Characteristics of white-tailed deer visits to cattle farms: implications for disease transmission at the wildlife-livestock interface

Bovine tuberculosis (bTB) is endemic in free-ranging white-tailed deer (Odocoileus virginianus) in MI, USA. Currently, the rates of farm visitation by deer and co-use of forage resources by cattle and deer are poorly understood. To evaluate the extent deer and livestock may share forage resources, we investigated farm, yard, and cattle-use area visitation by white-tailed deer and compared visitation with common livestock management practices. We fitted 25 female white-tailed deer near the bTB-infected zone in Michigan's Lower Peninsula with global positioning system collars. Livestock management practices associated with farm visitation included presence of confined feeding pastures, number of cattle water sources, and the number of cattle pastures. Fewer farm visits occurred at night than during the day. A higher proportion of nighttime visits occurred between midnight and sunrise. Visitation to yards and cattle-use areas were similar: a higher proportion of visits occurred at night, and a higher proportion of nighttime visits occurred between midnight and sunrise. Multiple visits during the same day were common. Visitation increased through spring and peaked during the fawning season. Results suggest that mitigation and control efforts to guard against potential transmission of bTB should include the season and time of day during which deer visitation occurs. Furthermore, specific livestock management practices may contribute to farm visitation by deer. Deer visiting multiple farms may contribute to local area spread of bTB. Focusing risk mitigation efforts on individual deer that are most likely to visit farms may reduce potential bTB transmission.