In seasonal environments, birth dates are a central component for a species' life history, with potential long-term fitness consequences. Yet our understanding of selective pressures of environmental changes on birth dates is limited in wild mammals due to the difficulty of data collection. In a context of rapid climate change, the question of a possible mismatch between plant phenology and birth phenology also remains unanswered for most species. We assessed whether and how the timing of birth in a mountain mammal (isard, also named Pyrenean chamois, Rupicapra pyrenaica pyrenaica) tracked changes in plant growing season, accounting for maternal traits, individual heterogeneity and population density. We not only focused on spring conditions but also assessed to what extent onset of autumn can be a driver of phenological biological events and compared the magnitude of the response to the magnitude of the environmental changes. We relied on a 22-year study based on intensively monitored marked individuals of known age. Births were highly synchronized (80% of kids born within 25 days) and highly repeatable (84%; between-female variation of 9.6 days, within-female variation of 4.2 days). Individual phenotypic plasticity allows females to respond rapidly to interannual changes in plant phenology but did not prevent the existence of a mismatch: a 10-day advance in the autumn or spring plant phenology led to 3.9 and 1.3 days advance in birth dates, respectively. Our findings suggest that plant phenology may act as a cue to induce important stages of the reproductive cycle (e.g. conception and gestation length), subsequently affecting parturition dates, and stressed the importance of focusing on long-term changes during spring for which females may show much lower adaptive potential than during autumn. These results also question the extent to which individual plasticity along with high heterogeneity among individuals will allow species to cope with demographic consequences of climate changes.

Over the last decades, climate change and agricultural intensification have been identified as two major phenomena negatively affecting biodiversity. However, little is known about their effects on the life-history traits of hibernating species living in agro-ecosystems. The European hamster (Cricetus cricetus), once a common rodent on agricultural land, is now on the verge of extinction in France. Despite the implemented measures for its protection, populations are still in sharp decline but the reasons for it remain unclear. To investigate how environmental change has affected this hibernating rodent, we used a data set based on 1468 recordings of hamster body mass at emergence from hibernation from 1937 to 2014. We reveal the adverse effects of increasing winter rainfall and maize monoculture intensification on the body mass of wild hamsters. Given the links that exist between body mass, reproductive success and population dynamics in mammals, these results are of particular importance to understand the decline of this species. In view of the rates of maize monoculture intensification and the predicted increase in winter rainfall, it is of the utmost importance to improve land management in Western Europe to avoid the extinction of this species.

The common hamster Cricetus cricetus was long considered to be a pest species for crops, but its populations are now dramatically declining. The conservation of this species can only be achieved via an up‐to‐date knowledge of its ecology. However, its diet composition has never been exhaustively reviewed and the last peer‐reviewed publication on its feeding ecology in farmlands dates back to 1974. This review of the literature aims to establish a list of plant and animal taxa consumed by common hamsters, providing knowledge to be applied to the conservation of hamsters and to identify the main avenues of future research. Hamsters consume four main categories of food: crops, weeds, trees/shrubs and animals, including mammals, birds, herptiles and invertebrates. Vegetable foods are more diverse (114 taxa) than animal foods (11 taxa). Hamsters mainly consume animals and green parts of plants (flowers and leaves) in spring and summer, and store energy‐rich and non‐perishable foods for winter. Weeds are the most diverse food category (61 taxa), followed by crops (31 taxa). However, diet shifts from crop products towards tree products in urban habitats, probably in response to a marked difference in availability. We conclude that hamsters have an opportunist diet that shows a high degree of plasticity, and that weeds make up an important part of their food supply. However, the studies published to date have considered diet composition without taking food availability into account, and therefore lack information on whether the hamsters select the foods consumed or simply consume them because other foods are not readily available. Research on food availability and selection is therefore needed. Moreover, we argue that there is a need for recent data on the feeding ecology of the hamster in relation to fitness. This would provide a crucial tool for the implementation of adapted conservation measures for this declining species of rodent.

Agriculture intensification, marked by the generalization of crop monoculture, by the increase in plot size and by the reduction of plant diversity, has led to huge decline in wildlife in European farmlands. In such habitat, research has long been biased towards birds and invertebrates, while very few studies have investigated the effect on small mammals. Considering the European hamster, Cricetus cricetus, we therefore review the different techniques that can be used to investigate the impact of environmental changes and conservation measures in small and endangered wild mammals. We suggest that only a multidisciplinary approach will allow exploration of these effects, combining experimental laboratory work on captive‐bred animals with the monitoring of wild individuals. In particular, individual energy balance has to be investigated and measured as accurately as possible, through either biochemical or bio‐logging techniques. It is, indeed, the most affected physiological trait in a changing environment, as it determines both the reproductive output and the survival of the individual. We also discuss the inconvenience of capture–release approaches for such an endangered species and emphasize the disturbance that experimental protocols could impose on the hamster.