Modelling population dynamics of the Common hamster (Cricetus cricetus): Timing of harvest as a critical aspect in the conservation of a highly endangered rodent

Abstract

The Common hamster Cricetus cricetus was an agricultural pest in large parts of Europe less than 50years ago. Currently the species is highly threatened or locally extinct and acknowledged as an important and even iconic species for nature conservation in farmland areas in Western Europe. The species was listed in the European habitats directive in 1992 to prevent a further decline, but the Common hamster is still declining in most parts of its European range despite large conservation efforts. Only a few local conservation successes have been reported so far. These disappointing conservation results raise the question: why is it so difficult to conserve this former pest species?Farming practices have been intensified in Europe and this has resulted in a more efficient way of harvesting cereals in combination with a strong reduction of spring sown cereals in favour of winter sown cereals. It is possible that these changes have become an important threat for survival of populations of this species. We developed both a deterministic and a stochastic population model for a better understanding of the current way of harvesting on the population ecology of this species and evaluated the effects of using different litter sizes on population growth and persistence. Our results suggest that under the current efficient harvest of cereals in Europe, it is highly unlikely that females of the Common hamster produce enough offspring for a sustainable population. Conservation projects for this species should focus on creating cereal fields which are not harvested until the end of August, as lack of cover is a major cause of high predation rates.