Living with Deer

Living with Deer

Living with Deer

In many parts of the country, where deer are hunted, people rarely get to see them as closely as we do in the Bay Area. It is charming to see a mother and her fawn living their lives in the open spaces around us. It may not be quite as engaging, however, when they have just eaten all the flowers and buds off your prized rose bushes.

Living with deer is now a fact of our lives in the Bay Area. We eliminated their major predators, mountain lions, and now urban sprawl has crowded them into less and less space. This combination, along with fences, have made these foraging mammals a common sight in most neighborhoods, and overpopulation is a big problem.
Nowhere is this more apparent than in places surrounded by water like Angel Island and Belvedere. Population control in these places inspires heated debate over how to coexist humanely. This is happening in other places, too.

An Elephant Parable

Human overpopulation has often been called "the elephant in the room" that no one wants to talk about, but this example is one from actual elephants.
A presentation given at the 15th Annual Wildlife & Aquatic Animal Medicine Club of U.C. Davis by Dr. Jeffery Zuba of the San Diego Wild Animal Park outlined the problem of population control in elephants in an African reserve. The elephant herd had gotten larger than the reserve could accommodate, and the elephants were destroying the habitat for all the other species that lived there. In a fascinating and amusing talk, Dr. Zuba outlined the problem: elephants are generally in decline, so culling the herd was unacceptable to the entire international community, but it is not possible to create more space for them without taking it from another endangered species.

Because he understood elephants' natural biology, Dr. Zuba's solution was field vasectomies for the males (read the article). Bull elephants guard their harem of cows jealously, and prevent other males from breeding with them. A vasectomy on just the dominant male prevents fertilization but does not affect his libido, so he still keeps the other males away. Humorously, this was somewhat successful (if tricky to accomplish), but the side effect was that all the cows came into oestrus much more frequently. Normally, conception would prevent that for three or more years after a birth. Between keeping his harem happy and fending off other males, the bull is kept pretty busy. This has been hard on him as well as on the veterinarians that had to perform a vasectomy on a 17-ton elephant.

A Study of Birth Control on Deer

A similar but opposite approach studied the use of surgical sterilization of female White-tailed Deer in Highland Park, Illinois from 2002-2005. The study, prepared by scientists and veterinarians from the University of Wisconsin-Madison and the Milwaukee County Zoo found that "tubal ligation, by ventral laparotomy, provides a safe, humane form of sterilization with low mortality in White-tailed Deer. The ability to capture, chemically immobilize and perform surgery on wild deer, under field conditions, was highly successful."

This study showed that the population level goal of five deer per mile could be maintained over time if an average of 32% of the female deer were sterilized per year. Under these circumstances, long-term maintenance would require sterilizing just six does per year until the effects of sterilization halted population growth. In 2005, the estimated cost per deer was approximately $750 per animal.

Again, this approach uses the natural biology of the deer. In the Bay Area we live with Black-tailed Deer, classified as a subspecies of the Mule Deer. Mule Deer are generally more associated with the land west of the Missouri River while White-tailed Deer are the dominant species in the midwest and eastern U.S. Although deer are found throughout the continental U.S., in general those in urban envionments use extremely small home ranges, so sterilization techniques used in a particular area tend to affect only that area.

What About My Roses?

Black-tailed Deer rarely travel far from water or forage, and tend to bed down within easy walking distance of both. Most Black-tailed Deer are "browse" eaters, feeding on the shoots and leaves of woody plants, instead of grasses. They like young plant buds, flowers and shoots, leaves, succulents, shrubs, bark, berries, and other fruits. Black-tailed Deer can survive for several days without water by getting moisture from succulent plants. They also help trim back poison oak.

Six- to eight-foot fences will protect your roses and vegetables by keeping deer out. If you want to plant outside of a fenced area, there are many ideas for deer deterrents, including mixing bad-tasting flowers like daffodils or alliums among the more delectable tulips and other tasty plants. Sometimes just protecting new plants with temporary fencing until they grow beyond deer reach is all that is needed.

Resources for Deer-resistant Plants

While no plants are deer proof, there are many that are far less attractive to deer. Deer tend to dislike plants that are thorny, poisonous or sticky, that have cottony leaves, or that just taste bad. Droughts and other extreme weather conditions can create a serious food shortage for deer, and consequently cause them to lose their inhibitions and eat plants which they would otherwise ignore. Under normal circumstances, however, planting your garden with less-preferred plants will help protect its beauty.

The following sites offer resources and information on deer-resistant gardening:

Las Pilitas Nursery: Gardens with Deer Problems
Las Pilitas Nursery: Deer and Fire List
The Garden Helper: Keeping Deer Out of Your Garden