Migratory Caribou Research Articles

Nitrogen allocation to offspring and milk production in a capital breeder

Nitrogen (N) is a limiting nutrient for many herbivores, especially when plant availability and N content are low during the period of maternal investment, which is common for arctic ungulates. We used natural abundance of N isotopes to quantify allocation of maternal nitrogen to neonatal calves and milk in wild migratory caribou (Rangifer tarandus). We contrasted female-calf pairs from two herds in northern Quebec/Labrador, Canada: Rivière-George herd (RG; low population size with heavy calves) and the Rivière-aux-Feuilles herd (RAF; high population size and small calves). We assessed whether females of both herds relied on body protein or dietary N to produce the neonatal calf and milk at calving and weaning. Female caribou of both herds relied mostly on body N for fetal development. RAF females allocated less body N to calves than did RG females (92% vs. 95% of calf N), which was consistent with the production of calves that were 8% smaller in RAF than in RG. Allocation of body N to milk was also high for both herds, similar at calving for RAF and RG females (88% vs. 91% of milk N, respectively), but lower in RAF than RG females (95% vs. 99% of milk N) at weaning, which was consistent with a small but significantly greater reliance on dietary N supplies to support milk production at weaning. Female caribou used body protein stores to ensure a constant supply of N for fetal growth and milk production that minimized the effects of trophic mismatches on reproduction. The combination of migration and capital investment may therefore allow females to produce calves and attenuate the effects of both temporal and spatial mismatches between vegetation green-up and calf growth, which ultimately would reduce trophic feedbacks on population growth. Our data suggest that small changes in maternal allocation of proteins over the long period of gestation produce significant changes in calf mass as females respond to changes in resources that accompany changes in the size and distribution of the population.

Spring-loaded reproduction: effects of body condition and population size on fertility in migratory caribou (Rangifer tarandus)

In many ungulates, female fecundity is affected by body condition and has important effects on population dynamics. In some species, females adopt a conservative strategy, reducing reproductive effort when population density is high. We investigated what factors affect the probability of gestation in adult female caribou (Rangifer tarandus (L., 1758)) from the Rivière-George herd in northern Quebec and Labrador over 5 years that spanned various population sizes and trends. Similar to other populations of migratory caribou, the probability that a female was pregnant in spring increased with body mass and percent body fat. The probability of gestation appeared to be reduced by high infestation of warbles (Hypoderma tarandi (L., 1758)). The proportion of females pregnant varied between years and was lower at high population size. Females of similar mass, however, were pregnant regardless of whether the population was increasing at low density, had reached a peak, or was declining. Compared with other ungulates that reduce maternal expenditure at high density, female caribou of the Rivière-George herd may have a risk-prone reproductive strategy.

CARMA’s approach for the collaborative and inter-disciplinary assessment of cumulative effects

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High genetic connectivity and introgression from domestic reindeer characterize northern Alaska caribou herds

Defining genetic populations and detecting hybridization with introduced or domestic taxa are two major concerns for the conservation of population-level diversity. We studied the genetic population structure of large, migratory caribou herds (Rangifer tarandus granti) on Alaska’s North Slope and their potential hybridization with introduced domestic reindeer (R. t. tarandus). Using a population genetics approach, we determined: (1) whether the four caribou herds could be differentiated; (2) how distance and population size appear to drive genetic population structure; and (3) how contact with reindeer has affected the genetic identity of herds. Samples from four caribou herds (n = 245) and reindeer (n = 67) were analyzed at 19 microsatellite loci. We found that North Slope caribou are isolated by distance, with no differentiation among herd pairs except for the most geographically distant herds (F st = 0.003, Jost’s D = 0.023; P-values < 0.001). We detected reindeer-caribou admixture in all populations except Kodiak Island, including 8 % of individuals in caribou herds and 14 % of individuals in Seward Peninsula reindeer herds. However, considering the stable or increasing trend in North Slope herds, reindeer introgression has had no apparent deleterious effect on herd demographics. Our findings indicate long-term genetic exchange among North Slope caribou herds when their ranges overlap, and suggest that herd size may influence susceptibility to reindeer introgression. As North Slope herd ranges are increasingly altered by industrial development, this study can provide a baseline for detecting potential future impacts to what are currently large, diverse, and naturally evolving herds.

Have geographical influences and changing abundance led to sub-population structure in the Ahiak caribou herd, Nunavut, Canada?

We examined the premise that changing abundance and environmental conditions influence the seasonal dispersion and distribution of migratory tundra caribou (Rangifer tarandus groenlandicus). The Ahiak herd’s (north-central Nunavut Territory, Canada) calving shifted from dispersed on islands to gregarious calving on the mainland coast. As abundance further increased, the calving ground elongated east and west such that we proposed a longitudinal climate gradient. As well, the calving ground’s east and west ends are different distances from the tree-line, which dips south closer to Hudson Bay. We proposed that whether caribou winter on the tundra or within boreal forest and the different climate across the long calving ground could contribute to differential survival and productivity such that sub-population structure would result. At the scale of the individual cows (identified through satellite-collars), we did not find inter-annual spatial fidelity to either the western or eastern parts of the calving ground. At the population scale (aerial surveys of calving distribution), we also did not find discontinuities in calving distribution. The spatial association of individual cows during calving compared with their association during the rut was inconsistent among years, but overall, cows that calve together, rut together. At this time and with the available evidence, we could not infer sub-population structure from shifts in dispersion and distribution as influenced by geography and changes in abundance for the Ahiak herd.

CircumArctic Rangifer monitoring and assessment (CARMA) network – origins, goals, accomplishments and future

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Standardized monitoring of Rangifer health during International Polar Year

Monitoring of individual animal health indices in wildlife populations can be a powerful tool for evaluation of population health, detecting changes, and informing management decisions. Standardized monitoring allows robust comparisons within and across populations, and over time and vast geographic regions. As an International Polar Year Initiative, the CircumArctic Rangifer Monitoring and Assessment network established field protocols for standardized monitoring of caribou and reindeer (Rangifer tarandus) health, which included body condition, contaminants, and pathogen exposure and abundance. To facilitate use of the protocols, training sessions were held, additional resources were developed, and language was translated where needed. From March 2007 to September 2010, at least 1206 animals from 16 circumpolar herds were sampled in the field using the protocols. Four main levels of sampling were done and ranged from basic to comprehensive sampling. Possible sources of sampling error were noted by network members early in the process and protocols were modified or supplemented with additional visual resources to improve clarity when needed. This is the first time that such broad and comprehensive circumpolar sampling of migratory caribou and wild reindeer, using standardized protocols covering both body condition and parasite disease status, has been done.

Monitoring habitat condition changes during winter and pre-calving migration for Bathurst Caribou in northern Canada

Many factors influence the abundance of migratory tundra caribou (Rangifer tarandus). To understand their interactions with caribou abundance, we need to quantify these factors. In this study, we documented the changes in habitat conditions during winter and pre-calving migration for the Bathurst Caribou herd, using remote sensing data and ground measurements. We found there was a significant decrease in forest area which has abundant lichen, the main caribou winter diet, during recent decades due to increase in burned area, which in turn was positively correlated with summer temperature. For winter forage accessibility, we examined the annual maximum snow depth and mean ice content in snow (ICIS). There was a significant increase in ICIS during 1963–2006, but no trend in the maximum snow depth. During the pre-calving migration, the percent snow cover showed large inter-annual variations but no significant trend.

DETECTION OF MYCOBACTERIUM AVIUM SUBSPECIES PARATUBERCULOSIS IN SEVERAL HERDS OF ARCTIC CARIBOU (RANGIFER TARANDUS SSP.)

Mycobacterium avium subspecies paratuberculosis (MAP) is a common pathogen in domestic ruminants that causes granulomatous inflammation of the small intestine leading to emaciation and wasting. Clinical disease (Johne's disease) is also reported for several wild ruminant species. Between 2007 and 2009 we collected 561 fecal samples from caribou (Rangifer tarandus ssp.) representing 10 herds of migratory caribou, two herds of caribou from Greenland, and three populations of boreal woodland caribou. Feces were tested for MAP by bacterial culture and PCR targeting the IS900 insertion sequence. In total, 31 samples from eight different populations representing all three ecotypes were found positive for MAP by PCR, with one sample from the Rivière-aux-Feuilles herd also being culture positive for the type II (cattle) strain. The proportion of positive animals was particularly high in the Akia-Maniitsoq herd in Greenland, and Rivière-aux-Feuilles and Riviè re-George herds in northeastern Canada (23.4, 11.5, and 10.0%, respectively). Our results indicate that MAP is present in several caribou herds of different ecotypes in northern Canada and Greenland and that MAP circulates within wildlife populations that do not have ongoing contact with domestic livestock. The epidemiology, pathogenicity, and effects on the health of caribou in northern ecosystems remain unknown.

Co-management of the migratory caribou herds in northern Québec: The perspective of the Hunting, Fishing and Trapping Coordinating Committee

Aboriginal people have a long relationship with caribou, and caribou - especially the large migratory herds- cross aboriginal territories and jurisdictional boundaries. These two points are key to understanding the intricacies and complexities of managing caribou.

Recent changes in summer distribution and numbers of migratory caribou on the southern Hudson Bay coast

The status of migratory woodland caribou inhabiting the coastal region in southern Hudson Bay is dynamic. The Pen Islands Herd within that region was defined in the 1990s, but opportunistic observations between 1999 and 2007 suggested that its status had significantly changed since the late 1980s and early 1990s. We undertook systematic surveys from the Hayes River, MB, to the Lakitusaki River, ON, in 2008 and 2009 to determine current distribution and minimum numbers of woodland caribou on the southern Hudson Bay coast from the Hayes River, Manitoba, to the Lakitusaki River, Ontario. We documented a significant change in summer distribution during the historical peak aggregation period (7-15 July) compared to the 1990s. In 2008 and 2009, respectively, we tallied 3529 and 3304 animals; however, fewer than 180 caribou were observed each year in the Pen Islands Herd’s former summer range where over 10 798 caribou were observed during a systematic survey in 1994. Over 80% of caribou were in the Cape Henrietta Maria area of Ontario. Calf proportions in herds varied from 8% of animals in the west to 20% in the east. Our 2008 and 2009 systematic surveys were focused on the immediate coast, but one exploratory flight inland suggested that more caribou may be inland than had been observed in the 1980s-1990s. The causes of change in the numbers and distribution in the coastal Hudson Bay Lowlands and the association of current caribou with the formerly large Pen Islands Herd may be difficult to determine because of gaps in monitoring, but satellite telemetry, genetic sampling, remote sensing, habitat analysis, and aboriginal knowledge are all being used to pursue answers.

Is mother condition related to offspring condition in migratory caribou (Rangifer tarandus) at calving and weaning?

Maternal characteristics can affect offspring traits, yet they are seldom included when considering density dependence of juvenile traits and population dynamics. We quantified the influence of population size and maternal traits on body condition of migratory caribou ( Rangifer tarandus (L., 1758)) calves at birth and weaning. We contrasted female–calf pairs of the Rivière-George (RG) herd, which has recently declined to low population size, with pairs of the much larger Rivière-aux-Feuilles (RAF) herd. Calves of the RAF herd were lighter, smaller, and leaner than calves of the RG herd at both birth and weaning. Differences between herds, however, were much greater at weaning than at calving, suggesting a combined effect of herd size and summer range conditions on calf growth. Maternal mass was positively related to calf body condition during both periods. The positive influence of maternal mass on calf body condition was greater for RAF than RG calves at birth, but it was similar for the two herds at weaning. Our results show that the negative effect of population size on calf body condition can be modulated by maternal mass at calving, and that the positive effect of maternal mass is greater at weaning.

Shifting targets in the tundra: Protection of migratory caribou calving grounds must account for spatial changes over time

Industrial development, expansion of human populations and climate change increasingly affect habitats of migratory species. Effective protection of critical habitats is urgently required because several large migratory species have declined over the last decades. Protection of critical habitats, such as the calving grounds of migratory ungulates, may however require consideration of temporal shifts in spatial location. We assessed changes in the location of calving grounds used by migratory caribou over 35years by the Rivière-George (RG) herd and 15years by the Rivière-aux-Feuilles (RAF) herd, in Northern Québec and Labrador, Canada. We also evaluated the proportion of annual calving ground within protected Wildlife Habitats established to protect caribou calving grounds. The annual size and location of calving grounds changed substantially over time: calving ground size remained relatively stable for the RAF but it declined over 85% for the RG. Calving grounds moved 300km northward in the Ungava peninsula for the RAF and shifted over 230km back and forth to the Labrador coast for the RG. Despite recent modifications, legally designated Wildlife Habitats in Québec protected less than 20% of the RG and RAF calving grounds. Protection of calving grounds of migratory caribou must consider the dynamic use of space by adult females. We present recommendations on the use of available monitoring data to better protect calving grounds of migratory caribou and critical habitats of large migratory species.

Factors affecting the body condition of female-calf pairs in two herds of migratory caribou in Northern Québec/Labrador

Factors affecting the body condition of female-calf pairs in two herds of migratory caribou in Northern Québec/Labrador

Variation in body condition of migratory caribou at calving and weaning: Which measures should we use?

Monitoring the body condition of ungulates is often considered an efficient way to assess habitat quality. It is therefore essential to select adequate measures to describe individual body condition. Because there is no consensus on which measurement(s) can best describe individual variability in body condition, field biologists often measure several variables, increasing processing time. From 2007 to 2009, we assessed body condition of female—calf pairs in 2 herds of migratory caribou in Northern Quebec/Labrador, Canada, using multiple measurements of size, mass, and fat depth. We sought to identify, using multivariate analysis, which measurement(s) had the greatest influence on a composite measure of body condition of females and calves at calving and weaning. Our results indicate that adult females are best described with a body bulkiness index opposing heavy and long/round-bodied females with high body protein reserves to light and short/slender-bodied females with low body protein reserves. At weaning, adult females can also be differentiated by a body fat index opposing fat to lean females. Calf body condition is best described by mass at birth and by a combination of mass and size measurements at weaning, opposing heavy and tall individuals with high protein reserves to light and short ones with low protein reserves. Overall, body mass appears to be the measurement that best describes individual variability in body condition of females and calves at calving and weaning. Our systematic comparison of body condition measurements will provide field biologists with guidance for future data collection.

Besnoitiosis in caribou: What we know and what we don't know

Besnoitia spp. are protozoan parasites known to occur in many species worldwide. Besnoitia tarandi has been described in caribou and reindeer in which it is often associated with hair loss, skin thickening and ulcerations. In Rangifer species, cysts of Besnoitia often induce inflammation and are observed mainly in the sclera and subcutaneous tissues, and to a lesser extent in other organs such as lungs and testes. Very little is known about the significance of this parasite on caribou health. However, it has been hypothesized that massive infections could impede the animal's tolerance to exercise and movement and therefore contribute to mortalities. In addition, extensive infections implicating the testicular appendages might impact the fertility of caribou as reported in other species. It is believed that B. tarandi has a two-host life cycle with caribou as intermediate hosts. Carnivores and biting arthropods have been respectively suggested as potential defini¬ tive hosts and vectors of B. tarandi. Presently, the gaps in understanding the life cycle of B. tarandi prevent any attempts to assess the potential effects of the changing arctic environment on the balance between this parasite and its hosts. In order to better characterize the ecology of this parasite in Canadian migratory caribou herds, our research team wishes to present data on the distribution of B. tarandi in association with body condition, gender and age and the potential association between intensity of infection with fertility and tolerance to exercise.

Winter habitat selection by caribou in relation to lichen abundance, wildfires, grazing, and landscape characteristics in northwest Alaska

Lichens are an important winter forage for large, migratory herds of caribou (Rangifer tarandus granti) that can influence population dynamics through effects on body condition and in turn calf recruitment and survival. We investigated the vegetative and physiographic characteristics of winter range of the Western Arctic Herd in northwest Alaska, one of the largest caribou herds in North America. We made 3 broad comparisons: habitats used by caribou versus random locations, burned versus unburned habitats, and habitats within the current winter range versus those in the historic winter range and potential winter ranges. We found that lichen abundance was more than 3 times greater at locations used by caribou than found at random. The current winter range does not appear to be overgrazed as a whole, but continued high grazing pressure and consequences of climate change on plant community structure might degrade its condition. Within the current winter range, lichen abundance was more than 4 times greater at unburned locations than at recently (< 58 y) burned locations. Other than lichen abundance, there were few vegetative differences between burned (mean = 37 ± 1.7 y) and unburned locations. The historic winter range has low lichen abundance, likely due to sustained grazing pressure exerted by the herd, which suggests that range deterioration can lead to range shifts. Recovery of this range may be slowed by continued grazing and trampling during migration of caribou to and from their current winter range, as well as by high wildfire frequency and other consequences of climate change. The area identified as potential winter range is unlikely to be utilized regularly by large numbers of caribou primarily due to low lichen abundance associated with extensive deciduous stands, large areas of riparian habitat, high moose (Alces alces) densities, and greater prevalence of wildfire. Our results suggest that lichens are important in the overwintering ecology of caribou that face the energetic costs of predator avoidance and migration.

Body Size Variations in Caribou Ecotypes and Relationships With Demography

ABSTRACT In many vertebrates size is one of the most influential and variable individual characteristics and a strong determinant of reproductive success. Body size is generally density dependent and decreases when intraspecific competition increases. Frequent and long‐distance movements increase energy expenditures and, therefore, may also influence body size, particularly in highly mobile species. Caribou (Rangifer tarandus, also known as reindeer) exhibit tremendous variation in size and movements and thus represent an excellent candidate species to test the relationships between body size, population size, and movements. We analyzed body measurements of adult female caribou from 7 herds of the Québec‐Labrador Peninsula, Canada, and we related their morphology to population size, movements, and annual ranges. The herds represented 3 ecotypes (migratory, montane, and sedentary). Ecotypes and herds differed in size (length), shape (roundness), and movements. The sedentary ecotype was larger and moved 4 to 7 times less than the migratory ecotype in the 1990s. At the start of a demographic growth period in the early 1960s, migratory caribou from the Rivière‐George (hereafter George) herd had longer mandibles than caribou of the sedentary ecotype. Mandible length in the George herd declined in the 1980s after rapid population growth, while individuals performed extensive movements and the herd's annual range increased. Migratory caribou then became shorter than sedentary caribou. After the George herd decline in the 1990s, mandible length increased again near levels of the 1980s. Caribou from the migratory Rivière‐aux‐Feuilles herd later showed a similar decline in mandible length during a period of population growth, associated with longer movements and increasing annual range. We hypothesize that the density‐dependent effect observed on body size might have been exerted through summer habitat degradation and movement variations during herd growth. Our study has 2 important implications for caribou management: the distinctiveness of different populations and ecotypes, and the correlations between population trajectories and changes in body condition and habitat.

Denésoliné (Chipewyan) Knowledge of Barren-Ground Caribou (&lt;i&gt;Rangifer tarandus groenlandicus&lt;/i&gt;) Movements

Semi-directed interviews relating to the traditional knowledge (TK) of barren-ground caribou (Rangifer tarandus groenlandicus) movements were conducted with elders and hunters from the Denésoliné (Chipewyan) community of Lutsël K’é, Northwest Territories, Canada. The objective was to document Denésôliné knowledge of past and present caribou migration patterns and record their explanations for perceived changes in movements. Elders recognized expected and unusual levels of variation in caribou movements. Local narratives show that Denésoliné communities have a fundamental awareness of caribou migration cycles. Most elders thought fire frequency and intensity had increased over their lifetimes and that caribou numbers and distribution had been affected. The majority of Lutsël K’é elders thought mining development was affecting caribou movements in some way. Elders believe that disturbance around traditional migration corridors and water crossings and disturbance of “vanguard” animals might be forcing caribou to use less optimal routes and influencing where they overwinter. Elders also believe that a lack of respect for caribou will cause the animals to deviate from their “traditional” migration routes and become unavailable to the people for a period of time. Wildlife management practices may need to further accommodate aboriginal perspectives in the future.

Decrease of lichens in Arctic ecosystems: the role of wildfire, caribou, reindeer, competition and climate in north-western Alaska

We review and present a synthesis of the existing research dealing with changing Arctic tundra ecosystems, in relation to caribou and reindeer winter ranges. Whereas pan-Arctic studies have documented the effects on tundra vegetation from simulated climate change, we draw upon recent long-term regional studies in Alaska that have documented the actual, on-the-ground effects. Our review reveals signs of marked change in Arctic tundra ecosystems. Factors known to be affecting these changes include wildfire, disturbance by caribou and reindeer, differential growth responses of vascular plants and lichens, and associated competition under climate warming scenarios. These factors are interrelated, and, we posit, unidirectional: that is, they are all implicated in the significant reduction of terricolous lichen ground cover and biomass during recent decades. Lichens constitute the primary winter forage for large, migratory caribou and reindeer herds, which in turn are a critical subsistence resource for rural residents in Alaska. Thus, declines in these lichens are a major concern for rural people who harvest caribou and reindeer for subsistence, as well as for sport hunters, reindeer herders, wildlife enthusiasts and land managers. We believe a more widely distributed and better integrated research programme is warranted to quantify the magnitude and extent of the decline in lichen communities across the Arctic.