Peary caribou, muskoxen and Banks Island forage: Assessing seasonal diet similarities

Peary caribou (Rangifer tarandus pearyi) and muskoxen {Ovibos moschatus) on Banks Island had considerable similarity in their annual diets, with monthly similarities ranging from 17.8-73.3%. Diet similarity was more pronounced in areas of high muskox density {ca. 1.65/km2) than in areas of low muskox density {ca. 0.4/km2). Willow (Salix arctica) and sedge (Carex aquatilis and Eriophorum spp.) represented >80% of the monthly diet of muskoxen. The caribou diet was more diverse, and was dominated by sedge, willow, Dryas integrifolia, and Oxytropis maydelliana, Lichen use was rare, likely as a consequence of low availability on Banks Island. Lichen standing crop was estimated at 2.96 g/m2. The differences in muskox diet between high and low density areas could not be explained by differences in forage distribution or standing crop. We discuss diet similarities of caribou and muskoxen and potential consequences for the current Peary caribou population in relation to winter weather conditions and increasing muskox density

Overwinter changes in urea nitrogen:creatinine and cortisol:creatinine ratios in urine from Banks Island Peary caribou

Over 200 snow urine samples were collected from Banks Island Peary caribou between March 1993 and May 1998. Most (n = 146) samples were collected during 3 time periods in 5 successive years: early winter (3 November-3 December), mid-winter (9 February-1 March), and late-winter (23 April-2 May). We determined the ratios of urea nitrogen:creatinine (U:C) and cortisol:creatinine (C:C) for each sample. U:C ratios had significant year, time, and year x time interaction effects. Mid-winter ratios were higher than early or late-winter ratios. U:C ratios ranged from 0.53 to 19.05 mg/mg, and were lowest in 1997-98. Five calf caribou sacrificed in February 1994 had significantly (P<0.02) higher U:C ratios than other caribou in mid-winter. Three adult male and 2 calf caribou sacrificed in November 1993 had U:C ratios similar to other caribou in early winter. Sacrificed caribou were in similar condition to animals that have been harvested for subsistent use in other years, not overly fat nor in an advanced state of starvation. U:C ratios for Peary caribou range from 10 to ca. 100-fold higher than those reported for barren-ground caribou; ratios > 60-fold higher than those indicative of prolonged undernutrition in barren-ground caribou were common. This difference is likely because the winter diet of Peary caribou has a higher crude protein content than that of barren-ground caribou. C:C ratios had significant year and year x time interaction effects, and were highest in 1996-97 and 1997-98. C:C ratios of sacrificed caribou were similar to those of other animals during early and mid-winter. C:C ratios for Peary caribou ranged from 0.0120 ug/mg to 0.2678 ug/mg; ratios indicative of morbidity in mule deer were common. C:C and U:C ratios from the same individuals were not correlated (R = -0.073). Monitoring U:C ratios of Banks Island Peary caribou may provide useful management information

Population demography of high arctic caribou on Banks and Melville Islands

Caribou numbers, Rangifer tarandus pearyi, (excluding calves) on Banks Island were estimated (standard error of the estimate) at 1005 (SE±133) in 1992, 709 (SE±128) in 1994 and 436 (SE±71) in 1998; no paired estimates were different (P<0.05). On Melville Island caribou numbers were similar in 1987 and 1997 with estimates of 729 (SE±104) and 787 (SE±97), respectively. We conducted annual sex and age classification surveys during July on Banks Island from 1994-2000 and on Melville Island from 1998-2000. The number of calves per 100 >two-year-old females ranged from 24.0 in 1994 to 74.3 in 1998 on Banks Island, and from 44.8 in 1999 to 80.0 in 1998 on Melville Island. Recruitment rate ranged from 18.6% during 1997/1998 to 27.5% during 1999/2000 on Banks Island and from 16.7% during 1997/1998 to 25.0% during 1999/2000 on Melville Island. There has been an increasing trend in the rate of recruitment on both islands during the last three years of the study

Calf Production, Calf Survival, and Recruitment of Muskoxen on Banks Island during a Period of Changing Population Density from 1986-99

Population estimates for muskoxen (Ovibos moschatus) (age > 1 year) on Banks Island increased from 29 168 (SE 2104) in 1985 to a peak of 64 608 (SE 2009) in 1994 and then declined to 45 833 (SE 1938) in 1998. From 1986 to 1999, annual sex and age classification surveys of muskoxen were conducted during summer. We estimated calf production (number of calves per 100 females aged 2 years or more), calf survival, and recruitment (number of yearlings per 100 females aged 2 years or more). Calf production ranged from 31.3 to 56.3 and was similar between periods of increasing and decreasing density (mean = 42.3 vs. 40.8). Calf survival ranged from 23% to 83% and was generally higher while density was increasing than during its decline (mean = 60 vs. 45). Survival at a given density was lower following the 1994 peak in density. Recruitment ranged from 10.0 to 41.7 and was higher (p = 0.06) during the period of increasing density than during the decline (mean = 28.0 vs. 17.2). Calf survival and recruitment were lowest following two consecutive severe winters, but animal density explained more of the variation in survival and recruitment than did late-winter snow depth. There was a positive relationship between the proportion of sedge (Carex spp., Eriophorum scheuchzeri) in the summer diet and calf survival and recruitment. Patterns of calf survival and recruitment plotted against density were consistent with those modelling a density-dependent relationship. Our results suggest that severe weather alone cannot explain the fluctuations in the population dynamics of Banks Island muskoxen and that underlying density-dependent responses acting upon calf survival and recruitment offer an alternative explanation.Les estimations de population du bœuf musqué (Ovibos moschatus) [âge = 1 an] sur l'île Banks ont augmenté de 29 168 (erreur-type 2104) en 1985 à une valeur crête de 64 608 (erreur-type 2009) en 1994 pour ensuite décliner jusqu'à 45 833 (erreur-type 1938) en 1998. De 1986 à 1999, on a procédé en été à des relevés annuels de classification par sexe et par âge des bœufs musqués. On a estimé la production de veaux (nombre de veaux par 100 femelles de 2 ans ou plus), la survie des veaux et le recrutement (nombre de petits d'un an pour 100 femelles de 2 ans ou plus). La production de veaux allait de 31,3 à 56,3 et était semblable durant la période d'augmentation et celle de diminution de densité (moyennes de 42,3 et 40,8 respectivement). La survie des veaux allait de 23 à 83 p. cent et était généralement plus élevée quand la densité augmentait que pendant son déclin (moyennes de 60 et 45 respectivement). La survie pour une densité donnée était plus faible après la crête de densité de 1994. Le recrutement allait de 10,0 à 41,7 et était plus élevé (p = 0,06) pendant la période d'augmentation de densité que pendant son déclin (moyennes de 28,0 et 17,2 respectivement). La survie des veaux et le recrutement étaient les plus faibles après deux hivers rigoureux, mais la densité des animaux expliquait mieux la variation dans la survie et le recrutement que l'épaisseur de la neige à la fin de l'hiver. Il y avait une relation positive entre la proportion de carex (Carex spp, Eriophorum scheuchzeri) dans l'alimentation estivale et la survie des veaux ainsi que le recrutement. Les tendances dans la survie des veaux et le recrutement tracées en fonction de la densité donnaient des courbes en accord avec celles représentant un modèle variant avec la densité. Nos résultats suggèrent que la rigueur du climat ne peut à elle seule expliquer les fluctuations dans la dynamique de la population du bœuf musqué de l'île Banks et que des réactions fondamentales variant avec la densité qui influent sur la survie des veaux et le recrutement offrent une autre explication

A PROGRAM TO MONITOR MOOSE POPULATIONS IN THE DEHCHO REGION, NORTHWEST TERRITORIES, CANADA

Moose (Alces alces) are an important traditional and spiritual resource for residents of the Dehcho Region of the Northwest Territories. Maintaining healthy and sustainable populations of moose for future generations is a goal of the Department of Environment and Natural Resources (ENR). Following a regional wildlife workshop with Dehcho First Nations, the need for a program to determine baseline information on moose populations and to foster community-based monitoring of moose in the Dehcho was identified. Such a program needed to be established prior to future proposed developments including the Mackenzie Gas Project. After extensive community consultation between local First Nations and ENR, a baseline aerial survey over a large area of the Dehcho was designed, and was to be followed by an annual monitoring program. Two key components identified for the annual monitoring program were an aerial survey and harvest sampling. The aerial survey would provide information on moose density and calf production, and harvest sampling would provide information on the relative health and physical condition of animals consumed by local residents. In light of increasing developmental pressures in the region, such information collected over time is important to harvesters, First Nations, wildlife managers, and land use planners alike because it should document change in the quantity and quality of a key traditional wildlife resource. Population estimates from the aerial surveys indicated that the estimated population density and calf:cow ratios were reasonable. Harvest data indicated low incidence of diseases and parasites, low levels of cadmium in organ tissue, and that moose were mostly in good or excellent body condition based on observation and fat indices. This study is an example of successfully combining the knowledge and cooperation of First Nation moose harvesters with the technical support of government biologists to secure valuable biological information for baseline data to monitor change associated with development in a region

Growth in Skull Length and Width of the Arctic Wolf: Comparison of Models and Ontogeny of Sexual Size Dimorphism

We compared four classical nonlinear growth curves (Gompertz, Logistic, Richards, and von Bertalanffy) in modeling observed skull condylobasal length and zygomatic width as a function of age in wild arctic wolves (Canis lupus arctos). We analyzed gender-specific growth patterns and the ontogeny of sexual size dimorphism in this species as revealed by the best model from these alternatives. For both genders and skull size measurements, the size-at-age data provided the best support for the von Bertalanffy model because of higher fitting degrees, lower root mean squared standard deviation of data points about the fitted growth curve, Akaike weight of 37.4% or higher, and fewer parameters derived directly from metabolic laws. Male asymptotic condylobasal length was 3.2% longer, and zygomatic width 4.1% wider, than in females. Sexual size dimorphism in this species develops in part because males grow faster, which might benefit them in terms of reproductive success and the capture and killing of large ungulate prey.Nous avons comparé quatre courbes de croissance non linéaires classiques (Gompertz, logistique, Richards et von Bertalanffy) se rapportant à la modélisation de la longueur condylobasale de crânes observés et à leur largeur zygomatique en fonction de l’âge chez les loups arctiques sauvages (Canis lupus arctos). Ensuite, nous avons analysé les tendances de croissance en fonction de la sexospécificité et de l’ontogenèse de dimorphisme sexuel chez cette espèce, tel que révélé par le meilleur de ces modèles. Dans le cas des données relatives au sexe et aux mesures de tailles de crânes, les données propres aux tailles selon l’âge ont fourni le meilleur support pour le modèle de von Bertalanffy en raison de degrés de raccord plus élevés, d’un écart-type moyen inférieur des points de données sur la courbe de croissance ajustée, d’un poids Akaike de ≥ 37,4 % et de moins de paramètres directement dérivés des lois métaboliques. La longueur condylobasale asymptotique du mâle était de 3,2 % plus prononcée et sa largeur zygomatique était de 4,1 % plus grande que celles de la femelle. Chez cette espèce, le dimorphisme sexuel se développe en partie parce que les mâles grandissent plus vite, ce qui pourrait avantager les mâles en matière de réussite de reproduction, de même que les aider à capturer et à tuer les grosses proies ongulées

Does seasonal variation in forage quality influence the potential for resource competition between muskoxen and Peary caribou on Banks Island?

Inter- and intra-annual variation in forage quality may influence population dynamics of Peary caribou and muskoxen on Banks Island. From 1993 to 1998 we collected 300 composite samples of sedge (Carex aquatilis and Carex spp.), willow (Salix arctica), legume (Oxytropis spp. and Astragalus spp.), and avens (Dryas integrifolia). Samples were collected in mid-June (start of the growing season), mid-July (peak of the growing season), mid-late August (senescence), and early (November), mid- (February), and late- (April/May) winter. We analysed forages for percent digestibility (in vitro acid-pepsin dry matter digestibility), crude protein (CP), fibre, lignin, and energy content. There was significant inter-annual variation in levels of lignin, fibre, and energy, and significant intra-annual (seasonal) variation for all quality measures and forages, which reflected the strong difference in quality between summer and winter. We discuss the relationship between forage quality and seasonal diet composition of Peary caribou and muskoxen, and the potential implications for the reduced Peary caribou and high muskoxen populations

Differences in radionuclide and heavy metal concentrations found in the kidneys of barren-ground caribou from the western Northwest Territories 1994/95 to 2000/01

Aluminum, nickel, cadmium, mercury, and lead concentrations were measured in the kidney tissue of known aged barren-ground caribou wintering in the western Northwest Territories harvested during winter 1994/1995 and during winters 2000/2001 and 2001/2002. 40K, 137Cs, and 210Pb concentrations were measured in the kidney tissue of known aged barren-ground caribou during winter 2000/2001 and compared to concentrations in winter 1993/1994 reported in Macdonald et al. (1996). Renal concentrations of aluminum were higher (P<0.001)in winter 2000/2001 than winter 1994/1995. Contrastingly renal concentrations of mercury were lower (P<0.001) in winter 2000/2001 than 1994/1995. 137Cs (P<0.02), 40K (P=0.01), 210Pb (P<0.01) had lower renal concentrations in winter 2000/2001 than 1993/1994. Renal concentrations of cadmium (P<0.001) and 137Cs (P<0.04) had a positive relationship with caribou age. We also document renal concentrations of arsenic, copper, selenium, zinc, 232Th, 226Ra, and 235U in the kidneys of caribou harvested in winters 2000/2001 and 2001/2002. Renal zinc concentrations were positively correlated with the age of caribou

PERSISTENT ORGANIC POLLUTANTS IN THE LIVERS OF MOOSE HARVESTED IN THE SOUTHERN NORTHWEST TERRITORIES, CANADA

Moose (Alces alces) are an important traditional and spiritual resource for residents of the southern Northwest Territories and local residents are concerned about contaminants that may be present in the country foods they consume. As part of a larger program looking at contaminants in moose organs, we collected liver samples from moose harvested in two separate but adjoining regions within the Mackenzie River drainage area, the Dehcho and South Slave. We analyzed liver samples for a wide range of persistent organic pollutants (POPs) including polychlorinated biphenyls (PCBs), DDT related compounds, toxaphene, brominated diphenyl ethers (PBDEs) and perfluorinated alkyl substances (PFASs). Overall concentrations of major groups of POPs (total (Σ) PCBs, ΣPBDEs, ΣPFASs were consistently low (generally < 2 ng/g wet weight) in all samples and comparable to the limited data available from moose in Scandinavia. PFASs were the most prominent group with geometric means (range) of 1.3 (0.81–2.5) ng/g ww in the Dehcho and 0.93 (0.63–1.2) ng/g ww in the South Slave region. Decabromodiphenyl ether (BDE-209) was the most prominent PBDE congener, similar to that found in other arctic/subarctic terrestrial herbivores. In general, BDE-209 and PFASs, which are particle-borne and relatively non-volatile, were the predominant organic contaminants