[Causes of death, zoonoses, and reproduction in the European brown hare in Switzerland].

To elucidate the importance of different causes of mortality which could explain the downward trend of the hare populations in Switzerland and for monitoring selected zoonoses, the health and reproductive status of 167 perished brown hares (Lepus europaeus) was assessed. Concerning causes of mortality, traumas were by far the most frequent diagnosis, 80% of the hares dying because of injuries. Animals killed by road traffic were highly represented. Predators (such as dogs, domestic cats, lynx, martens, buzzards, and golden eagles) killed 16% of the analysed animals. In juveniles, predation was significantly more frequent than in adults. Infectious diseases led to death in 15% of the animals, and cases of pasteurellosis, brucellosis, pseudotuberculosis, tularaemia, listeriosis, and toxoplasmosis were diagnosed. In 5% of the hares, the cause of death pertained to other categories or remained unclear. Reproductive performance was judged to be normal, since mean litter size was 2.5 per female and pregnancy rate in March-June was 74%. We conclude that neither a specific infectious disease, for which adult hares are particularly susceptible, nor an insufficient reproductive performance are responsible for the decline of brown hare populations in Switzerland. This phenomenon is rather a cause of a reduced survival rate in leverets.