The member of the deer family common to San Diego County is the mule, or black-tailed deer. The mule (including black-tailed) deer (O. hemionus) is identified by its tail, completely black on top but whitish underneath, like the rest of the deer's underside. A buck (male) can be 3 1/2 feet tall at the shoulder. Bucks weigh from 250 to 500 pounds, while females (does) are considerably lighter. The name mule deer comes from the animal's large ears that move independently.

Bucks begin to grow antlers in the spring, and their "rack" is fully developed by September. After the mating season in January or February, bucks shed their antlers and go without until a set of new velvet-covered stubs begins to sprout in May.

The first time they give birth, does usually produce a single fawn. From then on, they usually bear twins. Triplets are common, and even quintuplets are known.

Mule deer range in a variety of habitats, including forests, deserts, chaparral, and grasslands with shrubs. Their home range is 90 to 600 acres, depending on the sex. While they enjoy well-forested areas, they do most of their feeding in open areas with a good deal of greenery. As people have moved into deer habitat and planted vegetation, the deer have adapted to eating landscaped plantings, which has brought them into conflict with humans.

Deer are ruminants, meaning they have complex digestive systems divided into separate chambers containing microorganisms that break down the vegetable matter they eat. The food is at first quickly swallowed; then, after a period of digestion, it is regurgitated, thoroughly chewed (called chewing the cud), and swallowed again for further digestion. The whole process, which takes about 48 hours, is a survival adaptation for animals that often must snatch a few bites of forage and be on the move quickly to escape predators.

Most black-tailed deer are "browse" eaters, feeding on the shoots and leaves of woody plants, instead of grasses. Their most active browse times are early morning, from dusk into evening, and moonlit nights. They like young plant buds and shoots, leaves, succulent plants, 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.

Black-tailed deer have a complex social organization. A female will aggressively defend an area 100 to 200 acres in diameter where her fawn lies, as long as it stays still. If the fawn moves, the territory only increases about another 16 feet. Black-tailed deer live in large clans, which the bucks defend against other mule deer. They follow definite trails and can run 35 miles per hour, leap 30 feet, and clear 8-foot fences.

Deer use ridges and hills during the day as heated air rises, carrying scents from below up to the alert deer. At night, they stay in the lowlands, because cooler air settles, again carrying scents to the deer for identification.

Only the males grow antlers, which they use for sexual display and to establish dominance within the herd (yearly discarding and growing of antlers). Sunlight stimulates antler growth. The antlers are formed by living tissue supplied with blood from vessels within the soft skin known as "velvet." After underlying tissue hardens, the velvet is scraped off, and the antlers become mineralized dead tissue. A yearling buck usually has two points on each antler in the form of a Y, while an adult buck has an additional Y on each point, totaling four points on each antler.

Deer have a life span of 25 years in captivity and average 16 years in the wild.

Natural predators of black-tailed deer are mountain lions, and occasionally coyotes. Their chief enemy is humans. The destruction of habitat through logging and development has played a large part in the decrease of deer. Today, hunters and automobiles destroy an estimated 400,000 deer annually. Also, domestic dog packs often kill deer.

Though bucks can use their antlers as weapons, their main defense is their hooves, powered by the strong forelegs. Black-tailed deer, when threatened, bounce stiff- legged with their small, ropelike tail down. All deer become more excitable during the mating season, and males can be particularly dangerous then. Does will go to great lengths to defend their young. Never approach a deer at any time of the year, because humans are seen as a threat. Deer can attack, and serious injury or death can result.

Tips

1. Fawns wandering and crying are an indication that the mother has been hurt and not returned. If you are sure the mother has not returned for several hours and the fawn is so young it will let you pick it up, take it to Project Wildlife. If the fawn is older and stays around the area, it may need help getting enough food and water. You may put out a clean container of water and set out its normal browse food (cuttings from blackberry bushes, roses, pyracantha, alfalfa, or apples). Do not hand-feed deer.

2. Fawn in the Yard. Make sure the doe can get into the area. If this is not possible, find the hole in the fence through which the fawn got in, put the fawn outside of it, and close the hole. The mother will return for the fawn soon. If no humans are around when she returns, she will likely reclaim her fawn despite the human scent. Handle only fawns that are small enough to be carried. Wait for the mother to return or call Project Wildlife.

3. Anyone who comes upon a fawn should leave it alone and go away so its mother can feel free to return. Only if the fawn is obviously emaciated or injured, or if there is a pack of dogs roaming the area, should it be touched. If a doe is found dead and the fawn orphaned, call Project Wildlife.

4. Deer eating garden and landscaping plants. "Fence or share" is the general rule. Deer fencing should be 8 feet high if possible and made of high-tensile wire, mesh fencing, or electric wiring; placement may be angled to prevent the animal from jumping over. If fencing the entire area is too expensive, fencing individual plants is effective.

5. Black Dacron bird netting, purchased from a plant nursery, is effective when placed over planting beds or individual plants. The nets let new growth through, so they must be lifted and reset every few days to maintain protection. Netting can also be used as an extension above a fence that is too low.

6. Repellents can be effective through bad taste and others indirectly by sight, smell or sound. The following homemade concoction can be effective if sprayed directly on plants and reapplied weekly. Mix well two eggs, one glass of skim milk, one glass of water, and a spreader- thickener (a wetting agent purchased from plant nurseries). Apply.

Hang indirect repellents, including nylon stockings containing small amounts of human hair; mirrors; strips of tinfoil; or commercial smell repellents. Or hang rags soaked in ammonia on branches; replenish with ammonia regularly to maintain the odor. Deer are adaptable, so it is important to vary the methods, or the animals will learn that the repellents are not harmful and will no longer be deterred by them.

7. Planting deer-resistant plants can be an alternative, although none is totally guaranteed, especially when drought conditions constrict food sources.

8. Many people choose to share their yards with deer and other wildlife and purposely plant vegetation that will support wildlife.

9. Deer with broken leg or other injury. Leave the animal alone unless it can't stand up. In this case, call Project Wildlife. If the animal is getting around with a broken leg, leave it on its own. Even though the injury may take a long time to heal, this is far preferable to the trauma of chase and capture.

The secret to observing deer is choosing the right time of day: dawn or dusk, because deer feed in the open around those times. Position yourself near a good browsing area where there is enough cover, and make sure you are downwind of the site so the deer cannot detect your smell. Deer in the wild will probably not stay around long once they have noticed you. Do not attempt direct contact (deer can be carriers of Lyme disease ticks), and let the animals leave on their own.

By the end of the nineteenth century, mule deer in western America had been reduced through overhunting to one-tenth of their former population. Conservation efforts and habitat restoration begun early in this century have replenished deer populations. Today the black-tailed deer population is fairly stable, although some subspecies are threatened because they cannot adapt to human development.

Supplemental feeding of deer is not recommended except in extreme weather emergencies, because it is quite expensive and makes the deer dependent upon nonnatural food sources.

Nature Education & Wildlife Rehabilitation, San Rafael, CA.

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