Placeholder Effect

The 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.

At another fence opening, tagged does were entering a field that had previously been restricted by fencing.  Conflict develops at the boundary of this deer territory.

Conflict between tagged and untagged doe in field

A similar effect is observed in coyote populations,  Mississippi State University assistant professor Dr. Marcus Lashley says“A number of studies have shown that the alpha female is very good at defending her territory and keeping other coyotes away. If you kill her, others will move in and fight over the territory. You may actually end up with more coyotes than you had to begin with,” ...  

Another video of Doe 53 pushing an untagged doe out of her territory.

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.  

Tagged doe pushing untagged out

Below a view from another camera.

Doe 53 chases untagged doe out

A few moment later, Doe 53 appears to be guarding her territory.

Doe 53 in untagged out

In this later episode, again Doe 53 appears to push an untagged doe outside her territory.  In the picture below the untagged doe from outsdide the area is looking to enter.  Moments later chased away by Doe 53, a resident of the Villages.  Video below.

Doe 53 pushing untagged doe out