Placeholder Effect

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 deer challenge tagged from from coming into their terriroty.

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

The placeholder effect is based on the territorial nature of deer, outsiders are discouraged from entering the established range of resident does.  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.  This research is documented in this peer reviewed paper [page 159].

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