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The tours feature lively interviews and music with the rush of wind and the chirps, howls, and growls of wildlife, all downloadable to an audio video media player.
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Tarantulas in Mount Diablo State Park

Clayton Worsdell 

Tarantulas generally invoke some kind of emotion amongst humans...why? Well, for starters, tarantulas comprise a group of often hairy and very large arachnids. 

The tarantulas on Mount Diablo are brown or black and are classed as terrestrial types burrowers that live in the ground. They have eight standard legs and two additional appendages called pedipalps, which are used to crush and cut food. The terminal portion of the pedipalps is used by the males as part of the reproductive system. Two or three retractable claws are at the end of each leg. These claws are used to grip surfaces for climbing. Also surrounding the claws are hairs that aid the tarantula to better grip smooth surfaces such as slick rocks. 

Did you know that tarantulas can produce silk? They use this silk to line their burrows to stabilize the walls to make it easier to climb up and down. 

The tarantula is an invertebrate that relies on an exoskeleton for muscular support. A tarantula perceives its surroundings primarily by sensory organs. Touch is its keenest sense, and in hunting, it depends on vibrations given off by the movements of its prey. Tarantula hairs are very sensitive organs and are used to sense chemical signatures such as pheromones, vibrations, wind direction, and possibly even sounds. Their eight eyes (two rows of four), are small and not able to see much more than light, darkness and motion. 

Besides the normal hairs covering the body, tarantulas also have a dense covering of fine barbed hairs that they use for protection. Tarantulas kick these hairs off the abdomen or rub them against their target to irritate an enemy. They also can kick these hairs off by using their back legs to flick them into the air. The hairs can be lethal to small rodents. Some people are extremely sensitive to these hairs and develop serious itching and rashes. The hairs and any appendages lost by the tarantula do not grow back, but are replaced each time it molts. 

Tarantulas in Mount Diablo State Park hunt prey on or near the ground. They mainly eat insects and other arthropods, using ambush as their primary method of capture. They are venomous, but have never been known to cause a human fatality. A bite, however, can produce discomfort for a period of several days. 

Regardless of their fearsome appearance, tarantulas are an object of predation. The most specialized of these is a member of the wasp family known as “tarantula hawks”. The wasp delivers a sting to the underside of the tarantula, which paralyzes the spider. It then drags the tarantula back to its burrow to use as a host for its larvae.

Female tarantulas live longer than males. The females have been known to live for 30 or 40 years. 

During the months of September and October, knowledgeable docents of Mount Diablo State Park lead hikes to provide a chance for visitors to experience the tarantulas up close and personal. Check the events page on our website, www.mdia.org, to see when and where these hikes are conducted.