Animal Diversity Web

Ge­o­graphic Range

Smooth green snakes (Opheodrys ver­nalis) live in the north­east­ern and Mid­west­ern United States, as well as south­ern Canada, in­clud­ing south­ern Que­bec, On­tario, Man­i­toba, as far west as Saskatchewan. The largest con­tin­u­ous por­tion of their range stretches from Maine west­ward to North Dakota, with dis­junct pop­u­la­tions in the Mid­west­ern United States. There are pop­u­la­tions as far south as the south­ern coast of Texas. Their ge­o­graphic range also in­cludes North Car­olina, Kansas, Iowa, Illi­nois, Ten­nessee, Mis­souri, Mis­sis­sippi, and west­ern Vir­ginia. (Gilbart, 2012; Grob­man, 1992; Mitchell, 1974; Stu­art, et al., 2014)

• Biogeographic Regions
• nearctic
  • native

Habi­tat

Smooth green snakes are found in grassy, open areas, such as mead­ows, bogs, and open woods. The areas they in­habit typ­i­cally in­clude wet­lands or open water. Smooth green snakes are pri­mar­ily ter­res­trial, but they may also hang in low branches. Dur­ing the day, they can be found bask­ing on boul­ders or logs. (Gilbart, 2012; Grob­man, 1941; Grob­man, 1992; Mitchell, 1974; Mitchell, 2006; Stu­art, et al., 2014)

• Habitat Regions
• temperate
• terrestrial

• Terrestrial Biomes
• savanna or grassland
• forest
• scrub forest

• Aquatic Biomes
• lakes and ponds

• Wetlands
• marsh
• bog

Phys­i­cal De­scrip­tion

Smooth green snakes have smooth, bright green dor­sal scales and white or yel­low ven­tral scales. Their col­oration helps them cam­ou­flage in grass or on low branches. Their dor­sal scales are arranged in 15 rows with api­cal pits close to the cen­ter of each scale. Ju­ve­niles mea­sure 8.3 to 16.5 cm upon hatch­ing. Their col­or­ing is duller than adults and tends to range from olive-green to bluish grey.

Adult smooth green snakes mea­sure 30 to 50 cm and weigh 15.3 to 19.5 g. Their tails make up nearly half of their total body length. Their ver­te­bral scales range in width from 0.50 to 0.71 mm, with an av­er­age of 0.62 mm. Smooth green snakes have heads rang­ing from 0.74 to 0.83 mm in width.

Smooth green snakes ex­hibit sub­tle sex­ual di­mor­phism. Fe­males tend to be wider than males and males have longer, more slen­der tails. (Gray, 2005; Grob­man, 1941; Grob­man, 1992; Mitchell, 1974; Mitchell, 2006; Stu­art, et al., 2014)

• Other Physical Features
• ectothermic

• Sexual Dimorphism
• female larger
• sexes shaped differently

• Range mass

  15.3 to 19.5 g

  0.54 to 0.69 oz

• Average mass

  17 g

  0.60 oz

• Range length

  30 to 66 cm

  11.81 to 25.98 in

• Average length

  50 cm

  19.69 in

De­vel­op­ment

Smooth green snakes hatch from eggs, which in­cu­bate for up to 30 days and hatch in late April to Sep­tem­ber. Hatch­lings are 8 to 16 cm long and weigh 1.1 g at birth.

Ju­ve­nile smooth green snakes are not as brightly col­ored as adults and are around half the length. Ju­ve­niles are gray­ish brown in color, which helps them cam­ou­flage with their en­vi­ron­ment. Adults reach 30 to 66 cm in length and reach sex­ual ma­tu­rity at around 2 years old. Smooth green snakes shed their scales as they grow, grad­u­ally de­vel­op­ing their adult col­oration with each shed. They ex­hibit in­de­ter­mi­nate growth, mean­ing they do not stop grow­ing through­out their lifes­pans.

Smooth green snakes ex­hibit tem­per­a­ture-de­pen­dent sex de­ter­mi­na­tion. For eggs that de­velop at tem­per­a­tures above 28 °C, hatch­lings are more likely to be fe­male. For eggs that de­velop below 28 °C, hatch­lings are more likely to be males. Ini­tial in­cu­ba­tion tem­per­a­ture is an im­por­tant de­ter­mi­nant of sex. For ex­am­ple, if the ini­tial in­cu­ba­tion tem­per­a­ture is below 28 °C and changes to a higher tem­per­a­ture later dur­ing in­cu­ba­tion, the re­sult­ing hatch­lings will be males. Typ­i­cally, all of the hatch­lings from a sin­gle clutch of eggs will be one sex. Clutches of eggs typ­i­cally fail when tem­per­a­tures vary more than 10 °C above or below 28 °C. (Aldridge and Sem­l­itsch, 1992; Mitchell, 1974; Plum­mer, 1985a; Plum­mer, 1985b; Sac­er­dote-Ve­lat, et al., 2013)

• Development - Life Cycle
• temperature sex determination
• indeterminate growth

Re­pro­duc­tion

Smooth green snakes are polyg­y­nan­drous. Fe­males re­lease pheromones to sig­nal their sex­ual ma­tu­rity. Males de­tect the pheromones that fe­males re­lease and con­gre­gate in large num­bers to mate. Males crawl over and bump into fe­males be­fore mat­ing. When fe­males are ready to mate, they lift their tail and ex­pose their cloaca. Dur­ing cop­u­la­tion, males in­sert their hemipenes into the cloaca of their mate and re­lease sperm. (Grob­man, 1992; Naul­leau and Bon­net, 1995; Plum­mer, 1985a; Shine, 2003)

• Mating System
• polygynandrous (promiscuous)

Smooth green snakes re­pro­duce sex­u­ally. They breed once a year, and fe­males ges­tate eggs for an av­er­age of 50 days, lay­ing them be­tween June and Sep­tem­ber. Smooth green snakes lay 3 to 13 eggs per clutch, and eggs in­cu­bate for 4 to 30 days, de­pend­ing on the tem­per­a­ture, with an av­er­age of 27 days. Higher in­cu­ba­tion tem­per­a­tures re­sult in shorter in­cu­ba­tion pe­ri­ods be­fore eggs hatch.

Fe­male smooth green snakes lay their eggs in warm, pro­tected sites, such as mounds or bur­rows with rot­ting veg­e­ta­tion, or un­der­neath fallen logs. Smooth green snakes are sec­ondary cav­ity nesters, choos­ing ex­ist­ing bur­rows that have been va­cated rather than con­struct­ing their own.

Both male and fe­male smooth green snakes reach re­pro­duc­tive ma­tu­rity at around two years old. (Aldridge and Sem­l­itsch, 1992; Grob­man, 1992; Naul­leau and Bon­net, 1995; Plum­mer, 1985a; Seigel and Collins, 2001)

• Key Reproductive Features
• iteroparous
• seasonal breeding
• sexual
• oviparous

• Breeding interval

  Smooth green snakes breed once each year

• Breeding season

  Females lay eggs from June to September, young hatch in August or September

• Range number of offspring

  3 to 13

• Average gestation period

  50 days

• Average time to independence

  0 minutes

• Average age at sexual or reproductive maturity (female)

  2 years

• Average age at sexual or reproductive maturity (male)

  2 years

Smooth green snakes ex­hibit lim­ited parental in­vest­ment. Young are im­me­di­ately in­de­pen­dent upon hatch­ing. Fe­males lay their eggs in com­mu­nal nest­ing sites, typ­i­cally in areas that are pro­tected and en­cour­age egg de­vel­op­ment. Males ex­hibit no parental in­vest­ment be­yond the act of mat­ing. (Aldridge and Sem­l­itsch, 1992; Grob­man, 1992; Naul­leau and Bon­net, 1995; Plum­mer, 1985a; Sac­er­dote-Ve­lat, et al., 2013; Shine, 2003)

• Parental Investment
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female

Lifes­pan/Longevity

Smooth green snakes live an av­er­age of 5 years in the wild, with a max­i­mum recorded lifes­pan of 8 years. In cap­tiv­ity, smooth green snakes live 6 years on av­er­age. Mor­tal­ity in the wild is most often at­trib­uted to pre­da­tion or en­vi­ron­men­tal fac­tors such as flood­ing. (Plum­mer, 1985a; Plum­mer, 1985b; Plum­mer, 1997a; Plum­mer, 1997b; Sac­er­dote-Ve­lat, et al., 2013)

• Range lifespan
  Status: wild

  8 (high) years

• Range lifespan
  Status: captivity

  6 (high) years

• Average lifespan
  Status: wild

  5 years

• Typical lifespan
  Status: captivity

  6 (high) years

Be­hav­ior

Smooth green snakes are mostly soli­tary, al­though large groups form dur­ing breed­ing and nest­ing sea­son and dur­ing win­ter, when in­di­vid­u­als bru­mate to­gether. Smooth green snakes stay in the same gen­eral area through­out their life, but move around to find prey, mates, and shel­ter.

Smooth green snakes are di­ur­nal and ac­tive from April to Oc­to­ber. They are sec­ondary cav­ity nesters, mean­ing they take shel­ter in aban­doned mounds or bur­rows cre­ated by other an­i­mals such as ro­dents.

Smooth green snakes are docile. In cap­tiv­ity, they are not ag­gres­sive to other an­i­mals that do not threaten them. How­ever, when pro­voked, smooth green snakes often re­lease a foul-smelling sub­stance from their anal glands, which can deter po­ten­tial preda­tors.

Smooth green snakes mate be­tween late April and Sep­tem­ber. They are promis­cu­ous, mean­ing that males and fe­males both have mul­ti­ple mates within a sin­gle breed­ing pe­riod. (Grob­man, 1992; Plum­mer, 1997a; Plum­mer, 1997b)

• Key Behaviors
• arboreal
• terricolous
• diurnal
• motile
• sedentary
• hibernation
• solitary

Home Range

Smooth green snakes have an av­er­age home range of 25 km^2. They are not known to ac­tively de­fend a ter­ri­tory.

Com­mu­ni­ca­tion and Per­cep­tion

Smooth green snakes have forked tongues, which they use to de­tect chem­i­cal sig­nals in their en­vi­ron­ment. Smooth green snakes rely on their vomeronasal sys­tem, which di­rects chem­i­cals from their tongue and nose to their Ja­cob­son’s organ. Ja­cob­son’s or­gans help smooth green snakes de­ter­mine the di­rec­tion­al­ity of chem­i­cal sig­nals, which al­lows them to ef­fec­tively track prey, find mates, and avoid preda­tors.

Smooth green snakes also use tac­tile and acoustic meth­ods of com­mu­ni­cat­ing and per­ceiv­ing their en­vi­ron­ment. (Filo­ramo and Schwenk, 2009; Grob­man, 1941; Mitchell, 1974; Seigel and Collins, 2001; Shine, 2003; Stu­art, et al., 2014)

• Communication Channels
• tactile
• acoustic
• chemical

• Other Communication Modes
• pheromones

• Perception Channels
• visual
• vibrations
• chemical

Food Habits

Smooth green snakes are op­por­tunis­tic preda­tors. Around 85% of their diet con­sists of in­sects, such as ants (fam­ily Formi­ci­dae), moths (order Lep­i­doptera), cen­tipedes (class Chilopoda), spi­ders (order Araneae), slugs (class Gas­tropoda), and ter­res­trial worms (phy­lum An­nel­ida). Smooth green snakes use their vomeronasal sys­tems to de­tect chem­i­cals re­leased by prey species. (Mitchell, 1974)

• Primary Diet
• carnivore
  • insectivore
  • eats non-insect arthropods
  • vermivore

• Animal Foods
• insects
• terrestrial non-insect arthropods
• mollusks
• terrestrial worms

Pre­da­tion

Smooth green snakes serve as prey for a va­ri­ety of mam­malian, avian, and rep­til­ian preda­tors. Known mam­malian preda­tors in­clude hu­mans (Homo sapi­ens), black bears (Ursus amer­i­canus), rac­coons (Pro­cyon lotor), red foxes (Vulpes vulpes), and do­mes­tic cats (Felis do­mes­ti­cus). Avian preda­tors in­clude red-tailed hawks (Buteo ja­maicen­sis), great blue herons (Ardea hero­dias), rough-legged hawks (Buteo lago­pus). Larger snakes, such as milk snakes (Lam­pro­peltis tri­an­gu­lum), are also known preda­tors of smooth green snakes.

Smooth green snakes have bright green dor­sal scales, which help them cam­ou­flage in the grass­land and for­est habi­tats where they typ­i­cally live. Smooth green snakes are also small and fast, mak­ing them dif­fi­cult to catch if de­tected. (Aldridge, et al., 1990)

• Anti-predator Adaptations
• cryptic

• Known Predators

  • Humans (Homo sapeans)
  • Red-tailed hawks (Buteo jamaicensis)
  • Great blue herons (Ardea herodias)
  • Rough-legged hawks (Buteo lagopus)
  • Black bears (Ursus americanus)
  • Raccoons (Procyon lotor)
  • Red foxes (Vulpes vulpes)
  • Domestic cats (Felis catus)
  • Milk snakes (Lampropeltis triangulum)

Ecosys­tem Roles

Smooth green snakes serve as prey for mam­mals, birds, and other snake species. They also serve as hosts for par­a­sitic tape­worms (class Ces­toda), par­a­sitic ne­ma­todes (genus Baylisas­caris), and red mites (Der­manys­sus gal­li­nae). (Aldridge, et al., 1990; Grob­man, 1941; Grob­man, 1992; Mitchell, 2006; Red­der, et al., 2006)

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

Smooth green snakes are a part of the in­ter­na­tional pet trade and are oc­ca­sion­ally found in zoos. They also serve as a source of eco­tourism through­out their range. (Aldridge, et al., 1990; Grob­man, 1941; Red­der, et al., 2006; Sac­er­dote-Ve­lat, et al., 2013)

• Positive Impacts
• pet trade
• ecotourism

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

Smooth green snakes are not ven­omous, but can still bite hu­mans or pets. If left un­treated, their bites can cause in­fec­tions. There are no other known ad­verse ef­fects of smooth green snakes on hu­mans. (Aldridge, et al., 1990; Grob­man, 1941; Red­der, et al., 2006; Stu­art, et al., 2014; Aldridge, et al., 1990; Grob­man, 1941; Red­der, et al., 2006; Stu­art, et al., 2014)

• Negative Impacts
• injures humans
  • bites or stings

Con­ser­va­tion Sta­tus

Smooth green snakes are con­sid­ered a species of "least con­cern" on the IUCN Red List. They have no spe­cial sta­tus on other na­tional or in­ter­na­tional con­ser­va­tion lists. How­ever, habi­tat loss due to an­thro­pogenic de­vel­op­ment has neg­a­tively im­pacted pop­u­la­tions of smooth green snakes. In the Rocky Moun­tain re­gion, in­di­vid­u­als are being rein­tro­duced to habi­tats where de­for­esta­tion is not cur­rently a threat. (Aldridge, et al., 1990; Grob­man, 1941; Red­der, et al., 2006; Stu­art, et al., 2014)

• IUCN Red List

  Least Concern
  More information

• IUCN Red List

  Least Concern
  More information

• US Federal List

  No special status

• CITES

  No special status

• State of Michigan List

  No special status

Con­trib­u­tors

Lau­ren Mc­Claugh­erty (au­thor), Rad­ford Uni­ver­sity, Karen Pow­ers (ed­i­tor), Rad­ford Uni­ver­sity, April Tin­gle (ed­i­tor), Rad­ford Uni­ver­sity, Emily Clark (ed­i­tor), Rad­ford Uni­ver­sity, Cari Mc­gre­gor (ed­i­tor), Rad­ford Uni­ver­sity, Jacob Vaught (ed­i­tor), Rad­ford Uni­ver­sity, Galen Bur­rell (ed­i­tor), Spe­cial Pro­jects.

Ref­er­ences

Aldridge, R., J. Green­haw, M. Plum­mer. 1990. The male re­pro­duc­tive cycle of the rough green snake (Opheodrys aes­tivus). Am­phibia-Rep­tilia, 13/3: 165-172.

Aldridge, R., R. Sem­l­itsch. 1992. Fe­male re­pro­duc­tive bi­ol­ogy of the south­east­ern crowned snake (Tan­tilla coro­nata). Am­phibia-Rep­tilia, 13/3: 209-218.

Filo­ramo, N., K. Schwenk. 2009. The mech­a­nism of chem­i­cal de­liv­ery to the vomeronasal or­gans in squa­mate rep­tiles: A com­par­a­tive mor­pho­log­i­cal ap­proach. Jour­nal of Ex­per­i­men­tal Zo­ol­ogy Part B: Mol­e­c­u­lar & De­vel­op­men­tal Evo­lu­tion, 311A/1: 20.

Gilbart, M. 2012. Under Cover: Wildlife of Shrub­lands and Young For­est. Wildlife Man­age­ment In­sti­tute: US Fish & Wildlife Pub­li­ca­tions.

Gray, B. 2005. The Ser­pent's Cast. Lans­ing, Michi­gan: Her­peto­log­i­cal Pub­lish­ing and Dis­tri­b­u­tion.

Grob­man, A. 1941. A Con­tri­bu­tion to the Knowl­edge of Vari­a­tion in Opheodrys ver­nalis (Har­lan), with the De­scrip­tion of a New Sub­species. Uni­ver­sity of Michi­gan: Mis­cel­la­neous Pub­li­ca­tions.

Grob­man, A. 1992. Metamerism in the snake Opheodrys ver­nalis, with a de­scrip­tion of a new sub­species. Jour­nal of Her­petol­ogy, 26/2: 175-186.

Mitchell, J. 1974. The Snakes of Vir­ginia. Uni­ver­sity of Rich­mond: Vir­ginia Wildlife.

Mitchell, J. 2006. Sta­tus of the smooth green snake (Opheodrys ver­nalis) in North Car­olina and Vir­ginia. Ban­is­te­ria, 28: 37-43.

Naul­leau, G., X. Bon­net. 1995. Re­pro­duc­tive ecol­ogy, body fat re­serves and for­ag­ing mode in fe­males of two con­trasted snake species: Vípera aspis (ter­res­trial, vi­vip­a­rous) and Elaphe longíssima (semi-ar­bo­real, oviparous). Am­phibia-Rep­tilia, 16/1: 37-46.

Plum­mer, M. 1985. De­mog­ra­phy of green snakes (Opheodrys aes­tivus). Copeia, 41/4: 373-381.

Plum­mer, M. 1985. Growth and ma­tu­rity in green snakes (Opheodrys aes­tivus). Copeia, 41/1: 28-33.

Plum­mer, M. 1997. Pop­u­la­tion ecol­ogy of green snakes (Opheodrys aes­tivus) re­vis­ited. Her­peto­log­i­cal Mono­graphs, 11/1997: 102-123.

Plum­mer, M. 1997. Speed and en­durance of gravid and non­gravid green snakes, Opheodrys aes­tivus. Copeia, 41/1: 191-194.

Red­der, A., B. Smith, D. Keinath. 2006. "Smooth Green Snake (Opheodrys ver­nalis): A Tech­ni­cal Con­ser­va­tion As­sess­ment" (On-line pdf). So­ci­ety for Con­ser­va­tion Bi­ol­ogy. Ac­cessed March 27, 2015 at http://​www.​fs.​fed.​us/​r2/​projects/​scp/​assessments/​smoothgreensnake.​pdf.

Sac­er­dote-Ve­lat, A., J. Earn­hardt, D. Mulk­erin, D. Boehm, G. Glowacki. 2013. Eval­u­a­tion of head­start­ing and re­lease tech­niques for pop­u­la­tion aug­men­ta­tion and rein­tro­duc­tion of the smooth green snake. An­i­mal Con­ser­va­tion, 17/1: 65-73.

Seigel, R., J. Collins. 2001. Snakes: Ecol­ogy and Be­hav­ior. Cald­well, N.J: Black­burn Press.

Shine, R. 2003. Re­pro­duc­tive strate­gies in snakes. Pro­ceed­ings of the Royal So­ci­ety of Lon­don B, 270/1519: 995-1004.

Stu­art, B., J. Rosado, P. Brinkman. 2014. Al­bert Rogers Cran­dall's smooth green snake (Opheodrys ver­nalis) from North Car­olina. South­east­ern Nat­u­ral­ist, 13/4: 36-43.