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Technical Thematic Report No. 10. - Northern caribou population trends in Canada

Herd-specific assessments

 

Population estimate data were compiled for this report and for the online database of the Circum Arctic Rangifer Monitoring and Assessment Network (CARMA, 2010a). Where possible, publicly available documents containing methodology have been cited. As population estimates are occasionally recalculated based on new data and for consistency with more recent surveys, conflicting estimates appear in the literature for some herds and some years – in these cases, we have selected the most recent estimate that is published in a publicly available document.

The emphasis in these accounts is on trends in herd size and on vital rates such as calf survival, when the information is available, rather than an exhaustive account of population demography. We have also included some information on environmental trends for the herd ranges.

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Ahiak Herd

Ecozones+ Calving ground: Southern Arctic (also summer into fall); Southern Arctic and Taiga Shield fall and winter ranges

Status and trends

Caribou calving along the Queen Maud Gulf coast were first known from Inuit knowledge and from historical information on caribou distribution. Inuit elders from Gjoa Haven and Hudson Bay traders described how caribou used to calve on the islands along the Queen Maud Gulf coast (Gavin, 1945). The herd was first named after the Queen Maud Gulf (Heard et al. 1986) and then, in the early 1990s, the herd's name was changed to the Inuktitut word Ahiak.

Studies and surveys of the Ahiak Herd have been infrequent, which has hindered describing and interpreting trends. Information is from tracking of satellite-collared cows (1996 to 1997 and 2001 to 2010), pre-calving surveys in 1983 and 1995, and surveys of calving distribution in 1986 and 1996 (Gunn et al. 2000b; Gunn and D'Hont, 2002). In 1986, a stratified visual survey of the coastal calving ground estimated 11,265 ± 1615 (SE) caribou. In 1996, caribou were found calving further west than in 1986 as an elongated coastal calving ground and a lower coverage survey estimated 83,134 ± 5298 (SE) caribou (Gunn et al. 2000b). In 2006, the estimate for this calving ground was 123,226 ± 14,500 (SE) (Johnson, unpublished data). Between 2006 and 2010, annual surveys were flown to map calving distribution and estimate densities of caribou across the Queen Maud Gulf coast between Bathurst Inlet and Chantrey Inlet. There was a 60% decline in the number of caribou on the calving ground between 2006 and 2009, followed by an increase in caribou observed in 2010 compared to 2009 (Kelly, 2011, pers. comm.).

The first interpretation of the historical information and 1986 to 2006 aerial surveys was that the Ahiak Herd calved along the coast and was a discrete, tundra-wintering herd, although in some years the herd's wintering range extended into the boreal forest (Gunn et al. 2000b; Gunn and D'Hont, 2002). Between 2007 and 2009, six satellite-collared cows that had initially calved on the Beverly Herd's calving grounds had switched (Gunn et al. In Press; Nagy et al. 2011) to what had been defined as the traditional coastal calving ground of the Ahiak Herd (Gunn et al. In Press; Gunn et al. 2000b). Based on collar location analysis, Nagy et al. (2011) proposed an alternate interpretation and suggested that the Ahiak and Beverly herds were not discrete herds but have likely been linked as early as the mid-1990s with the gradual shift of Beverly cows to the Ahiak calving ground located in the western half of the Queen Maud Gulf. Nagy et al. (2011) also suggested that another tundra-wintering herd has an overlapping calving distribution with the western Queen Maud Gulf and that the calving ground extends across the eastern portion of the Queen Maud Gulf and across Chantrey Inlet.

Despite the uncertainty in the timing of the Beverly Herd's change in calving distribution, it is clear that there has been change since 2007, with satellite-collared cows from the Beverly Herd calving on the Ahiak Herd's calving ground. The timing and mechanism for the shift in calving is a key consideration in interpreting whether the initial increase in caribou calving in the Queen Maud Gulf was the previously identified tundra-wintering Ahiak Herd and/or the on-going northern shift of the Beverly Herd.

Due to two possible interpretations of the movement data of caribou calving in the Queen Maud Gulf area, we have not graphed the estimates of caribou on the calving grounds and acknowledge that the current status of the Ahiak Herd is uncertain. The Ahiak Herd may have gone through a sharp increase from 1986 to 2006 and a subsequent decline from 2006 to 2009, with signs of increase between 2009 and 2010. On the other hand, we may not have a recent estimate of the Ahiak Herd during calving in the Queen Maud Gulf, as Nagy et al. (2011) suggest the apparent increase between 1996 and 2006 may have been the slow colonization of the area for calving by the Beverly Herd.

Spring composition surveys to estimate calf:cow ratios have been undertaken since 2008. Satellite collaring from 1996 to 98 and again from 2001 to 2005 revealed that caribou calving on the Queen Maud Gulf coast wintered mostly on the tundra, although in some years (1997 and 2001) the winter distribution extended south of the treeline (Gunn et al. 2000b; Gunn and D'Hont, 2002). The herd is seasonally hunted by people from Gjoa Haven, Umingmaktok, and Cambridge Bay (Nunavut); Lutsel K'e (NWT); and, in some winters, the communities of northern Saskatchewan.

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Baffin Island herds

Ecozones+ Calving ground: Northern Arctic (also summer into fall and winter); some herds also use Arctic Cordillera

Status and trends

Inuit have reported on historic trends in distribution and changes in migration patterns based on observations of abundance of the caribou (Ferguson et al. 1998; Knight Piésold Consulting, 2010). Inuit on Baffin Island report that caribou numbers are cyclic, with 60 to 80 years between peaks in abundance. Historically, on southern Baffin, caribou numbers were low in the 1940s, followed by increases during the 1950s, peaking in the 1980s and early 1990s, depending on the geographic area (Ferguson et al. 1998). Subsequent trends are unreported, although a recent compilation of reports and local knowledge indicates that caribou numbers, at least on north Baffin Island, are at a low point in the cycle of abundance (Knight Piésold Consulting, 2010). No population surveys have been conducted in north Baffin and only one preliminary, non-systematic calf survey was completed in 1997 (Jenkins, 2007). This survey identified calving in the vicinity of the proposed Mary River iron ore open-pit mine.

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Bathurst Herd

Ecozones+ Calving ground:Southern Arctic (also summer into fall);Taiga Shield fall and winter ranges

Status and trends

The Bathurst Herd size and distribution has been monitored frequently and trends for herd abundance are relatively well-described. The herd increased during the early 1980s and peaked in 1986 (Figure 7). Then, between 1986 and 2006, the herd declined at a rate of 5% per year, based on censuses in 1996, 2003, and 2006. A population survey in 2009 found only 16,000 breeding females on the calving grounds, translating into a population estimate of 31,600 animals – over a 70% decline from the 2006 estimates. Supporting evidence for the decline comes from a trend of reduced calf survival and relatively low adult survival of cows. Calf survival from 2001 to 2006 was about half the rate of survival measured from 1985 to 1995. Then, in 2007 and 2008, calf survival (based on calf:cow ratios) increased, which may have partially reflected low cow survival (Boulanger et al. 2011). Calf survival and calving distribution are currently monitored annually.

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Figure 7. Caribou Herd population estimates.

Graph

Standard errors were not calculated for the visual surveys and no standard error figure was available for 1982. Estimates are of caribou one year and older. Surveys were all undertaken in June.

Source: based on data compiled for this report – 1977-1984: Case et al. (1996); standard error for 1984: Environment and Natural Resources (No Date[Bathurst]); 1986: Heard and Williams (1991a); 1990: Heard and Williams (1991b); 1996: Gunn et al. (1997); 2003: Gunn et al. (2005); 2006: Adamczewski et al. (2009); 2009: Adamczewski (2011b, pers. comm.)

Long Description for Figure 7

This bar graph shows Bathurst Caribou herd population estimates from 1977 to 2009. The herd increased during the early 1980s and peaked in 1986. Then, between 1986 and 2006, the herd declined at a rate of 5% per year. Populations varied between approximately 470,000 and 30,000.

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In 2010, the Wek'èezhìi Renewable Resources Board recommended sharply curtailing aboriginal harvesting and halting resident and commercial harvesting after extensive public hearings on a joint management proposal from the Tlicho Government and the Government of the Northwest Territories (WRRB, 2010).

Historically, based on Tlicho elders' recollections of the supply of caribou in fall hunting camps, there were high numbers of Bathurst caribou in the 1940s, low numbers in the 1950s, and increasing numbers during the 1970s and 1980s (Dogrib Treaty 11 Council, 2001). A similar pattern was determined by examining the frequency of hoof scars on spruce roots (Zalatan et al. 2006). The scar frequency distribution shows low caribou abundance during the 1920s, followed by a high peak during the mid-1940s, then a low period between 1950 and 1970. There was an increasing trend in caribou abundance after the 1970s, with a peak in the 1990s, followed by a significant drop in caribou abundance at the turn of the century.

Since 1996, the location of the calving ground has been relatively predictable and the annual use of post-calving and summer ranges, based on the movements of satellite-collared cows, has not shifted (Gunn et al. 2008). The fall and winter ranges are the largest seasonal ranges and the least predictable on an annual basis (Gunn et al. In Press). Since 1998, the southern boundary of the winter range has contracted (Gunn et al. 2011b). Based on movement data, as calculated from satellite collars on cows, there was a positive relationship between distance from winter range to calving grounds and both mean daily movement rates during May and date of entry into the peak calving area (Gunn and Poole, 2009). Environmental trends for the Bathurst range are consistent with trends recorded at the circumpolar and ecozone+ scales (Gunn and Poole, 2009).

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Beverly Herd

Ecozones+ Calving ground: Southern Arctic (also summer into fall); Taiga Shield fall and winter ranges

Status and trends

Studies and surveys of the Beverly Herd were frequent until the early 1990s. During the 1980s, the overall trend in herd size was an increase (Figure 8). Calf survival was high in earlier studies, but was not measured after 1993. The 1994 photographic survey (Williams, 1995) estimated 151,000 ± 48,700 (SE) caribou one year old and older on the calving grounds. A 2002 visual calving ground survey reported lower densities than in 1994 (Johnson and Mulders, 2009), suggesting that herd size likely peaked in the early to mid-1990s. Subsequently, the recent trends are uncertain as there are gaps in monitoring of caribou abundance between 1994 and 2002 and then between 2002 and 2006. Four calving ground delineation surveys from 2006 to 2009 found few cows and even fewer calves, despite extensive aerial coverage across and surrounding the traditional calving ground (Adamczewski et al. 2009). Previously, calving distribution was characterized by fidelity to a traditional calving ground, based on surveys from 1957 to 1974, 1978 to 1994, 2002, and 2006 to 2009 (Gunn and Sutherland, 1997; Gunn et al. 2007; Johnson and Mulders, 2009; Adamczewski et al. 2009).

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Figure 8. Beverly Caribou Herd population estimates.

Graph

Standard errors were not calculated for earlier visual surveys. Population estimates are of caribou one year and older.

Source: based on data compiled for this report – 1971 and 1978: Heard and Decker (1980); 1980: Gunn and Decker (1982); 1982-1988: Heard and Jackson (1990); 1993-1994: Williams (1995)

Long Description for Figure 8

This bar graph shows Beverly Caribou Herd population estimates from 1971 to 1994. The overall trend in herd size was an increase, from approximately 200,000 to 275,000 over the period. Visual calving-ground surveys from 1971 to 1980 show decreasing populations around 200,000 to 100,000. Calving-ground photo surveys from 1982 to 1994 show increasing populations from around 160,000 to 275,000.

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Satellite collaring of Beverly caribou did not start until 2006, which has hindered the description and interpretation of herd trends. Nagy et al.'s (2010; 2011) interpretation, based on an analysis of telemetry across the Northwest Territories and Nunavut, suggests that a large part of the Beverly Herd shifted its calving ground approximately 200 to 300 km in the 1990s to the western half of the Queen Maud Gulf coast. Nagy et al. (2010; 2011) interpreted patterns in satellite telemetry data to infer that the Beverly Herd is currently using two calving grounds, with the majority of the Beverly cows now calving on the western Queen Maud Gulf coast. While caribou calving along the Queen Maud Gulf coast declined significantly between 2006 and 2009 (Adamczewski et al. 2009), the decline of the Beverly Herd may not have been as drastic as previously thought because some Beverly cows have switched their calving area. In any case, the increased human land use on the Beverly traditional calving ground and its possible effects on either the possible calving ground shift or the extreme decline of the herd are of concern (Campbell and Dumond, 2011, pers. comm.).

An alternate interpretation is that the Beverly Herd declined, as did the neighbouring herds (Bathurst and Qamanirjuaq herds – see this report) from 1994 to 2009. Gunn et al. (In Press) interpreted the satellite telemetry for 2006 to 2009 and aerial survey data as a decline in fidelity to the traditional calving ground starting in 2007 as a consequence of the extreme low densities recorded in 2006. From 2007 to 2009, six collared cows switched between the traditional Beverly calving ground and the Queen Maud Gulf coast, the latter previously described as the calving ground of the Ahiak Herd (Gunn et al. 2000b). A shift in use of calving grounds by Beverly caribou is consistent with a substantial reduction in abundance of breeding cows and calves on the traditional ground, which could trigger a behavioural response of remaining cows to move on to a larger herd's calving ground to maintain the advantages of gregarious calving.

The use of the traditional Beverly calving ground is likely to have persisted for thousands of years, based on pre-calving migration across the Thelon River to the calving grounds near Beverly Lake (Gordon, 2005). The Beverly Herd's summer ranges included the Thelon Game Sanctuary and the tundra south of the sanctuary. In fall, the generalized migration pattern was south of the Thelon Game Sanctuary, across the tree-line, and toward northern Saskatchewan (BQCMB, No Date). The fall movements and rut generally were east of Great Slave Lake. Later in winter, the Beverly Herd tended to move west toward and around the East Arm of Great Slave Lake (Thomas et al. 1998). Thomas et al. (1998) related the overall direction and rate of movements to snow conditions in the boreal forest. They noted that in most years caribou moved from East to West across the winter range as snow depths tended to be deeper on the eastern ranges.

Since the 1980s, trends in seasonal distribution have only been reported during the calving season (Gunn et al. In Press; Gunn and Sutherland, 1997; Gunn et al. 2007; Nagy et al. 2011). The satellite-collar information also suggested that the Ahiak Herd's summer ranges overlapped with some known summer ranges of the Beverly Herd, at least since 2006. The Beverly Herd is seasonally hunted by people from Baker (Nunavut); Lutsel K'e (NWT); and, Black Lake, Stony Rapids, and Uranium City, northern Saskatchewan.

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Bluenose-East Herd

Ecozones+ Calving ground: Southern Arctic; winters in the Southern Arctic and the Taiga Plains

Status and trends

The Bluenose-East Herd was not officially recognized as a distinct herd until 1999 (Nagy, 2009b). A photographic post-calving survey was undertaken in 2000, providing an estimate of 104,000 ± 22,100 (95% CI) (Figure 9). This was followed by a decline to an estimated 70,100 ± 8,100 in 2005 and 66,800 ± 5,200 in 2006. This translates into a 10% exponential rate of decline from 2000 to 2006. However, by 2010, the post-calving herd estimate was 98,600 caribou ± 7,100. There are gaps in the information as demographic rates were not monitored and information on distribution based on collared caribou has not been analyzed.

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Figure 9. Bluenose-East Caribou Herd population estimates.

Graph

Estimates are for caribou one year and older. Surveys were conducted in July.

Source: based on data compiled for this report – 2000: Patterson et al. (2004); 2005: Nagy and Tracz (2006); 2006: Nagy et al. (2008); 2010: Adamczewski (2011c, pers. comm.)

Long Description for Figure 9

This bar graph shows Bluenose-East Caribou Herd population estimates from 2000 to 2010. Post-calving photos surveys show populations were just over 100,000 in 2000, decreasing to around 70,000 and 67,000 for 2005 and 2006 respectively, returning back to populations around 99,000 by 2010.

Trends in vital rates are uncertain as monitoring has been infrequent until recently. Spring calf:cow ratios ranged between 25 and 52 calves:100 cows and showed no trend between 2001 and 2009 (Popko unpublished data in Adamczewski et al. 2009).

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Bluenose-West Herd

Ecozones+ Calving ground: Southern Arctic; winters in the Southern Arctic and the Taiga Plains

Status and trends

Although the Bluenose-West Herd was not officially recognized as a distinct herd until 1999 (Nagy, 2009b), population estimates were derived for 1986, 1987, and 1992 based on locations of radio-collars during post-calving surveys of the Bluenose Herd. The herd peaked at 112,400 ± 25,600 (95% CI) in 1992 and then declined to 76,400 ± 14,300 in 2000, and 20,800 ± 2,040 in 2005 (Figure 10). The 2005 estimate was confirmed by an estimate of 18,050 ± 530 caribou in 2006. Since then, the trend appears to have levelled out, with a preliminary estimate for a July 2009 survey of 17,900 ± 1,300 caribou (Davison, 2009, pers. comm.).

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Figure 10. Bluenose-West Caribou Herd population estimates.

Graph

Population estimates are for caribou one year and older. Data obtained during photocensus surveys of the "Bluenose" Herd prior to 2000 were re-analyzed to estimate Bluenose-West population trends. These estimates should not be considered as reliable as the later estimates (Adamczewski, 2011a, pers. comm.).

Source: based on data compiled for this report – 1986-2006: Nagy (2009a); also for 2005 and 2006: Nagy and Johnson (2006); 2009: Davison (2009, pers. comm.). See also Government of the Northwest Territories web page for this herd (Department of Environment and Natural Resources, No Date[Bluenose-West]).

Long Description for Figure 10

This bar graph shows Bluenose-West Caribou Herd population estimates from 1986 to 2009. An increasing trend is seen in re-analysis of "Bluenose" photo surveys, with populations rising from almost 90,000 to 112,000 from 1986 to 1992. Post-calving photo surveys show a decreasing trend with populations lowering from over 75,000 to about 20,000, from 2000 to 2009.

Based on recommendations of the Wildlife Management Advisory Council (NWT), the Gwich'in Renewable Resources Board, and the Sahtu Renewable Resources Board, co-management boards in the herd's range, all non-aboriginal hunting of the Bluenose-West Herd ceased in 2006. The co-management boards made further recommendations to restrict aboriginal harvesting of the Bluenose-West Herd by establishing a total allowable harvest and the requirement for a tag to harvest, measures that were implemented in 2007.

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Cape Bathurst Herd

Ecozones+ Calving ground: Southern Arctic; winters in the Southern Arctic and the Taiga Plains

Status and trends

Although the Cape Bathurst Herd was not officially recognized as a distinct herd until 1999 (Nagy, 2009b), population estimates were derived for 1987 and 1992 based on locations of radio-collars during post-calving surveys of the Bluenose Herd (Nagy, 2009a). The herd peaked at 19,300 ± 5,400 (95% CI) in 1992, then declined to about 11,100 ± 1,800 in 2000, 2,430 ± 260 in July 2005, and 1,820 ± 150 in 2006 (Figure 11). This translates into a 17% exponential rate of decline. The preliminary estimate for a July 2009 survey of this herd is 1,930 ± 350, suggesting that the decline had halted.

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Figure 11. Cape Bathurst Caribou Herd population estimates.

Graph

Population estimates are for caribou one year and older. Data obtained during photocensus surveys of the "Bluenose" Herd prior to 2000 were re-analyzed to estimate Cape Bathurst population trends. These estimates should not be considered as reliable as the later estimates (Adamczewski, 2011a, pers. comm.).

Source: based on data compiled for this report – 1987-2006: Nagy (2009a); 2005-2006: Nagy and Johnson (2006); 2009: Davison (2009, pers. comm.). See also Government of the Northwest Territories web page for this herd (Department of Environment and Natural Resources, No Date[Cape Bathurst]).

Long Description for Figure 11

This bar graph shows Cape Bathurst Caribou Herd population estimates from 1987 to 2009. Re-analysis of "Bluenose" photo surveys shows an increase of approximately 12,000 to 19,000 between 1987 and 1992. Post-calving photo surveys show decreasing trends, with populations over 11,000 in 2000 to approximately 2,000 in 2009.

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The Wildlife Management Advisory Council (NWT) recommended an end to all harvesting, with non-aboriginal limitations implemented in 2006 and aboriginal limitations implemented in 2007. Preliminary estimates in 2009 indicate that the herd may have stabilized. As well as harvest restrictions, improved recruitment rates in 2008 and 2009 may have contributed to halting the decline (Davison, 2010, pers. comm.).

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Dolphin and Union Herd

Ecozones+ Calving ground: Northern Arctic (also summer into fall); and winter range is in the Southern Arctic

Status and trends

Historical information and Inuit hunter reports indicate that there may have been as many as about 100,000 caribou on Victoria Island in the early 1800s (Manning, 1960). By the early 1920s, numbers declined and migration across Dolphin and Union Strait halted. The causes were possibly a combination of icing storms and the introduction of rifles. The recovery was slow and caribou were rare until the 1970s. By the 1990s, numbers were increasing and 28,000 caribou were estimated in 1997 (Figure 12). Subsequently, the herd has been at best stable but possibly declining slightly between 1997 and 2007, based on preliminary analyses (Poole et al. 2010; Dumond, 2011, pers. comm.).

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Figure 12. Dolphin and Union Caribou Herd population estimates.

Graph

The 2007 estimate is considered preliminary.

Source: based on data compiled for this report – 1980: Jakimchuk and Carruthers (1980) as cited in COSEWIC (2004); 1997: Nishi and Gunn (2004); 2007: Dumond (2011, pers. comm.)

Long Description for Figure 12

This bar graph shows Dolphin and Union Caribou Herd population estimates from 1980 to 2007. A summer visual survey in 1980 shows populations around 3,400. Fall visual surveys show populations around 28,000 and 22,000 in 1997 and 2007 respectively.

Calving is dispersed over about half of northern and central Victoria Island and, based on sightings, the summer, fall, and winter ranges have increased in size since the early 1980s. A trend to an increasing size of winter range was manifested as fall migrations across the newly formed sea ice to the mainland coastal areas, which is a resumption of the migrations that were observed up until the 1920s. The caribou return across the sea ice to Victoria Island in April to May. The date of freeze-up is increasingly delayed – 8 to 10 days later than in 1982, a trend which may lead to changes in the fall migration across the sea ice (Poole et al. 2010).

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George River Herd

Ecozones+ Calving ground: Arctic Cordillera; summer and winter in the Taiga Shield

Status and trends

Trends in the size and distribution of the George River Herd have been relatively well-described based on monitoring and studies (Couturier et al. 2004; Bergerud et al. 2008; Couturier et al. 2009a; Couturier et al. 2009b). The herd increased from about 5,000 animals in the 1950s to a peak of about 776,000 ± 104,000 (90% CI) in 1993 (Figure 13). At that point summer habitat was degraded, which may have initiated the decline to about 385,000 ± 108,000 individuals in 2001, followed by a further decline to 74,100 ± 12,600, based on the 2010 post-calving photocensus. The trend in abundance revealed by the aerial photographic counts is also supported by trends in lichen abundance (Boudreau and Payette, 2004a; Boudreau and Payette, 2004b) and hoof scars in tree roots aged by annual tree growth rings (Boudreau et al. 2003).

Figure 13. George River Caribou Herd population estimates.

Graph

Estimates, based on calving ground (June) and (for 2001 and 2010) post-calving (July) surveys, are all extrapolated to provide total herd population estimates for October, including calves. No confidence intervals were calculated for the visual surveys.

Source: based on data compiled for this report – 1973 and 1975: Messier et al. (1988); 1976-1982: Couturier et al. (1990); 1984 and 2001: Couturier et al.(2004); 1993: Couturier and Courtois (1996); 2010: Ressources naturelles et Faune (2010) and CARMA (2011)

Long Description for Figure 13

This bar graph shows George River Caribou Herd population estimates from 1973 to 2010. Visual calving-ground surveys show populations increasing between 1973 and 1982, of approximately 105,000 to 360,000. Calving-ground photo surveys show populations around 640,000 and 780,000 for 1984 and 1993 respectively. Post-calving photo surveys show populations decreasing from almost 400,000 in 2001 to less than 100,000 in 2010.

Trends in vital rates, including pregnancy and calf survival, are monitored and summarized (Couturier et al. 2004; Bergerud et al. 2008; Couturier et al. 2009a; Couturier et al. 2009b). The monitoring has been supported with studies of body condition and body mass for calves and yearlings. Couturier et al. (2009b) suggest that monitoring trends in the birth and fall mass of calves will be useful in determining when herds approach their peak abundance.

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Leaf River Herd

Ecozones+ Calving ground: Northern Arctic and Southern Arctic; winters in the Taiga Shield

Status and trends

The Leaf River (Rivière-aux-Feuilles) Herd was identified as a herd in 1975. The herd increased from 56,000 caribou in 1975 to 101,000 ± 43,400 (90% CI) in 1983, 121,000 ± 56,400 in 1986, 276,000 ± 75,900 in 1991, and 1,193,000 ± 565,000 in 2001 (Figure 14), although Couturier et al. (2004) suggested using the lower confidence limit (628,000) for the 2001 population estimate. Body condition of adult females and calves, as well as recruitment, were poor in 2007 and 2008, suggesting that the population has likely decreased. The next survey (results not available at time of writing) was planned for the summer of 2011 (Ressources naturelles et Faune, 2010). Recruitment, mortality of collared animals, body condition of mature females and calves, and consistent field observations suggest that the herd has been decreasing since the 2001 census. Management measures consistent with a decreasing population trend are under development (Brodeur, 2011, pers. comm.).

Figure 14. Leaf River Caribou Herd population estimates.

Graph

Estimates, based on calving ground (June) and (for 2001) post-calving (July) surveys, are all extrapolated to provide total herd population estimates for October, including calves. No confidence interval estimate for 1975. The 2001 estimate shown is the lower limit of the confidence interval (recommended for management purposes).

Source: data from Couturier et al. (2004)

Long Description for Figure 14

This bar graph shows Leaf River Caribou Herd population estimates from 1975 to 2001. Visual calving-ground surveys show population increase from approximately 56,000 in 1975 to 101,000 in 1993. Calving-ground photo surveys show populations increase from approximately 121,000 in 1986 to 276,000 in 1991. A post calving survey in 2001 shows a population around 628,000.

Monitoring was conducted on movement rates (1986 to 2003) and environmental indicators (1973 to 2003) (Couturier et al. 2009b). The monitoring reveals complex interactions between caribou condition, weather, and population dynamics.

The location of the calving grounds has shifted substantially northward in recent years (Taillon, 2011, pers. comm.).

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Lorillard and Wager Bay herds

Ecozones+ Calving ground: Northern Arctic (also summer into fall); Southern Arctic fall and winter ranges

Status and trends

The Lorillard and Wager Bay are the two largest herds of possibly eight tundra wintering herds on the northeast mainland. There is relatively little information on the herds in the northeastern mainland (Gunn and Fournier, 2000; Gunn et al. 2000a; Oli, 2003), although an increase in the number of satellite collared caribou is improving understanding of seasonal movements (Campbell, 2005; Campbell, 2007; Nagy et al. 2011).

In the late 1970s, surveys found a combined total of about 4,000 caribou on the Lorillard and Wager Bay calving grounds (Donaldson, 1981 in Heard et al. 1986). Caribou numbers likely increased until the mid-1990s. Inuit hunters reported that there were fewer caribou and that the caribou were in poor health in the mid-1990s (Buckland et al. 2000). Pre-calving surveys in 1995, compared to 1983 surveys, found a decline in caribou north of Wager Bay. Further surveys of the Lorillard calving grounds found no change between 1999 and 2003, while the estimated number of Wager Bay caribou increased between 2000 and 2004 (Campbell, 2005; Campbell, 2007). Trends in abundance and distribution of the smaller herds on the northeastern mainland are uncertain.

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Peary caribou

Ecozone+ Northern Arctic

Status and trends

In 1961 there were about 26,000 Peary caribou on the Queen Elizabeth Islands and possibly about 22,000 Peary caribou on the larger southern islands and on the Boothia Peninsula (COSEWIC, 2004). Since then the overall trend has been a decline. The rate of decline has varied over time and among the different island populations, with both reversals of some declines and absence of recovery for other populations. Survey intervals are irregular and only two of the six geographic populations (Banks Island and Bathurst Island complex) have been surveyed at regular intervals. In 2001, the total number of Peary caribou was extrapolated to about 8,000 (COSEWIC, 2004). The most recent estimates are: about 4,000 Peary caribou in Nunavut, based on surveys from 2001 through 2008 (Jenkins et al. 2011), and about 2,000 in the Northwest Territories (Carrière, 2009, pers. comm.).

Populations

Melville and Prince Patrick islands

Surveys have been infrequent but have documented a steep decline between 1961 and 1972 to 1973. The rate of decline was less rapid between 1974 and the next surveys in 1987 and 1997. The survey intervals of 16 and 10 years mean that recoveries and subsequent losses would not have been detected. See Figure 15a and Figure 15b.

Prince of Wales-Somerset islands group

Peary caribou seasonally cross the sea ice between the islands in this group. Between 1974 and 1980, caribou numbers were stable in the range of 4,000 to 6,000, which was one of the largest Peary caribou populations in the 1970s and 1980s. There was then a 15-year hiatus in surveys until 1995, when only a few caribou were found. In 2004, no caribou were seen during an aerial survey of the islands. See Figure 15c.

Bathurst Island (and its satellite islands)

Between 1961 and 1974, Peary caribou numbers declined by an order of magnitude. Between 1974 and 1994, numbers recovered to the 1961 level. An abrupt decline followed and, by 1997, fewer than 100 caribou remained. A survey in 2001 revealed the trend was for a recovering population. See Figure 15d.

Banks Island

Peary caribou on Banks Island formed one of the larger populations as they peaked at about 12,000 in the early 1970s and remained relatively stable until 1982. Numbers declined to about 1,000 caribou by 1992 and an initial small recovery by 2001 was likely lost during an icing storm early in the winter of 2003 (Nagy and Gunn, 2006). A 2010 survey led to an estimate of 1,097 ± 343 (95% CI) non-calf caribou, which confirmed the persistence of low numbers on Banks Island. See Figure 15e.

Northwest Victoria Island

Trends in Peary caribou on northwest Victoria Island are less clear than on Banks Island as surveys have been less frequent. Numbers were high, about 2,600 in 1987, and declined during the 1980s until, in 1993, only a few caribou were seen during an aerial survey. The population then slowly recovered, based on estimates of 95 ± 60 (95% CI) in 1998 and 204 ± 103 in 2001. However, in 2005, the estimate was 66 + 61 non-calf caribou, which suggested that some recovery was lost during two winters (2002/03 and 2003/04) with icing events (Nagy and Gunn, 2006). A subsequent survey in 2010 returned an estimate of 150 ± 104 non-calf caribou, which confirmed the persistence of low numbers. See Figure 15f.

Boothia Peninsula

Peary caribou on the Boothia Peninsula increased throughout the 1970s and early 1980s. Caribou in this region were last estimated in 1994 and showed a decline from the 1985 estimate (Gunn and Dragon, 1998). Trends are difficult to distinguish as satellite telemetry has shown that both barren-ground caribou and Peary caribou use the peninsula (Gunn et al. 2000a).

Eastern Queen Elizabeth Islands (Ellef Ringnes, Amund Ringnes, Devon, Ellesmere, Axel Heiberg Islands, Cornwall, King Christian, Graham)

There is relatively little information available to assess trends. The islands were surveyed in 1961, although coverage was so low that the resulting estimate of close to 1,500 caribou was an approximation (Tener, 1963). Since 2001, the Nunavut Department of Environment has undertaken aerial spring surveys on the islands, resulting in the following population estimates of caribou 10 months and older (Jenkins et al. 2011):

  • Ellesmere Island (including Graham Island), surveyed partly in 2005 and partly in 2006: combined survey results yield an estimate of 1,021 caribou
  • Axel Heiberg Islands, surveyed 2007: 2,291 (95% CI of 1,636 to 3,208) caribou
  • Amund Ringnes, Ellef Ringnes, King Christian, Cornwall, and Meighen Islands, surveyed 2007: total of 282 (95% CI of 157 to 505) caribou
  • Lougheed Island, surveyed 2007: 372 (95% CI of 205 to 672) caribou
  • Devon Island, surveyed 2008: 17 caribou counted in an extensive survey

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Figure 15. Peary caribou population estimates.

Graphs

Data sources for Figure 15:

  1. Melville Island: 1961: Tener (1963) as cited in Miller et al. (1975); 1972-1974: Miller et al. (1977); 1987: Miller (1988); 1997: Gunn and Dragon (2002)
  2. Prince Patrick Island: 1961 : Tener (1963) as cited in Miller et al. (1975); 1973 and 1974 : Miller et al. (1977); 1986 : Miller (1987);1997 : Gunn and Dragon (2002)
  3. Prince of Wales, Russell, and Somerset islands: 1980: Gunn and Decker (1984) as cited in Gunn et al. (2006); 1995: Gunn and Dragon (1998); 2004: Jenkins et al. (2011)
  4. Bathurst Island complex: 1961 : data from Tener (1963) adjusted by Miller and Barry (2009) to standardize the size of islands used in calculations for comparability with later surveys; 1973 and 1974: Miller et al. (1977) as cited in Miller and Barry (2009);1975: Fischer and Duncan (1976) as cited in Miller and Barry (2009);1981: data from Ferguson (1987) adjusted by Miller and Barry (2009) to account for smaller islands not surveyed;1985 and 1988: Miller (1991); 1993 and 1994: data from Miller (1998) adjusted by Miller and Barry (2009) to account for smaller islands not surveyed; 2001: Jenkins et al. (2011)
  5. Banks Island: 1972: Urquhart (1973) cited in Gunn et al. (2000c); 1982: data from Latour (1985) reanalyzed by Nagy et al. (2009f); 1985: McLean et al. (1986); 1987: McLean (1992); 1989: McLean and Fraser (1992); 1991: Fraser et al. (1992); 1992: Nagy et al. (2009b); 1994 and 1998: Larter and Nagy (2001); 2001: Nagy et al. (2006); 2005: Nagy et al. (2009c); 2010: Davison et al. (In Prep.)
  6. Northwest Victoria Island: 1980: Jakimchuk and Carruthers (1980) cited in Gunn (2005); 1987: Gunn et al. (2000c); 1993 and 1994: Gunn (2005); 1998: Nagy et al. (2009d); 2001: Nagy et al. (2009e); 2005: Nagy et al. (2009a); 2010: Davison et al. (In Prep.)
Long Description for Figure 15

This graphic presents six bar graphs showing Peary caribou population estimates between 1960 and 2010. The graphs are described in the following set of points:

  1. Melville Island: Infrequent surveys show a steep decline between 1961 and 1974 (approximately 12,800 and 1,700 respectively). Declines are less rapid for the next surveys, about 900 in 1987 and 800 in 1997.
  2. Prince Patrick Island: Infrequent surveys show a steep decline between 1961 and 1974 (approximately 2,200 and 600 respectively). Declines are less rapid for the next surveys, about 150 in 1986 and 80 in 1997.
  3. Prince of Wales, Russell, and Somerset Islands: Between 1974 and 1980, caribou numbers were stable in the range of 4,000 to 6,000. There was then a 15-year hiatus in surveys until 1995, when only a few caribou were found. In 2004, no caribou were seen during an aerial survey of the islands.
  4. Bathurst Island complex: Between 1961 and 1974, Peary caribou numbers declined by an order of magnitude. Between 1974 and 1994, numbers recovered to the 1961 level. An abrupt decline followed and, by 1997, fewer than 100 caribou remained. A survey in 2001 revealed the trend was for a recovering population.
  5. Banks Island: Populations peaked at about 12,000 in the early 1970s and remained relatively stable until 1982. Numbers declined to about 1,000 caribou by 1992 and an initial small recovery by 2001. A 2010 survey confirmed the persistence of low numbers, approximately 1,000.
  6. Northwest Victoria Island: Infrequent surveys show a decline from around 4,500 in 1980 to 2,600 in 1987. Numbers declined through the 1980s until 1993 when only a few caribou were seen during an aerial survey. The population slowly recovered with estimates of 95 in 1998 and 200 in 2001, although surveys in 2005 and 2010 confirm the persistence of low numbers.

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Pen Islands and Cape Churchill herds

Ecozone+ Hudson Plains

Note: the following section is summarized with authors' permission from the Hudson Plains Ecozone+ ecosystem status and trends assessment (Abraham et al. 2012).

Status and trends

These two herds in northern Ontario and northeastern Manitoba are considered a migratory forest-tundra ecotype and have received sporadic monitoring and assessment over the last two decades.

The Pen Islands Herd is decreasing and its range is shifting to the east. The herd became the focus of attention in the mid-1980s after several years of observations of large numbers along the coast in summer. Periodic photographic counts of the Pen Islands Herd during summer along the Hudson Bay coast of Ontario and Manitoba from 1979 to 1994 estimated an increase from a minimum of 2,300 animals in 1979 to a high of 10,798 animals in 1994 (Abraham and Thompson, 1998). In approximately the last 10 years there have been major changes. The herd traditionally calved and summered on the Hudson Bay coast in the area of the Pen Islands and wintered inland near the boundary of the Boreal Shield and Hudson Plains ecozones+. Using photographic survey data (Thompson and Abraham, 1994), non-systematic surveys, and incidental observations from 1965 to 2003, Magoun et al. (Magoun et al. 2005) documented an eastward shift in use of coastal areas since the late 1990s, with caribou becoming more common east of the Severn River. Systematic spring and summer surveys in 2008 and 2009 over the southern Hudson Bay coastal area documented a major shift in summer use of coastal areas, with most caribou being observed even farther east, near Cape Henrietta Maria (Abraham et al. Accepted for publication). The surveys also indicated the probability of a significant decline in numbers. These results may represent: 1) a shift in range use of the Pen Islands Herd; and/or 2) an independent decrease in numbers of caribou in the former Pen Islands range coupled with an increase in caribou numbers in the east.

The Cape Churchill Herd, although not well studied, is thought to have increased in numbers at a fairly rapid rate starting in the mid-1960s and then remained stable in numbers over the past decade. Aerial surveys of the herd in 1965 estimated the population at approximately 58 individuals while another survey in 1988 estimated the population as ranging between 1,800 and 2,200 individuals (Campbell, 1995). The minimum population size was estimated in 1997/98 to be 3,013 adult caribou (Elliott, 1998). Parks Canada conducted an aerial survey on May 28-29, 2005 and along flight lines over the known calving area counted 644 animals (Stewart, 2009, pers. comm.). Three counts of an opportunistic aerial photograph survey taken on July 20, 2007 averaged 2,937 adult animals, suggesting no change in minimum population size from 1997/1998 (Abraham et al. 2012).

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Porcupine Herd

Ecozones+ Calving ground: Southern Arctic (calving and early summer) and Taiga Cordillera (also year round); Taiga Plains (spring, fall, and winter ranges)

Status and trends

The herd is intensively monitored, with locations of calving grounds identified every year since the early 1970s, early calf survival monitored every year since 1983, and comparable population estimates since 1976. Early movement of the herd from the Alaskan coastal plain and bad weather during late June and early July prevented population estimates being made from 2003 through 2009. There are currently 169,000 caribou in the herd, based on results from the 2010 census (Campbell, 2011). See Figure 16.

Figure 16. Porcupine Caribou Herd population estimates.

Graph

Survey method is aerial photo-direct count extrapolation. Total count – no variance estimates calculated. Includes calves.

Source: based on data compiled for this report – 1972-2001: Caikoski (2009), see also Joly et al. (2011); 2010: Campbell (2011)

Long Description for Figure 16

This bar graph shows Porcupine Caribou Herd population estimates from 1972 to 2010. Frequent surveys in the period show an increase from the early 1970s, through the 1980s. Populations peaked in 1989 at approximately 178,000, however numbers decreased through the 1990s to around 120,000 in 2001. In 2010 surveys found approximately 169,000 caribou in the herd.

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The Porcupine Herd reached a peak in 1989 (178,000) and declined at least until the 2001 census at a rate of 3.5% per year, based on censuses in 1992, 1994, 1998, and 2001. Of all herds in North America that increased in the latter quarter of the 20th century, the Porcupine Herd had the lowest rate of increase and is thus the least productive of the large migratory herds (Figure 4).

In general, the Porcupine Caribou Herd travels north from wintering grounds in central Yukon and Alaska, arriving on the foothills of the Brooks Range in Alaska and the British Mountains in the Yukon by late May. Calving takes place in early June either in the foothills of the coastal plain or on the coastal plain, depending on snow conditions (Russell et al. 1993; Griffith et al. 2002). Recent analysis of locations of radio-collared caribou indicates that shifts in calving and post-calving distribution may be related to variations in spring temperatures and snow conditions and their influence on vegetation (Russell, unpublished data). The warm spring weather in the 1990s resulted in more calving on the coastal plain; the relatively cooler springs of the 1980s and the 2000s resulted in more calving in the foothills, associated with higher predation rates on new-born calves. See the climate change section for discussion on the impacts of climate change and variation on population dynamics of the Porcupine Caribou Herd.

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Qamanirjuaq Herd

Ecozones+ Calving ground: Southern Arctic (also summer into fall); Taiga Shield fall and winter ranges

Status and trends

Numbers were low in the 1970s and increased during the 1980s until 1994 (496,000 caribou) (Figure 17). In 2008, the Government of Nunavut completed calving ground and fall composition surveys and estimated 349,000 ± 44,900 (SE) caribou, indicating the herd may have peaked then declined by about 30% since 1994. However, the decline is not statistically significant. The trend in spring cow:calf ratios was a decline from 50:100 in 1992, to 42:100 in 1996, to 30:100 in 1999, to 26:100 in 2003, and then to less than 20:100 between 2006 and 2008 (Campbell et al. 2010).

Figure 17. Qamanirjuaq Caribou Herd population estimates.

Graph

For years where no standard error is shown, none was calculated for the survey.

Source: based on data from Campbell et al. (2010)

Long Description for Figure 17

This bar graph shows Qamanirjuaq Caribou Herd population estimates from 1976 to 2008. Visual calving-ground surveys show low numbers from 1976 to 1980, increasing to approximately 180,000 in 1982. Calving-ground photo surveys show a generally stable population around 230,000 from 1983 to 1988, with a peak in 1994 up to approximately 500,000 and declining to 350,000 in 2008.

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Southampton Island Herd

Ecozones+ Calving ground: Southern Arctic (also summer into fall and winter); Northern Arctic: winter range

Status and trends

Trends for caribou on Southampton are known through relatively intense monitoring since the caribou were re-introduced in 1967 (Parker, 1975; Heard and Ouellet, 1994; Campbell, 2006; Campbell, 2007). Forty-eight caribou (28 of which were females) were introduced from Coats Island after caribou had been extirpated, in part through over-hunting, by 1952 (Parker, 1975). In the absence of wolves, which had become locally extinct by 1937, the caribou increased rapidly, by approximately 27% per year, and had peaked at about 30,000 by 1997. Between 1997 and 2007 the herd declined by 50% at an annual exponential rate of decline of 6%. The estimates in 2003 and 2005 were not significantly different: 18,000 ± 2,100 in June 2003 and 20,600 ± 3,100 in June 2005 (Figure 18).

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Figure 18. Southampton Island Caribou Herd population estimates.

Graph

Source: based on data compiled for this report – 1968-1991: Heard and Ouellet (1994); 1995-2005: Campbell (2006); 2007 and 2009: Wildlife Management Division, Department of Environment, Government of Nunavut (2009)

Long Description for Figure 18

This bar graph shows Southampton Island Caribou Herd population estimates from 1978 to 2009. Forty-eight caribou were introduced in 1967 and monitoring (aerial transect surveys) has been relatively intense. The caribou increased rapidly, by approximately 27% per year, and had peaked at about 30,000 by 1997. Between 1997 and 2007 the herd declined by 50% at an annual exponential rate of decline of 6%. Populations were estimated at 14,000 in 2009.

The increase in herd size was the basis for a commercial harvest in the 1990s and 2000s (see harvest section). During commercial harvesting, the caribou were sampled for health and condition. From 1995 to 1998, caribou condition slowly declined, then recovered to 1995 levels by 2000 (Campbell, 2006). Between 2004 and 2005, body condition declined while over the same period caribou diets shifted from primarily grasses and lichens to mosses (Campbell, 2006). Fall icing in 1998 and 2005 may have limited access to grasses in early and mid-winter, which could have influenced body condition (Campbell, 2006). In 2003, pregnancy rates declined from between 90 and 95% in the period 1997 to 2000 to 60% in 2003, followed by a further decline to 25% in February 2005, accompanied by a decline in body condition in 2005 (Campbell, 2007). Contributing factors to the low pregnancy rates may be the high incidence of Brucella suisand the low percentage of prime bulls (only 12% in April 2005) (Campbell, 2006).

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Tuktoyaktuk Peninsula Herd

In 2005, hunters reported that there were more caribou on the Tuktoyaktuk Peninsula after the private herd of reindeer had been moved away in about 2001. A systematic aerial count in September 2005 estimated 2,700 caribou (including calves), of which about 20% were domesticated reindeer (Department of Environment and Natural Resources, 2005). In March 2006, 26 caribou, including 19 females, were fitted with satellite-collars. This revealed that movements appeared to be relatively restricted to the upper peninsula (Department of Environment and Natural Resources, 2005). In July 2006, a post-calving photographic survey estimated 2,866 non-calf reindeer/caribou (Nagy and Johnson, 2006). The herd was surveyed again on 25 June 2007 (Davison et al. 2007) and again in 2009, when 2,752 ± 276 (95% CI) caribou were estimated (Department of Environment and Natural Resources, No Date[Tuktoyaktuk Peninsula]).

The trend in late winter productivity, as indexed by calf:cow ratios for 2008 to 2011, suggests consecutive years of higher calf:cow ratios following 2007, when the ratio was 30 calves:100cows (Davison and Branigan, 2011).

Harvesting is unrestricted except for a closure from 1 April to 15 June. This closure allows the neighbouring Cape Bathurst Herd to migrate through the Tuktoyaktuk Peninsula on the way to the Cape Bathurst calving grounds. The harvest total and the sex ratio of the harvest are unknown for the Tuktoyaktuk Peninsula Herd. Hunters have expressed concerns about predators as they report seeing large wolf packs in the caribou range. The proposed all-weather road from Tuktoyaktuk to Inuvik will cross the wintering range of the Tuktoyaktuk Peninsula Herd (Department of Environment and Natural Resources, No Date[Tuktoyaktuk Peninsula]).

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