Okanagan Mountain Park Bighorn Transplant Monitoring

Prepared by: Aaron Reid Ministry of Forests, Lands and Natural Resource Operations Fish and Wildlife Section Penticton, BC July 2012

Funding provided by the Habitat Conservation Trust Foundation

Executive Summary The south Okanagan California bighorn meta-population suffered a significant pneumonia related die-off in 1999, losing 70% of the population . One recommendation from the Recovery Plan, developed as a response to the die-off, was to re-introduce bighorns to suitable areas within their historic range.

California bighorn were transplanted into the Okanagan Mountain Park following habitat improvement from the wildfire of 2003. In 2007, 34 bighorns were transplanted from Keremeos and in January, 2009, an additional 15 bighorn from Kamloops were released into the park to augment the original transplant.

Since 2010, sightability models were used to correct bighorn survey observations for incomplete sightability in the program Aerial Survey. The model precision ranged from 24% to 44% of the estimate. The best precision (i.e. 24%) was from the November 2011 survey where the model estimated a population of 95 bighorn (CI 72-118).

In November 2011 we observed a total of 67 bighorn during the flight. The estimated population was 95 (CI 90% 72-118). The total sightability correction factor (SCF) was 1.42 or 70% for the survey. Observed and estimated lamb: ewe ratios were 30 and 31 (CI: 18-44), respectively, and the observed and estimated ram: ewe ratios were 64 and 71 (CI: 45-97), respectively.

We observed a total of 74 bighorn during the March 2012 survey. The estimated population was 115 (CI 90% 74-156). The total SCF was 1.55 or 65% for the survey. Observed and estimated lamb: ewe ratios were 24 and 24 (CI: 13-39), respectively and the observed and estimated ram: ewe ratios were 56 and 48 (CI: 21-75), respectively.

Over the first two winters post-transplant (2007/08 and 2008/09) we documented low lamb recruitment in the newly transplant herd. Overwinter lamb ratios were < 10 lambs: 100 ewes. After the winter 2009/2010 augmentation we observed lamb ratios > 30:100 in the transplant population. These positive late winter lamb ratios continued through 2011.

I calculated an observed rate of increase (r) of 0.190 for the population beginning after the augmentation in 2009 to account for the total transplant population. Given the current growth rate we would expect a doubling time of 44 months or 3.7 years. We do not know the habitat carrying capacity (K) but assuming we are under K we could see a population > 120 bighorn by 2014.

Singer et al. (2000) defined measures of success for bighorn transplants based on 100 translocations across six western states between 1923 and 1997. The measure for success was defined as:

 unsuccessful (extirpated or remnant) = < 29 bighorn;  moderately successful = 30 - 99 bighorn; and  successful = 100 - 350 bighorn

According to our estimates, the Okanagan Mountain Park transplant is on the threshold between moderate and successful and it is anticipated that current growth rates will place the transplant in the successful category by 2014.

Table of Contents Executive Summary ...... 2 List of Figures ...... 4 List of Tables ...... 4 Introduction ...... 5 Study Area ...... 5 Methods ...... 5 Survey Methods ...... 5 Classification ...... 6 Data Analysis ...... 6 Results ...... 7 Population Estimates ...... 7 Population Growth ...... 10 Distribution ...... 10 Other Species ...... 12 Discussion...... 12 Population Estimate ...... 12 Population Growth ...... 14 Distribution ...... 14 Transplant Success ...... 14 Future Management ...... 15 Acknowledgements ...... 15 Literature Cited ...... 15

List of Figures Figure 1: Classification diagram for bighorn sheep from Geist 1971 (Mountain sheep: a study in behaviour and evolution) ...... 6 Figure 2: Flight path and observation points scaled by group size for bighorn, mountain goat and elk in Okanagan Mountain (MU8-09) Park on November 4, 2011...... 8 Figure 3: Flight path and observation points scaled by group size for bighorn, mountain goat and elk in Okanagan Mountain (MU8-09) Park on March 21, 2012...... 9 Figure 4: fixed kernel density estimator with Hawth’s Analysis Tools in ArcGIS 9.3 to develop 95% isopleths for bighorn home range. We weighted survey data by total group size for all locations recorded during survey since 2007...... 11 Figure 5: Observed and estimated population numbers from 6 surveys in Okanagan Mountain Park from 2009 to 2012. Estimates were derived from Program Aerial Survey (Bell 223 Sheep model)...... 13

List of Tables Table 1: Classification of observed California bighorn sheep during aerial surveys in Okanagan Mountain Park (MU 8-09) from 2009 to 2010...... 7 Table 2: Bighorn sheep observation numbers and estimates for the Okanagan Mountain Park population (MU 8-09), surveyed on November 4, 2011. Estimated population data are corrected for incomplete sightability in the program Aerial Survey...... 7 Table 3: Bighorn sheep observation numbers and estimates for the Okanagan Mountain Park population (MU 8-09), surveyed on March 21, 2011. Estimated population data are corrected for incomplete sightability in the program Aerial Survey...... 9 Table 4: Incidental mountain goat and elk data collected during 4 surveys in Okanagan Mountain Park from November 2010 to March 2012...... 12 Table 5: Mule deer composition data, minus antler architecture, for Okanagan Mountain Park in November 2010...... 12

Introduction The South Okanagan California bighorn meta-population suffered a significant pneumonia related die-off in 1999, where 70% of the population died. One recommendation of the Recovery Plan (Harper, 2002) developed as a response to the die-off was to re-introduce bighorns to suitable areas within their historic range in the Okanagan Valley. Okanagan Mountain Park, from here in referred to as “the Park”, was one candidate area but was not suitable until the wildfire of 2003 improved the habitat .

The Habitat Conservation Trust Foundation helped support a transplant into the Park in 2007 and this project focuses on monitoring of that transplant herd. In January 2007, 34 bighorns were transplanted from Keremeos (HCTF 8-272) and then in January, 2009, an additional 15 bighorn form Kamloops were released into the Park to augment the original transplant.

Study Area The Okanagan Mountain Park is located in the Central Okanagan on the east side of Okanagan Lake between the city of Kelowna and Penticton. The majority of the park is boat access only which make this area one of few remote wilderness parks at low elevation in the Okanagan Valley. The park is over 11,000 hectares in size and supports vast areas of open, rugged, rocky terrain highly suitable for California bighorn sheep.

The area encompasses two Ecosections the lower elevations occur in the North Okanagan Basin and the higher elevations occur in the North Okanagan Highlands. The biogeoclimatic classification is primarily PPxh1, Okanagan very hot dry Ponderosa Pine variant at lower elevations (360-760m), which is characterized by hot, dry summers, cool winters with low snowfall. Forests are typically open parkland stands with Ponderosa pine (Py) and bluebunch wheatgrass understory.

Higher elevations (760-1100) move into the IDFxh1, Okanagan very dry hot Interior Douglars-fir variant. This is the warmest and driest subzone in the IDF with long growing seasons where moisture deficits are common. Climax forests include Douglas fir and Py with sparse shrub layers and pinegrass.

Methods

Survey Methods General survey standards were adopted from Aerial-based Inventory Techniques for Selected Ungulates (RISC, 2002). Surveys were conducted with a Bell 206 Jet Ranger equipped with rear bubble observation windows. Encounter transects were used to locate bighorn with transects spaced at approximately 500 m in open habitats and 200 m in more closed forested habitats. Transects typically followed contours from either low elevation to high or vice versa. Speeds of 50-80 km/hour were targeted while maintaining a distance of 50-300 m above the ground.

We used three people on survey at all time: one navigator in the front seat and two observers in the rear. The navigator used the track log function and real time navigation feature on a Garmin 60Cx handheld GPS to maintain transect width, monitor survey coverage, and mark waypoints of animal locations. In

5 addition, the navigator photographed bighorn whenever possible. Observers located, counted, classified, and recorded data from the rear seats.

Classification Classification were based on Geist (1971; Figure 1) and Aerial Based Inventory Techniques for Selected Ungulates (RISC 2002). We used a digital SLR camera with a 70-300 mm anti-vibration zoom lens to photograph bighorn observations whenever possible. Bighorn classification made during survey was then cross-referenced with photographs once in the office to correct for classification and groups size. When possible yearlings were classified further refining the lamb and ram ratios.

Figure 1: Classification diagram for bighorn sheep from Geist 1971 (Mountain sheep: a study in behaviour and evolution)

Data Analysis Sightability models were used to correct bighorn observations for incomplete sightability in the program Aerial Survey (Unsworth et al. 1999). I used the Bell 223 model for sheep developed in southern Idaho (Bodie et al. 1995). All population and ratio data are expressed with 90% confidence intervals, generated in the program Aerial Survey.

The Sightability model corrects for the proportion of animals within survey area that went undetected during surveys. Logistic regressions used in sightability models incorporate a combination of variables known to affect the probability of animal detection from the air. Variables affecting detection probability generally include a combination of group size, animal activity, snow cover on the ground, oblique vegetation cover and habitat type surrounding the animal(s).

We collected waypoints of bighorn observations and tracked our fight path during the survey with a Garmin GPSmap 60Cx. Data for each model parameter was collected including percent oblique vegetation cover around the first bighorn observed in each group. We used sketches depicting various vegetation classes in 5% increments (5-90%) to help assign cover. Other model parameter data collected included activity, moving or not moving, and habitat codes (e.g. timber, dissected cliff, open slope).

We used a fixed kernel density estimator with Hawth’s Analysis Tools in ArcGIS 9.3 to develop 95% isopleths for bighorn home range. Analysis included weighted observation point data by total group size for all locations recorded during survey since 2007.

Results

Population Estimates Multiple surveys were completed over several years within the study area as part of the transplant monitoring (Table 1). Since we had two different release years (i.e. 2007 & 2009), reporting has focused on observed classification data from 2009 onward to represent the total transplant population. The data suggests that we’ve seen an increasing trend in observed bighorn since 2009.

Table 1: Classification of observed California bighorn sheep during aerial surveys in Okanagan Mountain Park (MU 8-09) from 2009 to 2010.

Year Month Lambs Yearlings Ewes Class I Class II Class III ClassIV Unclass Total 2009 July 13 4 22 0 5 2 0 0 46 2010 June 9 6 11 4 0 0 0 7 37 2010 November 9 7 31 3 4 8 3 0 66 2011 March 10 7 25 5 8 2 2 1 60 2011 November 10 0* 33 2 2 12 5 3 67 2012 March 10 1* 40 3 6 9 5 0 74 * When photos were inconclusive "ewe-like" individuals were classified as ewes. For these surveys yearlings tended to be most difficult to classify. Since November 2011, monitoring surveys have included approximately 4 hours of survey time per flight and covered approximately 65km2 of habitat in the Okanagan Mountain Park area. Monitoring has occurred in November and March for the past two years (i.e. 2010/2011 and 2011/2012). The following results are for the most recent monitoring year.

In November 2011 we observed a total of 67 bighorn during the survey (Figure 2). The estimated population was 95 (CI 90% 72-118; Table 2). The total sightability correction factor (SCF) was 1.42 or 70% for the survey with a slightly lower SCF for ewes and lambs. Rams had the highest SCF for the survey at 1.52. Observed and estimated lamb: ewe ratios were 30 and 31 (CI: 18-44), respectively and the observed and estimated ram: ewe ratios were 64 and 71 (CI: 45-97), respectively.

Table 2: Bighorn sheep observation numbers and estimates for the Okanagan Mountain Park population (MU 8-09), surveyed on November 4, 2011. Estimated population data are corrected for incomplete sightability in the program Aerial Survey.

Total Ewe Lamb Class I Class II Class III Class IV Unclassified Observed 67 33 10 2 2 12 5 3

Total Ewe Lamb Class I,II,III, and IV combined Unclassified Estimated 95 45 14 32 4 90% CI 72-118 34-56 9-19 23-41 1-7 Correction Factor 1.42 1.36 1.40 1.52 1.33

Figure 2: Flight path and observation points scaled by group size for bighorn, mountain goat and elk in Okanagan Mountain (MU8-09) Park on November 4, 2011.

We observed a total of 74 bighorn during the March 2012 survey (Figure 3). The estimated population was 115 (CI 90% 74-156; Table 3). The total SCF was 1.55 or 65% for the survey with a slightly higher SCF for ewes and lambs. Rams had the lowest SCF at 1.39. Observed and estimated lamb: ewe ratios were 24 and 24 (CI: 13-39), respectively and the observed and estimated ram: ewe ratios were 56 and 48 (CI: 21-75), respectively.

Table 3: Bighorn sheep observation numbers and estimates for the Okanagan Mountain Park population (MU 8-09), surveyed on March 21, 2011. Estimated population data are corrected for incomplete sightability in the program Aerial Survey.

Total Ewe Lamb Class I Class II Class III Class IV Unclassified Observed 74 41 10 3 6 9 5 0

Total Ewe Lamb Class I,II,III, and IV combined Unclassified Estimated 115 67 16 32 0 90% CI 74-156 38-96 9-23 20-44 - Correction Factor 1.55 1.63 1.60 1.39 -

Figure 3: Flight path and observation points scaled by group size for bighorn, mountain goat and elk in Okanagan Mountain (MU8-09) Park on March 21, 2012.

Population Growth In many cases lamb ratios can be used as an indicator of population productivity. Demarchi et al. (2000) suggests that a minimum of 30 lambs per 100 ewes is required for a growing population. Over the first two winters post transplant, 2007/08 and 2008/09, we documented low recruitment in the newly transplanted herd. Overwinter lamb ratios were < 10 lambs: 100 ewes. After augmentation in the winter of 2009/2010, we began observing lamb ratios > 30:100 in the transplant population. Positive late winter lamb ratios continued through 2011 with observed and calculated lamb ratios of 40 and 33 (CI 12-54). In March 2012, the overwinter lamb ratio was slightly lower with an observed and calculated lamb ratio of 24 and 24 (CI: 13-39), respectively.

I calculated the observed rate of increase (r) for the population beginning after the augmentation in 2009 to account for the total transplant population (Caughley 1971). I used the average SCF (1.42 or 70%) from the surveys corrected for incomplete sightability to derive an estimate from the 2009 survey. I then calculated (r) based on one survey from each reproductive year since 2009 (n=3), which resulted in an observed rate of increase of 0.190. The population doubling time at this rate is 44 months (i.e. 3.7 years).

Distribution A total of 9 collars were deployed in the 2007 transplant and 5 in the 2009 augmentation. Unfortunately, many of the collars malfunctioned providing varied signal strengths and false mortality signals. As a result, the use of collar data was limited. We did confirm 3 collar mortalities since the original release: a ewe the first spring in 2007, a ewe in spring 2009, and a ram in 2010. The cause of mortality was unknown in all cases.

Monitoring from 2007 suggested that the majority of bighorns moved north of the release site (Commando Bay) to the western point of the park (Squally Point) and a small number moved south of the release point. It was felt that while monitoring the 2007 transplants (n=34) that at least one group (~10 bighorn) was not being detected during surveys. It is unknown where these animals were at the time; it is possible that they moved north towards Kelowna. At that time surveys didn’t cover the area northeast of the park boundary. Since 2010 this area has been included in surveys but no bighorn have been observed northwest of the park boundary to date.

The 2009 group (n=15) were released on the southern park boundary in the former Paradise Ranch Vineyard now owned by Mission Hill. Surveys suggest that this group remained within 3 km of the release site. Surveys showed a clear separation between the 2007 and 2009 ewe groups and mixing was not confirmed until 2011 when a local hunter provide pictures with ear tags of sheep from 2007 and 2009 in the same group.

Telemetry data suggest that rams from each group have combined and that they have made much larger movements possibly as far south as Penticton Creek. The local guide outfitter observed an ear tagged and collared bighorn from the Park as far south as Penticton Creek. The extent and timing of ram movement remains unknown at this point.

To the north of the Park, we have received several reports of bighorn as far north as Kelowna. In May 2010, a group of 3 bighorn were observed in Mission (a suburb of Kelowna). Again in 2011, we had

10 reports of bighorn on Gordon Avenue in Kelowan. In this case 5 bighorn were reported in contact with domestic sheep at a local farm. In the end 1 bighorn was destroyed to prevent potential spread of disease to the remainder of the herd. We were unable to locate the other 4 bighorn.

A home range analysis was completed from survey data collected from 2007 to 2012. Data was weighted for group size to produce the following 95% fixed kernel density maps (Figure 4). Figure 4 represents 95% of the bighorn home range in the Park. The darker the red equates to areas with higher the density of bighorns during surveys. The Kelowna and locations were excluded from this analysis.

Figure 4: fixed kernel density estimator with Hawth’s Analysis Tools in ArcGIS 9.3 to develop 95% isopleths for bighorn home range. We weighted survey data by total group size for all locations recorded during survey since 2007.

Other Species We observed several other species during the surveys including elk, mtn goat and mule deer. We did not classify elk and mule deer because of time constraints but we did classify adult and kid mountain goats. The observation data by survey is summarized in table 4; waypoints and group sizes can be seen in figure 2 and 3. Alternate species data collection was inconsistent across surveys and total counts were most common. The 63 mountain goats counted in March 2011 was the highest count to date in the study area. In November 2010, we collected basic mule deer composition data and calculated an observed buck ratio of 30 bucks: 100 does and an observed fawn ratio of 53 fawns: 100 does (Table 5).

Table 4: Incidental mountain goat and elk data collected during 4 surveys in Okanagan Mountain Park from November 2010 to March 2012.

Survey Species Unclassified Juvenile Adult Female Adult Male Total November 2010 Goat 14 6 19 Elk 11 32 75 23 141 March 2011 Goat 43 20 63 November 2011 Goat 30 30 Elk 38 38 March 2012 Goat 54 5 59 Elk 162 162

Table 5: Mule deer composition data, minus antler architecture, for Okanagan Mountain Park in November 2010.

Survey Species Unclassified Juvenile Adult Female Adult Male Total November 2010 Mule Deer 70 27 51 15 163

Discussion

Population Estimate Population estimates were derived for surveys from November 2010 onward. The model precision ranged from 24% to 44% of the estimate (Figure 5). The best precision (i.e. 24%) was from the November 2011 survey where the model estimated a population of 95 bighorn (CI 72-118). The poorest precision (44%) was from November 2010 were the model predicted 86 bighorn (CI 49-123).

Observed Estimate 180 160 140

120 100 80

60 No. of BighornNo. 40 20 0

Figure 5: Observed and estimated population numbers from 6 surveys in Okanagan Mountain Park from 2009 to 2012. Estimates and confidence intervals (90%) were derived from Program Aerial Survey (Bell 223 Sheep model).

The SCF calculated for the 4 surveys ranged from 1.55 (66%) to 1.3 (77%). Logistic regression analysis of the model variables suggest that the majority of SCF can be explained by bighorn activity (i.e. moving or standing) and habitat type (i.e. flats, open slopes or otherwise; Bodie et al 1995). Results from our surveys support this analysis. Surveys where the greater proportion of observed bighorn occurred in open slope habitats and where bighorn were moving calculated lower correction factors (i.e. assuming fewer animals were missed). In the East Kootenay Poole (2012) reported SCF ranges for surveys in 2008, 2010 and 2011 of between 68% and 81%. Poole also contributed the majority of variation in SCF to moment and habitat typing.

The most common habitat codes used in this study area were (1) open slopes and (2) dissected cliffs. The definitions for these habitat types are: (1) Flat areas above or below rock cliff areas and open slopes with grass or short brush (less than 36 in. high). (2) Rock cliff areas with chutes, caves, cubby holes or other areas where sheep can hide from observation. These codes describe the habitat in Okanagan Park fairly well. However, after reviewing the survey data we will consider being more selective with the use of the habitat type “dissected cliff” since there are many steep, rocky sites in the study area but the sightability is still fair. The resulting change would reduce future SCF.

I feel that the SCF calculated in the March 2012 survey may be too high and overestimate the population because of the over use of dissected cliff habitat code. Future surveys will help refine the model but it is likely that a SCF of between 1.42 (70%) and 1.33 (75%) would be more appropriate, which would put the current population estimate in the study area at approximately 100 bighorn.

Population Growth Shacketon et al. (1999) describes the growth potential for bighorn sheep as follows:

The intrinsic rate of natural increase (rm) represents the exponential rate of population growth when no resource is limiting, that is, when the population is increasing at its genetic potential (Caughley 1977). Following the assumptions of one lamb per year, birth of the first lamb when females are three years old, a unitary sex

ratio, a stable age distribution, and no mortality, Buechner (1960) calculated an rm for

bighorn of 0.258, but there is empirical evidence for rm s considerably higher than this. Between 1922 and 1929, the National Bison Range herd in Montana increased at a rate

of 0.288 (Hass 1989), and the Fort Peck herd had an rm of 0.265 over 11 years and an

rm of 0.305 over four years (Buechner 1960). The most conservative of Buechner’s assumptions is first breeding at three years of age; however, incorporation the

assumption that two-year-old females can produce lambs, the rm value becomes about 0.308 (doubling time – 2.25 years).

Buechner (1960) modeled the maximum rate at which a population with stable age distribution can increase (rm) at 0.258. For this transplant we calculated the observed rate of increase (r) of 0.190, which is the actual growth rate at a given time (i.e. 2009 – 2012). It is likely that real world influences such as predation are limiting the potential growth rate of bighorn in Okanagan Mountain Park. Regardless we are calculating positive growth and given the current rate we would expect a doubling time of 44 months or 3.7 years. We do not know the habitat carrying capacity (K) but assuming we are under K we could see a population > 120 bighorn by 2014.

Distribution Figure 4 suggests that the majority of bighorn are found within 2km of the lake shore during the survey periods. Figure 2 and 3 represent the difference in distribution of bighorn and changes is group size during the rut and early spring green-up. As expected, in November sheep are more dispersed and in smaller groups as rams peruse ewes and in spring animals are in larger groups, less dispersed and closer to the lake (i.e. lower elevation).

Transplant Success Singer et al. (2000) summarized factors for success and defined a measure of success for 100 bighorn translocations across six western states between 1923 and 1997. The measure for success was defined as:  unsuccessful (extirpated or remnant) = < 29 bighorn;  moderately successful = 30 - 99 bighorn; and  successful = 100 - 350 bighorn In the Singer et al. (2000) review, 30 of 100 transplants were unsuccessful (i.e. 13 extirpated and 17 remnant), 29 transplants were moderately successful and 41 were considered a success. According to our estimates the Okanagan Mountain Park transplant is on the threshold between moderate and successful and it is anticipated that recent growth rates will place the transplant in the successful category by 2014.

Results from Singer (2000) suggest that to maximize likelihood of bighorn transplant success, agencies should:  translocate bighorn only to areas without domestic sheep  translocate indigenous herds as sources stock  founder size should be greater than or equal to 41 bighorn  release in areas with large habitat patches, few barriers and potential for migration.  mix genetic source stocks is encouraged to increase diversity

The Okanagan Mountain Park transplant has met all the criteria identified in Singer (2000) to maximize bighorn sheep transplant success.

Future Management The bighorn population in the Park has reached levels (i.e. >75 observed animals) where hunting seasons can be implemented according to the Provincial Bighorn Harvest Procedure (FLNRO 2011). We will be being forward a proposal to open a hunting season in the Park for consultation during the next regulation cycle 2014-2016.

Acknowledgements We would like to thank the Habitat Conservation Trust Foundation for multiple years of transplant monitoring funding. Also we would like to thank the many volunteer observers during monitoring flights. Finally, thanks to Valhalla Helicopters, Range Helicopters, and Okanagan Mountain Helicopters for their excellent service throughout the monitoring period.

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