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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