Crotalus cerastesSidewinder

Geographic Range

Sidewinder rattlesnakes (Crotalus cerastes) inhabit the southwest corner of the United States of America, extending as far west as the Mojave Desert in southern California and as far east as the Sonoran Desert in Arizona. These reptiles also reside on the eastern coast of Baja California, and the northern coast of Gulf of California, and the Isla del Tiburon. (Frost, et al., 2007; Webber, et al., 2016)

Habitat

Sidewinders reside in terrestrial, desert landscapes such as sandy washes, sand dunes, and the open terrain of warm deserts. These snakes are highly concentrated near mammalian burrows—close to sandy washes and thickly vegetated areas. Sidewinders live in areas ranging from sea level to 1830 m. On average, most sidewinders reside in areas less than 1,200 m because mountainous terrains inhibit their locomotion. (Babero and Emmerson, 1974; Freymiller, 2016; Frost, et al., 2007; Mosauer, 1935; Secor and Nagy, 1994; Secor, 1994)

  • Range elevation
    0 to 1830 m
    0.00 to 6003.94 ft
  • Average elevation
    1200 m
    3937.01 ft

Physical Description

Sidewinders are distinguished among rattlesnakes by their horn-like superocular scales on their heads. This hornlike structure is why sidewinders are also called horned rattlesnakes. They also have a rattle on their tails; the number of segments of the rattle equates to the number of sheds the individual has completed.

Adult sidewinders have a snout-vent length averaging 50 cm (range 44.6 -61.5 cm). Sidewinders also exhibit sexual dimorphism. Females grow larger than males, an unusual trait because most rattlesnakes are monomorphic. Female sidewinders are slightly larger when they reach adulthood, greater than 38cm, whereas male sidewinders must be greater than 34 cm to reach the same stage. Adult can weigh 93.8 - 304 g (average 250 g), with older snakes weighing more than younger snakes. Sidewinders are camouflaged in a variety of earthen colors, such as light-brown, grey, and cream depending on their habitats.

Sidewinders subadults can have masses up to 65.0 g before they are classified as adults. Snout-vent length ranges from 16.5cm-43.6cm in subadults.

Sidewinders and other rattlesnakes are solenoglyphous, meaning they have front-facing, hinged venomous fangs that can fold down in their mouths.

The standard metabolic rate for sidewinders was measured 0.01 mL/g*h carbon dioxide produced at 20 degrees Celsius. Additional studies conducted on other rattlesnakes such as western diamondbacks (Crotalus atrox), black-tailed rattlesnakes (Crotalus molossus), and mottled rock rattlesnakes (Crotalus lepidus) postulate that rattlesnakes have a fraction (0.2-0.5) of the metabolic rate of all other snakes. (Beaupre, et al., 1998; Beaupre and Duvall, 1998; Beaupre, et al., 1998; Bullock and Fox, 1957; Cohen and Myres, 1970; Ernst, 1964; Lewis, 1949; Secor, 1994; Wozniak, et al., 1994)

  • Range mass
    93.8 to 304 g
    3.31 to 10.71 oz
  • Average mass
    250 g
    8.81 oz
  • Range length
    44.6 to 61.5 cm
    17.56 to 24.21 in
  • Average length
    50 cm
    19.69 in

Development

Sidewinders are viviparous rattlesnakes. Differentiation of the embryo increases at the beginning of embryonic formation (neurulation arises), but gradually slows by the end of the developmental stage. This is followed by two consecutive series of growth, which is followed by live birth.

Like most snakes, sidewinders exhibit indeterminate growth. They grow faster as juveniles, and growth rate decreases as the sidewinders age. Because rattles increase in the number of segments each time the rattlesnakes shed, the number of segments does not equate to age, but instead to the number of sheds. Female sidewinders are slightly larger when they reach adulthood, greater than 38cm, whereas male sidewinders must be greater than 34cm to reach the same stage. (Andrews and Mathies, 2000; Beaupre, et al., 1998; Blomsten, et al., 2016; Cochran, 2010)

Reproduction

Male sidewinders show annual sexual motivation regardless of ambient temperature. Female sidewinders’ reproduction is contingent on the temperature of the region. The distribution of females throughout the geographic range forces males to enhance their locomotion by searching for females by straight-line paths through the desert. Males fed more often during the reproductive season, as the demands for energy are high when distances traveled to females is high.

Upon finding a mate, by distinguishing scents via the vomeronasal organ and tactile efforts, the two will reproduce after courtship. Temporal distribution of females causes local polygyny, and females will fight for males to mate. (Beaupre and Duvall, 1998; Cochran, 2010; Macartney and Gregory, 1988; Webber, et al., 2016)

Sidewinder males can mate up to three times a year, while females are dependent on warm temperatures (which occur from April-July) to determine if they are suitable for mating.

Female sidewinders continuously feed during vitellogenesis (the beginning of their reproductive cycle) but show a tendency to lower their consumption during gestation (which typically last 4-5 months in rattlesnakes). This early feeding by females helps prepare them for the energetic demands for gestation and parturition. However, males increase food consumption to meet energetic needs for movement to find potential partners.

Female sidewinders typically have litters ranging from 4-11 young born alive. They are independent within 3 hours of live birth. Age of reproductive maturity for the genus Crotalus is 3 years for both sexes. (Keenlyne, 1978; Macartney and Gregory, 1988; Webber, et al., 2016)

  • Breeding interval
    Sidewinders males can mate up to three times a year, while females are dependent on warm temperatures to determine if they are suitable for mating.
  • Breeding season
    April-July
  • Range number of offspring
    4 to 11
  • Range gestation period
    4 to 5 months
  • Average time to independence
    3 hours
  • Average age at sexual or reproductive maturity (female)
    3 years
  • Average age at sexual or reproductive maturity (male)
    3 years

While most snakes do not provide maternal care, female sidewinders will guard new offspring up to 3 hours after birth before abandoning their young. Because this is energetically costly for females after giving birth, they have potential to die after straining themselves by protecting their young. Beyond the act of mating, males provide no parental care. (Keenlyne, 1978; Macartney and Gregory, 1988)

Lifespan/Longevity

Female sidewinders typically only live 5 years, whereas, males can live up to 13 years in the wild. However, in captivity, both male and female sidewinders can live up to 20 years. Females have a shorter lifespan because birthing exhausts the females to the point of death. Males and females are also subjected to natural deaths such as lillnesses and predation. Sidewinders also die from getting hit by motor vehicles. It has been estimated that 2383-4000 sidewinders get killed per year from vehicles. (Reiserer and Schuett, 2008; Rosen and Lowe, 1994; Secor, 1994)

  • Typical lifespan
    Status: wild
    5 to 13 years
  • Average lifespan
    Status: captivity
    20 years
  • Average lifespan
    Status: captivity
    27.3 years
    AnAge

Behavior

Sidewinders' home ranges are not in circular areas, but instead are convex polygons conforming to the landscape. Males typically have a larger home range than females because they travel greater distances over mating season. Average distance traveled in a 24-h block averaged 185.4m for males and 122.9m for females across all ages. Subadult males traveled the farthest, on average, 223 m per day. They can travel via their namesake, sidewinding, but also have been observed using rectilinear motions and lateral undulations.The sidewinding motions minimize their contact with the hot sands.

Sidewinders, especially males during mating season, are constantly on the move for new territories. To optimize movement throughout home range, males and female will typically move in straight lines to cover more distance, but this type of movement is energetically costly for sidewinders if they cannot find a mate.

Bouts between male rattlesnakes (between single or multiple species) can last over a day when it comes to territorial or mating disputes. Sidewinders are non-gregarious snakes, but group together during denning. Sidewinders exhibit diurnal and nocturnal periods throughout the year, but are strictly nocturnal during the warmest parts of the year. When trying to stay cool, they spend 80% of their time denning in rodent burrows, and 20% coiled up on the surface of the sand.

Sidewinders hibernate in the desert habitats, migrating to sandy-alluvial deposits when fall hibernation begins. They typically hibernate in the burrows of rodents or desert tortoises. When hibernation is complete, these snakes move to purely sandy areas of the desert. They also remain inactive for days at a time in two instances: after consuming prey (inactive for 5-10 days thereafter), or just before molting (3-5 days prior). (Beaupre and Duvall, 1998; Beck, 1995; Cowles, 1938; Cowles, 1956; Cunningham, 1959; Frost, et al., 2007; Secor, 1994; Young and Morain, 2003)

  • Range territory size
    7300 to 61000 m^2
  • Average territory size
    23000 m^2

Home Range

Home ranges for sidewinders in the Mojave Desert were the largest among rattlesnake species, about 23 ha for for sexes (range 7.3-61 ha). Although sidewinders are territorial, population densities are 0.48-1.18 per ha, meaning that some territories overlap. (Beaupre and Duvall, 1998; Beck, 1995; Cowles, 1938; Cowles, 1956; Cunningham, 1959; Secor, 1994)

Communication and Perception

Rattlesnakes have pits on the sides of their heads that detect infrared radiation, which sidewinders use to identify prey in their surroundings. Sidewinders, like all snakes, use their nose and flick their tongues (tactile) to smell their surroundings.

Sidewinders and other rattlesnakes have a vomeronasal organ, which is used from chemical recognition. Using the vomeronasal organ, sidewinders can detect chemical in prey, and have been shown to detect substances within the skin of kingsnakes Lampropeltis to avoid confrontation with them.

Sidewinders typically rely on the vomeronasal organ to detect prey instead of using sight, but sight is used as a lesser sense.

Tactile senses are used by male sidewinders during mate-searching, courtship, catching prey, and detecting predators like kingsnakes. They also move in a variety of methods (sidewinding, rectilinear motion, lateral undulations) and each method requires the snakes' tactile senses to feel body parts touching the sand (or alternate substrate).

They shake their rattles on their tails when they feel threatened, which could be perceived as an acoustic, visual, or vibrating effort as a way to communicate with the predator. (Jayne, 1988; Moore, 1978; Secor, 1994)

Food Habits

Siderwinders primarily consume desert reptiles such as glossy snakes (Arizona elegans), western ground snakes (Sonora semiannulata), and western zebra-tailed lizard (Callisaurus draconoides), western whiptail (Cnemidophorus tigris), and Colorado desert fringe-toed lizards (Uma notata). Sidewinders also consume mammals such as house mice (Mus musculus), desert pocket mice (Chaetodipus penicillatus), Botta’s pocket gopher (Thomomys bottae). Large sidewinders also consume birds such as lark sparrows (Chondestes grammacus), house sparrows (Passer domesticus), and cactus wrens (Campylorhynchus brunneicapillus). Lizards consist of over 50% of the sidewinders’ diet, and mammals consist of over 40% of the diet. Sidewinders ingest a greater proportion of mammals when they are nocturnal during late spring and summer. During early spring and fall, sidewinders consume more diurnal lizards because the temperature is cool enough for them to hunt during the day. (Freymiller, 2016; Funk, 1965; Mosauer, 1935; Wozniak, et al., 1994)

  • Primary Diet
  • carnivore
    • eats terrestrial vertebrates
  • Animal Foods
  • birds
  • mammals
  • reptiles

Predation

California kingsnakes, Lampropeltis getula californiae, coyotes Canis latrans, and red-tailed hawks Buteo jamaicensis are common predators of sidewinders in the southwest United States. Sidewinders typically react to these predators by puffing themselves up to appear larger, and strike predators with their venomous fangs.

Because sidewinders reside in dry, desert environments, humans rarely interact with sidewinders, much less harm them. (Beaupre and Duvall, 1998; Cochran, 2010; Cowles, 1938; Cowles, 1956; Fitch, et al., 1946)

Ecosystem Roles

Sidewinders can contain blood parasites from genera Haemogregarina and Hepatazoon. Both of these genera are from the phylum Apicomplexa. A nematode reported in sidewinders is Thubnaea cnemidophorus, which can be found in the esophagus, stomach, and intestines. (Babero and Emmerson, 1974; Wozniak, et al., 1994)

Commensal/Parasitic Species
  • Apicomplexan Haemogregarina
  • Apicomplexan Hepatazoon
  • Nematode Thubunaea cnemidophorus

Economic Importance for Humans: Positive

There are no known positive impacts of sidewinders on humans.

Economic Importance for Humans: Negative

Sidewinders utilize their venomous fangs for hunting prey, and as a mechanism of defense against predators. Moreover, sidewinder venom has increased levels of protease activity compared to other venomous snakes which allows these snakes to be active during day or night. Humans rarely encounter sidewinders, therefore, little is known about how sidewinder venom affects the human body. Anecdotal blog postings depict necrotic tissue, painful swellings, black and blue appendages, and victims describe intense burning for days, followed by painful joints weeks after the initial bite. Antivenom treatments are still being studied and tested in humans. (Cowles, 1938; Cowles, 1956; Crump, 2010; Rosen and Lowe, 1994; Webber, et al., 2016)

  • Negative Impacts
  • injures humans

Conservation Status

According to the IUCN Red List, sidewinders are a species of “Least Concern.” Furthermore, no special status is given to sidewinders via the U.S. Federal List, CITES, and the State of Michigan List. No conservation efforts are being made to protect sidewinders at this time. These snakes reside in many protected areas such as Death Valley National Park, Sequoia National Park, Desert National Wildlife Refuge, Mojave National Preserve, Joshua Tree National Park, Kofa National Wildlife Range, Organ Pipe Cactus National Monument and the Gila River Indian Reservation. (Frost, et al., 2007)

Contributors

Cole Faulkner (author), Radford University, Alex Atwood (editor), Radford University, Layne DiBuono (editor), Radford University, Lindsey Lee (editor), Radford University, Karen Powers (editor), Radford University, Joshua Turner (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

diurnal
  1. active during the day, 2. lasting for one day.
ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

female parental care

parental care is carried out by females

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

indeterminate growth

Animals with indeterminate growth continue to grow throughout their lives.

infrared/heat

(as keyword in perception channel section) This animal has a special ability to detect heat from other organisms in its environment.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

migratory

makes seasonal movements between breeding and wintering grounds

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

polygynous

having more than one female as a mate at one time

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

sexual ornamentation

one of the sexes (usually males) has special physical structures used in courting the other sex or fighting the same sex. For example: antlers, elongated tails, special spurs.

solitary

lives alone

tactile

uses touch to communicate

terrestrial

Living on the ground.

venomous

an animal which has an organ capable of injecting a poisonous substance into a wound (for example, scorpions, jellyfish, and rattlesnakes).

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

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