Sistrurus miliarius can be found in the southeastern portion of North America in the following states: North Carolina, South Carolina, Georgia, Florida, Alabama, Mississippi, Kentucky, Tennessee, Louisiana, Arkansas, Texas, Oklahoma, and Missouri (Farrell, 1999).

Biogeographic Regions: nearctic (Native )

endemic to a single nation

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (200,000-2,500,000 square km (about 80,000-1,000,000 square miles)) The range extends from eastern North Carolina to the Florida Keys, west to Oklahoma and eastern Texas, and north to southern Missouri and southwestern Kentucky (Conant and Collins 1991, Palmer and Braswell 1995, Werler and Dixon 2000, Campbell and Lamar 2004, Trauth et al. 2004).

A tiny rattle and a skinny tail can characterize Sistrurus miliarius. The tail rarely has more than a few rattles. This combined with the fact that the rattle is so small causes the sound of the rattle to be similar to the buzzing of an insect (Conant and Collins, 1998). The average size of this relatively small snake is 12-24" (30-61cm). Sistrurus miliarius, like all members of the family Viperidae has facial pits between the nostril and the eye that detect heat energy (King, 1999). Another characteristic of S. miliarius is the nine plates that are present on the crown of its head. The background color of the Pigmy Rattlesnake can vary greatly depending on the location and subspecies. The background color can vary from shades of gray, brown, or black, to even pinkish or reddish. In all species, there is a dark line that runs vertically through the eye that looks similar to the eye of a cat. This line also extends down the side of the face. There is a series of dark, circular spots that mark the center of the back. Along the mid-body line, there is a thin reddish-orange stripe. Along each side of the body you can find dark spots similar but smaller in size than the dorsal spots.

Young Sistrurus miliarius are characterized by a sulfur yellow tip on the tail, as well as a smaller size. The rest of the colorings and markings resembles those of the adult (Farrell, 1999).

Length: 78 cm

• Terrestrial
• Freshwater

Sistrurus miliarius is found in a variety of habitats that include: rocky and partially wooded hillsides, pine woodlands, along riverbanks, and marshes. The one trait that all of these habitats must have in common is that they are all in close proximity to water. Sistrurus miliarius is seldom found in dry habitats. Pigmy rattlesnakes are good swimmers.

Sistrurus miliarius can often be found in underground retreats. These burrows are not dug by the snakes, but by small mammals or by gopher tortoises (Gopherus polyphemus).

Habitat Regions: temperate ; terrestrial

Wetlands: marsh ; swamp

Other Habitat Features: riparian

Comments: Habitats include wet prairies, wet savannas and pastures, palmetto-pine flatwoods, swamps, hardwood-dominated floodplains, sandhills, mixed pine-hardwood forest, hilly second-growth forests, scrub pinewoods, borders of cypress ponds, vicinity of lakes and marshes, and along rice-field canals and roadside ditches, generally in moist or wet lowlands (Werler and Dixon 2000, Ernst and Ernst 2003). This snake is mainly terrestrial; it shelters under surface cover (logs, stumps, thickets, etc.) or in animal burrows. It swims well; rarely climbs into vegetation.

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Like most pit vipers Sistrurus miliarius prefers to sit and wait for its prey. When the prey comes in close range it will ambush it. While waiting for prey S. miliarius will remain in a coiled position; some have been observed to sit in this coiled, immobile position for two to three weeks (Florida Museum of Natural History, 1999). Sistrurus miliarius will also actively hunt for its prey and possibly use its yellowish colored tail to lure to catch its prey (Ernst, 1989). Their choice foods include mice, lizards, snakes, and frogs (Conant-Collins, 1998). They will also eat insects, spiders, centipedes, and nesting birds (Ernst, 1989).

Comments: Eats lizards, snakes, insects, centipedes, spiders, frogs, nestling birds, and small mammals.

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 - 300

Comments: This species is represented by a large number of occurences. On a range-wide scale, Campbell and Lamar (2004) mapped hundreds of collection sites.

100,000 - 1,000,000 individuals

Comments: Adult population size is unknown but presumably exceeds 100,000. This snake is common to locally abundant in some areas of suitable habitat in the core of the range.

In Florida, the maximum distance moved from the point of initial capture was 9-242 m (Hudnall 1979). Gravid females are mainly sedentary.

Sources of mortality include various raptors, mammalian carnivores, snake-eating snakes, habitat destruction, and automobiles (Ernst 1992).

Comments: In Florida, may be active in any month but seen most often July-November. In central Florida, found above ground at air temperatures of 14-32 C; prey capture occurred in all months but was lowest in winter; peaks in movement occurred in spring and fall (May et al. 1996). During the warmer months in Florida (Palm Beach County), active in late afternoon and/or at night, basked in the morning; from November to February, main activity was basking in the afternoon (Hudnall 1979). Seldom encountered except in late summer in Alabama (Mount 1975). Active mainly in late spring and early summer in Texas (Tennant 1984). In North Carolina, active March-November. In the north, activity seems to peak from June to September. See Ernst (1992).

Average lifespan

Status: captivity: 16.1 years.

Male-male interactions include pinning of the other's head and anterior trunk to the ground. Larger males are more likely to mate with females than smaller males. Once a dominant male is established, the courtship between the dominant male and the female begins. One of these male-female interactions includes mate-guarding behavior. The pair will stay in close proximity; possibly one coiled on top of the other for several days at a time. Mating most often occurs between September and January. Copulation can take several hours to complete. Once complete the female stores sperm from her mate or mates until approximately the following April.

Once the development of embryos begins the female will commonly bask in the sun in order to speed up their development. Unlike many Crotalid species, the female will feed very late into her gestation process. Sistrurus miliarius are oviparous (live bearing) and usually give birth during the month of August. The newborns usually remain close to the mother (usually with in a couple of feet) for several days, or until they complete their first shed (Farrell, 1999).

Mating in nature has been observed in September. Litter size is 2-32 (usually 4-10); 2-11, mean about 6, in central Florida (Farrell et al., 1995, J. Herpetol. 29:21-27). Births occur mostly July-September (mainly August in central Florida) (Farrell et al.. loc. cit.). Newborns are common in southern Florida in July and August (Dalrymple et al., Copeia 1991:294-302). Two Texas litters were born in early to mid-August (Ford et al., 1990, Texas J. Sci. 42:355-368). In central Florida, 26% of females were gravid in two consecutive years, 42% were gravid in one of two consecutive years, and 32% were not gravid in either year (Farrell et al., loc. cit.).

IUCN Red List of Threatened Species: least concern

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Global Short Term Trend: Relatively stable (=10% change)

Comments: Trend is undocumented, but extent of occurrence, area of occupancy, number of subpopulations, and population size probably are relatively stable or declining at a rate of less than 10 percent over 10 years or three generations.

Global Long Term Trend: Increase of 10-25% to decline of 30%

Comments: No major threats are known. Locally, habitat loss and degradation probably have reduced or eliminated some populations. Between September 1997 and March 1998, a severe skin, eye, and mouth disease (fungal dermatitis and stomatitis) was observed in a population of subspecies barbouri at the Lake Woodruff National Wildlife Refuge in Volusia County, Florida (Cheatwood et al. 2003).

One benefit of having S. miliarius in your area is that they will capture and eat small rodents and other possible pests to humans.

Comments: Venomous; dangerous to children, but probably incapable of inflicting a fatal bite on an adult human (see Ernst 1992).

Comments: See McCranie (1988) for discussion of evidence that Sistrurus is not a valid genus distinguishable from Crotalus. In contrast, genetic data presented by Knight et al. (1993) indicate that rattlesnakes comprise two sister clades, Crotalus and Sistrurus . However, Parkinson (1999) examined mtDNA variation and found that Crotalus is paraphyletic with regard to the monophyletic Sistrurus.