Description:S. miliarius is a small species, with adults usually growing to 16 to 24 inches in total length (including tail). At midbody, the rows of dorsal scales usually number 23. The dorsal pattern consists of a series of oval or subcircular spots with somewhat regular edges. The spots on the flanks are mostly round and not much higher than they are wide. Belly pigmentation towards the rear is more limited to indistinct blotches found on pairs of adjacent scales. Juveniles' color patterns are similar to the adults, although they may be paler or more vividly marked, and the tips of their tails are yellow.
Habitat:Sistrurus miliarius reportedly inhabits flatwoods, sandhills, mixed forests, and floodplains, and is also found near lakes and marshes.
Range:S. miliarius is found in the Southeastern United States from southern and eastern North Carolina, south through peninsular Florida and west to East Texas and Oklahoma.
Venom: Since S. miliarius is unable to produce much venom, it is unlikely to be able to deliver a fatal bite to a human adult. This snake produces cytotoxic venom that is strongly hemorrhagic and tissue toxic, but devoid of any neurotoxins. The venom was the basis for the development of the drug eptifibatide, which is used to prevent clotting during a heart attack. The venom is somewhat different in that it contains substantial amounts of serotonin and related tryptamine compounds.
Diet: The diet of S. miliarius includes small mammals and birds, lizards, insects, and frogs, as well as other snakes. Pygmy rattlesnakes also include giant desert centipedes in their diet, which they hunt by active pursuit, grabbing and flipping the centipedes around while simultaneously injecting venom to prevent injury by the victim. They also ambush lizards such as skinks by using their tails as lures, as is common in many other species of vipers. Caudal luring becomes less effective for adults, as the prey size and type changes. Their feeding strategy becomes sit-and-wait, with individuals remaining in a coiled position for days at a time.
Reproduction: Pygmy rattlesnakes' mating season occurs in early spring (March to April), with young typically born from July into September. Reproductively active snakes release chemical signals to inform potential mates that they are receptive. The potential mates detect these chemical signals by flicking their tongues over the snakes' bodies. Epidermal lipids found on the snakes' bodies allow males to determine the sex, size, and mating condition of a potential mate. Pygmy rattlesnakes are monogamous, with only one male successfully fertilizing a female. Males are not aggressive towards each other during mating seasons and many males will pursue one female without conflict. Multiple males will compete to mate with one female and will continue their attempts to mate until one male successfully fertilizes the female. Once a male fertilizes a female, all other males cease their mating attempts with the female snake. This occurs because the male leaves a gelatinous plug in the female after she has been fertilized, closing up the cloaca (the opening for the reproductive tract) and preventing the female from mating with other snakes. The male will continue to remain in close proximity to the fertilized female for most of her pregnancy. The male will "mate guard" the female and they can sometimes be found coiled around one another.
Pygmy rattlesnakes are iteroparous, meaning that females will reproduce multiple times throughout their lifetimes. Both male and female pygmy rattlesnakes reach sexual maturity at 2 years of age. They are also seasonal breeders, typically mating during the spring and giving birth to their young during the late summer. Female pygmy rattlesnakes will store sperm in instances of early-season mating. The females store the sperm until late March or April and then release it, allowing fertilization of the female eggs to occur. Males compete with each other to breed with one female. Males flick their tongues over other snakes bodies to determine sex, size, and mating condition of a potential mate. Breeding is on a first come, first serve basis, with the first male to successfully consummate with the female being the one who gets to fertilize her eggs. Once a male has successfully fertilized the female, the other males will no longer attempt to mate with her. Gestation period for pygmy rattlesnakes is approximately 3-5 months, with young being born between July and early September. Pygmy rattlesnakes are ovoviviparous. Young are born alive in an embryonic sac, which is broken immediately after birth. Litters vary from 2 to 12 young, with an average of 6 in each litter. Young are typically 1.8 to 5.0 grams at birth. Once born, young stay near their mother for 7 to 10 days for protection.
After fertilization, male pygmy rattlesnakes will often engage in "mate guarding," remaining close to the female in a protective manner. This guarding will continue for an extended period of time, sometimes for days, weeks, or even months at a time. The snakes often can be found coiled up together during this period of time. Males typically leave the females before the young are born. During gestation, female pygmy rattlesnakes bask in areas with more sun-exposure. This extra exposure causes the snakes' body temperature to rise above normal temperature levels, which in turn facilitates the growth of embryos. Once the young are born, they stay near their mother for 7 to 10 days for protection. The young tend to leave their mother after they shed their skin for the first time, ending parental involvement. Young are precocial, learning how to hunt and find territory on their own soon after birth. (
Status: Pygmy rattlesnakes are currently listed as a species of "Least Concern" on the IUCN Red List and are listed as "No special status" on the US Federal List, State of Michigan List, or on CITES appendices. The IUCN Red List reports that this species appears to be stable, but habitat loss and habitat degradation may negatively impact some populations.
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Disclaimer: ITIS taxonomy is based on the latest scientific consensus available, and is provided as a general reference source for interested parties. However, it is not a legal authority for statutory or regulatory purposes. While every effort has been made to provide the most reliable and up-to-date information available, ultimate legal requirements with respect to species are contained in provisions of treaties to which the United States is a party, wildlife statutes, regulations, and any applicable notices that have been published in the Federal Register. For further information on U.S. legal requirements with respect to protected taxa, please contact the U.S. Fish and Wildlife Service.
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