Western Pygmy Rattlesnake

Sistrurus miliarius streckeri
Venomous
Other Common Name
Ground Rattler
Family

Viperidae (vipers and pit vipers) in the order Squamata (lizards and snakes)

Description

The western pygmy rattlesnake is a small, colorful rattlesnake with a slender tail and tiny rattle. General color is light brownish gray, with a row of small, dark brown spots on the back and similar spots on each side. Most specimens also have a rust-colored stripe down the back. The belly is usually gray or dusky cream-colored, with numerous irregularly spaced bars. The head has a distinct black stripe that angles from the eye to the corner of the mouth, and a sensory pit located between each nostril and eye. The tail is thin and has a tiny rattle. Like other venomous snakes, they have “pits” on the sides of their heads, and the pupils are diamond-shaped in daylight (not round).

The disposition of this rattlesnake varies from individual to individual. Some will try to defend themselves vigorously by coiling, sounding their rattles, jerking their head, and striking at any movement. Others remain motionless and try to escape only when touched by a stick or snake hook. The sound of the vibrating rattle is a faint buzz, like the sound of a grasshopper, and can be heard for only about a yard away.

Similar species: Three other rattlesnakes are known from Missouri. The timber rattlesnake (Crotalus horridus) occurs statewide; adults are 3 to 5 feet long and have large rattles. Our other two rattlesnakes are massasaugas; they are rare and only found in northern Missouri.

Size

Length: 15 to 20 inches. This is one of the smallest species of rattlesnakes in North America.

Western Pygmy Rattlesnake in Galena, MO

Western Pygmy Rattlesnake coiled up on rocks. Its head is towards the camera, but the distinctive brown stripe and black spots are evident.
Western Pygmy Rattlesnake
Submitted by Seth Vermillion
Habitat and conservation

Prefers south-facing, rocky, partially wooded hillsides, near glades, in woods near rock ledges, and along the margins of forests and meadows. In late spring and early summer, it basks in rocky open areas, near brushpiles, or along roadsides near woodlands and glades. In July and August it tends to be nocturnal and can be seen crossing roads at night. It takes shelter under rocks in spring, early summer, and autumn. It also retreats into abandoned small mammal burrows, logs, and brushpiles.

Foods

Food includes a variety of small lizards, small snakes, mice, and occasionally small frogs and insects. Like other rattlesnakes, western pygmy rattlesnakes have hollow fangs to inject venom into their prey, and heat-sensitive pits between the eyes and nostrils that allow them to detect and accurately strike warm-blooded prey (such as rodents) even in total darkness.

Western Pygmy Rattlesnake distribution map
Distribution in Missouri

Extreme southern Missouri along the border with Arkansas, and in the eastern Missouri Ozarks and St. Francois Mountains.

Life cycle

This species is normally active from mid-April to mid-October. Courtship and breeding apparently occur in the spring, and young are born from late August through September, with 3–7 young per litter. Newborns are paler than the adults, have a yellow tail tip, and are about 4–7½ inches long. In our state, it appears that females typically only breed every other year.

Human connections

This small species is so secretive that few people encounter it. Although its bite is not fatal, a bite victim should seek immediate medical attention. The western pygmy rattlesnake should be respected and left alone. In extreme southern Missouri, this snake is called the “ground rattler.”

Ecosystem connections

Rattlesnakes are considered the most evolutionarily advanced group of snakes. In addition to hollow fangs and heat-detecting facial pits, their tail rattles warn would-be predators not to attack them, saving the snake from having to bite and the enemy from being bitten. But rattlesnakes are often preyed upon by hawks, kingsnakes, and other predators.