As the sun sets over the Rocky Mountains, thousands of hairy, eight-legged creatures will start to creep out of the ground on the eastern plains. It’s that time of year again — love is in the air for the tarantulas of Colorado.
In the coming weeks, male tarantulas in the southeastern part of the state will leave the safety of their burrows behind to search for females, who stay hidden in their own holes, said Mario Padilla, a lead entomologist at the Butterfly Pavilion in Westminster.
The mating season typically starts once the temperatures cools at night. This year, that likely means it will start in late August or early September and continue through early October or whenever hard freezes begin, he said.
The annual event is often mistaken as a migration because the nocturnal animals are more visible than normal and appear to be walking with a destination in mind.
“People see them out walking around, so they’re like, ‘Where are they going? They must be migrating,’” Padilla said. “They’re not truly migrating. And it’s only the males that walk around. You don’t see the females at all.”
The on-the-move tarantulas — the males — are longer, with a small abdomen and long, spindly legs to help them move quickly. The females, on the other hand, don’t need that kind of biological adaptation and are often larger.
When the males find a female’s burrow, they drum their legs at the entrance, almost like rapid, soft knocking on a front door, and wait for the female to come out to breed.
This has happened for countless years across the southeast, but when Denver7 published a story last year on this “migration,” many readers and viewers said that despite living in the state their whole lives, they had never heard of it before. Padilla said this isn’t surprising — it’s a relatively little-known event.
“Here in Colorado, we don’t always think that we have habitat for tarantulas,” he said. “A lot of people think tarantulas are super exotic, like they live in South America or Africa or Asia or wherever. And they do live in those places. But we do have beautiful, western tarantulas that live here too.”
Want to see it in person?
Has this “migration” piqued your interest? If you want to head out to the southeast part of the state to see these critters in action, there’s a few things to know beforehand.
One of the best places to go to see the tarantulas is the Comanche National Grassland near La Junta and Springfield. The scrubby grassland, which is at a lower altitude compared to the Front Range, contains more than 400,000 acres for recreating, said Michelle Stevens, recreation program manager for the grassland.
She said drivers often see tarantulas crossing the road because they’re easy to pick out on the pavement. She recommends driving on Highway 350 between La Junta and Trinidad, or Highway 109 between La Junta and the town of Kim to see them. But you can also stop in a local restaurant and ask residents where they’ve seen them, she said.
Stevens said the land ownership pattern in this area is more fragmented than other parts of the state, so when people are visiting and walking around, they should keep an eye on where public land becomes private.
It’s best to go in September. Padilla said Sept. 10 has been reported as the peak date for the “migration.”
Paula Cushing, a biologist with the Denver Museum of Nature and Science, said on any given evening, you’re likely to see a dozen or so tarantulas if you’re in an undisturbed area.
“So, go to Camache grasslands and really enjoy the views there,” she said. “Be sure to enjoy the local economy, be sure to enjoy the sunset, but be ready for your family to be out late if you want to see them.”
And what happens when you spot one?
First, know that they are much more terrified of you than you are of them, Padilla said. Despite common misconceptions, they’re not aggressive animals and won’t jump or attack a person. Their first option in the face of danger? Flee.
However, just because they’re calm creatures doesn’t mean it’s a good idea to try to catch one. Like all wildlife, people should never harass the animals, he said. It takes a lot of stress for a spider to bite a person, but it will happen under certain circumstances. If you find yourself in this unfortunate position, you can find a little piece of mind knowing that tarantula venom is not potent.
“You’re way more likely to get stung by a bee or a wasp, mostly a wasp, or something like that, than bit by a spider of any kind,” Padilla said.
Just like bison in Yellowstone or moose in the Rocky Mountains, it’s best to just leave them be.
“They’re an amazing part of our state and such a valuable, interesting part of the ecosystems where we live,” he said. “We should leave them alone. Not because we want to discourage people from being interested in them, but we want to encourage people to give them their space and respect their lives, just like anything else.”
If you can’t make it to the southeast region to check it out in person, you can see these native tarantulas — and other spider species from around the world — at the Butterfly Pavilion in Westminster.
And if you do visit the La Junta area, Stevens encourages you to enjoy the other family-friendly fall attractions, like farm stands, pumpkin patches and more.
About Colorado tarantulas
All of the tarantulas that call Colorado home fall under the genus Aphonopelma, Padilla said.
They’re usually a “drab brown color” that helps them camouflage into their environment, he said. Their bodies, excluding their legs, are typically two to three inches long.
“They’re bigger than any house spider that you would see,” Padilla said. “They’re bigger than a black widow or a daddy long leg or a little garden spider. They’re much bigger than that. I think that’s why people have that really visceral reaction. Seeing a really big spider — they’re bigger than any wolf spider. They’re the largest spider in the state, for sure. So, seeing that spider is kind of like, ‘Whoa!’”
Male tarantulas are sexually mature once they reach about 7 years old, and can live for about a decade. Females can live well beyond that — up to 30 years. The oldest tarantula on record was studied by scientists in Australia for 43 years , Cushing said.
Because this is not a true migration, the tarantulas stay in that region of the state year-round. They’re nocturnal, so they’re rarely seen in the daylight. When they hunt under a night sky, they typically stay in or near the burrows and eat their catches in the safety of their underground home.
While they have a few defenses — including urticating, barbed hairs they can flick off their abdomen into the face of a predator — they are far from the top of the food chain in southeast Colorado.
Large birds, lizards and small mammals prey on tarantulas, Padilla said.
Because of these threats, males don’t typically live long after they have mated. Death by predator, car or starvation — or rather, lack of interest in eating anything — typically follow. And in some cases, if the female is cranky, she may eat him, Cushing said.
She said she hopes the “migration” motivates more people to visit that part of Colorado.
“If you go down to watch them, enjoy it,” she said. “Enjoy that part of the state. It’s a really beautiful part of the state. I think a lot of people think about Colorado and think about the mountains, but the plains are gorgeous. Enjoy (the tarantulas), realize that they’re not going to do you any harm.”
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