Restoring the common hamster's farmland habitat-how crop associations might benefit Cricetus cricetus hibernation and reproduction.

Biodiversity decline is particularly pronounced in agricultural areas, where intensive farming practices have severely altered the ecosystems. In Alsace (France), this has led to the decline of the common hamster (Cricetus cricetus), a farmland-inhabiting hibernator. Previous work in laboratory conditions showed that diversifying the hamsters' diet through crop association is a promising strategy to improve their hibernation and reproductive success. However, little is known about the effect of such crop associations in the wild. In this study, we monitored the hibernation behaviour (in laboratory cages) and reproductive success (in mesocosms) of hamsters exposed to four different crop associations of variable nutritional content, selected for their technical and economic benefits for farmers. Hamster hibernation behaviour depended mainly on the ingested energy and only marginally on the nutritional quality of the diet. Hamsters on lipid-rich diets showed a higher body mass before reproduction. All hamsters successfully reproduced in semi-natural conditions, even in wheat monoculture, where food supplements (weeds, invertebrates) prevented protein deficiencies. Associations richer in proteins and lipids such as legume-oleaginous crop mixes doubled reproductive outputs and increased pup growth. These results should help to improve hamster conservation measures and promote farmland biodiversity.