Tarantulas on the Move! What to Know About Southeastern Colorado’s Annual Spider Trek

As one would expect with any good horror flick, these antagonists prefer to emerge when the light fades. They crawl up out of their burrows, their furry, brown bodies barely rustling the prairie grasses as their legs (all eight of them) pad lightly across the soil. They’re on the prowl—but not with any malevolent intentions. In fact, arachnid experts from Westminster–based Butterfly Pavilion, which has focused on tarantula research since 2010, say the creatures are relatively harmless. They’re just a bunch of bachelors looking for The One.

Each September and October, when the nights in Southeastern Colorado turn chilly (but before hard freezes begin), male Oklahoma brown tarantulas begin their quest for love. They’ll amble around 20 to 100 meters each evening to find it. More and more, visitors are heading to the spiders’ neck of the grasslands to watch. “It’s becoming a big deal,” says Lorna McCallister, target species manager at Butterfly Pavilion and a member of the team working with Colorado State University and the Southern Plains Land Trust to study Oklahoma brown tarantulas’ burrow site selection. “It’s a very cool ecological thing that’s turning into a tourism opportunity.”

Dubbed a “mategration” (it’s not technically a migration since there isn’t persistent movement or a significant relocation to a new habitat, McCallister says), the journey is a long time coming for these spiders: It generally takes males between seven and 10 years and females 10 to 12 years to reach reproductive readiness. By then, the spiders have grown to roughly 5 inches in diameter, and the males have finally grown pedipalps, a pair of appendages attached to their head.

Come fall, the of-age males wander around in search of a female’s burrow. Upon finding one, he will stand outside and drum his pedipalps. If the female is a willing partner, she’ll crawl to the surface, and the male will hold her up above him so that they’re facing each other. It’s a quick coupling—and for good reason. “He tries to get in there, mate, and get out without being eaten,” McCallister says, adding that roughly one-third of female tarantulas strike at their mates and around 20 percent actually kill them, which is not necessarily retribution for poor performance. “If you’re a female, and you know you’re about to raise a hundred-something babies, you’re probably going to take whatever meal you can get.”

Yet even males that do escape their partners’ clutches have numbered days. “Within about a year of doing the [odyssey] and mating, they die,” McCallister says. “That’s basically the last hurrah of their life.”

Tarantulas eat primarily beetles, grasshoppers, crickets, and other small insects, while dodging becoming a meal themselves for coyotes, foxes, snakes, some birds, and 2-inch-long tarantula hawks, a nasty breed of wasp that lays an egg in the tarantula’s abdomen so the larvae can eat the living host as they grow.

There’s still a lot to learn about these eight-legged creatures. For example, McCallister points out that they don’t know how the Oklahoma browns survive the sub-freezing temperatures of winter in southeastern Colorado, since most invertebrates struggle to move even when it’s 40 degrees outside. Nor can they explain how the spiders live through the spring flood season.

Arachnologists are just starting to understand what their burrows look like after Jackie Billotte, a doctoral candidate at Colorado State University who works with Butterfly Pavilion, took what’s believed to be the first-ever plaster molds of Oklahoma browns’ homes. “Spiders, including tarantulas, tend to be misunderstood and understudied,” Billotte says. “Public interest is important to encouraging increased research and getting the message out about the importance of the tarantulas to their ecosystems and how they can serve as a source of ecotourism for the nearby cities.”

That interest seems to be growing. Officials at Comanche National Grassland offer anecdotal evidence that there’s more traffic through their region during the tarantula mating season and an uptick in calls for information regarding how, where, and when to see the spiders.

The town of La Junta in southeastern Colorado has been promoting what it refers to as the Tarantula Trek since 2018 and added a Tarantula Fest to the lineup last year. Visitors attended from as far away as Vancouver, Canada. “The tarantula trek is an unexpected adventure for people to experience,” says Pamela Denahy, director of tourism for Visit La Junta. “We’ve definitely seen the tourism draw and the economic impact that tarantula tourism has had for our community.”

McCallister sees events like the festival, and tarantula-related tourism in general, as beneficial for all parties involved, no matter how many legs they have. “Public interest and support [are] vital for the success of conservation efforts,” she says. “It is crucial that we utilize opportunities like ecotourism during the mategration as educational tools to spread awareness about the importance of tarantulas, their roles in our ecosystem, and why we should care about researching and conserving this unique species.”

Ready to Go Spider Spotting?

Here are McCallister’s top tips for spying tarantulas this fall.

• Though the spiders are often easy to spot as they scuttle across major roadways south of La Junta like CO 109 and U.S. 350, try to go elsewhere if possible. Comanche National Grassland, for example, offers plenty of opportunity for sightings without the danger of semi-trucks barreling along nearby.
• Start looking around dusk when the male tarantulas are most active, but it’s still light enough outside to watch them moving around without a headlamp.
• Be content with seeing a handful (or even just one or two) tarantulas. “It’s not like the wildebeest migration where you see thousands at once,” McCallister says.
• Oklahoma browns are quite docile. They move slowly, and their bite is relatively harmless (unless you’re allergic). Still, it’s not a good idea to pick them up. Not only is it stressful for the spider, but they have urticating hairs, which have small barbs that can get stuck in human skin. “Getting haired by a tarantula is an itchy, not-fun experience,” Billotte says.
• If you can’t make it down to southeastern Colorado to see the males hunting for mates, head to Butterfly Pavilion instead. Its Spiders Around the World exhibition, which runs through October 31, features hundreds of orb-weaver spiders and a new Itsy-Bitsy Spiderling Nursery showcasing four distinct baby tarantula species.

Spider-Spotting Hikes

Lace up your hiking boots, head to La Junta, and keep your eyes on the ground. It’s time to track down some tarantulas.

Timpas Picnic Area Nature Trail

• Trailhead: Timpas Picnic Area
• Distance: 0.5 to 6.5 miles roundtrip

If time is limited, start at the picnic area and take the mellow 0.5-mile loop out to Timpas Creek. For an even better chance of tarantula sightings, however, McCallister recommends splitting off from the nature loop on the north side to follow the Santa Fe National Historic Trail for three miles out to the Sierra Vista Interpretive Site.

Prairie Tail

• Trailhead: Vogel Canyon Picnic Area
• Distance: Three miles roundtrip

Though four hiking trails lead out from the Vogel Canyon Picnic Area, McCallister says the Prairie Trail, which moves through juniper woodlands and shortgrass prairie, is her pick for spider-sighting opportunities. Also, be sure to scan the canyon walls for rock art left behind by American Indians who called the canyon home 300–800 years ago.

Picket Wire Trail

• Trailhead: Withers Canyon Trailhead
• Distance: 17 miles roundtrip

Hike down 250 feet into the Picket Wire Canyonlands and amble along the Purgatoire River Valley bottom. Keep an eye out for tarantulas on the flatter parts of the trail, McCallister says.