ICAR Research Data Repository for Knowledge Management

The data for this study and represented in this file were obtained from several sources.

Data on reindeer populations throughout Norway were obtained from annual reports submitted by herders for 78 populations covering a majority of the Norwegian reindeer herding area (Tveraa et al., 2007). Reindeer populations were grouped into ten management regions as in Tveraa et al. (2014). Population density was included as an area-adjusted predictor, calculated as a herd’s population size divided by the area of that herd’s summer pasture land in square kilometres. The previous autumn/winter average juvenile slaughter weight was used as a measure of herd body condition previous to birth, as per Tveraa et al. (2014).

Plant productivity was measured by the normalized difference vegetation index (NDVI) for locations within the herds’ summer grazing land, data for which were collected by the Advanced Very High Resolution Radiometer (AVHRR) instrument deployed on a satellite system and available for full years since 1982. Average altitudes of the areas from which NDVI values were taken were also recorded. NDVI values were recorded twice a month, and the average NDVI value for all pixels (each pixel is 1km2) within a herd’s summer pasture was calculated for each time point. The average altitude, latitude, and longitude of the summer pastures were calculated for each herd using the GRASS GIS software.

Availability of high-quality forage for reindeer was measured by the day of the year (DOY) when the maximum NDVI value first occurred for each herd’s location and each year. Spring onset for each year and each herd’s location was considered as the DOY when NDVI first reached 50% of its yearly maximum. Both the DOY when maximum NDVI occurred and spring onset were calculated from the AVHRR data. Daily snow depth (mm) for each of the herding districts from 1984 to 2013 were obtained from the Norwegian Meteorological Institute. The area under the spline curve (AUC) of ground snow depth was calculated for each year at the summer grazing pastures using daily snow depth values from September to September. The onset of winter for a given year was defined as the first DOY which had at least two consecutive weeks of snow on the ground (snow depth > 0 mm).

References Cited:

Tveraa, T., Fauchald, P., Gilles Yoccoz, N., Anker Ims, R., Aanes, R., and Arild Høgda, K. (2007). What regulate and limit reindeer populations in Norway? Oikos, 116(4):706–715.

Tveraa, T., Stien, A., Brøseth, H., and Yoccoz, N. G. (2014). The role of predation and food limitation on claims for compensation, reindeer demography and population dynamics. Journal of Applied Ecology, 51(5):1264–1272.