To the reader - British Columbia · 2020-06-09 · 3. Environmental variation in demographic rates is high for R (coefficient of variation (CV) =0.30) and relatively low for S m and

To the reader:

In October 2019, Nature Wise Consulting produced a report titled “A Review of Northern Caribou Harvest Management and Science” for the Ministry of Forests, Lands, Natural Resource Operations and Rural Development.

This report provides scientific background and guidance to the government for caribou harvest management in British Columbia.

The Province will carefully consider the recommendations in this report. Implementation of actions will depend on government priorities, budgetary constraints and legal, social and economic factors. Successful delivery of caribou management in BC will require the commitment and cooperation of partners across the Province.

The report does not represent an official position or program of government and may support the development of herd and harvest management strategies which are subject to consultation with First Nations and the public.

A Review of Northern Caribou Harvest Management and Science

Version 1.0

Prepared for and in co-operation with:

The Provincial Caribou Harvest Policy Team B.C. Ministry of Forests, Lands, Natural Resource Operations and Rural Development

Prepared by:

Ian W. Hatter, MSc., RPBio Nature Wise Consulting

October 31, 2019

Review of Northern Caribou Harvest Management and Science

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Table of Contents 1. Executive Summary ............................................................................................................................... 5

2. Purpose ................................................................................................................................................. 6

3. Herd Status of Northern Caribou in British Columbia ........................................................................... 6

4. Limiting Factors for Northern Caribou .................................................................................................. 8

5. Demographic Rates of Northern Caribou ............................................................................................. 9

6. Caribou Hunting in British Columbia ..................................................................................................... 9

7. Harvest Rates ...................................................................................................................................... 10

7.1 Sustainable Harvest Rates ........................................................................................................... 11

7.2 Sustainable Harvest Rates in Stochastic Environment................................................................ 12

a) Bull-Only Hunting ........................................................................................................................ 13

b) Either-Sex Hunting ...................................................................................................................... 15

7.3 Age-Selective Bull Hunting .......................................................................................................... 18

7.4 Unreported Human-Caused Mortality Rate................................................................................ 19

8. Minimum Population Size for Hunting a Herd of Northern Caribou .................................................. 21

9. Conclusions ......................................................................................................................................... 22

10. Recommendations .......................................................................................................................... 23

11. Acknowledgements ......................................................................................................................... 24

12. Literature Cited ............................................................................................................................... 24

Appendix 1. Provincial caribou herds in British Columbia. ......................................................................... 29

Appendix 2. Average caribou days hunted and harvest from 1980–2017. ................................................ 30

Appendix 3. Average caribou harvest age and harvest from 1980–2017. ................................................. 31

Appendix 4. Hunting statement from Strategy for Recovery of Northern Caribou in the SMNEA in BC ... 32

Appendix 5. Hunting statement from Northern Mountain Population Management Plan ....................... 33

Appendix 6. Caribou Harvest Management Standards –Wildlife Harvest Strategy, BC ............................. 34

List of Figures Figure 1. Relationship between recruitment rate (R) and adult mortality rate (M) and wolf density from North American caribou studies (Bergerud and Elliott 1986). Also shown is the relationship between the population growth rate (λ) and wolf density where λ = (1-M)/(1-R) (Hatter and Bergerud 1991). Population growth is stable (λ = 1) when wolf density = 6.5 wolves/1000 km2. .......................................... 8


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Figure 2. Relationship between late winter calf/cow ratio (R), sustainable harvest rates for bulls (Mh) and growth rates (λ). Mh = bull harvest/late winter herd size. Maximum sustainable harvest rates are those that result in late winter adult sex ratios of 35 bulls/100 cows. ...................................................... 12

Figure 3. Monte Carlo simulations showing the effect of different harvest rates on average bull/cow ratios under varying levels of calf recruitment. .......................................................................................... 13

Figure 4. Monte Carlo simulations showing the probability of < 35 bulls/100 cows under various calf recruitment (R) and harvest rates (Mh). ..................................................................................................... 14

Figure 5. Monte Carlo simulations showing the effect of different harvest rates on mean growth rates under varying levels of calf recruitment. .................................................................................................... 14

Figure 6. Monte Carlo simulations showing the probability of λ < 1 under various calf recruitment and harvest rates. .............................................................................................................................................. 15

Figure 7. The effect of bull-only versus either-sex hunting on the bull/cow ratio as harvest rates increase when the average recruitment is 30 calves/100 cows. M Harv refers to bull-only hunting and M&F Harv refers to either-sex hunting. For either-sex hunting, 50% of the harvest was assumed to be adult cows.16

Figure 8. The probability that the adult sex ratio < 35 bulls/100 cows as harvest rates increase when the average recruitment is 30 calves/100 cows. M Harv refers to bull-only hunting and M&F Harv refers to either-sex hunting. For either-sex hunting, 50% of the harvest was assumed to be cows. ....................... 16

Figure 9. The effect of bull-only versus either-sex hunting on the population growth rate as harvest rates increase when the average recruitment is 30 calves/100 cows. M Harv refers to bull-only hunting and M&F Harv refers to either-sex hunting. For either-sex hunting, 50% of the harvest was assumed cows. 17

Figure 10. The probability that the population is declining (λ<1.0) as harvest rates increase when the average recruitment is 30 calves/100 cows. M Harv refers to bull-only hunting and M&F Harv refers to either-sex hunting. For either-sex hunting, 50% of the harvest was assumed to be cows. ....................... 17

Figure 11. Bull harvest by age-class from 1996-2016 and estimated selectivity/vulnerability (S/V) coefficients in Region 5 with Mh = 2%. See text for calculation of relative S/V coefficients. The S/V coefficients are approximations as they are based on a modelled stationary age distribution. ............... 18

Figure 12. Bull harvest by age-class from 1996-2016 and estimated selectivity/vulnerability (S/V) coefficients in Region 6 with Mh = 2%. See text for calculation of relative S/V coefficients. The S/V coefficients are approximations as they are based on a modelled stationary age distribution. ............... 19

Figure 13. Bull harvest by age-class from 1996-2016 and estimated selectivity/vulnerability (S/V) coefficients in Region 7 with Mh = 2%. The S/V coefficients are approximations as they are based on a modelled stationary age distribution.......................................................................................................... 19

Figure 14. Contour plot showing the range of population growth rates (λ) based on cow survival rates (Sf) and calf recruitment (R) where λ = Sf·(1+[R/2]) (adapted from DeCesare et al. 2012 and Guthery and Shaw 2013). ................................................................................................................................................. 20


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Figure 15. Monte Carlo simulations showing the effect of licenced hunting (R/NR Harv) and all human-caused mortalities (All HC Mort) on the average bull/cow ratio under various harvest rates. Average recruitment was 30 calves/100 cows. ........................................................................................................ 21

Figure 16. Monte Carlo simulations showing the effect of licenced hunting (R/NR Harv) and all human-caused mortalities (All HC Mort) on mean growth rates under various harvest rates. Average recruitment was 30 calves/100 cows. ........................................................................................................ 21

Figure 17. The probability that a caribou herd under varying initial sizes (N = 100 to 500) will contain at least 100 caribou after 10 years with bull-only hunting (Mh = 2%). .......................................................... 22

List of Tables Table 1. List of Northern Caribou Herds in British Columbia. ....................................................................... 7


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1. Executive Summary This document provides a review of caribou harvest science and management practices pertinent to northern caribou in British Columbia, a primarily terrestrial lichen-winter feeding ecotype of the woodland caribou (Rangifer tarandus caribou). The purpose was to provide science-based advice to support the development of a Northern Caribou Harvest Management Procedure for British Columbia. It focuses on herd status, sustainable harvest rates, bull-only hunting, either-sex hunting, age-selective bull hunting, unreported human-caused mortality, and the minimum herd size to sustain a hunting season. Conclusions from this study include:

1. Northern caribou herds exist at low density, within highly seasonable environments and are considered predator-limited with high neonatal calf mortality.

2. Demographic rates for a “stable” northern caribou herd are characterized by a natural survival rate of bulls (Sm) = 80%, a natural survival rate of cows (Sf) = 89%, and a calf recruitment rate (R) = 25 calves/100 cows.

3. Environmental variation in demographic rates is high for R (coefficient of variation (CV) =0.30) and relatively low for Sm and Sf (CV = 0.10).

4. Calf recruitment is the primary factor determining herd growth rates. 5. Sustainable harvest rates (bulls only) are about 2% for stable populations, 0–1% for declining

herds and 3–4% for increasing herds. These rates, however, may require further adjustments if other sources of human-caused mortality are prevalent.

6. Current bull harvest rates (bull harvest/population size) from licenced hunting are approximately 0.5% for Region 5, 1.5% for Region 6 and 1.4% for Region 7.

7. Bull-only hunting affects adult sex ratios and has a smaller effect on population growth rates. 8. Either-sex hunting affects population growth rates and has much less effect on bull/cow ratios. 9. Age-selective harvesting under the 5-point bull regulation protects younger bulls (1–5 yr.-olds)

and selects for 6–10 year-old bulls. 10. Maintaining a minimum of 35 bulls/100 cows in caribou herds (post-season) should help to

ensure that harvest rates are low enough to minimize evolutionary concerns of harvesting 5–point bulls.

11. A General Open Season (GOS) with a 5-point bull regulation is likely conservative. Limited Entry Hunting (LEH) seasons, however, may be required where a GOS results in adult sex ratios < 35 bulls/100 cows.

12. The minimum population size to support a licensed hunting season is estimated at 250. This should ensure a low (P < 0.05) probability of a herd declining to 100 animals within 10 years due to environmental and demographic effects.

Twelve recommendations for harvest management of northern caribou in BC were provided. It is recommended that hunted herds listed as Threatened under the Species at Risk Act should contain a minimum of 350 animals, while herds listed as Special Concern, especially those in proximity to other large herds, should contain a minimum of 250 animals. A population viability assessment (PVA) should be undertaken for all unhunted herds prior to opening a licensed hunting season in order to ensure harvests are sustainable.


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2. Purpose This document provides a review of caribou harvest science and management practices pertinent to northern caribou in British Columbia, a terrestrial lichen-winter feeding ecotype of the woodland caribou (Rangifer tarandus caribou). The purpose is to provide science-based advice to support the development of a Northern Caribou Harvest Management Procedure for BC. It focuses on herd status, sustainable harvest rates, bull-only hunting, either-sex hunting, age-selective bull hunting, unreported human-caused mortality and the minimum herd size to sustain a hunting season. There are other factors that influence harvest management either directly or indirectly such as herd accessibility, levels of human disturbance, habitat fragmentation and loss, and climate change which are not covered in this review.

3. Herd Status of Northern Caribou in British Columbia The herd1 is the basic management unit for northern caribou. The status of northern caribou herds in BC has been previously reviewed by Bergerud (1978), Heard and Vagt (1998) and Thomas and Gray (2002), and more recently within provincial and federal caribou management plans (NCTAC 2004, Environment Canada 2012). As of the last assessment (2018), there were an estimated 14,174 northern caribou within 30 extant herds in BC which are located within Region 5 (Cariboo, n = 694, 3 herds), Region 6 (Skeena, n = 9761, 11 herds), Region 7A (Omineca, n = 783, 6 herds) and Region 7B (Peace, n = 2936, 10 herds) (Table 1, Appendix 1). Fifteen herds were classified as decreasing, 2 herds were increasing, 1 herd was stable and 12 herds had an unknown trend. Fourteen herds had less than 250 caribou and 16 herds had 250 or more caribou. The average herd size was 472 (range: <25 to 3000). Twenty of the 30 herds have licenced hunting seasons.

Seventeen of the 30 northern caribou herds in BC belong to the Northern Mountain Population of Woodland Caribou (NMP, Environment Canada 2012). These herds have an average density of 0.101 caribou/km2 (Table 1) and are considered to be of “Special Concern” under the federal Species at Risk Act. Licensed hunting is a permitted activity within the NMP, but harvest rates should be sufficiently conservative to ensure the herd remains sustainable. The remaining 13 herds belong to the Southern Mountain Population of Woodland Caribou (SMP, Environment Canada 2014). These herds have an average density of 0.019 caribou/km2 (Table 1) and are considered to be “Threatened” under the Species at Risk Act. SMP Northern caribou herds within the SMP are further divided into two groups based on ecological and evolutionary distinctions – the Northern Group (NG) and the Central Group (CG). Licenced hunting is closed for all but three BC herds within the SMP (Chase, Wolverine and Itcha-Ilgachuz). The SMP recovery plan states “Where hunting occurs, it is important to monitor the level of hunting in order to understand the potential impact of hunting on the viability of a LPU (“local population unit”), including potential impacts on other sub-populations (herds) within that LPU. Should regulated hunting be determined to be having a negative effect on the population growth of the three

1 For the purposes of this report a herd is a locally-occurring caribou population, or sub-population that normally does not interbreed with another herd.


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sub-populations where it is still permitted, it should be closed at least until the population trajectory becomes positive” (Environment Canada 2014, p. 39).

Table 1. List of Northern Caribou Herds in British Columbia.

Herd ID #1

Ecotype Grouping2

Herd Name Estimate Year

Herd Trend3

Herd Estimate4

Herd Density5

Region6 Hunted7

18 SMP_CG Narraway 2018 Decreasing 26 0.004 7B No

19 SMP_CG Quintette 2018 Decreasing 74 0.012 7B No

20 SMP_CG Kennedy Siding 2018 Decreasing 63 0.021 7A No

22 SMP_CG Klinse-za 2018 Decreasing 66 0.012 7B No

24 SMP_NG Graham 2016 Decreasing 230 0.025 7B No

30 SMP_NG Itcha-Ilgachuz 2017 Decreasing 637 0.067 5 Yes

31 SMP_NG Charlotte Alplands 2001 Decreasing < 25 < 0.009 5 No

32 SMP_NG Rainbows 2016 Decreasing 32 0.008 5 No

33 SMP_NG Tweedsmuir 2018 Decreasing 175 0.013 5/6/7A No

34 SMP_NG Telkwa 2018 Decreasing 26 0.008 6 No

35 SMP_NG Takla 2018 Decreasing 49 0.023 7A No

36 SMP_NG Wolverine 2018 Decreasing 266 0.025 7A Yes

37 SMP_NG Chase 2017 Decreasing 290 0.023 7A Yes

38 NMP Thutade 2015 Unknown 90 0.013 7A Yes

39 NMP Finlay 2018 Unknown < 25 < 0.003 7A Yes

40 NMP Pink Mountain 2018 Decreasing 350 0.037 7B Yes

41 NMP Muskwa 2018 Decreasing 450 0.021 7B Yes

42 NMP Gataga 2001 Stable 340 0.068 7B Yes

43 NMP Frog 2010 Unknown 250 0.050 7B Yes

44 NMP Rabbit 2007 Unknown 1000 0.085 7B Yes

45 NMP Liard Plateau 2017 Unknown 150 0.030 7B Yes

46 NMP Horseranch 1999 Unknown 600 0.034 6/7B Yes

47 NMP Little Rancheria 1999 Unknown 1200 0.171 6 Yes

48 NMP Swan Lake 2007 Unknown 700 0.127 6 Yes

49 NMP Level-Kawdy 1999 Unknown 1500 0.133 6 Yes

50 NMP Atlin 2007 Increasing 800 0.117 6 Yes

51 NMP Carcross 2015 Increasing 860 0.271 6 Yes

52 NMP Tsenaglode 2015 Unknown 825 0.335 6/7B Yes

53 NMP Edziza 2017 Unknown 75 0.032 6 Yes

54 NMP Spatsizi 1996 Unknown 3000 0.192 6/7B Yes


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1 Herd ID corresponds to herd numbers shown in Appendix 1.

2 Ecotype grouping is based on federal recovery and management plans (Environment Canada 2012, 2014). SMP refers to Southern Mountain population and includes the CG (Central Group) and NG (Northern Group) herds. NMP refers to Northern Mountain population. 3 Long-term trends based on three generations (27 years) (SMP, Environment Canada 2014). 4 Herd estimates include “expert opinion” (n=22), “survey observation” (n=2), and “modelled or corrected” estimate (n=6). 5 Caribou density (#/km2) was based on the herd estimate and herd boundary spatial polygons. It does not include matrix habitat. 6 Region(s) responsible for caribou herd management (note that some herds occur within more than one region). 7 Yes refers to herds that were hunted during the 2018 licensed hunting season.

4. Limiting Factors for Northern Caribou Wolves are the primary limiting factor of northern caribou (Bergerud 1978, Bergerud and Elliott 1986, Edmonds 1988, Seip 1992, Bergerud 1996, Bergerud and Elliott 1998, Wittmer et al. 2005), although bear and wolverine predation may be important sources of calf mortality in some herds (Bergerud and Page 1987, Gustine et al. 2006, McNay 2009). Bergerud and Elliott (1986) showed that rates of caribou calf recruitment in fall or late winter (R) and adult (>1-year-old) mortality (M) across North America are related to wolf density, and that positive growth (λ > 1.0) occurs when wolf densities are < 6.5 wolves/1000 km2 (Fig. 1). Hebblewhite et al. (2007) suggested that subpopulations of caribou in Jasper National Park are only likely to persist when wolf densities are below 2.1-4.3 wolves/1000 km2 while Wilson (2009) recommended that wolf densities for be managed to <1.5 wolves/1000 km2 to generate a significant, positive population response by southern mountain caribou in BC. Wolf densities in BC typically range from 6 to 14 wolves/1000 km2 regionally where caribou are present (Kuzyk and Hatter 2014), suggesting that many caribou herds may be declining from wolf predation. Other potential limiting factors include climate change (Hegel et al. 2010), habitat fragmentation and loss (Johnson et al. 2015), human disturbance (Seip et al. 2007), overhunting (Bergerud 1978, Thomas and Gray 2002), health (Kutz et al. 2013) and apparent competition (Serrouya et al. 2017).

Figure 1. Relationship between recruitment rate (R) and adult mortality rate (M) and wolf density from North American caribou studies (Bergerud and Elliott 1986). Also shown is the relationship between the population growth rate (λ) and wolf density where λ = (1-M)/(1-R) (Hatter and Bergerud 1991). Population growth is stable (λ = 1) when wolf density = 6.5 wolves/1000 km2.

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0

0.05

0.1

0.15

0.2

0.25

0.3

0 3 6 9 12 15

Carib

ou G

row

th R

ate

(λ)

Recr

uitm

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Wolves/1000 km2

R M λ


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5. Demographic Rates of Northern Caribou Demographic rates for northern caribou have been extensively reviewed (Bergerud 1978, Bergerud 1980, Bergerud 1992, Seip and Cichowski 1996, Farnell et al. 1998, Bergerud 2000, Smith 2004, Hegel 2015). A caribou cow has one calf per year and cows do not generally breed until they are 2 years old. Although pregnancy rates are generally high, neonatal calf mortality is also high resulting in low calf recruitment rates. Bergerud (1992) defined stabilizing calf recruitment (Rs) where Rs equals the annual mortality of adults (>1-year-old caribou) (R = M, λ = 1.00). For caribou, Rs = 25–26 calves/100 cows (Bergerud 1992), which occurs when calves are 6 to 12 months of age (Bergerud 19922, Cichowski 2015). Assuming a 50:50 sex ratio in caribou calves at birth (Bergerud 2000, Smith 2004), Rs = 12.5 female calves/100 cows. Thus, the annual adult cow survival rate (Sf) required to stabilize population growth (λ = 1.0) when R = Rs is ~ 89% (i.e. Sf = 0.89). Stabilizing density (Ds) is defined as the density (#/maximum annual herd range) that results in Rs and was estimated by Bergerud (1992) at Ds = 0.064 caribou/km2. Low densities allow northern caribou to space out and reduce predation risk (Bergerud 2000). Naturally regulated bull/cow ratios observed from unhunted herds in the Yukon appear to be about 50 bulls/100 cows (Environment Yukon, 2016) which suggests that natural survival rates for bull caribou should be ~ 80% (i.e. Sm = 0.80). McNay (2009) reported that adult mortalities of northern caribou occur primarily in winter (Nov.–Mar.) and spring (Apr.–May), while most calf mortalities occur in summer (Jun. –Aug.). As with many ungulate populations, northern caribou growth rates are most sensitive to small changes in adult survival, while highly variable calf recruitment is the most important parameter driving population change (Bergerud 1978, Gaillard et al. 2000). Smith (2004) studied two northern caribou herds in Alberta and determined that annual variability of adult female survival rates due to environmental variation was low (CV = 10%) whereas the variation in calf recruitment was much higher (CV = 34%).

6. Caribou Hunting in British Columbia In BC, licensed hunting of northern caribou has been restricted to 5-point bulls3 since 19874. The primary rationale for the 5-point bull regulation was to maintain a general open season (GOS) while limiting the harvest to older bulls, thus maintaining bull recruitment into the older (mature) age classes (MELP 1996). As an additional measure to ensure older bulls are retained, a provincial objective was established in 1996 to maintain > 35 bulls/100 cows post-hunt (MELP 1996). The GOS in Region 6 and 7A occurs from Aug. 15 to Oct. 15, while the season extends from Aug. 15 to Sep. 30 in Region 7B. There is currently no GOS for caribou in Region 5. Limited entry hunting (LEH) for any bull occurs in some areas of Region 6, while all caribou hunting in Region 5 (the Itcha-Ilgachuz herd) occurs on LEH and is restricted to 5-point bulls. All successful licensed caribou hunters in BC are required to submit an incisor and antlers for compulsory inspection by government employees or contractors who record the location of the kill and remove an incisor for aging. Hunter effort (days hunted) is estimated annually from mail-

2 Hegel and Russell (2011) suggest that the late winter recruitment rate may be estimated by subtracting 4.3 calves/100 cows from the fall recruitment rate. 3 A 5-point bull has one antler bearing at least five points, including the tip of the main beam above the rear point. Prior to 2001 bulls with an antler mean beam of at least 75 cm in length were also legal in Region 5. 4 Some LEH seasons have maintained hunts for any bull.


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out questionnaires sent to a random sample of caribou hunters. Reporting of non-resident hunter effort is mandatory and obtained from guide declarations.

First Nation rights to harvest caribou are constitutionally protected and are not subject to BC hunting regulations when hunting within their traditional territory. As First Nation harvest is not regulated, their harvest statistics (e.g. harvest rate, sex and age of harvest) are generally not available. Northern caribou have and continue to remain important to First Nations for food, social and ceremonial purposes. In recent years, some First Nations have voluntarily forgone the right to hunt to conserve caribou populations.

Provincially, licensed caribou harvests increased from 1980 (n = 337) to 1996 (n = 465) and then declined, although numbers have been relatively stable since 2014 (�̅�𝑥 = 213, SD = 16) (Appendix 2). Non-resident hunters took slightly more than one-half (52%) of the licensed harvest from 1980 to 2017. In Region 5, harvests averaged 31 caribou/year (SD = 11) from 1980–2016, and were reduced to 3 in 2017 when LEH was introduced. Harvests have been relatively stable in Region 6 from 1980–2017 (�̅�𝑥 = 166, SD = 27). A linear regression analysis of harvest by year in Region 7A had a negative slope (b) from 1980 (n = 49) to 2017 (n = 4) indicating that the harvest declined during this period (b = -1.23, F = 120.65, P < 0.001). In Region 7B, harvests increased from 1980 (n = 90) to 1996 (n = 220) (b = 6.31, F = 23.65, P < 0.001) and then steadily declined to 47 in 2017 (b = -6.99, F = 68.46, P < 0.001).

The mean age of the licensed bull caribou harvest in Region 5 ranged from 3.4 years in 1980 to 8.0 years in 1996 (Appendix 3). A linear regression analysis of mean age by year had a positive slope (b) from 1980–2017 (b = 0.038, F = 11.18, P = 0.002) indicating that mean age increased during this time period. In Region 6, the mean age ranged from 4.9 in 1981 to 7.5 in 1995 with an increasing trend from 1980–2017 (b = 0.012, F = 2.85, P = 0.10). In Region 7A, the mean age ranged from 4.7 in 2017 to 8.1 in 2011 with an increasing trend from 1980–2017 (b = 0.020, F = 3.68, P =0.063). In Region 7B, the mean age ranged from 4.9 in 2005 to 8.5 in 1995 with an increasing trend from 1980–2017 (b = 0.021, F = 3.57, P = 0.067). Appendix 4 and 5 provide hunting statements from northern caribou management plans, and Appendix 6 provides previous caribou harvest management guidelines for BC.

7. Harvest Rates The harvest rate is defined as the licensed harvest/late winter herd estimate. Harvest rates [(average of 2014–2016 harvest)/most recent herd estimate for hunted herds] were approximately 2.9% for Region 5 (23/784)5, 1.5% for Region 6 (140/9560) and 1.4% (45/3211) for Region 7 (Regions 7A and 7B combined). There are several factors that determine how harvest rates affect a caribou herd. These include: (1) the herd’s trend or finite rate of increase (λ); (2) the harvest rate in relation to herd size (Mh); and (3) the sex ratio of the harvest (proportion of cows in the harvest). Sustainable harvest rates for northern caribou are defined, for the purpose of this report, as those that maintain bull/cow ratios at > 35 bulls/100 cows with λ > 1.0.

5 The caribou harvest in 2017, after introduction of LEH was 3 bulls. The 2018 population estimate was 637 which suggests the current harvest rate in Region 5 is about 0.5%.


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The rationale for maintaining 35 bulls/100 cows (post-hunt) is to retain a sex and age structure than includes mature males, and to minimize evolutionary concerns with harvesting 5-point bulls (Appendix 6, MELP 1996). Yukon Environment (2016) noted that a sex ratio of 30 bulls per 100 cows should ensure all cows have the opportunity to reproduce since caribou are functionally polygynous and mature bulls are able to breed numerous receptive cows within the mating herd (Bergerud 1977). Holand et al. (2003) found that calving rates in captive reindeer were not affected even when males comprised 10% of the herd. However, they also found that calving dates were later when there were a high proportion of young males in the herd. Later calving dates could affect calf survival as there may be less time during the summer for calves to gain the body weight necessary to survive the winter (Holand et al. 2003, Yukon Environment 2016).

The rationale for λ > 1.0 is to maintain stable populations and to ensure that licensed hunting does not contribute to population declines. Unless R is >30 calves/100 cows, there is little opportunity to sustain a cow harvest (Hegel 2015, Yukon Environment 2016). Consequently, northern caribou licensed hunting in both the Yukon and BC is focussed on bulls. Environment Yukon (2016) concluded that for declining herds in the Yukon, a bull-only harvest of up to 1% of the total population size may be considered, for stable herds a bull-only harvest rate of 2% was likely sustainable, and for increasing herds a harvest rate of 3–4% was sustainable. These rates were based on population modelling of a largely unhunted caribou herd in southwestern Yukon that was considered to be stable from 2003–2013 (Hegel 2015).

7.1 Sustainable Harvest Rates There has been little research on sustainable harvest rates for northern caribou in BC, or any other jurisdictions for woodland caribou in North America, with the exception of the Yukon (Hegel 2015). I therefore used a population modelling approach similar to Hegel (2015) to evaluate the applicability of the Yukon harvest rate guidelines to BC. My approach, however, was based on the demographic rates and mortality timing for a “stable” northern caribou as outlined in Section 4. I used the following stage-based population model where calf recruitment occurs just prior to calving:

𝑀𝑀𝑡𝑡 = �𝑀𝑀𝑡𝑡−1 + (0.5 𝑥𝑥 𝐽𝐽𝑡𝑡−1) −𝐻𝐻𝑚𝑚,𝑡𝑡�𝑆𝑆𝑚𝑚

𝐹𝐹𝑡𝑡 = �𝐹𝐹𝑡𝑡−1 + (0.5 𝑥𝑥 𝐽𝐽𝑡𝑡−1)−𝐻𝐻𝑓𝑓,𝑡𝑡�𝑆𝑆𝑓𝑓

𝐽𝐽𝑡𝑡 = 𝑅𝑅𝑡𝑡𝑥𝑥𝐹𝐹𝑡𝑡

where Mt = adult (1+ year old) bulls in year t, Ft = adult (1+ year old) females, Jt = calves (<1 year old), Hm,t = adult bull fall harvest, Hf,t = adult female fall harvest, Rt = calf recruitment (calves/cow) , Sm = natural adult bull survival rate and Sf = natural adult cow survival rate. This model assumes that harvest mortality is additive to natural mortality (Bergerud 1978, Thomas and Gray 2002). I developed a deterministic version of this model using Microsoft Excel (Microsoft, Redmond, WA, USA) to evaluate sustainable harvest rates.

The deterministic model indicated that a bull harvest of 2.3% of the population size was sustainable (i.e. λ > 1, post-hunt bull/cow ratio > 0.35) when R = Rs (Fig. 2) which agrees with the Yukon findings of 2% (Hegel 2015, Environment Yukon 2016). There was no sustainable harvest when R < 13 calves/100 cows,


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while a 6% harvest was sustained when R = 50 calves/100 cows. There was no sustainable harvest that would maintain λ > 1 when R < Rs.

Figure 2. Relationship between late winter calf/cow ratio (R), sustainable harvest rates for bulls (Mh) and growth rates (λ). Mh = bull harvest/late winter herd size. Maximum sustainable harvest rates are those that result in late winter adult sex ratios of 35 bulls/100 cows.

7.2 Sustainable Harvest Rates in Stochastic Environment The sustainable harvest rates determined from the deterministic model did not account for the effects of temporal variation in demographic rates, or uncertainty in the population estimate used to determine an allowable harvest. Consequently, deterministic models may give overly optimistic results when estimating sustainable harvest rates (Morris and Doak 2002). I therefore used a stochastic version of the deterministic population model (Section 6.1) that incorporated temporal variation in adult female and male survival [coefficient of variation (CV = 10%)], and calf recruitment (CV = 30%) (Gaillard et al. 2000, Smith 2004). I modelled the population composition and trend over a 10 year period, as this is slightly longer than the generation time6 for caribou (~ 7–9 yrs., Thomas and Gray 2002), corresponds to the average interval between resurveys of northern caribou in BC (~ 9.3 yrs., Table 1), and likely covers the full range of variation in annual calf recruitment (Hegel 2015). The annual licensed harvest used during the simulation was based on the total initial population abundance at the start of each simulation. (i.e. H = Mh x 𝑁𝑁�0, where H is the annual allowable harvest, Mh is the harvest rate and 𝑁𝑁�0 is the initial population estimate). I accounted for uncertainty in the initial estimate by including a sampling error with CV = 0.15. This CV roughly corresponds to a survey with 95% CI’s and an allowable error of + 20% of the estimate, which is considered to be a survey standard for BC (RISC 2002).

6 Thomas and Gray (2002) defined a generation as the average or median age of females of breeding age.


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I performed 5000 Monte Carlo iterations for each simulation of 10 years, and recorded both the mean bull/cow ratio in year 10 and the population growth rate (λ) where λ = (N10/N0)(1/10). I also recorded the proportion of iterations where the adult sex ratio in year 10 was less than 35 bulls/100 cows, and where λ < 1.0. For bull-only hunting, I varied the harvest rates from 1% to 5%, and calf recruitment rates from 15 calves/100 cows to 35 calves/100 cows. Performance measures included: (1) the average bull/cow ratio in year 10, (2) the probability that the bull/cow ratio in year 10 was < 35 bulls/100 cows; (3) the average population growth rate (λ) over the 10 year period and (4) the probability that the average growth rate over 10 years was λ < 1.0. For either-sex hunting I assumed 50% of the harvest was comprised of cows. I also varied the harvest rates from 1% to 5% but maintained the recruitment rate at 30 calves/100 cows where a small cow harvest should be sustainable. All simulations were done with Microsoft Excel (Microsoft, Redmond, WA, USA) using the add-in program PopTools, version 3.0; http://www.poptools.org).

a) Bull-Only Hunting

With bull-only hunting, the mean adult sex ratio (Fig. 3) was: (1) 38 bulls/100 cows when R = 15 calves/100 cows, Mh = 0%; (2) 36 bulls/100 cows when R = 20 calves/100 cows, Mh = 1%; (3) 36 bulls/100 cows when R = 25 calves/100 cows, Mh = 2%; (4) 37 bulls/100 cows when R = 30 calves/100 cows, Mh = 3%, and (5) 38 bulls/100 cows when R = 35 calves/100 cows, Mh = 4%.

Figure 3. Monte Carlo simulations showing the effect of different harvest rates on average bull/cow ratios under varying levels of calf recruitment.

The probability that the bull/cow <35/100 (Fig. 4) was: (1) 5% when R = 15 calves/100 cows, Mh = 0%; (2) 34% when R = 20 calves/100 cows, Mh = 1%, (3) 37% when R = 25 calves/100 cows, Mh = 2%; (4) 34% when R = 30 calves/100 cows, Mh = 3%, and (5) 28% when R = 35 calves/100 cows, Mh = 4%.


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Figure 4. Monte Carlo simulations showing the probability of < 35 bulls/100 cows under various calf recruitment (R) and harvest rates (Mh).

Population growth rates (Fig. 5) were: (1) λ = 0.95 when R = 15 calves/100 cows, Mh = 0%; (2) λ = 0.97 when R = 20 calves/100 cows, Mh = 1%; (3) λ = 1.00 when R = 25 calves/100 cows, Mh = 2%; (4) λ = 1.02 when R = 30 calves/100 cows, Mh = 3%; and (5) λ = 1.04 when R = 35 calves/100 cows, Mh = 4%.

Figure 5. Monte Carlo simulations showing the effect of different harvest rates on mean growth rates under varying levels of calf recruitment.

The probability that the population was declining (λ < 1) (Fig. 6) was: (1) 94% when R = 15 calves/100 cows, Mh = 0%; (2) 78% when R = 20 calves/100 cows, Mh = 1%; (3) 52% when R = 25 calves/100 cows, Mh = 2%; (4) 31% when R = 30 calves/100 cows, Mh = 3%, and (5) 16% when R = 35 calves/100 cows, Mh = 4%.


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Figure 6. Monte Carlo simulations showing the probability of λ < 1 under various calf recruitment and harvest rates.

Results from the stochastic model were similar to the deterministic model where a harvest rate of 2% and an average recruitment of 25 calves/100 cows yielded a mean adult sex ratio of 36 bulls/100 cows. The probability, however, that the adult sex < 35 bulls/100 cows was 37%. Mean growth rates (λ) increased as calf recruitment rates increased while the probability that λ was <1 declined as calf recruitment increased. Bull harvesting had a much great impact on bull/cow ratios than it did on population growth rates.

b) Either-Sex Hunting

Bull-only hunting had a greater effect on the bull/cow ratio than did either-sex hunting as harvest rates increased (Fig. 7). A bull-only harvest rate of 3% was the maximum rate that maintained > 35 bulls/100 cows while harvests rates of 4–5% with either-sex hunting maintained > 35 bulls/100 cows. The probability that the adult sex ratio < 35 bulls/100 cows was also much higher under bull-only hunting (Fig. 8).

Either-sex hunting, however, had a much greater effect on the population growth rate as harvest rates increased (Fig. 9). While bull-only harvest rates up to 5% maintained positive growth rates, either-sex harvests greater than 3% resulted in a population decline. The probability of a herd declining with increasing harvesting rates was also much higher with either-sex hunting (Fig. 10).


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Figure 7. The effect of bull-only versus either-sex hunting on the bull/cow ratio as harvest rates increase when the average recruitment is 30 calves/100 cows. M Harv refers to bull-only hunting and M&F Harv refers to either-sex hunting. For either-sex hunting, 50% of the harvest was assumed to be adult cows.

Figure 8. The probability that the adult sex ratio < 35 bulls/100 cows as harvest rates increase when the average recruitment is 30 calves/100 cows. M Harv refers to bull-only hunting and M&F Harv refers to either-sex hunting. For either-sex hunting, 50% of the harvest was assumed to be cows.


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Figure 9. The effect of bull-only versus either-sex hunting on the population growth rate as harvest rates increase when the average recruitment is 30 calves/100 cows. M Harv refers to bull-only hunting and M&F Harv refers to either-sex hunting. For either-sex hunting, 50% of the harvest was assumed cows.

Figure 10. The probability that the population is declining (λ<1.0) as harvest rates increase when the average recruitment is 30 calves/100 cows. M Harv refers to bull-only hunting and M&F Harv refers to either-sex hunting. For either-sex hunting, 50% of the harvest was assumed to be cows.

These results are consistent with ungulate population dynamics theory where adult female survival has a much greater impact on population growth than adult male survival (Caughley 1977). This is because one bull can breed numerous cows, and because population growth rates are determined primarily by the reproductive rates of cows and survival of their calves (DeCesare et al. 2012).


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7.3 Age-Selective Bull Hunting Age-selective bull hunting occurs in BC due to the 5-point bull regulation and the desire of some hunters to harvest a mature bull. The mean age at harvest under the 5-point bull regulation ranges from 6 to 8 yrs. old (Appendix 3). I determined the relative selectivity/vulnerability (S/V) of bull caribou by age-class (N1 to N15) by generating a stationary age distribution of bulls (Sm = 0.8, Sf = 0.89, R = 0.25) and then finding the age-specific vulnerability coefficients (S/Va) where the expected age-specific harvest (𝐻𝐻�𝑎𝑎) matched the observed harvest (𝐻𝐻𝑎𝑎). I set the harvest rate at Mh = 2% as this is the sustainable harvest rate when λ = 1.0 (see Section 6.1). I determined S/V for each age-class by minimizing the chi-square value, i.e. χ2 = [(𝐻𝐻𝑎𝑎–𝐻𝐻�𝑎𝑎)2/𝐻𝐻𝑎𝑎] where 𝐻𝐻�𝑎𝑎= Mh x Na x S/Va using Excels’ Solver. Age-specific S/V coefficients for bulls increased up to 6 yrs.-of-age in Region 5 (Fig. 11) and up to 7 yrs.-of-age in Regions 6 (Fig. 12) and Region 7 (Region 7A and 7B, Fig. 13) indicating that younger bulls (aged 1 to 5 yrs.) are less vulnerable to hunting than older bulls (6+ yrs.-of-age) under the 5-point bull regulation. This suggests that the 5-point bull regulation is effective in protecting younger bulls, thus ensuring recruitment into the older age-classes. Harvesting large antlered bulls (e.g. with the 5-point bull regulation), however, could have evolutionary consequences that may lead to smaller antler size or alter antler phenotypes if there is strong selective hunting pressure (Ginsberg and Milner-Gulland 1994, Mysterud et al. 2002, Perez et al. 2011). Options to reduce this possibility include directing harvest to post-breeding males, establishing a network of large protected areas to allow genetic rescue (Festa-Bianchet 2016), and reducing harvest pressure of 5-point bulls. Of these three options, the easiest to implement is a reduction in harvest rates. Bull harvest rates of 1–3% may be sufficiently conservative to guard against this concern. Maintaining 35 bulls/100 cows helps to ensure that harvest is not excessive.

Figure 11. Bull harvest by age-class from 1996-2016 and estimated selectivity/vulnerability (S/V) coefficients in Region 5 with Mh = 2%. See text for calculation of relative S/V coefficients. The S/V coefficients are approximations as they are based on a modelled stationary age distribution.

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Figure 12. Bull harvest by age-class from 1996-2016 and estimated selectivity/vulnerability (S/V) coefficients in Region 6 with Mh = 2%. See text for calculation of relative S/V coefficients. The S/V coefficients are approximations as they are based on a modelled stationary age distribution.

Figure 13. Bull harvest by age-class from 1996-2016 and estimated selectivity/vulnerability (S/V) coefficients in Region 7 with Mh = 2%. The S/V coefficients are approximations as they are based on a modelled stationary age distribution.

7.4 Unreported Human-Caused Mortality Rate Licensed and First Nation’s hunting are likely the leading sources of human-caused mortality of northern caribou in BC. While the First Nation harvest is unknown, it may be significant in some herds. Farnell et

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al. (1998) suspected that the First Nation harvest in the Yukon was equal to that of licensed hunters. Other non-hunting human caused mortalities may also be significant. Road/rail mortalities, while generally small and largely unreported, may represent a source of additive mortality. Hegel and Russell (2011) noted that the addition of road kills could have the potential to impact the growth of the Little Rancheria herd which is harvested in both Yukon and BC. Poaching is another source of human-related mortality that is largely unknown, but potentially significant for some caribou herds (Thomas and Gray 2002). Loss of caribou cows is of most concern as adult female mortality rates are one of the key determinants of population growth (DeCesare et al. 2012, Fig. 14).

Figure 14. Contour plot showing the range of population growth rates (λ) based on cow survival rates (Sf) and calf recruitment (R) where λ = Sf·(1+[R/2]) (adapted from DeCesare et al. 2012 and Guthery and Shaw 2013).

I assessed the combined effect of licenced harvest and unreported human-caused mortality where the unreported mortality was assumed to equal the licenced harvest. I also assumed that the unreported mortality was unselective, i.e. bulls and cows were removed in proportion to their relative abundance. I used the same Monte Carlo modelling approach described in Section 6.2, and considered harvest rates from 0 to 5% and recruitment rates from 15–30 calves/100 cows. Bull/cow ratios were slightly lower when all sources of human mortality were included (Fig. 15). Growth rates were substantially lower from the combined effect of hunting and other human-caused mortality (Fig. 16). While Fig. 15 and 16 were based on an average recruitment of 30 calves/100 cows, similar findings were observed from other recruitment rates.


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Figure 15. Monte Carlo simulations showing the effect of licenced hunting (R/NR Harv) and all human-caused mortalities (All HC Mort) on the average bull/cow ratio under various harvest rates. Average recruitment was 30 calves/100 cows.

Figure 16. Monte Carlo simulations showing the effect of licenced hunting (R/NR Harv) and all human-caused mortalities (All HC Mort) on mean growth rates under various harvest rates. Average recruitment was 30 calves/100 cows.

8. Minimum Population Size for Hunting a Herd of Northern Caribou In the Yukon, herds with less than 200 caribou are recommended to be closed to licensed hunting (Appendix 5). I evaluated the Yukon guideline of 200 animals by assessing the effect of different initial herd sizes using the stochastic model described above (Section 6.2). I included demographic as well as environmental stochasticity since demographic stochasticity becomes increasingly important when


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populations are small (Morris and Doak 2002). Population parameters were set for a stable population with CV=0.10 for Sm and Sf, CV = 0.30 for R, CV = 0.15 for survey error and Mh = 2% (bulls only). Demographic stochasticity was modelled by drawing from a binomial distribution with parameters St, Rt and Nt (Akcakaya 1991). Following Wielgus (2002), I assumed that a minimum population size to support a licensed hunting season must be large enough to ensure there is an acceptably low (P < 0.05) probability that the herd would decrease to 100 animals within 10 years. NCTAC (2004) defined sustainable herds of northern caribou as those with a stable or increasing trend and a minimum of 100 animals. I therefore used 100 animals as the minimum size. I used 10 years as this is slightly longer than the generation time for caribou (~7–9 yrs., Thomas and Gray 2002), corresponds to the average interval between resurveys of northern caribou in BC (~ 9.3 yrs., Table 1), and likely covers the full range of variation in annual calf recruitment (Hegel 2015). I used P < 0.05 as it is a scientific standard. Initial population sizes varied from 100 to 500. Based on these parameters, the minimum population size to allow for a hunting season on a northern caribou in BC was 250 (Figure 17). Wittmer et al. (2010) states that caribou PVA (Population Viability Analysis) models which fail to incorporate the effects of changes in vital rates with habitat changes may lead to overly optimistic assessments of the probability of population persistence. As I did not account for the effects of habitat fragmentation on population persistence, 250 animals should be considered a minimal estimate for the size of a caribou herd that is hunted in BC.

Figure 17. The probability that a caribou herd under varying initial sizes (N = 100 to 500) will contain at least 100 caribou after 10 years with bull-only hunting (Mh = 2%).

9. Conclusions 1. Northern caribou herds exist at low density, within highly seasonable environments and are

considered predator-limited with high neonatal calf mortality.


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2. Demographic rates for a “stable” northern caribou herd are characterized by a natural survival rate of bulls (Sm) = 80%, a natural survival rate of cows (Sf) = 89%, and a calf recruitment rate (R) = 25 calves/100 cows.

3. Environmental variation in demographic rates is high for R (CV =0.30) and relatively low for Sm and Sf (CV = 0.10).

4. Calf recruitment is the primary factor determining herd growth rates. 5. Sustainable harvest rates (bulls only) are about 2% for stable populations, 0–1% for declining herds

and 3–4% for increasing herds. These rates may require further adjustment if other sources of human-caused mortality are prevalent.

6. Current bull harvest rates (bull harvest/population size) from licenced hunting are approximately 0.5% for Region 5, 1.5% for Region 6 and 1.4% for Region 7.

7. Bull-only hunting primarily affects adult sex ratios and has a much smaller effect on population growth rates.

8. Either-sex hunting primarily affects population growth rates and has a smaller effect on adult sex ratios.

9. Age-selective harvesting under the 5-point bull regulation protects younger bulls (1–5 yr.-olds) and selects for 6–10 yr.-old bulls.

10. Maintaining a minimum of 35 bulls/100 cows in caribou herds (post-season) should help to ensure that harvest rates are low enough to minimize evolutionary concerns of harvesting 5–point bulls.

11. A GOS with a 5-point bull regulation is likely conservative. LEH seasons, however, may be required where a GOS results in adult sex ratios < 35 bulls/100 cows.

12. The minimum population size to support a licensed hunting season is estimated at 250. This should ensure a low (P < 0.05) probability of a herd declining to 100 animals within 10 years due to environmental and demographic effects.

10. Recommendations 1. Herds should remain the basic unit for caribou management. 2. The current guidelines of maintaining > 35 bulls/100 cows in each herd should be maintained. 3. GOS’s with 5-point bull regulations should be maintained as they appear to be effective for most

herds in maintaining objective of > 35 bulls/100 cows. 4. Where GOS seasons result in adult sex ratios < 35 bulls/100 cows, consideration should be given to

LEH seasons for 5-point bulls. 5. Harvest rates for bull caribou should be adjusted in accordance with late winter calf recruitment (R)

and/or growth rates (λ) for each caribou herd. Various approaches to determine R and λ include: a. successive population surveys (i.e. repeat surveys over a number of years); b. a big game stock assessment (analysis of population and hunter harvest information); or c. reliable field observations from a variety of sources.

Harvest rates should be further reduced where other sources of human-caused mortality are prevalent, as per the guidelines below:


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Winter Calves/100 Cows (R)

Population Growth Rate (λ)

Bull Harvest Rate (Mh)*

< 15 calves/100 cows λ < 0.95 Mh = 0% (0%)

20 calves/100 cows λ = 0.97 Mh = 1% (<1%)

25 calves/100 cows λ = 1.00 Mh = 2% (1%)

30 calves/100 cows λ = 1.02 Mh = 3% (2%)

> 35 calves/100 cows λ > 1.04 Mh = 4% (3%)

*Mh = bull harvest/total herd abundance in late winter. Harvest rates in parentheses are recommended where other human-caused mortality is prevalent.

6. Harvest rates should be determined for each caribou herd to ensure they are sustainable using the guidelines in #5.

7. In the absence of either calf recruitment or herd growth rate data, a bull harvest rate of 1% for herds with >250 caribou may be considered providing other sources of human-caused mortality are low.

8. Where detailed population-specific information for a herd is available, herd-specific harvest rate recommendations may be developed, and not be restricted to the guidelines in #5.

9. While some cow hunting may be sustainable for increasing herds, licensed harvests should normally be limited to bulls.

10. Unreported human-caused cow mortality may be a significant limiting factor for some herds. Where possible, herd harvest rates should be adjusted to account for this additional mortality.

11. A population viability assessment (PVA) should be undertaken for unhunted herds prior to opening a licensed hunting season in order to ensure harvests are sustainable.

11. Acknowledgements Gerry Kuzyk from the BC Wildlife and Habitat Branch initiated the study, wrote the project proposal, and oversaw the contract. The Provincial Caribou Harvest Policy Team reviewed the document and made numerous suggestions for its improvement. This team consisted of 10 employees from the Ministry of Forests, Lands, Natural Resource Operations and Rural Development and included: Gerry Kuzyk, Kaitlyn Schurmann and Michael Burwash (Wildlife and Habitat Branch), Dan Lirette and Carolyn Shores (Region 5: Cariboo), Conrad Thiessen (Region 6: Skeena); Shelley Marshall and Michael Klaczek (Region 7A: Omineca Region), and Michael Bridger and Agnes Pelletier (Region 7B: Northeast Region). Special thanks to Kaitlyn Schurmann for preparing Appendix 1, 2 and 3, and to Nicola Dodd (Ministry of Environment and Climate Change) for providing the herd status information in Table 1.

12. Literature Cited Akcakaya, H.R. 1991. A method for simulating demographic stochasticity. Ecological Modelling 54:133-

136.


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Bergerud, A.T. 1977. Rutting behaviour of Newfoundland caribou in Geist, V. and F. Walther (eds.).

Behaviour of ungulates and its relation to management. IUCN No. 24, pp. 395-435. Bergerud, A.T. 1978. The status and management of caribou in British Columbia. Report to BC Fish and

Wildlife Branch, Victoria, B.C. 138 p. Bergerud, A.T. 1980. A review of the population dynamics of caribou and wild reindeer in North

America. In D. Reimers, E. Gaare, and S. Skenneberg (editors). Proceedings of the 2nd International Reindeer/Caribou Symposium, Roros, Norway.

Bergerud, A.T.1992. Rareness as an antipredator strategy to reduce predation risk for moose and

caribou. In: McCullough D.R., Barrett R.H. (eds.) Wildlife 2001: Populations. Springer, Dordrecht.

Bergerud, A.T. 1996. Evolving perspectives on caribou population dynamics, have we got it right

yet? Rangifer, Special Issue No. 9: 95-116. Bergerud, A.T. 2000. Caribou. Chapter 31 In Demarais, S. and P.R. Krausman (eds). Ecology and

Management of Large mammals in North America. Prentice Hall. Pp. 658-683. Bergerud, A.T. and J.P. Elliott. 1986. Dynamics of caribou and wolves in northern British Columbia.

Canadian Journal of Zoology 64: 1515-1529.

Bergerud, A.T. and J.P. Elliott. 1998. Wolf predation in a multiple-ungulate system in Northern British Columbia. Canadian Journal of Zoology 76:1551-1569.

Bergerud, A.T. and R.E. Page. 1987. Displacement and dispersion of parturient caribou at calving as an antipredator tactic. Canadian Journal of Zoology 65: 1597 - 1606.

Caughley, G. 1977. Analysis of vertebrate populations. John Wiley and Sons, London. 234 pp.

Cichowski, D. 2015. Tweedsmuir-Entiako caribou population status and background information summary. Prepared for Ministry Forests, Lands and Natural Resource Operations, Smithers, B.C. 139 pp.

DeCesare, N. J., M. Hebblewhite, M. Bradley, K.G. Smith, and D. Hervieux. 2012. Estimating ungulate recruitment and growth rates using age ratios. Journal of Wildlife Management 76:144-153.

Edmonds, E. J. 1988. Population status, distribution, and movements of woodland caribou in west central Alberta. Canadian Journal of Zoology 66:817-826.

Environment Canada. 2012. Management Plan for the Northern Mountain Population of

Woodland Caribou (Rangifer tarandus caribou) in Canada. Species at Risk Act Management Plan Series. Environment Canada, Ottawa. vii + 79 pp.

Environment Canada. 2014. Recovery Strategy for the Woodland Caribou, Southern Mountain population (Rangifer tarandus caribou) in Canada. Species at Risk Act Recovery Strategy Series. Environment Canada, Ottawa. viii + 103 pp.


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Environment Yukon. 2016. Science-based guidelines for management of Northern Mountain caribou in Yukon. Yukon Fish and Wildlife Branch Report MR-16-01. Whitehorse, Yukon, Canada

Farnell, R., R. Florkiewicz, G. Kuzyk, and K. Egli. 1998. The status of Rangifer tarandus caribou in Yukon, Canada. Rangifer:131-137.

Festa-Bianchet, M. 2016. When does selective hunting select, how can we tell, and what should we do

about it? Mammal Review 47:76-81. Gaillard, J.-M., M. Festa-Bianchet, N.G. Yoccoz, A. Loison, and C. Toïgo. 2000. Temporal variation in

fitness components and population dynamics of large herbivores. Annual Review of Ecology and Systematics 31:367-393.

Ginsberg, J.R. and E.J. Milner-Gulland. 1994. Sex biased harvesting and population dynamics in

ungulates: implications for conservation and sustainable use. Conservation. Biology 8:157-166. Gustine, D.D., K.L. Parker, R. J. Lay, M.P. Gillingham, and D.C. Heard. 2006. Calf survival of woodland

caribou in a multi-predator ecosystem. Wildlife Monographs 165:1-32.

Guthery, F.S. and J.H. Shaw. 2013. Density dependence: Applications in wildlife management. Journal of Wildlife Management 77:33-38.

Hatter, I.W. and W.A. Bergerud. 1991. Moose recruitment, adult mortality, and rate of change. Alces 27:65-73.

Heard, D. and K. Vagt. 1998. Caribou in British Columbia: A 1996 status report. Rangifer, Special Issue No. 10: 117-123.

Hebblewhite, M., J. Whittington, M. Bradley, G. Skinner, A. Dibb and C.A. White. 2007. Conditions for caribou persistence in the wolf-elk-caribou systems of the Canadian Rockies. Rangifer, Special Issue No. 17:79-91.

Hegel, T. 2015. Identifying Sustainable Harvest Rates for Northern Mountain Caribou in Yukon. Unpublished manuscript prepared for Fish and Science-based guidelines for Northern Mountain caribou management in Yukon 18 Wildlife Branch, Department of Environment, Yukon Government.

Hegel, T.M. and K. Russell. 2011. Status of northern mountain caribou (Rangifer tarandus caribou) in

Yukon, Canada. Rangifer Special Issue No. 21: 59-70. Hegel, T. M., A. Mysterud, F. Huettmann, and N. C. Stenseth. 2010. Interacting effect of wolves and

climate on recruitment in a Northern Mountain caribou population. Oikos 119:1453-1461. Holand, Ø., K. H. Røed, A. Mysterud, J. M. Kumpula, M. Nieminen, and M. E. Smith. 2003. The effect of

sex ratio and male age structure on reindeer calving. Journal of Wildlife Management 67:25-33.

Johnson, C.J., L.P.W. Ehlers and D.R. Seip. 2015. Witnessing extinction – Cumulative impacts across landscapes and the future loss of an evolutionarily significant unit of woodland caribou in Canada. Biological Conservation 186:176-186.


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Kutz, S., J. Ducrocq, C.Cuyler, B.Elkin, A. Gunn, L. Kolpashikov, D. Russell, and R.G.White. 2013. Standardized monitoring of Rangifer health during International Polar Year. Rangifer: 91−114.

Kuzyk, G.W. and I.W. Hatter 2014. Using ungulate biomass to estimate abundance of wolves in British Columbia. Wildlife Society Bulletin 38:878-883.

McNay, R.S. 2009. Spatial and temporal patterns of predation risk on woodland caribou in the Wolverine and Chase herds, north-central British Columbia, 1991-2006. Peace/Williston Fish and Wildlife Compensation Program Report No. 323. 28 pg. plus appendices.

Ministry of Environment, Lands and Parks (MELP). 1996. Wildlife Harvest Strategy. Improving British Columbia’s Wildlife Harvest Regulations. 73 pp.

Morris, W.F. and D.F. Doak. 2002 Quantitative Conservation Biology: Theory and Practice of Population Viability Analysis. Sinauer Associates, Inc. Publishers.

Mysterud, A., T. Couslon and N. C. Stenseth. 2002. The role of males in the dynamics of ungulate populations. Journal of Animal Ecology 71:907-915.

Northern Caribou Technical Advisory Committee (NCTAC). 2004. A strategy for the recovery of Northern Caribou in the Southern Mountains National Ecological Area in British Columbia. Version 1.0.

Perez, J.M., E. Serrano, M. Gonzalez-Candela, L. Leon-Vizcaino, G.G. Barbera, M. A. de Simon, P. Fandos,

J.E. Granados, R.C. Soriguer and M. Festa-Bianchet. 2011. Reduced horn size in two wild trophy-hunted species of Caprinae. Wildlife Biology 17:102-112.

Resources Inventory Standards Committee (RISC). 2002. Aerial-based inventory methods for selected

ungulates: Bison, mountain goat, mountain sheep, moose, elk, deer and caribou. Standards for Components of British Columbia’s Biodiversity. No. 32. V.2.0. Minist. Sustain. Res. Manage., Victoria, B.C. 91 pp

Seip, D. 1992. Factors limiting woodland caribou populations and their interrelationships with wolves and moose in southeastern British Columbia. Canadian Journal of Zoology 70:1492-1503.

Seip, D., and D.B. Cichowski. 1996. Population ecology of caribou in British Columbia. Rangifer, Special Issue No. 9:73-80.

Seip, D., C. Johnson and G. Watts. 2007. Displacement of mountain caribou from winter habitat by snowmobiles. Journal of Wildlife Management 71:1539-1544.

Serrouya, R., B.N. McLellan, H. van Oort, G. Mowat and S. Boutin.2017. Experimental moose reduction lowers wolf density and stop decline of endangered caribou. PeerJ 5:e3736; DOI 10.7717/peerj.3736.

Smith, K. 2004. Woodland caribou demography and persistence relative to landscape change in west-central Alberta. MSc. thesis, University of Alberta. 112 p.

Thomas, D. C. and D. R. Gray. 2002. Update COSEWIC status report on the woodland caribou Rangifer tarandus caribou in Canada. Pages 1–98 in COSEWIC assessment and update status report on


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the woodland caribou Rangifer tarandus caribou in Canada. Committee on the Status of Endangered Wildlife in Canada, Ottawa, Ontario.

Wielgus, R.B. 2002. Minimum viable population and reserve sizes for naturally regulated grizzly bears in British Columbia. Biological Conservation 106: 381-388.

Wilson, S. 2009. Recommendations for predator-prey management to benefit the recovery of mountain caribou in British Columbia. Prepared for BC Ministry of Environment, Victoria, B.C. 19 p.

Wittmer, H.U., A.R.E. Sinclair, B.N. McLellan. 2005. The role of predation in the decline and extirpation of woodland caribou. Oecologia 144:257-267.

Wittmer, H.U., R.N.M. Ahrens, and B.N. McLellan. 2010. Viability of mountain caribou in British Columbia, Canada: effects of habitat change and population density. Biological Conservation 143:86-93.


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Appendix 1. Provincial caribou herds in British Columbia.

Population trends correspond to those shown in Table 1. The long-term trend is based on a three generation (27 years) trend from available survey and/or population vital rates data (SMP, Environment Canada 2014).


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Appendix 2. Average caribou days hunted and harvest from 1980–2017.


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Appendix 3. Average caribou harvest age and harvest from 1980–2017.


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Appendix 4. Hunting statement from Strategy for Recovery of Northern Caribou in the SMNEA in BC (NCTAC 2004, pp. 10-11).

General Principles for Harvesting

• Only local populations that are considered viable should be considered for hunting. • Sport hunting should continue to be limited to bulls and, where possible, restricted to an

identifiable subgroup of bulls (e.g., five-point bulls). The annual allowable harvest (AAH) should be determined from a conservative estimate of the size and growth rate of the population and should account for both environmental and demographic stochasticity in population growth rates.

• The AAH should not affect the effectiveness of recovery actions within the SMP. • Where there are competing demands for use of animals, either for translocation to recover

endangered local populations or for harvest, the priority should be for transplant. If necessary, a temporary hunting moratorium may be established until the source population has recovered to pre-transplant removal levels or to a specified population target as determined by the Recovery Implementation Group3 (RIG).

• The size and composition of First Nations’ harvest should be incorporated into the determination of the AAH available for the licensed hunter harvest.

• Allocation of the AAH to user groups should follow provincial policy. Evaluation Criteria

• Local populations designated as Endangered or Threatened should not be harvested. • Harvesting of local populations designated as Vulnerable or Not at Risk should be carefully

evaluated to ensure their conservation. • Hunting should be limited to local populations that have a stable-to-increasing population trend. • The annual harvest should not significantly alter the projected future growth of the population

from that expected in the absence of hunting. • Local population surveys should be conducted every 3 to 5 years to update population estimates,

revise the AAH, and monitor recruitment and adult sex ratios. • If a survey of a local population has not been conducted within 5 years of the previous survey

estimate, the hunting season should be closed. • All harvests must be inspected to ensure accurate information on the date and location of the kill

and the sex and age of the animal. • Where local populations of hunted caribou occupy accessible areas (e.g., accessible by road or

ATV trail), hunting should be controlled through limited-entry permits, by restricting hunting to the pre-rut period only, or by completely closing the hunting season.


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Appendix 5. Hunting statement from Northern Mountain Population Management Plan (Environment Canada 2014). The ability of caribou herds to sustain harvest depends to a large extent on population size, calf recruitment, adult female survival and harvest rate. Recruitment rates are affected by environmental factors such as climate, habitat quality and predation levels. Recruitment rates can vary from excellent (>35 calves/100 cows at end of winter), to good (25-35 calves/100 cows at end of winter) to poor (<25 calves/100 cows), indicating populations that are increasing, stable to increasing or declining respectively. In YT, a harvest rate of two to three percent (adults) is generally considered to be sustainable given a relatively stable, naturally regulated caribou population (Environment Yukon 1996; Hayes et al. 2003). Harvest in excess of three percent generally leads to a decline (Bergerud 1980). Herds in decline (recruiting fewer than 25 calves/100 cows for more than three years) may not be able to sustain any level of harvest. Small herds (<200) are more vulnerable to stresses and less likely to withstand harvest (based on professional opinion or local knowledge). In YT, herds with populations of less than 200 animals are recommended to be closed to licensed hunting (Environment Yukon 1996). For some small populations, BC restricts the licensed harvest to bulls-only, either through limited entry hunting or a 5-point bull only season. In many areas First Nations harvest is not reported, making sustainable harvest rates difficult to calculate for wildlife managers. The influence of hunting on the NMP has implications for the management of both the caribou population and habitat (Bergerud 1978; Calef 1981; Valkenburg et al. 1994, Farnell et al. 1998). If herds are managed for sustainable harvest, their habitat must be managed to support healthy populations that are able to withstand harvest pressures. New road development and subsequent off-road trails often accompany industrial activity and facilitate hunting access. If access to a given herd increases for any reason, management initiatives must meet the challenge of a potential increase in hunting pressure. Access management is therefore integral to harvest management.


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Appendix 6. Caribou Harvest Management Standards –Wildlife Harvest Strategy, BC (from MELP 1996, pp.12-14).

Management Constraints and Opportunities All caribou in British Columbia belong to the woodland subspecies (Rangifer tarandus caribou), but they can be considered as two different ecotypes: the “mountain” ecotype and the “northern” ecotype (sometimes called Osborn caribou). The mountain ecotype occurs within suitable montane ecosystems of the east-central and south-eastern portions of the province. Caribou in these ecosystems are primarily limited by the availability of arboreal lichens in winter. Long-term habitat losses have been sustained through logging, fire, creation of water reservoirs, agriculture, and railroad and highway construction. Within northern ecosystems, the primary factor currently limiting caribou populations appears to be predation. Although less affected by large-scale habitat loss, increasing resource extraction activities and associated new access are also concerns in the management of northern caribou and their habitats.

Caribou have less capability for sustaining high harvest levels than other cervid species. Low calf recruitment, migratory habits, dependence on critical seasonal habitats, and vulnerability of mature bulls to hunting during the rut necessitates greater restriction of harvest opportunities than for deer, elk, and moose. Provincial Harvest Management Goals In general, caribou will be managed to optimize population sustainability within ecosystems while allowing for options and opportunities associated with viewing and hunting. Hunting regulations which have allowed the heavy harvest of bulls have skewed bull age structures and adult sex ratios. One management goal, therefore, will be to maintain or (where necessary) restore appropriate sex and age ratios. Because the mountain ecotype is blue-listed (either or both species/habitat considered vulnerable), it will be managed more conservatively than the northern ecotype. Hunting Policy Statement Where caribou hunting seasons are prescribed, the level of harvest will be adjusted to meet hunter demand within the constraints of conservation and allowance for non-hunting uses (e.g., nature study, wildlife viewing). Wherever possible, caribou hunting regulations will be kept simple, uniform within ecosystem units, and consistent over time. Regulations to increase resident hunter harvest opportunities, including the harvest of “any bull,” cows, and calves, may be considered for the northern ecotype providing population surveys indicate increased harvests are sustainable. Regulations will require that hunters remove the edible portions of the carcass to a place of consumption.


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Regulating Harvest In lightly hunted populations, bull caribou will normally be harvested through a general open season (GOS) “any-bull” regulation. For moderately hunted populations antler regulations such as the “5-point bull regulation” may be applied. Heavily hunted populations may require a combination of regulations, including limited entry hunting (LEH), in order to achieve population objectives. Caribou may also be managed under LEH “any bull” or “any caribou” regulations in provincial parks and selected highly accessible areas. Harvest levels will be regulated to ensure that adult sex ratios are maintained above 35 bulls/100 cows post-season. Archery only seasons, where in effect, will usually occur prior to the bull GOS.

Opening Dates General Open Seasons Limited Entry Hunting Any bull Aug. 15; Sept. 1, 10, 20 Bulls with 5 or more points Aug. 15; Sept. 1, 10, 20 Any caribou Aug. 15; Sept. 1, 10 ,20

Closing Dates: the latest closing date will normally be October 15. One legal definition for the “5-point bull” regulation is preferred because it would simplify regulations and their enforcement. The recommended definition is “one antler which bears at least 5 points (each point or tine being at least 2.5 cm in length), including the tip of the main beam above the rear point”. Both sexes may require harvesting to meet population objectives.

Harvest Monitoring Compulsory inspection of all harvested caribou will continue. The Annual Hunter Sample and Guide-Outfitter returns will also continue so that data from unsuccessful and successful caribou hunters can be consolidated. Annual MU estimates of the number of hunters, number of days spent hunting, and number of caribou harvested will continue to be used to monitor trends in hunter demand and the harvest. Population Monitoring Whenever possible, absolute abundance and sex/age composition will be monitored within established provincial caribou survey units every three to five years. For the northern ecotype, the survey method will be the stratified random block survey, conducted during winter with adjustments for sightability. Herd composition counts during fall, when caribou are concentrated on rutting ranges, may also be conducted to obtain calf recruitment rates. For the mountain ecotype, the primary survey method will be total counts in late winter subalpine habitats, with adjustments for sightability. Population modelling will be used to monitor population trends at the ecosystem level and, for the northern ecotype, may utilize cohort analyses for bulls, which incorporate harvest rate estimates (determined from population surveys) and harvest age composition data.

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To the reader - British Columbia · 2020-06-09 · 3. Environmental variation in demographic rates is high for R (coefficient of variation (CV) =0.30) and relatively low for S m and