Seasonal Movements of the Bathurst Caribou Herd
(Revised May 1998)
Organization / Researcher: GNWT, Anne Gunn
Length of Project: 5 years (1996-2001)
Personnel involved: Two principal researchers and a statistician.
Total Project Expenditures: $552,900
This project gathered information on caribou movements by collaring Bathurst caribou with satellite transmitters so they could be tracked throughout the year. The Ekati and Diavik mines are located on spring migration, summer, fall and rut ranges of the Bathurst herd, and the movement information will assist in assessing whether these mines and other projects are affecting the movements of the caribou. It also provided crucial information on the range of the herd and helped determine the core calving area each year. Other details, such as snow depth and rates of spring snow melt, and temperatures and amount of wind (which affect insect activity) were recorded to assess their significance in the movements of the caribou within the calving ground.
This project was done in cooperation with the Dogrib Traditional Knowledge: Relationship between Caribou Migration Patterns and the State of Caribou Habitat and the Tuktu and Nogak Project to provide a more holistic knowledge base. The study was allied closely with the new Bathurst Caribou Calving Ground Studies: Influence of Nutrition and Human Activity on Calving Ground Location and Influence of Parasites on Calving Ground Location study.
The project originally collared 10 cows. In late 1998 an increase to 20 collars was approved. Researchers attempted to randomly collar cows; with cows being chosen because the movement information would help determine the time and location of calving each year. Several caribou died natural deaths or disappeared during the course of the study, or were shot, and a few of the collars did not transmit consistently, so that the number of cows tracked at any one time ranged from six to 19. Over the life of the study 31 different cows were collared. Most collaring-related captures were observed by elders or community representatives.
The study has provided baseline data on weekly and seasonal movements of the herd. Caribou movements were tracked daily by satellite during calving and post-calving, and weekly after that. Maps were produced and distributed.
The number of caribou collared is small compared to the 350,000 caribou estimated to make up the Bathurst herd. In analyzing the caribou movement patterns, the researchers assumed that the collared caribou represent overall herd movement rates; an assumption they think is reasonable during migration periods. They investigated how representative the movements of the collared cows were in relation to the entire herd by overflying the area around the cows, but did not present specific conclusions.
The range of the herd has been found to be much larger than earlier estimates, with summer range being the most predictable year to year and the area used during rut varying the most. In addition to their previously defined wintering area north of Great Slave Lake to the treeline, the Bathurst herd was found to be wintering southeast of the lake in what had formerly been considered to be exclusively winter range for the Beverly herd. Longer term data seems to indicate that changes in areas used for winter range may be rotations to areas of greater forage availability: areas not used for some time and which have not been burned, and where snow conditions do not limit availability.
Winter Range: For 1996-1997, the collars showed the caribou wintering north and west of Great Slave Lake. However the following year, 1997-1998, they appear to have largely wintered south and east of Great Slave Lake. Information from the collars for the winters of both 1998-99 and 1999-2000 suggests the winter range is more extensive than previously thought, with some animals traveling south and east of Great Slave Lake and some to the north and west. The overlap between successive winter ranges was variable, from no overlap some winters to 75% overlap in others; the herd appeared to switch their winter range from northwest of Great Slave Lake to southeast of the lake all the way into northern Saskatchewan.
Summer Range: The collared cows were in an area west of Bathurst Inlet near the Hood River during calving in 1997, 1998, 1999 and again in 2000. The location of calving grounds varied less than other seasonal ranges but was not exactly the same year to year. Each summer the calving ground was made up of about half the previous year's range plus additional land; but over the course of five years of study, only 1.4% of the combined area of calving grounds was repeatedly used.
Though the location of the calving grounds appears to be fairly predictable, the winter range varies considerably, so migration routes to the calving grounds are not predictable. Daily travel during calving related migrations was about 20 km/day. There was only a weak suggestion that mosquito and warble fly activity affected caribou movements.
Limited data on timing of cotton grass flowering and snow depth was gathered as it relates to the core calving area. The Study suggested that snow cover likely affected the rate of spring migration, but noted that effects of snow depth were studied in greater detail in the WKSS Calving Grounds research. Data on the timing and amount of cotton grass flowering showed that timing varied from year to year while production remained fairly constant. The Calving Grounds research also did more research on this subject.
Seasonal Movements of the Bathurst Caribou Herd
Movement and Distribution of the Bathurst and Ahiak barren-ground caribou herds (2005 Annual Report)
Figures of 2005 Annual Report