Coexistence of roof rats and carnivores in barns on an urban livestock farm in Japan

Abstract

Abstract Brown rats (Rattus norvegicus), roof rats (Rattus rattus), and house mice (Mus musculus) are three of the most important rodent pest species in the world. Because these rodents infest livestock farms, rodent control on such farms is an important issue for the livestock industry. Although the diel activity patterns of rodents are key to their control, information on this aspect of their ecology is limited. Furthermore, the effect of carnivores on rodent activity patterns, as well as the carnivore species present, on urban livestock farms is unclear. Here, we set camera traps in an open-type cow barn and in an enclosed pig barn on the same urban livestock farm in Japan from August through October 2021. The only rodents observed in both barns were roof rats, and the carnivore species observed were dogs (Canis familiaris), cats (Felis catus), and Japanese weasels (Mustela itatsi). The relative abundance index of cats was similar between the barns, while dogs and Japanese weasels were observed only in the cow and pig barns, respectively. These results suggest that cats and Japanese weasels could easily enter the enclosed barn. We also found that roof rats showed different patterns of activity and behavior between the barns. However, because the pattern in both barns was nocturnal, the activity patterns of roof rats and carnivores showed a moderate to high degree of overlap. Therefore, roof rats did not appear to shift their activity patterns to avoid nocturnal carnivores. Taken together, the present study provides valuable information for rodent control in urban livestock farms.