Moose habitat in the Lower Goldstream Valley, Jan 2007

Transcription

1 Moose habitat in the Lower Goldstream Valley, Jan 2007 Moose population monitoring in the Lake Revelstoke (Management Units 4-38 and 4-39) and North Thompson (MUs 3-43 and 3-44) valleys, January 2006 and 2007 Prepared by: Robert Serrouya 1 and Kim Poole 2 March 30, Columbia Mountains Caribou Project, Box 9158, RPO# 3, 1761 Big Eddy Rd., Revelstoke, BC, V0E 3K0; rserrouya@telus.net 2 Aurora Wildlife Research, 2305 Annable Rd., Nelson, BC, V1L 6K4; kpoole@aurorawildlife.com

2 i Table of Contents PREFACE... 1 SUMMARY... 1 INTRODUCTION... 2 STUDY AREA... 5 METHODS... 5 Sampling strategy...5 Lake Revelstoke Valley...5 North Thompson Valley...7 Data analysis...7 RESULTS... 8 Lake Revelstoke Valley survey: relative abundance survey: population size and density...9 Composition and distribution...11 Estimates by subzone-mu...12 Other species...12 North Thompson Valley...13 Population size and density...13 Composition and distribution...14 Other Species...14 Discussion Lake Revelstoke Valley...16 Changes in composition...18 Potential Biases...18 North Thompson Valley...19 Potential Biases...19 Management Implications Acknowledgements Literature cited... 21

3 1 PREFACE This report presents results of 2 abundance censuses of moose (Alces alces) in adjacent areas the Lake Revelstoke Valley (Management Units [MU] 4-38 and 4-39), and the North Thompson Valley, north of Blue River (MUs 3-43 and 3-44) during In the Lake Revelstoke Valley the 2007 census was a follow-up to a 2003 census (Poole and Serrouya 2003). We also conducted a shortened census in 2006 in the Lake Revelstoke Valley, but it was not completed because of low snow depths. However, the 2006 census will be presented as a measure of relative change. The 2007 census was the first to report absolute moose abundance for MUs 3-43 and 3-44 in the North Thompson Valley, but there was a reconnaissance-level census done in 2005 (Lemke 2005). SUMMARY As recovery options for mountain caribou (Rangifer tarandus caribou) are implemented, managing the predator/prey system will play a key role, at least in the short term. Moose are a key component of the predator/prey system in caribou range, therefore, in January 2007 we conducted absolute abundance moose censuses in the Lake Revelstoke (MUs 4-38 and 4-39) and North Thompson valleys (MUs 3-43 and 3-44). The Lake Revelstoke census was a stratified random block design, whereas in the North Thompson Valley all moose winter range was surveyed because of a smaller study area. In both areas, standard sightability correction factors were applied based on estimates of vegetation cover when a group of moose was observed. In the Lake Revelstoke Valley we estimated a population of 806 (611 1,002, 90% CI) moose, down from 1,650 in 2003 (1,235 2,066), a 51% decline. Mean densities decreased to 0.96/km 2, from 1.58/km 2 in 2003 (study area size decreased in 2007 because of the high snow pack). A relative abundance index survey done in 2006 suggested a decline of 29% from 2003, or a population of approximately 1,172 moose. It appears that the decline accelerated between 2006 and 2007, despite a greatly reduced moose harvest. Collared wolves (Canis lupus) do not seem to have dispersed since 2003 and kill rates remained high, so the per capita predation rate on moose may have increased. Bull:cow ratios in 2007 (85:100 (53 104)) were similar to 2003, as were calf:cow ratios (28:100 (21 36)). No density dependent increase in calf production has occurred despite a much reduced population. There appears to have been a faster rate of decline in MU 4-38, on the east side of the lake, where hunting pressure was higher due to better access. We suggest that rapid declines of moose populations without proportional decrease in predators may increase the predation risk to caribou, until predator numbers decrease. The estimate for the North Thompson study area was 252 ( ) moose with a density of 0.96/km 2, identical to Lake Revelstoke. However, using the same sightability correction model used in Lake Revelstoke (because the Lake Revelstoke analysis was done using a slightly different model to remain consistent with the 2003 estimate), the estimated density was 0.90/km 2. The bull:cow ratio was 128:100 (71 185) and calf:cow ratio was 55:100 (25 85), nearly twice that of Lake Revelstoke. Calf:cow ratios were variable across the census zone, with the northwestern portion of the study area at 77:100. Comparatively few wolf tracks were seen in areas of high calf ratios. Areas closer to Blue River had many more wolf tracks and wolf kills, with calf counts as low as 18:100.

4 2 INTRODUCTION Changing large mammal communities have been implicated in the decline of mountain caribou (Rangifer tarandus caribou), which is an endangered ecotype of woodland caribou (Heard and Vagt 1998). Where their ranges overlap, wolves (Canis lupus) appear to be a main limiting factor of woodland caribou populations (Bergerud and Elliot 1986, Seip 1992, Rettie and Messier 1998, Wittmer et al. 2005). Moose (Alces alces) affect caribou/wolf dynamics because moose are often the wolves primary prey, and changing moose densities can increase predation risk to caribou because wolves are numerically linked to moose (Messier 1995). In the southern distribution of mountain caribou range (approximately south of Downie Creek within the Lake Revelstoke area), cougar (Puma concolor)/deer (Odocoileus spp.) dynamics appear to have a similar influence on caribou as moose/wolf interactions do further to the north (Wittmer et al. 2005). McLellan et al. (2006) hypothesised that it is not only the abundance of alternative ungulates and their predators that affect caribou, but also the rate at which these populations change. This hypothesis was based on the observation that following a record-deep snow year in , deer populations declined rapidly. Based on hunter-harvest indices and problem cougar-kills, it appears that cougars declined 1 2 years after this deer crash. In the meantime, the first ever reported kills of cougars on radiocollared caribou in the Revelstoke study area occurred, while none occurred from in the earlier years of the study. McLellan et al. (2006) suggested that the rapid decline of deer forced cougars to increase searching effort to find prey, and thus encountered and killed caribou with increasing frequency, until the cougar numbers declined. This hypothesis predicts that rapid changes in non-caribou ungulates will affect caribou populations by changes in incidental predation rates. In 2003, the absolute abundance estimate of moose in the Lake Revelstoke Valley was 1,650 (90% CI 1,235 2,066), yielding mean densities of 1.58/km 2, with the Goldstream Valley (the core moose winter range) at 3.54/km 2 (Poole and Serrouya 2003). The Ministry of Environment agreed to reduce this population by 25% from to enhance hunting opportunities. To do so, the number of resident limited entry hunting (LEH; a lottery) and guide-outfitter permits increased more than 7 fold between 2002 and 2004 (Appendix A), with a corresponding 5.5 fold increase in estimated harvest (Fig. 1). The number of permits was reduced in 2006 because a relative abundance census in January 2006 suggested that the population reduction target was likely met. Because of negative implications to caribou of reducing ungulate numbers too quickly without reducing the number of predators, we conducted a second absolute abundance estimate in January 2007 as a follow-up to the 2003 census. We also conducted an absolute abundance census in the North Thompson Valley (MUs 3-43 and 3-44) because of a concurrent caribou and wolf study in that area, which is adjacent to the Lake Revelstoke Valley (Fig. 2). No absolute abundance estimate of 3-43 and 3-44 has been made in the past, although a reconnaissance census was done in 2005 and mainly quantified moose composition (Lemke 2005). Our objectives were to present results of the 2006 and 2007 censuses in the Lake Revelstoke Valley, and compare these results to the 2003 census. We also present reasons for why we think population changes have occurred. Our final objective was to present results of the 2007 census from the North Thompson Valley.

5 3 Bull Cow, calf, or spike bull Bull % CCSB % Est. moose harvest % success Figure 1. Estimated harvest and harvest success rates for moose sex/age classes in Management Units 4-38 and 4-39, Lake Revelstoke Valley, from

6 4 Figure 2. Map of the Lake Revelstoke and North Thompson study areas for moose inventories done in January Black polygons indicate survey boundaries, and grey outlines indicate management unit boundaries (3-43, 3-44, 4-38, and 4-39).

7 5 STUDY AREA The study areas are located in the northern Columbia Mountains (51 o N, 118 o W; Fig. 2), centred on 2 major drainages and associated tributaries: the North Thompson River and the Lake Revelstoke Valley, which is a portion of the Columbia River. The Lake Revelstoke Valley study area is km 2, and the North Thompson study area is km 2 (Fig. 2). From west to east, major landscape features are the Cariboo Mountains, the North Thompson River, the Monashee Mountains, the Revelstoke Reservoir, and the Selkirk Mountains. The area is steep and rugged with elevations ranging from 610 m to >3,000 m, and is also wet with most precipitation falling as snow. The maximum annual snowpack at 2,000 m elevation averaged 350 ± 63 cm (1 SD) between (Glacier National Park, unpublished data). The lower slopes (<1,400 m) of the study areas are in the wet cool and very wet cool Interior- Cedar-Hemlock (ICHwk and ICHvk, respectively) biogeoclimatic subzone (Meidinger and Pojar 1991), and are dominated by climax stands of western hemlock and western redcedar. Stands of Douglas-fir (Pseudotsuga menziesii), western white pine (Pinus moniticola), and white birch (Betula papyrifera) are present on drier sites in the ICH, but less common in the ICHvk. Mid and upper slopes (1,400 1,900 m) are in the very wet cold Engelmann Spruce-Subalpine Fir subzone (ESSFvc) and the wet cold subzone (ESSFwc). These forests are usually dominated by Engelmann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa) but mountain hemlock (Tsuga mertensiana) is common in some stands (Coupé et al. 1991). Interspersed throughout both the ICH and ESSF are <30-year-old regenerating clearcut forests. Due to high snowfall and steep terrain, avalanche paths are common at all but the lowest elevations. Snow depths differed significantly among the study years. In 2003 in the Lake Revelstoke Valley, snow accumulation was 326 mm (snow water equivalent; SWE) on February 1 at 980 m elevation, 504 mm in 2006, and 672 mm in 2007, whereas the average is 509 mm. In the North Thompson Valley, the SWE at 670 m elevation is 250 mm on average, but was 380 mm in 2007 (River Forecast Centre 2007). METHODS Sampling strategy Our censuses were based on dividing each study area into sample units (SUs) and conducting an aerial survey from a helicopter. The selection of SUs to survey differed somewhat among study areas and year of survey. Details are below. Lake Revelstoke Valley 2006 In 2003 all SUs were categorized as expected high, medium and low moose densities. Of the 53 SUs in 2003, 21 units were surveyed (all 9 high SUs, 7 of 18 mediums, and 5 of 26 lows; Poole and Serrouya 2003). In 2006 it was apparent that snow coverage was complete only in the northern two-thirds of the study area. No stratification flight was conducted in 2006 because we assumed moose distribution was similar to 2003, so we retained the same SU boundaries and moose density stratification as None of the 25 moose we radio-collared north of Downie Creek in 2004 or 2005 moved south of Downie Creek by the time of the 2006 census (R. Serrouya, unpublished data), suggesting no broad-scale shift in distribution. In 2006 we flew 5 SUs in areas of complete snow coverage: 3 high SUs in the Goldstream Valley and 2 medium SUs, 1 in Pat Creek and 1 in upper Downie Creek. These SUs were flown as an index of change relative to We present comparisons of raw moose counts to the same 5 SUs we flew in 2003, and moose numbers corrected for sightability. See below (2007) for details on how the SUs

8 6 were surveyed (i.e., helicopter speed, transect width, sexing and ageing of animals), and how sightability correction was applied Similar to 2003, we followed a stratified-random block design, using procedures modified from Gasaway et al. (1986), Timmermann (1993), Timmermann and Buss (1997), and Resource Information Standards Committee (RISC 2002). To stratify the survey we used information on moose distribution from surveys conducted in 2003 (Poole and Serrouya 2003) and 2006, and from stratification flights conducted in We initially retained the study area and sample units (SUs) as used in 2003 to include all potential moose winter range within each MU. This included both sides of the Columbia River and Lake Revelstoke, from Revelstoke north to Kinbasket Lake (to Potlatch Creek on the east side, and Encampment Creek on the west side), including the Jordan River northwest of Revelstoke, and the Illecillewaet and Tangier rivers northeast of town (the latter of particular interest to Parks Canada). Snow depths in 2007 were considerably deeper than encountered in 2003 and moose distribution within and among SUs appeared to differ between years. Therefore, we conducted stratification flights to reclassify SUs into expected high, medium, and low strata. We used a Cessna 337 fixed-wing aircraft, with a pilot, a navigator and 2 backseat observers. All persons participated in locating animals and tracks. Flight speed was km/h at an altitude of m above ground level. We recorded moose (not classified) and moose tracks (recorded as Few, Some, Many for relative numbers). Flight path and sightings were recorded on a global positioning system (GPS). Our stratification flight pattern generally meandered among our areas of interest (Gasaway et al. 1986), with a focus on determining relative distribution of moose sign, and determining how high in elevation moose were present. Based on the stratification flights, we removed 4 SUs as non-moose winter range, and dropped the upper elevation boundary for all other SUs to 1,000 m elevation, except 2 SUs in the upper Goldstream Valley, where we used a 1,100 m boundary. The resulting study area was 838 km 2, down from 1,044 km 2 in We selected all high SUs and a minimum of 5 randomly selected medium and low SUs for initial survey. Additional SUs were surveyed to reduce the variance of the estimate. We used a Bell 206B Jet Ranger helicopter equipped with bubble windows during the census, with a pilot and 3 observers. The same navigator/observer was present for all but one day, and the primary rear-seat observer also was present for all but one day. All occupants participated in locating animals. Each selected SU was surveyed at km/h airspeed at m above ground. We searched each SU along m wide transects, usually flown along parallel lines back and forth across the SU or contouring steeper terrain. We occasionally flew above the upper elevation boundary of study area to check if moose resided outside the SUs. We used a real-time GPS geographic information system (GIS) interface to track our flight path within each SU and ensure complete and accurate coverage. We used the DNR Garmin extension for ArcView (Version 5.1.1; T. Loesch, Minnesota Dept. of Natural Resources; to provide locations from a Garmin 76 GPS (Garmin Industries, Olathe, Kansas, USA) to an ArcView (Environmental Systems Research Institute, Redlands California, USA) coverage run on a laptop computer. Moose locations and flight path were recorded on the GPS, which were then uploaded to the ArcView coverage. We also recorded locations of wolf and wolf tracks, and sightings of wolverine (Gulo gulo) and other ungulates. We circled all moose groups to determine sex and age of each animal (Timmermann and Buss 1997) and determine if the group was within the SU along boundaries. Smaller body size and a shorter face identified calves. Cows were identified by the presence of a white vulva patch and by even, light colour of the face, and the absence of pedicel scars. Bulls were separated into teens, sub-prime, prime (Classes 1 to 3, respectively; RISC 2002) or antlerless. Some adult animals could not be approached closely to be classified, and were designated as unknown adults. Perhaps because of the deep snow, many moose were reluctant to get up out of their beds, or had snow on their rear ends or kicked up snow when

9 7 running, making it difficult to determine the presence of a vulva patch. Therefore, we were forced to use the facial colour to sex a large proportion (~35%) of the adults. For each moose group (1 or more animals) observed we estimated oblique cover as percent vegetative cover (perhaps best described as screening cover) around the first animal seen in the group. Vegetative cover was estimated to the nearest 10% starting at 5% (e.g., to 5%, 15%, 25%, etc.) measured obliquely within a 9 10 m radius around each group of moose (Anderson and Lindzey 1996, Unsworth et al. 1998, Quayle et al. 2001). We regularly discussed and standardized our estimates of vegetative cover. North Thompson Valley The North Thompson survey followed the same design as the 2007 Lake Revelstoke survey, with the following changes: Information on moose winter distribution was obtained from Kevin Van Damme, Conservation Officer, Clearwater, BC. A stratification flight was conducted using a Cessna 336 to determine relative moose distribution. Twelve SUs were delineated and rated into 2 strata (high and low). Because of the relative small study area size (262 km 2 ) and number of SUs in each stratum, we conducted a complete census by counting all SUs, and then applied the sightability correction to each moose group (Quayle et al. 2001). Data analysis For the Lake Revelstoke Valley area, we determined the population estimate using program MOOSEPOP (Version 2.0; R.A. DeLong and D.J. Reed, Alaska Department of Fish and Game, Fairbanks, Alaska, USA) with sightability correction applied to each stratum calculated using program AERIAL SURVEY (Unsworth et al. 1998). MOOSEPOP was not used for the North Thompson census because all SUs were surveyed. The optimization option in MOOSEPOP was also used to help decide whether additional medium or low-density SUs should be surveyed to reduce survey variance for the Lake Revelstoke Valley survey. Detection probabilities as applied in AERIAL SURVEY were determined using sightability data from a BC model (Table 1; Quayle et al. 2001). A model updated with data compiled from an additional 20 sightability trials conducted in Prince George in 2001 (J. Quayle, Ministry of Environment (MoE), unpublished data) was not used for this analysis to enable more relevant comparison with the 2003 survey 3. In the BC model, 5 cover classes were used, separated at the 20%, 40%, etc. boundaries of percent vegetation cover. We calculated the population estimate using a spreadsheet program developed by MoE staff (HEARDPOP; J. Quayle, MoE, unpublished data), where the estimate variance was calculated as a sum of the sampling, sightability and model variances between the 2 programs. The high stratum degrees of freedom (df) were adjusted to n 1 moose counted, since it was a count, not a sample of moose in that stratum, and the total df were adjusted to the sum of the strata (D. Heard, MoE, personal communication). We also plotted a histogram of proportional moose locations by elevation class, stratified by study area. Finally, all data were entered into Wildlife Species Inventory (WSI; the BC provincial wildlife database. 3 In 2003 in the Lake Revelstoke census, we used the Kamloops only sightability correction model (i.e. we did not include the Prince George data, which was not available at that time), so in 2006 and 2007 we used the same model to make estimates comparable. In the North Thompson area, we used the combined Kamloops and Prince George model (because this updated model may be more robust), but also present the North Thompson data with the Kamloops only sightability, to enable more direct comparisons with the Lake Revelstoke Valley survey.

10 8 Table 1. Vegetation cover classes and their associated detection probability and sightability correction factors (program AERIAL SURVEY, Unsworth et al. 1998, as modified using Quayle et al. 2001). Kamloops is as published in Quayle et al. 2001; Kamloops and PG is with data from Prince George sightability trials, 2001 [J. Quayle, MoE, unpublished data]). Kamloops Kamloops and PG Vegetation Class Percent vegetation cover Detection probability Sightability correction factor Detection probability Sightability correction factor Class Class Class Class Class RESULTS Lake Revelstoke Valley 2006 survey: relative abundance The 5 SUs we sampled had complete snow coverage. Weather conditions were good, with 3 to 4 C temperatures, generally high overcast skies, and light winds. The flights occurred on January We flew 12.6 helicopter hours, and during 9.8 hours on survey we counted 205 moose (Table 2). The average sightability correction factor was 1.395, and we surveyed at an effort of 4.5 minutes/km 2, compared to 4.2 minutes/km 2 for the same SUs in Moose numbers in all SUs declined except the only SU we sampled on the west side of Lake Revelstoke, which increased by a factor of 1.72, once corrected for sightability. Table 2. Number of moose counted and estimated in 5 sampling units (SU) in 2003 and 2006 in the Lake Revelstoke Valley. Raw counts Corrected for Sightability SU No. Strata Area % of % of M Pat Ck S % % 53 H Goldstream Upper % % 63 M Downie Upper % % 49 H Goldstream Front N % % 58 H Goldstream Mid % % Total (mean) (69%) (71%)

11 survey: population size and density In 2007, weather conditions during the stratification and survey flights were generally good with mostly high overcast or clear skies and light winds, although moderate winds were encountered during one day of the helicopter survey. Temperatures ranged from 20 to 5 C. Snow cover was complete and comparatively deep. The stratification flights occurred January During 4.6 hours we counted 73 moose and recorded 235 groupings of tracks. Final SUs averaged 17.1 km 2 in size (±0.89 [SE]; range km 2, n = 49). The helicopter survey was conducted 8 17 January. We surveyed all 7 high-density SUs, 9 of 16 medium-density SUs, and 5 of 26 low-density SUs. Two low-density SUs were flown prior to the stratification flights to match SUs flown in 2003, and were therefore not randomly selected in 2007, but were randomly selected in 2003, thus no practical bias occurred. We flew 37.7 hours, and spent 26.3 hours on survey; average survey intensity was 4.0 minute/km 2 (±0.18; range min/km 2 ). We counted 356 moose in 235 groups (Table 3). Group size ranged from 1 to 5 moose. We calculated a naïve (uncorrected for sightability) estimate of 508 moose (Table 3). When the sightability correction was applied, our estimate was 806 moose (±196 moose or 24.3% [90% confidence interval]; 611 1,002 moose; CV = 0.15)(Table 5). The overall sightability correction factor was 1.58, with far higher correction for the low stratum compared with the medium and high strata (Table 3). Density corrected for sightability averaged 0.96 moose/km 2 within the census zone (Table 3, Fig. 3). Three radio-collared moose were within SUs surveyed (R. Serrouya, unpublished data). The collars were not readily visible from the helicopter, but after the SU was completed using telemetry equipment and GPS locations of sighted moose we verified that we had located 2 of the 3 animals during surveys. Table 3. Moose population estimate statistics for Lake Revelstoke Valley, Columbia Mountains, January Parameter Stratum 1 (low) Stratum 2 (medium) Stratum 3 (high) No. of SU in stratum Total No. of SU surveyed Total stratum area (km 2 ) Area of surveyed SUs (km 2 ) Moose observed Uncorrected (naïve) estimate Sightability correction factor Corrected population estimate Standard error Coefficient of variation Corrected density (moose/km 2 )

12 10 Figure 3. Lake Revelstoke Valley moose inventory study area, 8 17 January The polygons on the map show the location of the sample units (SUs), shaded to stratification density (low, medium, high). Average density for the whole study area was 0.96/km 2. As an index of population decline we compared the number of moose observed per hour on survey (uncorrected for sightability) from 2003 (21.3 moose/hr) and 2007 (13.6 moose/hr) and found a 36% reduction. The comparatively smaller study area in 2007 likely resulted in a more concentrated population, and thus the observation rate would likely be biased high and the index of reduction between years greater than 36%.

13 11 Composition and distribution The bull:cow ratio in the study area was approximately 73 85:100, and the calf:cow ratio was 26 28:100 (Table 4). Calculated bull and calf ratios differed between models because of the average higher vegetation cover observed near bulls and the higher cover near calves compared with cows, the assumption in AERIAL SURVEY of equal SU size, and subtle differences between models in accounting for un-surveyed areas; the sightability corrected ratios should generally be more accurate. Average sightability correction was higher for bulls (1.57) than calves (1.47) and cows (1.35). Of the 107 bull moose observed, only 2 had antlers (one Class 1 bull and one Class 3 bull), and the rest were antlerless. Assuming unclassified moose (all adults) were found in the same ratio of cows to bulls as for classified animals, we estimated approximately 325 bulls for the study area. Two sets of cows with twin calves and one lone calf were observed. Using observed animals only, MU 4-39 (west side; n = 187) had a higher calf ratio (30 versus 23 calves:100 cows) and higher bull ratio (64 versus 53 bulls:100 cows) than MU 4-38 (east side; n = 169). Moose were distributed throughout a 560 m elevation band from 450 1,010 m (Fig. 4). Only one animal was located above 1,000 m elevation. Table 4. Observed and estimated (corrected for sampling and sightability) sex and age classification and ratios for moose for Lake Revelstoke Valley area, January The observed ratios were corrected for sampling using MOOSEPOP. The estimated ratios were corrected for sightability using AERIAL SURVEY. Because AERIAL SURVEY assumes equal SU size, the numbers of each sex and age category were corrected to result in a total of 806 animals. Numbers in brackets are 90% CI. Unclass. Bulls:100 Calves:100 Cows Bulls Calves adults Total cows cows Observed (55 91) 26 (22 30) Estimated ( ) 85 (47 123) 28 (21 36) Lake Revelstoke North Thompson Proportion of moose (%) Elevation (m) Figure 4. Approximate elevation distribution of moose observed during the survey of the Lake Revelstoke (MUs 4-38 and 4-39) and North Thompson valleys (MUs 3-43 and 3-44), January 2007.

14 12 Estimates by subzone-mu Management units 4-38 and 4-39 are each subdivided into 3 subzones (D, E and F; Fig. 3), and based on the area and expected moose density by SU we estimated the number of moose in each subzone (Table 5). These numbers should be treated cautiously because as the samples are divided, the estimates within each smaller unit are less reliable. Table 5. Estimates of total moose and bulls by LEH subzone and management unit, Lake Revelstoke Valley, January Subzone/MU Estimated total Estimated bulls 4-38D E F total D E F total Total Other species Six wolves were observed during the helicopter portion of the survey (2 in the back of the Jordan River drainage, 2 on the west side of the reservoir opposite Downie Creek, 1 on the west side opposite the Goldstream River, and 1 in the lower Goldstream; Fig. 3). Two wolves were observed during the stratification flight on the west side about 10 km north of Revelstoke; these appeared to be the same pair seen 3 days earlier in the upper Jordan. Sixteen sets of fresh wolf tracks were recorded during the helicopter survey (1 in Nagle Creek, 1 south of Pat Creek, 2 north of Bigmouth Creek, 2 in Hoskins Creek, 4 in the lower Goldstream and 1 in the upper Goldstream, 1 near Kirbyville Creek, 2 in the mid- Downie, and 2 sets north of Revelstoke on the west side; Fig. 3), and 3 sets were observed during the stratification flight. One wolverine (Gulo gulo) was observed in the lower Goldstream. Two sets of cougar tracks were observed in the Nagle Creek area. Four coyotes (Canis latrans), 6 unknown deer, 6 mule deer (O. hemionus), 2 white-tailed deer (O. virginianus), and 1 elk (Cervus elephus) were also observed. Similar to 2003, we spent additional time surveying the Illecillewaet and Tangier drainages northeast of Revelstoke. This reconnaissance was requested by Parks Canada in We observed 5 moose (2 within SU 28 which was surveyed completely), and from our coverage and observed tracks suggest that roughly moose may inhabit these drainages, with a concentration in the Tangiers and a few scattered animals along the valley bottom of the Illecillewaet River.

15 13 North Thompson Valley Population size and density Weather conditions during the stratification and survey flights were generally good with high overcast or clear skies. Temperatures ranged from 14 to 5 C and snow cover was complete. The stratification flight occurred on 17 January During 1.9 hours we counted 21 moose and recorded 165 sets or groupings of tracks. Based on this flight we delineated the census zone and developed 12 SUs, which averaged 21.8 km 2 in size (± [SE]; range km 2 ). The helicopter survey was conducted January, the delay a result of a lengthy period of poor flying conditions. We surveyed the entire census zone. We flew 14.2 hours, and spent 12.8 hours on survey; average survey intensity was 3.0 minute/km 2 (±0.13; range min/km 2 ). We counted 141 moose in 82 groups (Table 6), and group size ranged from 1 to 9 moose. Moose were distributed higher in elevation compared to Revelstoke (Fig. 4), and all moose but 1 were below 1,250 m elevation. When the sightability correction was applied (including the Prince George data in the sightability model), our estimate was 252 moose (±115 moose or 46% [90% confidence interval]; moose; CV = 0.28)(Table 6). The overall sightability correction factor was Corrected density averaged 0.96 moose/km 2 within the survey area. To enable comparisons with the Revelstoke moose densities, we also ran the analysis using the sightability correction model without the Prince George data. This method resulted in an estimate of 237 moose and a density of 0.90/km 2. Table 6. Moose population estimate statistics for North Thompson Valley (Management Units 3-43 and 3-44), January Parameter Total No. of SU in stratum 12 No. of SU surveyed 12 Total stratum area (km 2 ) Area of surveyed SUs (km 2 ) Moose observed 141 Uncorrected (naïve) estimate 141 Sightability correction factor 1.79 Corrected population estimate 252 Standard error 41 Coefficient of variation 0.28 Corrected density (moose/km 2 ) 0.96

16 14 Composition and distribution The observed bull:cow ratio in the study area was 102:100, and the calf:cow ratio was 50:100 (Table 7). Average sightability correction was higher for bulls (1.85) than calves (1.63) and cows (1.48). Average sightability correction of unclassified moose was 3.52, as they were generally found in dense vegetation. Two sets of a cow with twin calves were observed, both in the Upper Thompson Valley. One group of 2 calves together with no adult cow in attendance was observed in the main valley just north of the town of Blue River. Of the 53 bull moose observed, only 1 had antlers (Class 1 bull). Assuming unclassified moose (all adults) were found in the same ratio of cows to bulls as for classified animals (using corrected ratios), we estimated approximately 118 bulls for the study area. When moose numbers were split by MU, we estimated 50 moose for MU 3-43, and 202 moose for MU 3-44 (Table 7). These estimates were based on applying sightability correction to each individual animal and to which MU they occurred in. Although sample sizes were unbalanced (~50 moose in MU 3-43 and ~200 moose in MU 3-44), differences were apparent between MUs. The bull ratio was slightly higher and the calf ratio greatly higher in MU 3-44 compared with MU Accounting for unknown adult animals, we estimated approximately 23 bulls for MU 3-43 and 95 bulls for MU Table 7. Observed and estimated (corrected for sightability) sex and age classification and ratios for moose in the North Thompson area, Thompson region, January The estimated ratios were corrected for sightability using AERIAL SURVEY. Numbers in brackets are 90% CIs. Total area Cows Bulls Calves Unclass. Adults Total Bulls:100 cows Calves:100 cows Observed Estimated ( ) 128 (71 185) 55 (25 85) MU 3-43 Observed Estimated MU 3-44 Observed Estimated Other Species During the stratification flight we saw a pack of 12 wolves bedded north of Bone Creek. We also observed 3 white-tailed deer; 2 were in separate groups 3 km southwest of Blue River, and 1 was located where the North Thompson River heads sharply west from its north-south orientation. One wolverine was seen north of the junction of the North Thompson River and Manteau Creek. We recorded 15 sets of wolf tracks within the survey unit boundaries, with the heaviest concentration in Mud Creek and in the middle of the study area (Fig. 5). We saw 1 wolf 5 km west of the town of Blue River.

17 15 Figure 5. North Thompson Valley study area showing sample unit (SU) boundaries (black lines) and numbers (dark red), moose group size, wolf tracks and wolf sightings seen during the moose census. These locations include only sightings from the survey, not the stratification flight, except the wolf sighting north of Bone Creek (12 animals).

18 16 DISCUSSION Lake Revelstoke Valley The moose population in the Lake Revelstoke Valley appears to have declined by more than 50% between 2003 and 2007, and the 90% confidence limits between the 2 censuses do not overlap (Fig. 6). We are confident in the degree of change. Survey effort was almost identical between years (4.1 versus 4.0 min/km 2 for 2003 and 2007, respectively), suggesting no bias resulting from effort or its affects on sightability (Gasaway et al. 1986). The rate of moose sightings per hour of survey (uncorrected for sightability) suggests at least a 36% reduction, with likely greater reduction if the smaller study area is factored in. Taken together, these results suggest a real ~40 50% drop in the population over the 4 years. Other independent indices corroborate the moose population decline. Moose pellet transects sampled annually (see Poole and Serrouya 2003 for details) indicate that 63% of pellets were deposited in spring 2006 compared to spring 2003 (R. Serrouya, unpublished data). Sampling in June 2007 will confirm whether the decline has continued and matches our 2007 winter census. Also, by monitoring 30 radio-collared adult moose (60% females) across 33 moose-years from 2003 to 2006 we recorded 7 mortalities (R. Serrouya, unpublished data), which roughly equates to an annual adult survival rate of This survival rate, along with the observed calf ratios, is suggestive of a declining ungulate population (Hatter and Bergerud 1991, Bergerud 1992) Population estimate Harvest rate (%) 0 Jan 2003 Jan 2004 Jan 2005 Jan 2006 Jan Figure 6. Population estimates (solid circles) for January of 3 winters in MUs 4-38 and 39, and harvest rates (squares; harvest rates actually apply to the previous fall, e.g. fall 2002, fall 2003 fall 2006, calculated as no. harvested in fall/population estimate the following January). January 2006 population estimate was an abbreviated census, an index of relative change. Harvest rates for fall 2003 and 2004 were based on interpolations of the population estimate (open circles) for January 2004 and Error bars are 90% CIs.

19 17 Based on our censuses, the decline in moose population size yields an average annual finite rate of increase (λ) of 0.84 for the period. This rate is in sharp contrast to λ of 1.08 we estimated between 1994 and 2003 (Poole and Serrouya 2003). Using the 2006 census as an index of change, λ would have been 0.89 between 2003 and 2006, then decreased to 0.69 the following year. Even if the 2006 census is ignored, the moose population has declined by more than what can be accounted for by hunting during the period. Hunters killed approximately 600 moose during the fall hunting seasons (Appendix A), but the population declined by 844 animals over the same period. The difference of 244 moose is a very conservative estimate of non-hunting deaths, because it ignores annual recruitment 4. There are 3 non-mutually exclusive reasons why the moose declined by more than what can be accounted for by hunting: 1) As with most predator-prey relationships, wolf numbers are linked to moose numbers (Fuller 1989, Messier 1995) and thus in the Lake Revelstoke Valley, wolf numbers likely responded to increasing moose numbers up to However, wolves may not have declined in response to declining moose numbers, because their search time for prey would be relatively short because moose densities are still above the threshold where search time is predicted to increase (~0.7 moose/km 2 ; see Messier 1995: Fig. 7a). It is thus probable that the same number of wolves would kill the same number of moose but out of a smaller moose population, thereby increasing the per capita predation rate on moose (Messier 1995). 2) The deep snow year of 2007 may have facilitated predation by wolves. Huggard (1993) found that kill rates by wolves on elk increased substantially with increasing snow depth. 3) Starvation or other density independent factors associated with the deep snow year of The second and third factors are less likely to be significant because the census was conducted in mid-january and therefore there was only 6 weeks of deep snow. There is greater reason to support the first factor. When wolves are killing moose at a certain rate at high moose density, the same number of wolves would kill the same absolute number of moose at a lower moose density, because the kill rate would not yet move off the upper asymptote of the predator/prey functional curve. Wolves would still have a relatively short search time because moose densities are still above a threshold (approximately 0.7/km 2, based on Messier s (1995) meta analysis) and the handling time would be unchanged. Because wolves would still be satiated, there would be no mechanism to prompt wolves to disperse or reduce production. Several empirical lines of evidence support the first factor: 1a) Of the 7 radio-collared moose deaths, 3 were due to wolves, 1 due to an unknown predator, and 3 due to hunters. Thus, based on this admittedly small sample, at least as many moose were predated upon as hunted. 1b) Calf:cow ratios were unchanged from 2003, despite a much reduced moose population. Thus, the anticipated density-dependent increase in recruitment did not occur (Messier et al. 2004). It is possible that this result was due to 6 weeks of deep snow causing starvation of calves, but it is more probable that this result was caused by predation, rather than food limitation. 1c) Within the Goldstream Valley, Stotyn et al. (2005) found that the wolf kill rate was 2.9 moose killed/wolf/100 d in 2003 at a moose density of 3.54/km 2, which places the kill rate almost exactly on the asymptote of Messier s curve (Fig. 7a; Messier s predicted kill rate would be 2.97 at a density of 3.54/km 2 ; Messier 1995). According to Messier s analysis, moose would have to be reduced to at least 0.7/km 2 before wolves would substantially increase their search rate. This increase in search rate is likely the mechanism that would cause a declining wolf numerical response. Until that threshold is reached, the 4 During the period, we estimate that >2,200 calves would have been born, based on bull:cow ratios reported here and in Poole and Serrouya (2003), pregnancy rates of ~90% (24 moose-years of data, Serrouya unpublished data), and the population estimate from 2003 (1,650) with an annual λ of 0.84.

20 18 per capita predation rate on moose by wolves would increase (Messier 1995: Fig. 7c). Using GPS collars, we are gathering wolf kill-rate information for the current ( ) winter. If the kill rate is still at a high level (i.e. on the asymptote reported by Messier 1995, and similar to what was reported by Stotyn et al. 2005), then the per capita kill rate on moose will continue to increase until moose are reduced to very low numbers and are able to escape this potential predator pit. Such a rapid decline in moose numbers is suggestive of an unstable system that may have negative consequences for caribou. When an atypical weather even such as a severe winter impacts a population it is often called density-independent, meaning that the effects of the severe winter would impact a certain percentage of the population, regardless of population size. If the population is large, a greater absolute number of animals are killed than if the population were smaller. It is possible that reducing moose through hunting from lessened the impact of the 2007 severe winter by reducing the absolute number of moose killed over 1 winter. Changes in composition Overall, calf:cow ratios were unchanged from 2003 (28 calves:100 cows [90% CI 21 36] in 2007 compared to 24:100 [17 32] in 2003), but appear to be higher on the west side of Lake Revelstoke (MU 4-39). If wolves had responded numerically to lower moose numbers, then calf ratios should have increased in a density-dependent manner. The bull:cow ratio was unchanged from 2003, and was still relatively high (>85 bulls:100 cows). In 2003 the high bull ratio was indicative of a lightly hunted population, but recently the high bull ratio likely was maintained because cows were also heavily harvested (Fig. 1). The higher harvest success rate and greater number of hunter kills on the east side of Lake Revelstoke appears to have reduced moose at a greater rate than on the west side of the lake. Although the SU stratifications were re-done in 2007, we note that high and medium density SUs had 38% and 21% higher densities (uncorrected for sightability), respectively, on the west side compared to the east side. These comparisons are notable and of interest, but cannot readily be translated into differing density estimates between MUs (Table 5) because it would violate variance assumptions (i.e., the survey was conducted on the study area as a whole, not on independent MUs). Another possibility for differences in moose rates of change on either side of the lake is that moose may have swam from the east to the west side, perhaps due to greater hunting pressure on the east side or local difference in snow depth. However, based on 33 moose-years of telemetry data (30 different moose collared from 2003 to 2007), no crossings occurred from east to west (although 3 moose crossed from west to east, but 2 of those returned to the west side). Potential Biases The model used to correct for sightability was developed primarily in south-central British Columbia northwest of Kamloops (Quayle et al. 2001), with additional data available from the Prince George area (J. Quayle, unpublished data). The model has been widely applied throughout the Kootenays, the Southern Interior, the Prince George area, and in portions of the rest of the province. Addition of the Prince George data to model development resulted in subtle changes to detection probabilities (higher detection probabilities at the lower vegetation cover classes and lower probabilities at the higher classes; Table 1). A limited number of trials (~17%) to develop the model were conducted in heavier vegetation cover (>60%), thus the model has greater uncertainty correcting for moose in heavier cover. Differences in snow depth among years and areas may influence moose use of cover, but the model should account for these differences, acknowledging that correction factors in heavier cover are more prone to error.

21 19 North Thompson Valley Although absolute moose numbers in the North Thompson Valley study area were less than one third those found in Lake Revelstoke, densities were similar between the 2 areas. Using the Kamloops only sightability model, the estimated density was 0.90/km 2 and 0.96/km 2 for North Thompson and Lake Revelstoke, respectively. However, the North Thompson had significantly higher calf:cow ratios relative to Revelstoke, thus the actual adult density was slightly higher in the Lake Revelstoke Valley (North Thompson Valley adults: 197/262.1 km 2 = 0.75/km 2 ; Lake Revelstoke Valley adults: 710/837.7 km 2 = 0.85/km 2 ). Our census estimate for the North Thompson was lower than the existing MoE estimate of 400 moose (150 for 3-43 and 250 for 3-44), but the existing estimate was based on information such as hunter harvest data and a reconnaissance survey (Lemke 2005). In 1995 the estimate was 260 moose (100 for 3-43 and 160 for 3-44; D. Jury, MoE, pers. comm.). The ecosystems within the 2 study areas are similar in terms of temperature and precipitation but have different histories of moose harvest. The moose population in the Lake Revelstoke Valley had a light harvest policy (Fig. 6) during a period of rapid population growth that resulted in the apparent doubling of the population between 1994 and 2003 (Poole and Serrouya 2003). Subsequently, harvest was increased for 3 years, then reduced again in 2006 (Figs. 1, 6). The North Thompson moose harvest was much more stable (Appendix B). Furthermore, the North Thompson moose are subject to a major highway (Hwy. 5) and railway, which may result in more collision-mortalities compared to the Lake Revelstoke Valley. In fact we saw 4 fresh rail kills during 3 days of moose census in the North Thompson Valley. This mortality source is a density-independent factor that may be accentuated during a deep snow year like In contrast, in the core of the Lake Revelstoke Valley, there is 1 low-volume dead-end highway on the east side of the lake, with limited or no road access on the west side. Thus, it is likely that the North Thompson Valley population has been kept below its forage biomass carrying capacity. Lemke (2005) reached a similar conclusion during their 2005 classification counts. Mean calf ratios were almost twice as high in the North Thompson compared to Lake Revelstoke, but there was substantial variation among areas within the North Thompson study area. The northern SUs (7 12) had calf ratios of 78:100 (n=16 cows), the middle SUs (1, 2, 4 6) had 21:100 (23 cows), and the SU furthest to the south (3) had 54:100 (11 cows). These ratios appeared roughly correlated to observed wolf sign, with 4, 10, and 1 group of tracks seen in these respective zones. Lemke (2005) also noted higher calf ratios in northern portion of MUs 3-43 and 3-44 (54:100), and lowest calf ratios in Mud Creek (15:100) in the south where wolf sign was heaviest. Three wolf-killed moose were also seen in the middle zone, along with a pack of 12 wolves during the stratification flight. Overall, the high calf ratios further support the notion that the North Thompson population is below carrying capacity, with the potential to increase rapidly if limiting factors such as predation, hunting, and rail kills are reduced. Potential Biases The survey effort in the North Thompson Valley was 3.0 minutes/km 2, compared to 4.0 minutes/km 2 for the Lake Revelstoke Valley census. However, 2 factors contributed to the faster survey intensity in the North Thompson Valley. Firstly, proportionately twice as many moose had calves in the North Thompson compared with Lake Revelstoke, which decreased the amount of circling needed in the helicopter to identify the sex of the adult moose. Secondly, the North Thompson Valley has many open flatland areas, particularly around Mud Creek and along the North Thompson Valley bottom. We could survey greater distances from the helicopter, and thus could increase flying speed and transect width. The 2007 deep snow year may have caused moose to move to the south of the study area where snow depths were considerably less. We conducted a valley-bottom reconnaissance flight for 20 km south of the study area and found no evidence that large numbers of moose occurred just outside the study area. We saw scattered moose and sign, at similar or lower densities to what we observed within the