Central Northwest Territories Research Articles

Drivers of extreme wildfire years in the 1965–2019 fire regime of the Tłı̨chǫ First Nation territory, Canada

ABSTRACT Exceptionally large areas burned in 2014 in central Northwest Territories (Canada), leading members of the Tłı̨chǫ First Nation to characterize this year as ‘extreme’. Top-down climatic and bottom-up environmental drivers of fire behavior and areas burned in the boreal forest are relatively well understood, but not the drivers of extreme wildfire years (EWY). We investigated the temporal and spatial distributions of fire regime components (fire occurrence, size, cause, fire season length) on the Tłı̨chǫ territory from 1965 to 2019. We used BioSIM and data from weather stations to interpolate mean weather conditions, fuel moisture content and fire-weather indices for each fire season, and we described the environmental characteristics of burned areas. We identified and characterized EWY, i.e., years exceeding the 80th percentile of annual area burned for the study period. Temperature and fuel moisture were the main drivers of areas burned. Nine EWY occurred from 1965 to 2019, including 2014. Compared to non-EWY, EWY had significantly higher mean temperature (>14.7°C) and exceeded threshold values of Drought Code (>514), Initial Spread Index (>7), and Fire Weather Index (>19). Our results will help limit the effects of EWY on human safety, health and Indigenous livelihoods and lifestyles.

Temperature and fuel availability control fire size/severity in the boreal forest of central Northwest Territories, Canada

The north-central Canadian boreal forest experienced increased occurrence of large and severe wildfires caused by unusually warm temperatures and drought events during the last decade. It is, however, difficult to assess the exceptional nature of this recent wildfire activity, as few long-term records are available in the area. We analyzed macroscopic sedimentary charcoal from four lakes and pollen grains from one of those lakes to reconstruct long-term fire regimes and vegetation histories in the boreal forest of central Northwest Territories. We used regional estimates of past temperature and hydrological changes to identify the climatic drivers of fire activity over the past 10,000 years. Fires were larger and more severe during warm periods (before ca. 5000 cal yrs. BP and during the last 500 years) and when the forest landscape was characterized by high fuel abundance, especially fire-prone spruce. In contrast, colder conditions combined with landscape opening (i.e., lower fuel abundance) during the Neoglacial (after ca. 5000 cal yrs. BP) were related with a decline in fire size and severity. Fire size and severity increased during the last five centuries, but remained within the Holocene range of variability. According to climatic projections, fire size and severity will likely continue to increase in central Northwest Territories in response to warmer conditions, but precipitation variability, combined with increased abundance of deciduous species or opening of the landscape, could limit fire risk in the future.

Lithostratigraphy of Devonian basinal mudrocks in frontier areas of northwestern Canada augmented with ED-XRF technique

Rock materials from three Arctic wells drilled through Middle-Upper Devonian basinal mudrocks between 1969 and 1973 were surveyed with the energy-dispersive X-ray fluorescence tool (ED-XRF) Bruker Tracer IV-SD™. The logs of major oxides acquired from cuttings of two wells on Banks Island show that lithological signals can be seen through sample contamination, and therefore are capable of significantly increasing litho-chemostratigraphic resolution of old borehole logs. Survey of major and trace elements on a cored section through visually monotonous black shales of the Kugaluk N-02 well in northern mainland N.W.T. reveals new details, which allows for the correlation of this reference section with a better-studied succession in the central Northwest Territories, as well as the interpretation of anoxic horizons which correlate globally as the “Devonian anoxic events”. Despite shortcomings in accuracy, ED-XRF proves to be a rapid non-destructive technique to gain new information from old exploration wells in remote frontier areas.

Influence of late-Holocene climate change on the solid-phase speciation and long-term stability of arsenic in sub-Arctic lake sediments

Sediment cores were collected from two lakes in the Courageous Lake Greenstone Belt (CLGB), central Northwest Territories, Canada, to examine the influence of late-Holocene warming on the transport and fate of arsenic (As) in sub-Arctic lakes. In both lakes, allochthonous As-bearing minerals (i.e. arsenopyrite and scorodite) were identified in sediment deposited during times of both regional warming and cooling, suggesting that weathering of bedrock and derived surficial materials provides a continual source of As to lakes of the CLGB. However, maximum porewater As (84 μg·L−1 and 15 μg·L−1) and reactive organic matter (OM; aquatic and terrestrial-derived) concentrations in each lake are coincident with known periods of regional climate warming. It is inferred that increased biological production in surface waters and influx of terrigenous OM led to the release of sedimentary As to porewater through reductive dissolution of As-bearing Fe-(oxy)hydroxides and scorodite during episodes of regional warming. Elevated sedimentary As concentrations (median: 36 mg·kg−1; range: 29 to 49 mg·kg−1) are observed in sediment coeval with the Holocene Thermal Maximum (ca. 5430 ± 110 to 4070 ± 130 cal. years BP); at these depths, authigenic As-bearing framboidal pyrite is the primary host of As in sediment and the influence of organic matter on the precipitation of As-bearing framboidal pyrite is apparent petrographically. These findings suggest that increased biological productivity and weathering of terrestrial OM associated with climate warming influences redox cycles in the near-surface sediment and enhances the mobility of As in northern lakes. Knowledge generated from this study is relevant for predicting future climate change-driven variations in metal(loid) cycling in aquatic systems and can be used to interpret trends in long-term environmental monitoring data at historical, modern, and future metal mines in northern environments.

Late Holocene climatic variability in Subarctic Canada: Insights from a high-resolution lake record from the central Northwest Territories.

We examined late Holocene (ca. 3300 yr BP to present-day) climate variability in the central Northwest Territories (Canadian Subarctic) using a diatom and sedimentological record from Danny’s Lake (63.48ºN, 112.54ºW), located 40 km southwest of the modern-day treeline. High-resolution sampling paired with a robust age model (25 radiocarbon dates) allowed for the examination of both lake hydroecological conditions (30-year intervals; diatoms) and sedimentological changes in the watershed (12-year intervals; grain size records) over the late Holocene. Time series analysis of key lake ecological indicators (diatom species Aulacoseira alpigena, Pseudostaurosira brevistriata and Achnanthidium minutissimum) and sedimentological parameters, reflective of catchment processes (coarse silt fraction), suggests significant intermittent variations in turbidity, pH and light penetration within the lake basin. In the diatom record, we observed discontinuous periodicities in the range of ca. 69, 88–100, 115–132, 141–188, 562, 750 and 900 years (>90% and >95% confidence intervals), whereas the coarse silt fraction was characterized by periodicities in the >901 and <61-year range (>95% confidence interval). Periodicities in the proxy data from the Danny’s Lake sediment core align with changes in total solar irradiance over the past ca. 3300 yr BP and we hypothesize a link to the Suess Cycle, Gleissberg Cycle and Pacific Decadal Oscillation via occasional inland propagation of shifting air masses over the Pacific Ocean. This research represents an important baseline study of the underlying causes of climate variability in the Canadian Subarctic and provides details on the long-term climate variability that has persisted in this region through the past three thousand years.

Reconstruction of Holocene hydroclimatic variability in subarctic treeline lakes using lake sediment grain-size end-members

Current climate trends are expected to result in the northward expansion of the subarctic treeline leading to changes in vegetation cover and permafrost distribution, as they did during the Holocene Climate Optimum when the treeline was 150 km north of its current position. The impacts of these changes on the region’s hydrology are still poorly understood. The grain-size distributions of treeline lake sediments provide an important proxy related to spring melt conditions that can be used to reconstruct hydroclimatic variability. End-member mixing analysis was used to model depositional end-members in 55 modern lake sediment samples and two sediment cores spanning the mid- to late Holocene collected from above and below the treeline in the central Northwest Territories, Canada. Cold climatic intervals (e.g. ‘Dark Ages Cold Period’, ‘Little Ice Age’) were characterised by an increase in the very coarse silt and the fine sand end-members. This was interpreted to be a response to degradation of vegetation cover and/or permafrost development. We observed increases in fine and coarse silt end-members during warmer climatic intervals (e.g. Medieval Climate Anomaly) and over the past c. 300 yr BP. This pattern is probably the result of extended melt seasons, with greater losses to evaporation and increased infiltration. The most pronounced palaeo-hydroclimatological change over the past c. 8000 yr BP was the abrupt increase in a very coarse silt end-member (mode = 50–200 µm) at c. 6300 yr BP. We interpreted the sedimentological change as an increase in winter precipitation and more energetic spring melt conditions, leading to the spring melt becoming the dominant lacustrine sediment delivery mechanism. These results place modern hydrological changes in a millennial context and show that analysis of temporal changes in the hydroclimatological system can provide insight into the future states of these sensitive subarctic ecosystems.

New occurrences of the White River Ash (east lobe) in Subarctic Canada and utility for estimating freshwater reservoir effect in lake sediment archives

The freshwater reservoir effect (FRE) in the Canadian Subarctic complicates development of high-resolution age-depth models based on radiocarbon dates from lake sediments. Volcanic ashfall layers (tephras) provide chronostratigraphic markers that can be used to estimate age offsets. We describe the first recorded occurrence of a visible tephra in a lacustrine sequence in the central Northwest Territories. The tephra, observed in Pocket Lake, near Yellowknife, is geochemically and stratigraphically attributed to the White River Ash east lobe (WRAe; 833–850 CE; 1117–1100cal BP), which originated from an eruption of Mount Churchill, Alaska. We also observed the WRAe as a cryptotephra in Bridge Lake, 130km to the NE, suggesting that records of this tephra are potentially widespread in CNT lakes. The identification of this tephra presents opportunities for use of the WRAe as a dating tool in the region and to quantify the magnitude of the FRE in order to correct radiocarbon age-depth models. Two well-dated sediment cores from Pocket Lake, containing a visible WRAe record, indicate a FRE of ~200years at the time of the ash deposition, which matches closely with the estimated FRE of ~245years at the lake sediment-water interface. Although additional results from other lakes in the region are required, this finding implies that FRE estimates for the late Holocene in the region, may be based either on down-core WRAe/radiocarbon age model offsets, or on radiocarbon dates obtained from the sediment-water interface.

Holocene fire regimes and treeline migration rates in sub-arctic Canada

Holocene climate change resulted in major vegetation reorganization in sub-arctic Canada near modern treeline. However, little is known of the effects of long-term climate change on boreal forest composition and fire regimes below treeline in this region. We present a high-resolution vegetation and fire history from two sites within the modern boreal forest in the central Northwest Territories, Canada, to provide new insight on sub-arctic vegetation response to Holocene climate dynamics and the role of fire in boreal ecosystems. Palynological analysis of sediments retrieved from Waite and Danny's lakes (informal) is used to reconstruct regional vegetation dynamics and boreal fire regimes. The longer Danny's Lake record documents treeline expansion beginning at ca. 7430–7220calyr BP. Integration of our new data with previous work shows that treeline expanded between ca. 4050cal. yr BP and ca. 3840calyr BP at a rate of ca. 50m/yr in response to the 1–2°C increase in temperature estimated for the Holocene Thermal Maximum. Forest fires were relatively frequent during the early Holocene, before declining in frequency in response to development of cooler and wetter climate conditions associated with the Neoglacial (beginning after ca. 2200–2320calyr BP). We document a trend of increasing fire frequency in the 20th century that is correlated with warming at this time. These dynamics south of modern treeline provide insight into factors creating heterogeneity in plant community responses to large-scale climate events in high northern latitudes and suggest that large scale reorganization of boreal vegetation and fire regimes can be expected over the coming decades.

Reference Section for the Horn River Group and Definition of the Bell Creek Member, Hare Indian Formation in central Northwest Territories

Abstract A stratigraphically complete section, exposed along a tributary to the Mountain River in the Northwest Territories, provides a reference section for the Devonian Horn River Group (Hare Indian, Ramparts, and Canol formations). Detailed whole rock geochemical data and total organic carbon content variations are related to the lithostratigraphy, thus providing a standard for regional correlation. The name ‘Bell Creek Member’ is proposed for the upper part of the Hare Indian Formation known as the “grey shale member”, and is defined at the Mountain River section. This member is heterogeneous and consists of two lithofacies: 1) a green-grey, silty shale and limestone facies (Bell Creek Member, grey facies); and 2) a dark grey, silty shale and limestone facies (Bell Creek Member, dark facies). The dark grey facies is described from a reference section along the Carcajou River, and is distributed south of 65°N latitude. The Bell Creek Member is Givetian in age.

Middle to late Holocene chironomid-inferred July temperatures for the central Northwest Territories, Canada

We analyzed subfossil chironomids, sed- iment organic matter and sediment particle size data from a 1.11-m-long freeze core collected from Carl- eton Lake (unofficial name), located approximately 120 km north of the modern treeline. This well-dated core spans the last ca. 6,500 years. Two chironomid transfer functions were applied to infer mean July air temperatures. Our results indicated that the chirono- mid-inferred temperatures from this lake sediment record did not pass a significance test, suggesting that other factors in addition to temperature may have been important in structuring the chironomid community through time. Although not statistically significant, the chironomid-inferred temperatures from this site do follow a familiar pattern, with highest inferred tem- peratures occurring during the Holocene Thermal Maximum (*6-4 cal kyr BP), followed by a long- term cooling trend, which is reversed during the last 600 years. The largest change in the chironomid assemblage, which occurred between ca. 4,600 and 3,900 cal yr BP is possibly related to the well- documented northward advance and subsequent retreat of treeline in this region.

Distribution and Biology of Bull Trout (&lt;i&gt;Salvelinus confluentus&lt;/i&gt;) in the Mackenzie Valley, Northwest Territories, with Notes on Sympatry with Dolly Varden (&lt;i&gt;Salvelinus malma&lt;/i&gt;) + Online Appendix 1 (See Article Tools)

Streams were surveyed along the Mackenzie Valley, Northwest Territories, to investigate the distribution and biology of riverine char. Bull trout ( Salvelinus confluentus ) were captured in 24 of 43 streams sampled from three watersheds: the Kotaneelee River, the South Nahanni River, and the Central Mackenzie Mountains. The first confirmed sympatric bull trout and Dolly Varden ( Salvelinus malma ) populations in the Northwest Territories are reported from the Gayna River (~65˚17′ N, 129˚21′ W). This location represents a geographical range extension for bull trout approximately 200 km northwest of the previous northernmost published location in the central Northwest Territories (~64˚30′ N and 125˚00′ W, Great Bear River). It also extends the geographical range of Dolly Varden south approximately 300 km from the closest known populations located in the Peel River basin. The identification of this geographic range expansion is a result of extending both our sampling range and our ability to identify riverine chars accurately. In bull trout, we observed two different growth patterns, which correspond to non-migratory and migratory life histories. Northern bull trout populations are relatively small and widespread, and they are separated from one another by large distances and in some cases by natural barriers. Although these populations share similar biological traits with their southern counterparts, the northern fish mature later and do not spawn as often, which increases their sensitivity to exploitation and other anthropogenic perturbations.

Paleoclimatological assessment of the central Northwest Territories, Canada: Implications for the long-term viability of the Tibbett To Contwoyto Winter Ice Road

Paleoclimatological assessment of the central Northwest Territories, Canada: Implications for the long-term viability of the Tibbett To Contwoyto Winter Ice Road

Threatened fishes of the world: Salvelinus confluentus (Salmoninae)

Common name: Bull Trout; Bull Charr. Conservation status: Vulnerable IUCN Red List; Threatened, U.S. Fish and Wildlife Service (1999). Identification: Adults to 14 kg, olive green to brown body fading to white on belly with yellow spots dorsally grading to red to orange laterally. White leading edges on rayed fins, solid colored dorsal fin (Cavender 1978; Markle 1992) (Illustration: copyright Joseph R. Tomelleri). Distribution: Northern California to Alaska, eastward extent Nevada, Montana, and Idaho (Cavender 1978; Haas and McPhail 1991). Canadian distribution includes British Columbia, Central Northwest Territories, and western Alberta (Reist et al. 2002). Currently extirpated from California with local extirpations scattered throughout the remainder of the species’ range (USFWS 1999). Habitat and ecology: Highly variable movement behavior spanning a continuum between resident and migratory individuals. Spawning and rearing confined to colder ( 12 years (Zymonas 2006). Autumn to early winter spawning in headwater streams (Fraley and Shepard 1989; McPhail and Baxter 1996). Fecundity ranges from 2,000 to 12,000 eggs, with emergence of fry in late winter to early spring (Fraley and Shepard 1989). Threats: Threats include angling (Schmetterling and Long 1999), habitat loss and fragmentation (Dunham and Rieman 1999), nonnative trout, hybridization (Baxter et al. 1997), disease (Post et al. 2003; USFWS 1999), and pollution (Post et al. 2003; USFWS 1999). Bull trout are particularly vulnerable to threats due to long embryo incubation, relatively old age at maturity and reliance on pristine habitat (Pratt 1992; Rieman and McIntyre 1993). Conservation actions and recommendations: Address known threats, public outreach, research evolutionary history, ecology, and conservaEnviron Biol Fish (2010) 89:161–162 DOI 10.1007/s10641-010-9708-8

Vegetation of the Continental Northwest Territories at 6 ka BP

Pollen records are used to reconstruct vegetation in the continental Northwest Territories at 6 ka (6000 14C yr BP). Picea glauca, P mariana, Larix laricina, Populus tremuloides, P. balsamifera, Alnus crispa and A. incana were present throughout their modern ranges in the Boreal and Subarctic Forest Zones by 6000 BP. Pinus banksiana, however, had not yet reached its present northern limits. Population densities of the dominant trees, Picea glauca and Picea mariana, were close to, or as high as, present. In the Mackenzie Delta region the range limit of Picea glauca was approximately 25 km north of its modern location just prior to 6000 BP. In contrast, the northern limits of the forest in central Canada were similar to present. The tundra vegetation close to the edge of the forest was similar to modern Low Arctic Tundra. Development of extensive Sphagnum peatlands had begun in the forested areas and the adjacent Low Arctic Tundra. Palaeoecological information regarding vegetation at 6000 BP remains lacking for the northeastern half of the study area. Therefore, the nature of the vegetation in much of the area now occupied by Low Arctic and Middle Arctic Tundra remains unknown. Important vegetation changes that occurred following 6 ka include : (1) the advance of Pinus banksiana to its present northern range limits, (2) the retreat of the northern range limits of Picea glauca in the Mackenzie Delta region between 6000 and 3500 BP and (3) the rapid and marked increase in the population density of Picea mariana in the treeline zone of the central Northwest Territories at 5000 BP followed by a decline at 4000 BP.

Long-term Abundance Patterns of Barren-ground Caribou Using Trampling Scars on Roots of Picea Mariana in the Northwest Territories, Canada

ABSTRACTThe aim of this study was to reconstruct population dynamics of barren-ground caribou (Rangifer tarandus groenlandicus) herds from the frequency of trampling scars on tree roots of black spruce (Picea mariana [Mill.] BSP) in the forest-tundra of central Northwest Territories, Canada. Two groups of sites were sampled that roughly corresponded with the migration routes of the Bathurst and Beverly caribou herds. The caribou migrate annually for long distances from the forest to the open tundra in late spring, and return to the forest in the autumn. The scar frequency distribution was determined by careful crossdating and the influence of root age was assessed to account for the increasing underestimation of caribou abundance with the increasing age of the roots. The scar frequency distributions (dated from A.D. 1760 to 2000) from both groups of sites showed similar abundance patterns through time. Caribou numbers were high during the mid-1940s, and 1990s, and were very low during the 1920s, 1950s–1970s, and at the turn of the 21st century. These abundance patterns determined from scar frequencies correlate strongly with data obtained from traditional knowledge of Dogrib elders in the region and animal counts based on aerial photography. The scar frequency distribution developed in this study is the longest proxy record of caribou abundance to date.

The Mid-Canada Radar Line and First Nations’ People of the James Bay region, Canada: an evaluation using log-linear contingency modelling to analyze organochlorine frequency data

Abandoned radar line stations in the North American arctic and sub-arctic regions are point sources of contamination, especially for PCBs. Few data exist with respect to human body burden of organochlorines (OCs) in residents of communities located in close proximity to these radar line sites. We compared plasma OC concentration (unadjusted for total lipids) frequency distribution data using log-linear contingency modelling for Fort Albany First Nation, the site of an abandoned Mid-Canada Radar Line station, and two comparison populations (the neighbouring community of Kashechewan First Nation without such a radar installation, and Hamilton, a city in southern Ontario, Canada). This type of analysis is important as it allows for an initial investigation of contaminant data without imputing any values. The two-state log-linear model (employing both non-detectable and detectable concentration frequencies and applicable to PCB congeners 28 and 105 and cis-nonachlor) and the four-state log-linear model (using quartile concentration frequencies for Aroclor 1260, PCB congeners [99,118,138,153,156,170,180,183,187], beta-HCH, p,p'-DDT +p,p'-DDE, HCB, mirex, oxychlordane, and trans-nonachlor) revealed that the effects of subject gender were inconsequential. Significant differences (p < 0.05) between the groups examined were attributable to the effect of location on the frequency of detection of OCs or on their differential distribution among the concentration quartiles. In general, people from Hamilton had higher frequencies of non-detections and of concentrations in the first quartile (p < 0.05) for most OCs compared to people from Fort Albany and Kashechewan (who consume a traditional diet of wild meats that does not include marine mammals). An unexpected finding was that, for Kashechewan males, the frequency of many OCs was significantly higher (p < 0.05) in the 4th concentration quartile than that predicted by the four-state log-linear model, but significantly lower than expected in the 1st quartile for beta-HCH. The levels of PCBs found for women in Fort Albany and Kashechewan were greater than those reported for Dene (First Nation people) and Métis (mixed heritage) of the western Northwest Territories (NWT) who did not consume marine mammals, and for Inuit living in the central NWT (occasional consumers of marine mammals). Moreover, the levels of total p,p'-DDT were greater for Fort Albany and Kashechewan women compared to these same aboriginal groups.

Microsatellite analysis of North American pine marten (Martes americana) populations from the Yukon and Northwest Territories

Elucidating the population genetic structure of a species gives us insight into the levels of gene flow between geographic regions. Such data may have important implications for those trying to manage a heavily harvested wildlife species by determining the genetic connectivity of adjacent populations. In this study, the population structure of 12 North American pine marten (Martes americana) populations from the Yukon through to the central Northwest Territories was investigated using 11 microsatellite loci. Genetic variation within populations across the entire geographic range was relatively homogeneous as measured by: mean number of alleles (5.89 ± 0.45) and the average unbiased expected heterozygosity (He) (65.6 ± 1.7%). The overall unbiased probability of identity showed more variance between populations (1/10.25 ± 7.84 billion) than did the mean number of alleles and the Heestimates. Although some population structure was found among the populations, most regions were not strongly differentiated from one another. The low level of structure among the populations can, in part, be attributed to isolation by distance rather than to population fragmentation, as would be expected in more southerly regions in which suitable habitat is more disjunct. Furthermore, the low levels of population genetic structure were likely due to high levels of gene flow between regions and to large effective marten populations in the northern part of their distribution.

Limnological Characteristics of 70 Lakes Spanning Arctic Treeline from Coronation Gulf to Great Slave Lake in the Central Northwest Territories, Canada

AbstractLatitudinal transects across subpolar ecozones display striking changes in lakewater chemistry reflecting steep gradients in vegetation, climate, and other variables. This paper explores the relationships among chemical and physical lakewater characteristics of 70 lakes spanning arctic treeline in Canada's Central Northwest Territories. Principal components analysis (PCA) was used to examine trends and relationships among environmental variables and these 70 sites. In general, lakes in this data set were dilute, slightly acidic to slightly alkaline, and nutrient‐poor. However, a strong trend toward more concentrated lakewater conditions in densely forested areas was observed relative to tundra regions. Interrelationships among measured limnological variables appear to be strongly influenced by catchment characteristics associated with proximity of sites to treeline.

STREAMFLOW MEASUREMENT USING SALT DILUTION IN TUNDRA STREAMS, NORTHWEST TERRITORIES, CANADA1

ABSTRACT: With the recent increased exploration and mining activity in the Northwest Territories, there has been growing interest in streamflows. However, streamflow monitoring in Canada's north is limited, especially in the central Northwest Territories where the exploration activity is concentrated. To complicate matters, the standard approach of measuring discharge with current meters or weirs is often inadequate or prohibitively expensive, as many streams in the region are shallow, braided and rocky. In response, alternative techniques such as salt dilution can be used. A salt tracer's competence in turbulent and rocky channels makes it ideal for discharge measurements in these situations. This paper summarizes the work performed by Indian and Northern Affairs Canada and Canamera Geological Ltd. staff in determining the stream discharge of a lake outlet using a potassium chloride (KC1) tracer. A variety of streamflow measurement methods were performed and compared to determine the viability and rigor of the dilution method. Results suggest the dilution method compares favorably to other measurement techniques both in accuracy and operational ease.

Parelaphostrongylus andersoni (Nematoda: Protostrongylidae) in caribou (Rangifer tarandus) of northern and central Canada

Woodland (Rangifer tarandus caribou) and barren ground (R. t. groenlandicum) caribou are reported for the first time as hosts of Parelaphostrongylus andersoni, greatly extending the known geographic range of this muscle nematode. Up to 56% of caribou in the Beverly herd, central Northwest Territories, passed dorsal-spined first-stage larvae in their feces. Animals less than 3 years old were more frequently infected and passed greater numbers of larvae than older animals. Larval output in winter and spring did not differ. Adults of the four elaphostrongyline nematodes known to occur in caribou are distinguished by their location in the host, the size of the worms, and the size and morphology of the male copulatory structures. There is an urgent need for tested and improved methods of differentiating larvae of P. andersoni and other elaphostrongyline nematodes from those of P. tenuis that cause neurologic disease in various North American cervids. Demonstration of the occurrence of P. andersoni in Rangifer sp. in North America raises the possibility that it originated in Eurasian cervids and may still occur in the Old World.