the père david's deer has been in isolation from the wild for more than 1200 years, causing humans to be the primary perceived threat due to a long-term lack of exposure to other natural predators. when encountering humans, the deer's response varies according to gender. female-only groups display a lower degree of caution towards humans than in male-only groups. it was hypothesized that the presence of a single type of threat may be sufficient to maintain anti-predator responses in the face of relaxed predation pressure. during rutting season, the does will display increased vigilance and heightened threat perception, likely in response to the mating activities of the males .