Colorado Tarantula Season: It’s Not a Migration, It’s a Mating Trek

If you’ve heard about “hordes of tarantulas descending on Southern Colorado” and pictured something out of a horror movie, take a breath — it’s not an invasion, and it’s not really a migration either. It’s love season for one of Colorado’s strangest, hairiest residents, and one of the state’s most fascinating wildlife spectacles.

Why It’s Called a “Migration” — And Why That’s Not Quite Right

The nickname stuck decades ago because so many tarantulas can appear on the move at once, and most news coverage still uses it. But a true migration involves a population traveling somewhere and, typically, returning. That’s not what’s happening here.

What’s actually going on: mature male tarantulas, once they reach breeding age at around 8 to 10 years old, leave their burrows for the first and only time in their lives to find a female. They don’t migrate as a group to a single destination — each male goes on a solo trek, guided by scent and vibration, searching for a receptive female’s burrow. Once mating season ends, the males that survive don’t return home. Females, meanwhile, never leave their burrows.

Meet the Spider: Oklahoma Brown Tarantula

The species behind the spectacle is Aphonopelma hentzi, commonly called the Oklahoma brown tarantula — though locals in southeastern Colorado have taken to calling it the “Colorado brown” tarantula. It’s dark brown to black, with a body up to 2 inches long and a leg span of up to 5 inches.

Females spend their entire lives — sometimes 25 to 30 years, per the Oklahoma Department of Wildlife Conservation — inside a single silk-lined burrow, rarely surfacing except to hunt after dark. Males live a fraction of that. Most die within a year of reaching maturity: picked off by predators, run over by cars, or — in some cases — eaten by the very female they came to court.

After mating, the female lays eggs and attaches them to the webbing inside her burrow. They hatch in six to eight weeks, and the spiderlings stay with her for only a few days before striking out to dig their own burrows.

When to See the Colorado Tarantula Trek

Peak activity runs from mid-September through October, occasionally stretching into early November depending on weather. Within a day, the best window is the hour before sunset — roughly 5:45 to 6:30 p.m. — when temperatures start to drop, and the males become most active.

One thing to set expectations: despite dramatic headlines about “thousands marching” across the road at once, most visitors will spot a handful of tarantulas over an evening, not a wall-to-wall crawl. Some evenings, you may see none at all — it’s wildlife viewing, not a scheduled show.

Where to See the Colorado Tarantula Trek

The heart of the action is the Comanche National Grassland in southeastern Colorado, near La Junta and Lamar — roughly a two-and-a-half-hour drive southeast of Colorado Springs. Highway 109 south of La Junta is one of the most reliable viewing corridors, along with Highways 10 and 350 and the county roads that connect them.

La Junta leans fully into its role as trek headquarters, with a dedicated Tarantula Trek guide and an annual Tarantula Fest — complete with a parade, bike rides, tarantula tours, and spider-themed festivities — held the last Friday and Saturday of September in downtown La Junta.

Tarantula Viewing Tips

• Leave the spiders alone. A male has only a matter of weeks to find a mate — don’t be the reason he doesn’t. Snap photos, don’t pick them up.
• Watch your step. Tarantulas blend into the terrain more than you’d expect.
• Pull off the road safely. Many of these highways have no shoulder — find a turnout rather than stopping in the roadway.
• Respect private property. Stay on public roads and grassland; don’t cross fences or block driveways.
• Leave burrows undisturbed. A female tarantula’s burrow can be her home for two decades or more.
• Don’t panic if you get bitten. It’s very unlikely if you leave them be, and their venom isn’t dangerous to humans — comparable to a bee sting.
• Watch for tarantula hawks. These large wasps hunt tarantulas and are often a sign there are spiders nearby — an oddly useful (and slightly unsettling) tracking tip.

Frequently Asked Questions

Is the Colorado tarantula migration real?

Not in the strict sense. Thousands of male tarantulas do become active across southeastern Colorado every fall, but they’re not migrating as a group to a destination—each is individually searching for a mate. “Migration” is the popular nickname; “mating trek” is the more accurate description.

When is tarantula season in Colorado?

Mid-September through October, with activity sometimes continuing into early November. Peak daily activity is the hour before sunset.

Where can I see tarantulas in Colorado?

The Comanche National Grassland near La Junta and Lamar in southeastern Colorado, particularly along Highway 109, Highway 10, Highway 350, and the connecting county roads.

Are Colorado tarantulas dangerous?

No. Their venom isn’t harmful to humans — bites (which are rare and only occur if a tarantula is provoked) feel similar to a bee sting. The bigger safety concern is traffic on unshouldered rural highways, not the spiders themselves.

Why do only male tarantulas appear during the trek?

Females spend their entire lives in a single burrow and rarely leave it. Once males reach sexual maturity around age 8 to 10, they leave their burrows for the first and only time to search for a mate — which is why virtually every tarantula seen out in the open during this season is male.

Myth vs. Reality

The Colorado tarantula trek is one of the most surprising wildlife experiences in the state — and once you know the real story, it’s arguably even better than the myth. Happy trekking!