Effects of weather and snow conditions on reproduction and survival of semi-domesticated reindeer (R. t. tarandus)

Abstract

In this work we investigated the effects of local weather and snow conditions on the reproduction and survival of semi-domesticated reindeer (Rangifer t. tarandus) from 1962 to 1987 in four separate study areas in northern Finland. Reindeer density had no negative effect on calf percentage in slaughter (October-January) in any area. The higher the number of very warm days or mean temperatures in summer, the lower was the calf percentage in all forested areas (Sodankylä, Muonio and Ivalo). In the Muonio area, calf percentage was also reduced by winters with abundant snow accumulation. In the open, mountainous Kevo area, calf percentage was reduced with a high number of warm days (mean T>0°C) during the previous December. However, if the previous May was warm in that area, it had an opposite effect. High reindeer densities seemed to increase mortality only in the Sodankylä area. Abundant snow accumulation during winter reduced the survival index of reindeer both in the Sodankylä and Ivalo areas. In the Muonio area, mortality of reindeer was increased with a high number of warm days in December. In the Kevo area, reindeer density or any climatic parameters could not explain yearly differences in mortality. This study indicated that permanent changes in climatic conditions could have different impacts in woodland as opposed to open, mountainous regions. In general, if global climatic change means weather instability in early winter and more snow, it also brings more difficulties for reindeer. However, if climate change means that snow melts earlier in the spring, some conditions could become more favourable for reindeer.