Comparison of caribou physical characteristics from Yukon and neighboring caribou herds

Data on seven external body measurements of caribou from six woodland and two barren-ground caribou herds from Yukon, Alaska, Alberta and British Columbia were compared. Comparisons between females in the fall and winter and mature males in the fall revealed that (1) barren-ground Porcupine caribou were consistently smaller than caribou from other herds, (2) British Columbia and Alberta caribou tended to be larger than Yukon caribou, or the Alaskan caribou studied, (3) central Yukon caribou were intermediate in body size, (4) no difference was found between Yukon «mountain» and «woodland» type caribou in body size, and (5) the barren-ground Fortymile caribou were more similar in physical characteristics to Yukon woodland or mountain caribou than to those of the barren-ground Porcupine herd. These data support Banfield's (1961) view of a gradient of decreasing physical size from the northern British Columbia — Alberta herds through the Yukon mountain or woodland herds to the northern barren-ground herds

An Ancient Wolf, Canus lupus, Den and Associated Human Activity in the Southwestern Yukon Territory

The recovery of an ancient hunting artifact in an active Wolf den indicates that Wolf denning sites may be reused for many centuries. It also suggests that traditional practices of predator management by humans may have great antiquity

Population ecology of two woodland caribou herds in the southern Yukon

Since the mid 1980's, the Aishihik herd of woodland caribou (Rangifer tarandus caribou) declined from approximately 1500 to 583 animals. During the same period a nearby herd, the Wolf Lake Herd increased from approximately 664 to 1249 animals. This paper compares aspects of the ecology of these two herds to determine how these relationships conform to a general model of caribou population ecology described by Seip (1992). Comparisons include caribou demographic characteristics and distribution patterns, predator densities, abundance of alternate prey, human hunting and snow depth on caribou winter range. Ecological differences between herds were apparent in the ratio of prime bulls to cows, the abundance of moose (Alces alces), the occurrence of coyotes (Canis latrans), late winter snow conditions, and access to hunting. We hypothesize that the Wolf Lake herd was able to grow because wolves {Canis lupus) preyed mainly on the relatively abundant moose population. A highly clumped winter caribou distribution may have further reduced the impact of wolf predation on the Wolf Lake herd. In contrast, the decline of the Aishihik herd was accompanied by a relative scarcity of moose, few prime aged caribou bulls probably due to a more liberal trophy harvest, and wider late-winter dispersion that offered wolves greater access to caribou. The decline may have been exaggerated by the peak in the snowshoe hare (Lepus americanus) cycle which may have temporarily improved wolf pup survival. We suspect that moose are normally the primary prey of wolves in the Yukon and that a decline in moose eventually results in their being too scarce to offer an economical prey choice, prompting a prey switch to caribou. Results of our analyses conform incompletely to Seip's (1992) model for woodland caribou population ecology, particularly because the Wolf Lake herd prospered where moose were relatively abundant

Genetic relationships of three Yukon caribou herds determined by DNA typing

In this paper we examine genetic relationships of caribou (Rangifer tarandus caribou) in the Aishihik, Chisana, and Wolf Lake herds in the Yukon using DNA fingerprinting. The assignment test used in this analysis showed that the caribou herds were distinct. This finding is consistent with movement data from radio-collared caribou which demonstrates home range fidelity. We found a high level of heterozygosity and a genetic basis for population boundaries. DNA fingerprinting may provide an effective means to compare ecological and genetic relationships

User needs, benefits and integration of robotic systems in a space station laboratory

The methodology, results and conclusions of the User Needs, Benefits, and Integration Study (UNBIS) of Robotic Systems in the Space Station Microgravity and Materials Processing Facility are summarized. Study goals include the determination of user requirements for robotics within the Space Station, United States Laboratory. Three experiments were selected to determine user needs and to allow detailed investigation of microgravity requirements. A NASTRAN analysis of Space Station response to robotic disturbances, and acceleration measurement of a standard industrial robot (Intelledex Model 660) resulted in selection of two ranges of low gravity manipulation: Level 1 (10-3 to 10-5 G at greater than 1 Hz.) and Level 2 (less than = 10-6 G at 0.1 Hz). This included an evaluation of microstepping methods for controlling stepper motors and concluded that an industrial robot actuator can perform milli-G motion without modification. Relative merits of end-effectors and manipulators were studied in order to determine their ability to perform a range of tasks related to the three low gravity experiments. An Effectivity Rating was established for evaluating these robotic system capabilities. Preliminary interface requirements were determined such that definition of requirements for an orbital flight demonstration experiment may be established

Non-Invasive Hall Current Distribution Measurement in a Hall Effect Thruster

A means is presented to determine the Hall current density distribution in a closed drift thruster by remotely measuring the magnetic field and solving the inverse problem for the current density. The magnetic field was measured by employing an array of eight tunneling magnetoresistive (TMR) sensors capable of milligauss sensitivity when placed in a high background field. The array was positioned just outside the thruster channel on a 1.5 kW Hall thruster equipped with a center-mounted hollow cathode. In the sensor array location, the static magnetic field is approximately 30 G, which is within the linear operating range of the TMR sensors. Furthermore, the induced field at this distance is approximately tens of milligauss, which is within the sensitivity range of the TMR sensors. Because of the nature of the inverse problem, the induced-field measurements do not provide the Hall current density by a simple inversion; however, a Tikhonov regularization of the induced field does provide the current density distributions. These distributions are shown as a function of time in contour plots. The measured ratios between the average Hall current and the average discharge current ranged from 6.1 to 7.3 over a range of operating conditions from 1.3 kW to 2.2 kW. The temporal inverse solution at 1.5 kW exhibited a breathing mode frequency of 24 kHz, which was in agreement with temporal measurements of the discharge current

Maternal demographic and placental risk factors in term low birth weight in Ghana

Background: Several studies report on factors that associate preterm birth and intrauterine growth restriction with low birth weight (LBW). However, few studies discuss risk factors that associate with LBW for full-term births. No such studies exist that involve a population from Ghana. Method: We used a nested case-control study approach to examine maternal socio-demographic and placental factors that contribute significantly to term LBW in Ghana. We assessed also the incidence of LBW in general at a major teaching hospital facility in Ghana. Results: Univariate and multivariate logistic regression analysis were used to investigate maternal sociodemographic and placental factors that associate with LBW. Following the preliminary univariate analysis, a stepwise logistic regression analysis showed that unstable income source, single motherhood, combined effect of pre-eclampsia and anaemia; ORs of 5.366 (95% CI: 1.986 to 14.497), 21.390 (95% CI: 3.610 to 126.734) and 3.246 (95% CI: 1.074 to 9.814), respectively, and placental weight and irregular insertion of the umbilical cord (variables scaled by a factor of 10-2 to aid interpretation) ORs 0.28 (95% CI: 0.115 to 0.683), 0.010 (95% CI: 0.001 to 0.173 respectively) on the chorionic plate, were risk factors for LBW. The socio-demographic and placental factors reveal a core role of maternal and infant nutritional deficiencies in term LBW in Ghana. The general prevalence of LBW in the Hospital facility was 6.2%. Conclusion: We conclude that poor maternal and infant nutrient supply is key factors in term LBW in Ghana. These factors are amenable to appropriate nutritional and educational interventions. a, Tettey Yaob, Gyasi Richard, Obed Samuel, Farnell Damian Joseph John, Quaye Isaac Kweku

Ethnographic and Archaeological Investigations of Alpine Ice Patches in Southwest Yukon, Canada

Since the original 1997 discovery of ancient hunting implements in melting alpine ice patches of southern Yukon, approximately 146 well-preserved, organic artifacts have been recovered. Most of the artifacts, variously made of antler, bone, wood, and stone, represent complete or partial examples of throwing-dart (atlatl) and bow-and-arrow technology. Radiocarbon dates obtained thus far range from 8360 BP to 90 BP (uncalibrated). Our research indicates that in southern Yukon, throwing-dart technology persisted from at least 8360 BP to approximately 1250 BP, when it was abruptly replaced by bow-and-arrow technology. The collection has afforded archaeologists and First Nation researchers a unique opportunity to learn about past hunting technologies and practices and thus greatly improve our understanding of the enduring relationships between humans and caribou.Depuis la découverte en 1997 d'anciens objets de chasse dans les plaques de glace alpines du sud du Yukon, environ 146 artéfacts organiques bien conservés ont été récupérés. La plupart des artéfacts, faits de bois d'animal, d'os, de bois ou de pierre, représentent des exemples complets ou partiels de propulseur lance-javelins (atlatl) et d'une technologie axée sur l'utilisation d'arc et de flèches. La datation au radiocarbone varie de 8360 ans B.P. à 90 ans B.P. (non étalonné). Les recherches effectuées rélèvent que dans le sud-est du Yukon, la technologie reposant sur l'utilisation du lance-javelines a été en usage de 8360 ans B.P. au moins jusqu'à environ 1250 ans B.P., époque à laquelle elle fut soudain remplacé par la technologie reposant sur l'utilisation de l'ensemble arc et flèche. Grâce à cette collection, les archéologues et les chercheurs des premières nations ont pu en apprendre davantage sur les technologies et les méthodes de chasse utilisées à cette époque et ainsi améliorer leur compréhension des relations durables entre l'humain et le caribou

Multidisciplinary Investigations of Alpine Ice Patches in Southwest Yukon, Canada: Paleoenvironmental and Paleobiological Investigations

Since the discovery of dung-rich alpine ice patches in southwest Yukon in 1997, continuing multidisciplinary studies have provided a unique window on the biology, climate, and hunting activity in this region over much of the Holocene. Aerial surveys have identified 72 ice patches of variable size, and 65 patches have been ground-surveyed for organic remains. Of these, 35 yielded an abundance of biological specimens, including caribou and other rare large mammal remains, mummified small mammals and birds, and artifacts spanning 8000 years. The dung provides pollen and plant macrofossils for analysis and paleoenvironmental reconstruction, as well as dietary, genetic, and parasitic information. Stratigraphically controlled sampling of dung within ice layers has yielded a geochronology placing their formation as early as 8300 to 8000 years BP. Ice patch formation was nearly continuous except for an interval between 6700 and 4700 years BP and another between 1440 and 1030, when warm or dry conditions (or both) resulted in no net ice accumulation. Resumption of ice accumulation over the following 500 years likely culminated in the Little Ice Age. The size of the ice patches during this period is made evident by a lichen-free zone that haloes each patch. More recently, interpretation of air photos from 1946 to 2001 has found a significant reduction in ice patch dimensions. Daily temperature records for Whitehorse (1942-2001) were used to calculate melting degree-day values that account for a large part of the variation in ice patch size, indicating that while considerable melting has likely occurred since the end of the Little Ice Age, the ice patches are highly sensitive to decadal changes in temperature.Depuis la découverte de plaques de glace alpines riches en excréments d'animaux dans le sud-ouest du Yukon en 1997, des études multidisciplinaires continues offrent une fenêtre unique sur la biologie, le climat et les activités de chasse de la région pendant presque toute la période de l'Holocène. À l'aide de relevés aériens, il a été possible d'identifier 72 plaques de glace de tailles différentes. Des relevés sur le terrain ont été effectués sur 65 de ces plaques pour récupérer des restes organiques, et 18 d'entre-elles ont révélé une abondance d'espèces biologiques et des restes de grands mammifères rares (y compris le caribou), des petits mammifères et des oiseaux momifiés, et des artéfacts datant jusqu'à 8000 ans. Les excréments d'animaux permettent d'analyser des macrofossiles de pollen et de plantes afin de faire une reconstruction paléoécologique, ainsi que d'obtenir des renseignements sur le régime alimentaire, la génétique et les parasites. À l'aide de la géochronologie, l'échantillonnage des excréments d'animaux contrôlé par stratigraphie a permis de dater la formation des excréments à aussi loin que 8300 à 8000 ans B.P. La formation des plaques de glace a été presque continue, à l'exception d'une période entre 6700 et 4700 ans B.P. et d'une autre entre 1440 et 1030, lorsque des conditions chaudes ou sèches ou les deux n'ont pas permis à la glace de s'accumuler. La reprise de l'accumulation de glace au cours des 500 dernières années a vraisemblablement provoqué le petit âge glaciaire. La taille des plaques de glace au cours de cette période est facilement calculable grâce aux zones sans lichen qui encerclent chaque plaque. Des études plus récentes de photos aériennes prises entre 1946 et 2001 ont permis de constater une réduction marquée de la taille des plaques de glace. Les données des températures quotidiennes de Whitehorse (de 1942 à 2001) ont été utilisées pour calculer la valeur du degré-jour de fonte qui est en grande partie responsable de la variation de la taille des plaques de glace. Ces données indiquent que même si le plus gros de la fonte s'est produit depuis la fin du petit âge glaciaire, les plaques de glace réagissent beaucoup aux changements de température décennaux

In Pursuit of Prehistoric Caribou on Thandlät, Southern Yukon

In 1997, the first author noted a large concentration of caribou (Rangifer sp.) fecal pellets and a caribou antler on a permanent snow patch in the Kusawa Lake area of southern Yukon. Caribou are completely absent from this area today. Coring of the snow patch revealed continuous deposits of fecal pellets to depths of at least 160 cm. The proximal portion of a wooden dart or arrow shaft fragment recovered on the edge of the snow patch represents one of the few organic examples of mid-Holocene hunting technology ever found in Canada. An age of 2450 BP ± 50 years was obtained for the fecal material from approximately 1.6 m below the surface of the snow patch, and the dart was dated at 4360 BP ± 50 years. These dates indicate that aboriginal Yukon hunters have been harvesting caribou at this location for at least 4000 years. The Thandlät site offers a rare opportunity to explore a number of questions regarding the prehistoric ecology of large caribou populations, the implications of climate change for caribou populations, and human use of high-elevation hunting sites.En 1997, le premier auteur a découvert une concentration élevée de boulettes fécales (Rangifer sp.) et des bois de caribou sur une congère dans la région du lac Kusawa, dans le sud du Yukon. Il n'y a plus de caribous dans cette région. Le carottage de la congère a révélé des dépôts de boulettes jusqu'à une profondeur de 160 cm. Un fragment de dard ou de la flèche en bois trouvé sur le bord de la congère représente une des rares découvertes au Canada relatives à ce type d'arme. Il a été déterminé que les matières fécales prélevées dans la congère, à environ 1,6 m de profondeur, sont âgées de 2450 BP ± 50 ans, et que le dard aurait 4360 BP ± 50 ans. Ces dates montrent que les Autochtones du Yukon chassaient déjà le caribou à cet endroit il y a 4000 ans. Le site Thandlät est un des rares endroits où l'on peut observer divers aspects préhistoriques des grandes populations de caribou, des effets des changements climatiques sur les populations de caribous et des activités de chasse à grande altitude