Reindeer remains one of the least studied animals from the point of view of genetics and reproduction of all animals that are use by humans in economic activities. In Russia, reindeer is use as a farm animal to produce environmentally friendly meat with high nutritional value. Reindeer is also the basis of economic activity for the indigenous peoples of the Arctic. Depending on the climatic zone, there are two methods of breeding reindeer - tundra and taiga. For more effective breeding and planning of reproduction work of this species of animals, it is necessary to have clear knowledge about the features of their reproductive cycle. Reindeer are animals with a pronounced seasonal reproduction; in addition, the timing of calving and rutting season can shift significantly depending on changes in weather conditions. According to researchers, the gestation period of northern females has a very high variability. The aim of this work was to conduct research on the differences in the timing of the beginning and end of the calving and rutting periods, their dynamics, as well as the duration of pregnancy in female reindeer in reindeer herding farms in the taiga and tundra climatic zones. To compare the dynamics and timing of calving and rutting, data were collected on the recording of matings and calvings in reindeer herding farms in the tundra zone of the Arctic regions of the Russian Federation (Taimyr Peninsula and Yamal Peninsula) and in the taiga zone (Buryatia). Because of the research, it was found that not only the timing of the rut, but also the timing of calving have differences in time in the tundra and taiga habitat zones of reindeer, in addition, they can shift even within the same climatic zone depending on weather conditions. The pregnancy period under unfavorable weather conditions can be shorten or extend.