Resource: Tarantulas

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Tarantulas live their long lives (from 10 to 30 years) in warm environments, such as desert and rainforest habitats. North American species, including those in the desert Southwest, dig burrows or find abandoned rodent holes in which to live; other species find shelter under rocks or logs or in tree bark. Despite their fearsome reputation, tarantulas are not normally lethal to humans. Most of the 300 or more species worldwide feed on insects, including crickets, beetles, and moths, as well as on other spiders. Only species like the massive South American goliath tarantula eat larger prey that includes frogs, small snakes, and even birds.

Unlike many other spiders, tarantulas capture prey without a web. Instead they rely on the element of surprise, a set of piercing fangs, and powerful venom. A tarantula may set out a strand of silk along the open ground. When an insect or other animal walks past or over the strand, vibrations alert the hidden tarantula to the prey. The spider comes out of hiding and bites the victim. A tarantula's venom does two things. First, it paralyzes the prey. Then, it gradually breaks down the prey's body tissue to a liquid, which the tarantula can easily take in and digest.

Juvenile male and female tarantulas look largely alike. However, mature males are typically black in color, while mature females are brown. Color disparity is an expression of sexual dimorphism, or a difference in form—apart from reproductive organs—between sexes of a species. Sex-specific differences found in other species of organisms include the presence or absence of body parts such as tusks or antlers, and overall body size.

For continuation of a species, the reproductive success of an organism is paramount. Female tarantulas are larger than their male counterparts because the females must generate eggs, and this requires a lot of energy. Female tarantulas will also outlive males, sometimes by as much as 20 years or more. While females often kill their male mates for food—accounting for part of the discrepancy—males also exhibit riskier behavior when they reach maturity. They leave their protective shelters in search of female mates, sometimes traveling miles in the open, where they are exposed to predators.

To learn more about how desert creatures are adapted to survive in an extreme environment, check out Desert Biome.

Print Questions for Discussion

• Describe two of the ways in which tarantulas protect themselves from predators.
• Describe how tarantulas hunt for prey.
• What would happen to a human if he or she were bitten by a tarantula?
• Why do you think that tarantula males and females have different behaviors, life spans, and sizes?
• How might these differences between the sexes help the species to survive?