mt. Revelstoke NP Woolsey Creek Illiciliwaet River Tangier River Downie River Standard Cr. Sorcerer Cr e ek M ountain Cr eek Beaver River N Downie River Standard Cr. Sorcerer Cr e ek M ountain Creek Beaver River N Lake Revelstoke Carnes Creek Lake Revelstoke Carnes Creek Fang Glacier National Park Fang Cr. Glacier National Park Cr. Laforme Cr. Mt. Revelstoke NP Woolsey Creek Illiciliwaet River Tangier River Laforme Cr. Mt. Revelstoke NP Woolsey Creek Tangier River Illiciliwaet River Caribou Group Size : Figure 3. Group sizes of caribou observed during census in 1997, 2002, 2004, 2006, 2008 and 2009 in the Columbia South subpopulation.

11 11 Acknowledgements Funding for this census was provided by Parks Canada. Jen Theberge, John Flaa, Kelsey Furk, and Andrew Johns were observers. Thanks to pilots at Arrow Helicopters, Selkirk Mountain Helicopters and Silvertip Aviation. Literature Cited Bergerud, Arthur T Rareness as an antipredator strategy to reduce predation risk for moose and caribou. Pages in D.R. McCullough and R.H. Barrett, (ed). Proceeedings of Wildlife 2001: Populations. Elservier Applied Sciences. London Flaa, J.P., and B.N. McLellan Population characteristics of the Lake Revelstoke caribou. Pages In At Risk: Proceedings of a Conference on the Biology and Management of Species and Habitats at Risk. February 15-19, 1999, Kamloops, British Columbia. Ministry of Environment, Lands and Parks, Victoria, British Columbia, Canada. Gustine, D.D., K.L. Parker, R.J. Lay, M.P. Gillingham, and D.C. Heard Calf survival of woodland caribou in a multi-predator ecosystem. Wildlife Monographs 165:1-32. Hooge, J., B.N. McLellan, and J. Flaa Population ccensuses of caribou in the Columbia Forest District. B.C. Ministry of Forests and Canadian Parks Service, Revelstoke, British Columbia, Canada. McLellan B.N., J. Flaa and J. Woods Mountain caribou censuses in the North Columbia Mountains. B.C. Ministry of Forests and Canadian Parks Service, Revelstoke, British Columbia, Canada. McLellan B.N., R. Serrouya, and J. Flaa Mountain caribou censuses in the North Columbia Mountains. B.C. Ministry of Forests and Canadian Parks Service, Revelstoke, British Columbia, Canada. McLellan B.N., R. Serrouya, K. Furk Mountain caribou censuses in the North Columbia Mountains. B.C. Ministry of Forests. Revelstoke, British Columbia, Canada.

12 12 Seip, D. R Factors limiting woodland caribou populations and their interrelationships with wolves and moose in southeastern British Columbia. Canadian Journal of Zoology 70: Simpson, K., and G. P. Woods Movements and habitats of caribou in the mountains of southern British Columbia. British Columbia Ministry of Environment. Bulletin B-57 Victoria, B.C. Wittmer, H.U., B.N. McLellan, D.R. Seip, J.A. Young, T.A. Kinley, G.S. Watts and D.H. Hamilton. 2005a. Population dynamics of the endangered mountain ecotype of woodland caribou (Rangifer tarandus caribou) in British Columbia, Canada. Canadian Journal of Zoology. 83: Wittmer, H.U., A.R.E. Sinclair, and B.N. McLellan. 2005b. The role of predation in the decline and extirpation of woodland caribou. Oecologia 144: White NOREMARK: population estimation for mark-resighting surveys. Wildlife Society Bulletin 24:50-52.

13 Appendix Table 2. Summary of 2009 census data. Daily summary. Search time Date (Hours ) Area covered Subpopulation Observers 05-Apr Apr Apr Mt Rev, Glacier, Tangier, Mt. Creek Downie, Sorcerer, Keystone Laforme, Carnes, Kelly Columbia South Columbia South Columbia South Kelsey Furk, John Flaa, Jen Theberge Kelsey Furk, John Flaa, Andrew Johns Kelsey Furk, Dave Mair Aircraf t A-star Long Ranger Sighting conditions Total Calves Marks Marks Frequencie available Seen s found scattered cloud, >0c at noon in the pass nil scattered cloud, , 4c at lift nil Cessna 337 part cloud 0 nil Frequencies missed Table 3. Summary of 2009 census data. Location data. SIGHTING ID DATE TIME COUNT? ZONE DATUM EASTING NORTHING HABITAT Block WITTMER05 SUB POP 1 05-Apr-09 10:00 Yes 11 NAD MU 4-38 Columbia South 2 05-Apr-09 10:18 Yes 11 NAD MU 4-38 Columbia South 3 05-Apr-09 12:18 Yes 11 NAD MU 4-38 Columbia South 4 05-Apr-09 13:05 Yes 11 NAD MU 4-37 Columbia South 5 05-Apr-09 13:10 Yes 11 NAD MU 4-37 Columbia South 6 06-Apr-09 12:00 Yes 11 NAD MU 4-38 Columbia South 7 06-Apr-09 12:17 Yes 11 NAD MU 4-38 Columbia South 8 06-Apr-09 12:35 Yes 11 NAD MU 4-38 Columbia South

14 14 SIGHTING ID TOTAL TOTAL W/ TRACKS CALF YEARLIN G UNCLASSIFIE D ADULT MALES ADULT FEMALES ADULT FREQUENCY 1 FREQUENC Y 2 NOTES DRAINAGE very likely tracks from group of three located just to the east, don't count towards total estimate W. Woolsey one may have been a juvenile W. Woolsey Mt. Fidelity Mt. Shaughness cow calf y Mt. Shaughness y Downie, north side Downie, south side Standard one track seen Creek