Tarantulas to start mating journey near end of month in Colorado

(LA JUNTA, Colo.) — Every fall, thousands of tarantulas can be seen crossing highways near La Junta and Las Animas, Colorado, as they search for a mate, and the “mate-gration” is about to begin again.

From late August through early October, male tarantulas spread across the grasslands of southern Colorado in search of females, often crossing highways as they go looking for love. “I call it a “mate-gration” because it’s not really a migration,” said Dr. Ritch Reading, Vice President of Science and Conservation at the Butterfly Pavillion “It’s a bunch of males going out in a haphazard way, just scattering about looking for females.”

The females stay near their burrows while the males seek them out. When a male finds a female’s burrow, he taps the ground in a drumming dance. If she’s receptive, the female emerges to meet him. When male tarantulas mature and prepare to embark on their courtship journey, they develop a unique set of clasps on their front legs known as “tibial hooks.” These hooks have a specific function: they latch onto the underside of the female’s fangs during mating, helping the male stay out of harm’s way while he engages in courtship. These hooks allow the male to survive to mate another day, but they also prevent him from molting later, which is fatal.

Tarantulas thrive in grasslands or pastures, but many grasslands have been converted into farmland, leading to habitat loss. The combination of habitat loss and predators like wasps poses a threat to the tarantula population. During mating season, another danger is the risk of being hit by traffic as they cross roads.

According to Dr. Reading, the Butterfly Pavilion is collaborating with the Colorado Department of Transportation (CDOT) to implement protections for tarantulas, including underpasses and fencing to guide them toward these safe crossings. They are also looking at installing “pull-out” shoulders to expand the side of the road, giving drivers a safe space to stop and look at the tarantulas.

Dr. Reading warned that people should be careful when stopping to see the traveling spiders. “When we go down there, we see people on the roads, and these cars and trucks do move quite fast. You see people on their hands and knees taking pictures, and I would not recommend that because if a truck comes speeding at 65 to 70 miles an hour and you’re on your hands and knees, you might not be able to evade that vehicle. We would hate to see that happen, of course.”

Tarantulas pose little danger to people, but they can release tiny hairs as a defense mechanism, which may irritate the skin, according to Dr. Reading. They rarely attempt to bite, as their venom requires significant resources to produce, and they prefer to save it for prey. If people want to observe the tarantulas, they can get fairly close but should stay far enough away to avoid threatening the spiders and to be careful not to harm them.

Dr. Reading says the best place to see the tarantulas is near La Junta. Highways 109 and 350 both have large tarantula populations near them and are common places to have sightings. The timing depends on the weather. “Tarantulas use hydraulics, instead of muscles, to move their legs,” said Dr. Reading. “If it’s too hot or too cold, those hydraulics don’t work very well and so they actually won’t move when the weather’s really warm. The best time to see them at this time of year is in the mornings and the evenings when it’s a little bit more moderate.”

La Junta has an annual Tarantula Fest taking place this year from Friday, September 27, through Saturday, September 28. The event features vendors, tarantula tours, live art, an education pavilion, and a parade.

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