The Arctic habitats are characterized by extreme climatic and environmental conditions with high seasonality and restriction of resources for the development of vegetation. Therefore, faunas adapted to these conditions have developed different strategies to cope with them, such as migration or hibernation. Arctic rodents have the particularity to maintain an activity all throughout the year, especially during the cold season, constituting thus the main resources for numerous predators in this ecosystem, and the cyclic dynamics of these key-species is a major driver of the fluctuations of the tundra food web. For the past fifty years, these habitats are undergoing significant changes, leading to new constraints on the organisms causing imbalance in the communities, as observed by Russian colleagues on the Yamal Peninsula (Siberia). These colleagues have a large collection of rodents for this time span on a North-South transect along this Peninsula, from different biological stations, with associated data (densities of prey-predator, climatic parameters). This project aims to study rodent populations subjected to degrading ecological conditions and therefore probably to important stress that will be evaluated by different proxies including morphological variability. Following a first exchange (as they came in France during last February), the Russian colleagues propose to us to access on the one hand to this material and on the other hand to make additional field missions to target key study species in an ecological monitoring. To do so, the project requests funding for field missions and for acquisition of materials (field measurements for 2D and 3D morphometrical analyses).