This paper examines the implementation of a white-tailed deer management program in the Blue Hills Reservation outside of Boston, Massachusetts. Drawing on the concepts of biopolitics, we explore how white-tailed deer became an object of concern and ultimately targets of lethal management in this suburban park. Through interviews, document analysis, and observation of public meetings, we examine the changes in and controversy over the presence, perception, and management of deer in the park. We argue that the implementation of the deer management program is only partially explained by the growing numbers of white-tailed deer, and must also be understood in the context of concerns about human health and shifting imaginaries of urban green spaces and global biodiversity. The case illustrates the entanglements of harm and care in the management sub/urban ecosystems and highlights how differences in the ethical and ontological understandings of deer create tensions in efforts to advance multispecies urban planning.