Non-lethal Deer Management Project in San Jose

A deer sterilization project starting in 2013 was approved by the California Department of Fish and Wildlife to control the deer population at a retirement community in San Jose.  Some does had ovariectomies while others had tubal ligations.  It was expected that deer from outside the community would migrate in, so all does were sterilized, but no new deer migrated into the community.  The population has fallen below the target the community later set.  

As shown at right, openings were created in fencing to encourage migration of new deer into the area in an effort to restore some of the population.  Two fawns were later born from sterilized does, sterilization is not typically 100 percent effective, but one was a buck and one died at a young.  The population continues to decline as the remaining deer age.

This article by Hasan Z Rahim gives some history of the project.  This peer reviewed research paper also provides a summary and a deer population model. The paper describes a startling difference in the results of at this site and a similar project done by Cornell University, where they reported a dramatic increase in the buck population.  As the data reported below and as discussed in the research paper linked above, the buck population at this location fell dramatically.

Deer Count:  At the start of the sterilization project in January, 2013, the deer count was 175 with 105 does and 70 bucks, falling to 47 deer in spring, 2019, with 42 does and 5 bucks. Reporting stopped after Spring, 2019.

Spring, 2019 deer count (April):   42 does and about 5 bucks, 47 deer including a few does photographed (some on this page) after the count.

Fall, 2018 deer count:   56 inside the community, 50 does and about 6 bucks.  The count was done later than in 2017, during October when deer are in the rut (mating) and moving more often. 

Spring, 2018 deer count:   49 deer inside the community, 42 does and 6 or 7 bucks in April.  A few deer are spending time outside the count area.

Fall, 2017 deer count:   55 deer, 49 does and 6 bucks in August.  

Two Fawns Born

The trail camera photo below verified the reports of the first fawn seen in the area for years, pictured below her mother, Doe 100. See more on her page.  According to the records, Doe 100 had an ovariectomy at a very young age.  Doe 100 was found dead on September 10, 2016, no apparent cause. She seemed fatigued in the last video recorded. 
 
A test on one of the approximately 10 deer that died starting in September, 2016, came back positive for Blue Tongue, a hemorrhagic disease that is not infectious to humans or other deer, but is spread by insect bites. expected to be a result of Blue Tongue. The video below shows the fawn nursing

Doe 100 Nursing Her New Fawn


Other does were seen keeping watch over the orphaned who was old enough to survive on his own.  The fawn was sighted two times during the deer count at the end of October and also on November 6, then throughout November.   The photo below of the fawn, showing the beginning of antlers, was taken at the end of November, 2016. 



A second fawn at the Villages:  During the summer of 2019 there were reports of a tagged doe with a fawn.  Photos from one resident confirmed that Doe 16, who had received an ovariectomy, was taking care of a fawn.  Speculation was that this was an orphaned fawn born outside the area.  Reports that Doe 16 had been seen nursing the fawn were confirmed by photos that the doe was lactating, demonstrating conclusively that she had given birth to the fawn.  The fawn died of unknown causes a few months later.  

Trail cameras were used to keep traffic of conditions and movement of these deer from summer 2016 to summer 2019.  Impressive antlers on this buck, photo taken in July, 2017.
Buck 45M, tagged as a youngster by mistake thinking he was a doe, was found dead outside the fence during the deer count in April, 2017.  Doe 73 was found dead on January 29, 2017.  She was one of the deer with a radio collar.  According to our records she was probably 10-11 years old.  No signs of injury other than scavenger damage after her death.

Tagged Does Using Fence Opening Created to Encourage Migration of New Does into the Area to Increase the Population


The tagged does in the video above were all sterilized and are easy to visually distinguish from fertile, untagged does outside the fence.  This community is fenced except for a large open gate at the front entrance that also allows for deer to move in and out of the area.  After three years of no observations of new deer moving in the area, the community agreed to do a survey to find a good location for an opening to encourage deer migration into the community.  The video above shows the first opening that was designed to be high enough to prevent feral hogs from entering, but low enough that deer could jump in and out.   

Although deer were observed outside the opening, few deer ventured in.  One reason may be attributed the the "placeholder effect" where resident deer will discourage outside deer from entering their territory.  As shown in the video below, Doe 53 became the gatekeeper of the first opening, chasing untagged deer from outside the neighborhood back through the opening.

Doe 53 Chases an Untagged Doe Out of The Area


Given the lack of success at the first opening, a second opening was created at another location.  As with the first opening there were deer observed outside of the opening and some venture in but none stayed.  The two videos below show first an untagged doe jumping in, the jumping back out only a few minutes later.  

Untagged Doe Jumps in at the Second Opening


Untagged Doe Jumps Right Back Out.


No fawns were ever observed with the deer photographed outside the fence and the number of deer seen outside declined over the three years that trail cameras were in operation.  Competition from feral hogs and dry weather were contributing factors.  At the beginning of the project, fences were reinforced eliminating openings that the deer may have used to migrate into the areas which was much better habitat than outside the area, reducing the food supply of outside deer.  The video below shows three untagged does in a field outside the fenced area during the California winter.  In California, the dry summer is the most difficult time for deer to find food and water.

Three Untagged Does in a Field Outside the Fence


Although the fence openings were placed where no feral hogs were observed in the camera surveys used to select locations, the hogs appeared outside the second opening for a few weeks.  The fence design proved to be effective as while the hogs came right up to the opening, none were able to jump the fence.  See the video below.

Feral Hogs at Fence



As this picture of a buck in flight below shows, deer were able to use the opening to enter.  The opening proved to be an effective hog filter.


One of the few remaining bucks, still has his antlers in April

Here's one without the antlers

Doe 11 likes to move around a lot.  She is one of the does equipped with a radio collar allowing her movements to be tracked remotely.