By Tina Mitchell
As we waited to pull onto U.S. Hwy. 50 from Coaldale on a September afternoon, a scampering movement low on the asphalt caught our attention. Four tarantulas skittered across the road toward the river. Whoa – tarantulas? In Colorado? What were those hairy arachnids up to here?
Autumn looms right around the corner, and so too does tarantula mating season. During breeding season, mature males head out in search of females, providing surprise viewing opportunities while soundlessly beating many feet across pavement. (The tarantula genus name Aphonopelma derives from Greek for “silent foot”: aphono, “silent”; pelma, “foot.”) On a mission to mate, the usually nocturnal males roam the grasslands – and adjacent roads, trails, yards, bike paths, and sidewalks – in daylight, evoking intrigued stares or, for some watchers, horrified shudders wherever they appear.
While more than 800 species of tarantulas exist worldwide, only four species inhabit southern Colorado. The largest spider in the state, the Oklahoma brown tarantula (Aphonopelma hentzi) is the most common tarantula species. A female averages a body size of about two inches, with a leg span up to 5½ inches; a mature male’s body runs slightly smaller, although he has longer legs. Two other tarantula species have been reported in southeastern Colorado – Sugar City brown (A. coloradanum) and Colorado chocolate brown (A. echinum). A much smaller species, Grand Canyon black (A. marxi), occurs primarily in southwestern Colorado (Dolores, Mesa, Montezuma, Montrose and San Miguel counties).
Your odds of encountering a tarantula are highest throughout the counties bordering and south of the Arkansas Valley (Fremont to Prowers). The fuzzy arachnids have also been spotted in the southern parts of El Paso County, as well as Cheyenne Mountain State Park. Perhaps their range is expanding north.
Almost all tarantulas seen during the day this time of year are migrating mature males. Among the shyest of spiders, tarantulas typically stay in the vicinity of their burrows throughout their entire lives. Their burrows can eventually extend more than a foot deep. The tarantula remains hidden within, emerging at dusk and lurking at the edge of the burrow to ambush passing prey such as cockroaches, beetles, crickets and grasshoppers. The spider seals itself in the burrow during the cold months.
Males mature about 7-10 years after hatching; females require an additional 1-2 years to reach maturity. Female tarantulas may live as long as 35 years, but males typically die within months of their first (and therefore only) mating. The female lays eggs in a silk sack up to eight months later, turning the eggs periodically, and even moving them if the temperature drops. Hatching 50-60 days later, the young spiderlings settle near the mother’s burrow. Initially they establish themselves at the base of a nearby grass clump, gradually expanding their burrows over the next several years.
When harassed, a tarantula relies on two defensive strategies. First, an irritated spider can rear up on its back legs, thereby exposing its fangs. If the disturbance continues, the spider will attempt to bite its adversary. A second tactic focuses on specialized hairs on the top rear of the animal’s abdomen – urticating hairs containing venom. The spider uses its hind legs to flick these hairs from its abdomen, creating a small cloud of extremely fine hairs that can cause severe irritation. Yet a tarantula can still fall prey to a variety of predators including skunks, birds, lizards, snakes and toads, to name just a few. The tarantula hawk wasp utilizes a particularly gruesome approach to predation. The adult female wasp stings, paralyzes, and drags a tarantula to a “nursery,” where she lays one egg on or near the spider. Once hatched, the larva burrows into the spider and devours the still-living victim. Even if you’re not a fan of spiders, you’ve got to feel a bit of sympathy for any creature dying that way.
In case of an unexpected, unwanted tarantula encounter, your best response is just to walk on by. As with most spiders, tarantulas devour many nuisance insects and pose no threat to humans. In fact, no records have noted serious harm to humans from tarantula bites.
So – fall is in the air, turning leaves. Ephemeral early snows are dusting the mountain peaks. Crisp nights, and shaggy, leggy tarantulas are on the move and looking for love.
After a quarter-century in Colorado, Tina and her family recently migrated to Southern California, where she’ll spend the next quarter-century trying to remember that the mountains lie to the east.