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| Autumn provides a brief glimpse into the workings of nature in the desert.
At no other time is the intimate connection between life and death represented
so clearly. |
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| One of the species that best embodies this relationship between life
and death is the desert tarantula, Aphonopelma iodium. Tarantulas, the
largest spiders in North America, are typically two to three inches long
and are covered with thousands of fine hairs ranging in color from tan
to dark brown. Besides its eight legs, the basic sections of a tarantula’s
body are its cephalothorax (a fused head and thorax, or chest) and its
abdomen. |
| Many tarantulas have a bald spot on the abdomen as a result of a unique
defensive behavior. When cornered by a predator, the tarantula will rub
its hind legs over its abdomen, brushing hairs into its enemy’s eyes.
Tarantulas have many natural predators including larger lizards, snakes,
and birds. However, the most ferocious is the tarantula hawk, a large,
metallic blue and orange wasp. A single tarantula hawk can sting and paralyze
a tarantula, drag the spider back to a prepared burrow, and lay eggs upon
the still-living creature’s abdomen. The wasp then seals its paralyzed
prey inside the burrow. Upon hatching, the wasp larvae will eat the tarantula
alive. Although this outcome may seem grisly from our human perspective,
nature knows only one standard: survival. |
| When a male tarantula reaches sexual maturity, between eight and ten
years of age, he begins a journey that will both aid the survival of his
species and cost him his life. Should you observe a desert tarantula in
Joshua Tree National Park this autumn, it is likely to be a male in search
of a mate. The male follows the scent of a female tarantula to the receptive
female’s burrow, which she has typically excavated in dry, sandy
soil and lined with silk webbing. Tarantulas are solitary animals; there
is only one spider in this burrow. |
| To alert the female of his presence, the male taps one of his legs against
the ground until the female emerges. The male must then participate in
a dangerous mating dance, wherein he fends off the female, who wishes to
devour him, by using hooks on his front legs. His death will give the female
a needed boost of nutrition, as she must now produce 500 to 1,000 eggs
and a silk cocoon where the eggs will be protected. Even if the male escapes
being eaten by the female, he will still die within a few months. Females,
on the other hand, often produce eggs for 25 years or more. |
| When not involved in the ritual of reproduction, tarantulas typically
do not eat each other. Insects like beetles and grasshoppers make up a
good portion of the tarantula diet, and tarantulas in the desert may also
devour small lizards, mice, and even scorpions. Although tarantulas have
the ability to spin silk, they chase down their prey rather than snaring
it in webs. Their eight closely set eyes are not useful in hunting. Instead,
thousands of sensitive hairs on the spider’s body allow it to detect
subtle movements in its immediate environment and “hone in” on
a victim. The tarantula strikes with its fangs, injecting venom. There
is a struggle while the venom takes effect, and the tarantula must grasp
its prey with the palps, two arm-like appendages between the mouth and
legs. If successful, the tarantula wads up its semi-paralyzed victim, secretes
digestive juices onto it, and sucks up the liquefied prey. One creature’s
death leads to another’s survival; the pattern of life in the desert
continues. |
| If you encounter a tarantula, take time to observe its body, its behavior,
and its connection to the fabric of desert life, but please do not disturb
this delicate connection. Wildlife should never be touched, chased, or
fed, and the tarantula is no exception. Contrary to appearance and reputation,
the tarantula is a timid creature and will not bite human beings unless
seriously provoked. Like all animals in Joshua Tree National Park, the
desert tarantula deserves our respect, not just for surviving, but for
thriving in a place where the boundary between life and death is always
shifting. |
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http://www.nps.gov/jotr/nature/animals/arthropods/tarantulas/tarantulas.html
last modified: 11/13/03
web editor: Sandra kaye |
