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It’s the time of year when the tarantulas come out onto the trails and are seen frequently by visitors in the park. What are these spiders doing and why are they most frequently seen in the fall?
These large, hairy spiders are mostly from the family Theraphosidae. There are over 900 species of tarantula worldwide. Most tarantulas are found in Central America, South America and Mexico, but some are from North America. One, is found right here in the park: the California Tarantula
Like all spiders, they have eight legs and two parts to their bodies. The head and chest are combined into a part called a cephalothorax and the lower part is the abdomen. Tarantulas have two parts in front of the mouth called chelicerae where their two fangs are. They either hold or are connected to the spider's venom glands. These are used to inject venom into their prey.
So, just how big are these spiders? Depending on the species, they can average between 0.2 - 4.3 inches (0.5-11 cm) long. The smallest kind is the endangered Spruce-Fir Moss Spider. Found in the Appalachians, this spider measures a mere 0.10 - 0.15 inches (0.25-0.38 cm). By contrast, the Goliath Birdeater is the largest. It is found in the northern part of South America and is the largest spider in the world, weighing in at 6.2 ounces (175 g), with a body length of 5.1 inches (13 cm). However, it is not the longest spider. That distinction goes to the Giant Huntsman spider whose leg span can reach up to 1 foot (30 cm).
Tarantulas are by no means tiny, but they will on occasion try to make themselves look even bigger. If they are threatened, they will raise their front two pairs of legs in the air. They do this to try to scare off potential predators. In addition to this intimidation tactic, many New World species have hairs called urticating hairs that the spider can flick off into the face of a predator. These hairs can cause irritation to the skin and eyes.
So, how can you tell that big, hairy spider is actually a tarantula? Look at their fangs. Tarantula fangs face downwards, as opposed to those of other spiders, whose fangs face each other. All tarantulas are venomous. Their venom is not deadly to humans, but some bites cause pain and can become serious, particularly if the person bitten is allergic. Like other spiders, tarantulas are carnivorous. They will eat insects, centipedes, and millipedes. These spiders can also go for extended periods without eating. One account says they have been known to survive on water alone for about 2 years.
Tarantulas have two or four spinnerets, depending on the species. Spinnerets are flexible, tube-like structures from which the spider makes its silk. Tarantulas are also able to shoot silk from their front feet to help them cling to slick surfaces.
Tarantulas periodically shed their external skeletons in a process called molting. A young tarantula may do this several times a year, while full-grown spiders may molt only once a year; to regenerate lost limbs or urticating hairs. They may regenerate lost organs in this manner as well. When spiders have reached sexual maturity, they no longer molt, and as a result, can no longer regenerate their legs.
Tarantulas can live for many years and most species take two to five years to reach maturity. After they reach adulthood, males live about one year more. At this time, usually in the fall, the male tarantulas will go out and search for a mate. This is when most people will see a tarantula. They are often seen on roads and trails as they make their way to the burrow of a female spider to mate. Male tarantulas rarely molt again once they reach adulthood. Females will continue to molt after reaching maturity and have been known to live 30 to 40 years. The oldest tarantula on record lived to be 49 years old!
Tarantulas can be seen in September and October walking out in the park looking for mates. Keep an eye out, you may get lucky and see one of these awesome spiders up close!
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