The presence of tarantulas in Wyoming may seem counterintuitive given the state’s rugged mountains and harsh winters. However, these large, hairy spiders are not limited solely to the hot, arid deserts of the American Southwest. Tarantulas are definitively found in the state, though their distribution is highly localized. This presence demonstrates their surprising adaptability to climates outside of typical tropical zones.
Identifying Wyoming’s Tarantula
The species of tarantula found in the state belongs to the genus Aphonopelma, which includes nearly all species native to the United States. These spiders are recognizable by their substantial size, often being the largest arachnids encountered in the region. An adult Aphonopelma can achieve a leg span of 4 to 5 inches, with a stocky body covered in dense, dark hairs. Their coloration is typically a uniform dark brown or black, though some individuals may display lighter hairs on the carapace or abdomen.
As New World species, they possess specialized barbed bristles known as urticating hairs on their abdomen. These hairs serve as a defensive measure, used only when the spider feels threatened. Like other members of the genus, their fangs move parallel to each other and downward, classifying them as mygalomorphs. This makes the identification of a true tarantula distinct from other large spiders like the common wolf spider.
Preferred Habitat and Range
The tarantula population is concentrated in the southern and southeastern portions of the state, particularly within the Great Basin ecosystem. This region provides the necessary arid, grassland, and steppe environments, mimicking conditions in neighboring states with established populations. Sightings are rare in the northern or high-altitude mountainous areas. The habitat is defined by low precipitation and terrain that allows for the construction of deep, stable burrows.
Their survival during cold winters is directly linked to these burrows, which can extend over a foot into the ground. This subterranean retreat is lined with silk and acts as a microclimate regulator, insulating the spider from temperature extremes. The tarantula seals itself inside during the winter months, entering a state of dormancy to survive the freezing temperatures above ground. This adaptation allows the Aphonopelma to exist far north of the expected tarantula range.
Encountering the Spiders
The likelihood of encountering one of these spiders is low, as they are primarily nocturnal and spend most of their lives concealed within their burrows. The most common time to see a tarantula is during the late summer and early fall, when mature males begin their seasonal wandering. These males leave their burrows in search of a mate, traveling across open ground during the day and night.
Despite their intimidating appearance, these tarantulas are non-aggressive, and their primary instinct is to flee from a perceived threat. Should a person handle one, the spider’s first line of defense is usually to kick its urticating hairs toward the source of irritation. The bite of an Aphonopelma tarantula is not considered medically significant to humans; the venom is mild, often described as comparable in pain level to a common bee sting.