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Regina alleniStriped Crayfish Snake

By Sara Jackrel

Geographic Range

Regina alleni is distributed broadly throughout much of Florida, except for the Florida Keys and the westernmost part of the panhandle. The species extends into extreme southern Georgia, with museum records from six counties. (Gibbons and Dorcas, 2004)

Habitat

Regina alleni is a cryptic, semi-aquatic, semi-fossorial snake species generally found in lentic and slow-moving waters with dense quantities of floating aquatic vegetation such as cypress swamps and floodplains. Striped crayfish snakes are often associated with choked waterways of water hyacinth (Eichhornia species), an aquatic plant that is native to the neotropics. Large numbers of snakes are often found among water hyacinths and in dense mats of floating vegetation, where their bodies are either entirely or partially elevated above the water. Godley (1980) estimated density of R. alleni to be as high as 1289 individuals per hectare of hyacinth dominated habitat. Water hyacinth also attracts high densities of crayfish, due to an abundance of decaying plants available for detritivorous crayfish. In addition to prey items, dense mats of water hyacinth provide striped crayfish snakes with protection from predators. High densities of R. alleni are associated with waters of a neutral pH and low dissolved Calcium, because these conditions typically limit the development of thick crustacean exoskeletons. Individuals have been found in crayfish burrows, particularly during the dry winter and spring seasons, and in underwater burrows densely covered with aquatic vegetation. (Franz, 1977; Gibbons and Dorcas, 2004; Godley, 1980)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams
  • temporary pools

Physical Description

Striped crayfish snakes are dark olive-brown with three brown, dorsal, longitudinal stripes extending the length of the body. The throat is yellow with some individuals displaying a mid ventral row of spots. They are differentiated from other crayfish snakes by smooth scales, with the exception of keeled scales in male individuals on the back of the tail and above the cloaca. Striped crayfish snakes are the smallest species in the genus Regina. Individuals greater than 280 mm snout-vent length (SVL) are considered adults. Adults typically have a SVL ranging from 300 to 550 mm and an average mass of 45.1 g. Neonates have an average mass of 3.1 g, average SVL of 133 mm, and differ little in coloration from adults.

Striped crayfish snake have evolved morphological adaptations of the skull that facilitates their feeding specialization. The snake skull is the most complex system of bones in the body and reveals considerable information about the trophic specialization of a particular species. Regina alleni and Regina rigida share similar morphological characteristics of the skull that are distinct from other crayfish snakes and water snakes. These two species also share a dietary specialization on hard-shelled crayfish, a substantially harder prey item than prey of other natricine snakes. Striped crayfish snakes have unique, hinged palatine teeth modified for grasping the hard exoskeleton of crayfish, a characteristic not shared with species feeding on freshly-molted crayfish. (Dorcas, et al., 2003; Dwyer and Kaiser, 1997; Gibbons and Dorcas, 2004; Godley, 1980; Rossman, 1985)

As seen in other natricine snakes, male R. alleni are smaller in size, and likely mature earlier, than females. The largest documented female and male were 537 mm SVL, 705 mm total length and 507 mm SVL, 606 mm total length, respectively. (Demuth, 1997; Gibbons and Dorcas, 2004)

  • Sexual Dimorphism
  • female larger
  • Average mass
    45.1 g
    1.59 oz
  • Range length
    705 (high) mm
    27.76 (high) in

Development

Little is known regarding gestation in Regina alleni. Individuals likely become sexually mature by their second year, once at least 300 mm SVL. (Demuth, 1997; Gibbons and Dorcas, 2004)

Reproduction

Regina alleni reproduces sexually, but there is little available information about mating system or mating behaviors for this species.

Little is known about striped crayfish snakes beyond what is common to the reproduction of all natricine snakes. Mating is assumed to occur in the spring, as in other natricine snakes, but nothing is known about courtship or frequency of reproduction. All of the natricine snakes in North American are viviparous. Regina alleni can bear between four and twelve (but most frequently six) live young in the water between July and September. (Brimley, 1903; Gibbons and Dorcas, 2004; Godley, 1982)

  • Breeding interval
    Breeding interval in Regina alleni is unknown.
  • Breeding season
    Breeding is thought to occur from early spring to September.
  • Range number of offspring
    4 to 12
  • Average number of offspring
    6
  • Average age at sexual or reproductive maturity (female)
    2 years
  • Average age at sexual or reproductive maturity (male)
    2 years

Little is known specifically about Regina alleni, but few snakes are known to provide parental investment beyond gestation.

  • Parental Investment
  • no parental involvement
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

There are no available, reliable records of lifespan in R. alleni.

Behavior

Striped crayfish snakes bask in direct sunlight during cool days and remains in the shade or underwater during hotter days. They are more active and have a higher feeding rate in spring and early summer than in cooler winter months. Daily activity patterns are debated, but they bask during the day and likely forage at night or during crepuscular hours. (Godley, 1980)

Home Range

There are no data available regarding the home range of striped crayfish snakes.

Communication and Perception

Striped crayfish snakes appear to initiate foraging behavior based on chemosensory cues from their prey, but they ultimate rely on movement by crayfish for targeting precise striking locations. Predator avoidance also likely relies on a combination of chemical, visual, and vibrational cues. (Franz, 1977)

Food Habits

Regina alleni is considered to be the most specialized of crayfish-eating snakes with extensive morphological adaptations to facilitate its stenophagic diet. Adult R. alleni feed nearly exclusively on crayfish (Procambarus). Unlike two congeners, Regina septemvittata and Regina grahami, striped crayfish snakes have no preference for crayfish in a particular molt stage. While other crayfish snakes have evolved chemosensory mechanisms for detecting freshly-molted crayfish, R. alleni has evolved morphological adaptations to consume hard-shelled individuals. Two crayfish species abundant in Florida and frequently found in the diet of R. alleni are Procambarus fallax and Procambarus alleni. Other prey items include amphibians and insects, such as beetles (Coleoptera), leafhoppers and their relatives (Homoptera), grasshoppers (Orthoptera), and butterflies and moths (Lepidoptera).

Godley (1980) documented evidence of an ontogenetic dietary shift in Regina alleni. Juvenile individuals, less than 200 mm SVL, consumed decapod crustaceans (mostly shrimp in the family Palaemonidae) while seven of eight juveniles greater than 200 mm SVL contained larval Odonata. Prey orientation during ingestion appears to rely on size relative to the snake. Decapods were ingested caudally regardless of prey size while odonate naiads were mostly ingested head first except for the smallest nymphs which were eaten tail first. Adult R. alleni consume crayfish abdomen first and lateral with respect to the skull of the snake, regardless of size or molt-stage. (Dwyer and Kaiser, 1997; Franz, 1977; Godley, 1980)

  • Animal Foods
  • insects
  • aquatic crustaceans

Predation

Striped crayfish snakes are consumed by a wide range of predators, including birds, mammals, kingsnakes, and even crayfish. Crayfish were observed killing and feeding upon neonate R. alleni in captivity. Other accounts of predators include eastern cottonmouths (Agkistrodon piscivorus) and southern black racers (Coluber constrictor). Additionally, in a sample of Regina alleni mostly from Paynes Prairie Preserve State Park, 54% of the snakes were infested with an intestinal trematode of a previously undescribed species in the genus Telorchis. These parasites typically attach externally to the exoskeleton of crustaceans, and likely gain entry into R. alleni during feeding. Further study supported placing this new species of trematode in an entirely new genus as Paratelorchis dollfusi.

A number of anti-predator behaviors have been documented. Striped crayfish snakes retreat beneath water when threatened. Unlike many other natricine snakes, those in the genus Regina rarely bite. However, they will discharge cloacal contents and anal gland secretions upon handling. Releasing of this musk is believed to deter some mammalian predators. Godley (1982) described a display behavior of gaping the mouth widely, swaying, and arching the back. Other defensive behaviors include coiling the body into a ball, concealing the head beneath the coil and laterally flattening the body. O’Brien (1998) described an unsuccessful response of R. alleni to an attack by a southern black racer (Coluber constrictor). The animal wound its body tightly around vegetation, making consumption more difficult for the predator. (Franz, 1977; Gibbons and Dorcas, 2004; Godley, 1980; Godley, 1982; O’Brien, 1998; Stunkard and Franz, 1977)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

While striped crayfish snakes are preyed upon by a diverse assemblage of organisms, it is not believed to comprise a notable portion of the diet of any species. As a unique predator in aquatic ecosystems, R. alleni may play an important role in maintaining ecosystem stability. With little if any depth to this functional guild, R. alleni may be a dominating influence on crayfish populations where these snakes are present in high densities. Any role R. alleni may have on regulating crayfish populations likely has wider implications because, as detritivores, crayfish play an important role in nutrient cycling of aquatic systems.

Commensal/Parasitic Species
  • trematodes (Paratelorchis dollfusi)

Economic Importance for Humans: Positive

Striped crayfish snakes are not known to have any positive economic importance for humans, other than potentially maintaining ecosystem stability and function.

Economic Importance for Humans: Negative

There are no known adverse effects of Regina alleni on humans.

Conservation Status

Populations of Regina alleni are believed to be stable throughout its range. Populations in southern Florida may have declined due to changes in natural water flow. Overall however, anthropogenic change has likely increased suitable habitat for R. alleni because of the introduction of water hyacinths. (Gibbons and Dorcas, 2004)

Other Comments

Much of what is known about Regina alleni was documented by J.S. Godley (1980) in the seasonally wet prairies and marshes of Rainey Slough in Glades County, Florida. (Godley, 1980)

Contributors

Sara Jackrel (author), The College of New Jersey, Keith Pecor (editor), The College of New Jersey, 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

bog

a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

crepuscular

active at dawn and dusk

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

freshwater

mainly lives in water that is not salty.

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.

insectivore

An animal that eats mainly insects or spiders.

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).

marsh

marshes are wetland areas often dominated by grasses and reeds.

natatorial

specialized for swimming

native range

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

nocturnal

active during the night

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

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

solitary

lives alone

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

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

Brimley, C. 1903. Notes on the reproduction of certain reptiles. The American Naturalist, 37: 261-266.

Demuth, J. 1997. Regina alleni (striped crayfish snake). Size. Herpetological Review, 28: 90-91.

Dorcas, M., S. Poppy, C. Ernst, J. Gibbons. 2003. The striped crayfish snake (Regina alleni). SSAR Catalogue of American Amphibians and Reptiles, 778: 1-4.

Dwyer, C., H. Kaiser. 1997. Relationship between skull form and prey selection in the thamnophiine snake genera Nerodia and Regina. Journal of Herpetology, 31: 463-475.

Franz, R. 1977. Observations on the food, feeding behavior, and parasites of the striped swamp snake, Regina alleni. Herpetologica, 33: 91-94.

Gibbons, J., M. Dorcas. 2004. North American Watersnakes: A Natural History. Norman: University of Oklahoma Press.

Godley, J. 1982. Predation and defensive behavior of the striped swamp snake (Regina alleni). Florida Field Naturalist, 10: 31-36.

Godley, J. 1980. Foraging ecology of the striped swamp snake, Regina alleni, in southern Florida. Ecological Monographs, 50: 411-436.

O’Brien, C. 1998. Regina alleni (striped crayfish snake). Antipredator behavior. Herpetological Review, 29: 46-47.

Rossman, D. 1985. Liodytes resurrected, reexamined, and reinterred. Journal of Herpetology, 19: 169-171.

Stunkard, H., R. Franz. 1977. Paratelorchis dollfusi n.g., n. sp., a digenetic trematode from the striped swamp-snake, Regina alleni: systematic and taxonomic considerations. Transactions of the American Microscopical Society, 96: 383-389.

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