The deer placeholder effect is based on the territorial nature of deer. Outsiders are discouraged from entering the established range of resident does. A sterile doe will defend her territory, reducing the immigration of fertile deer into an area managed by non-lethal methods. This research is documented in a peer reviewed paper [page 159], based on observations documented by some representative images on this page.

As part of an effort to encourage deer to migrate into the Villages -- a community in San Jose, California -- after a sterilization program reduced the deer population below the community's desired level, fences were modified to allow outside deer to enter. The images on this page show a sterilized deer, tagged as number 53, blocking entrance of an untagged deer from outside the community. At another interface, outside does challenge tagged does who come into their territory.

In the image below, Doe 53 can be seen intimidating a doe from outside the community. The fence marks the boundary of the community.

The deer placeholder effect has also been observed at a project started in 2011 in Baltimore County, Maryland. From their website: "We observed how they [deer] continue to stay together and the surgery does not change their family dynamic. We know that even though they still reside in the community, they serve as infertile placeholders who help keep out new deer while consuming much less."

The videos below, taken a few days later than the image at left, shows the sequence of Doe 53 pushing the untagged doe out of the community. Times on the two different cameras were not perfectly synchronized, so the time on one of the cameras was off a little.