Reptiles of North Carolina
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NC Records

Coluber constrictor - North American Racer


Photo: Steve Hall
Photo: F. Williams, S. Williams
Photo: R. Newman
Taxonomy
Class: Reptilia Order: Serpentes Family: Colubridae Subfamily: Colubrinae Other Common Name(s): Black Racer
Taxonomic Comments: Coluber is a monotypic genus of long, slender snakes, ranging widely across much of North America, from extreme southwestern Canada down the Pacific Coast, across the midwest, and across most of the Atlantic Coast and Gulf of Mexico.

The generic placement of snakes in the genus Masticophis relative to Coluber is a matter of debate among experts; some synonymize the eleven Masticophis species within Coluber, while others exclude Coluber, leaving it monotypic. Recent molecular phylogenetic studies support the generic distinction between Coluber and Masticophis (Myers et al., 2017; O'Connell and Smith, 2018; Myers et al., 2024).

Species Comments: Coluber constrictor, the North American Racer, is one of two Coluber in North Carolina. This species is one of the most wide-ranging in the USA, with populations across most of the country excepting the extreme northern Midwest and parts of the American Southwest. They can be found across North Carolina state-wide, except at extremely high elevations.

Some authors recognize as many as 11 subspecies, and some references and field guides list C. c. constrictor (Northern Black Racer) and C. c. priapus (Southern Black Racer) as occurring in North Carolina; most in North Carolina would be assigned as "Northern Black Racers", except a few limited populations on the Coastal Plain. These subspecies were morphologically delimited based solely on hemipenal structure, but those delimitations do not hold up under genetic scrutiny; Burbrink et al. (2008) showed that Racers across North Carolina are part of the same genetic clade, which they refer to as the "Eastern" lineage. These findings were recently supported by Myers et al. (2024) with more extensive sampling and genomic data, again showing that all Racers in the state correspond to the same lineage and subspecies identification is unwarranted.

Coluber constrictor is one of four snakes originally described by Linnaues that still retains its original name. The generic epithet Coluber is Latin for "snake". The specific epithet constrictor is derived from the Latin con, meaning "together" and strictus, meaning "drawn together"/"tight", though contrary to its name, this species does not constrict its prey.

Taxonomic References: Wilson (1978); Burbrink et al. (2008); Myers et al. (2017); O'Connell and Smith (2018); Myers et al. (2024).
Identification
Description: North American Racers are medium-to-large sized, slender snakes with heads slightly wider than the neck. Coloration and pattern are highly variable range-wide, but in North Carolina, adult dorsal coloration is uniformly black, leading to the often used common name "Black Racer". The venter is black or dark gray, occasionally with white mottling. The head is also black, usually with a white to light gray chin patch.

Juvenile Racers are distinctly patterned prior to undergoing an ontogenetic color change as they mature. Juveniles are gray to light brown dorsally, with darker gray to red-brown body blotches with pale centers most pronounced anteriorly, especially as the snake ages. The blotches may be ovular to square, sometimes appearing split or at an angle. The head of juveniles is similarly blotched with gray and reddish brown, with noticeably large eyes relative the the head size.
Morphological Features: Racers typically have 17 smooth scale rows at midbody, reducing to 15 posteriorly. Ventral counts range from 151-193 (171-191 in NC specimens; Palmer and Braswell, 1995), with 66-120 subcaudals (85-108) and usually a divided anal plate. Head scale counts are typically as follows: 7 supralabials, 9 infralabials, 1 small loreal, 2 nasals, 2 preoculars, 2 postoculars, and 2+2+2 temporals. Palmer and Braswell (1995) noted some variation in scalation across multiple specimens in NC.

These are typically long snakes, with a maximum recorded total length of 191.1 cm (75.3 inches). Palmer and Braswell (1995) reported a 151.0 cm female and a 155.7 cm male specimen from NC. Tails account for 22-28% of total length. There are few, if any, reliable external morphological differences between sexes.

Racers do not have enlarged posterior teeth or Duvernoy's glands, meaning they are incapable of producing venom. This snake is essentially harmless to humans and pets, but their bites can pierce skin and draw blood. Their typical response to a threat is to flee quickly, but if blocked or captured, they will vibrate their tails, gape their mouths, strike and bite repeatedly, and spray musk.
Technical Reference: Palmer and Braswell (1995); Ernst and Ernst (2003).
Field Guide Descriptions: Palmer and Braswell (1995); Ernst and Ernst (2003); Beane et al. (2010).
Online Photos:    Google   iNaturalist   GBIF
Observation Methods: Racers are frequently encountered active during the day, and may be sampled using drift fences and cover objects.
Distribution in North Carolina
County Map: Clicking on a county returns the records for the species in that county.
Key Habitat Requirements
Habitat: Habitats include various types of forests, shrublands, fields, and wetland edges (Palmer and Braswell, 1995; Beane et al., 2010; and Gibbons, 2017).
Biotic Relationships: Racers are active, visual predators with a cosmopolitan diet; they will consume essentially any prey item they can catch and successfully swallow (Fitch, 1963; Brown, 1979; Palmer and Braswell, 1995; Ernst and Ernst, 2003; Halstead et al., 2008; Elliot, 2016).

Recorded prey items include: various arthropods (including cicadas, dipteran larvae, lepidopteran larvae, moths, orthopterans, spiders), small/nestling birds and their eggs (including various icterids, sparrows, and warblers), anurans (chorus frogs, ranids, toads, and treefrogs), salamanders (D. fuscus), lizards (anoles, fence lizards, glass lizards, and skinks), nonvenomous snakes (including Carphophis amoenus, Diadophis punctatus, Haldea striatula, Heterodon platirhinos, Lampropeltis getula, Masticophis flagellum, Nerodia sipedon, Opheodrys aestivus, Pantherophis alleghaniensis-quadrivittatus, Regina septemvittata, Rhadinaea flavilata, Storeria dekayi, S. occipitomaculata, Tantilla coronata, Thamnophis saurita, T. sirtalis, and Virginia valeriae), juvenile venomous snakes (Agkistrodon contortrix, Crotalus horridus, Sistrurus miliarius), small mammals (mice, squirrels, rats, voles, and shrews), and even juvenile turtles (including Chrysemys picta, Kinosternon subrubrum, Malaclemys terrapin and Terrapene carolina). Cannibalism by larger racers on smaller or juvenile individuals is also common.

Racers are known prey of ophiophagous snakes (including cottonmouths, rat snakes, garter snakes, kingsnakes, and other racers), glass lizards, predatory birds (including hawks, kestrels, owls, and shrikes), and mammals (bobcats, domestic cats, rodents, opossum, badgers, and skunks).
Life History and Autecology
Breeding and Courtship: Per Ernst and Ernst (2003), males reach sexual maturity usually in their second year, between body lengths of 50–68 cm. Females mature usually in their third year, at body lengths 50–71 cm, though Palmer and Braswell (1995) noted the smallest sexually mature female they examined was 71.5 cm total body length. Mating occurs in the spring and early summer (April to July), with most North Carolina records in May.
Reproductive Mode: Racers are oviparous and typically lay eggs in summer (June to early August) that hatch in later summer or early Fall (sometimes as late as November in parts of their range). Clutches average approximately 14 white, elongate, nonadherent, granular eggs that average 29 mm long (Palmer and Braswell, 1995), but may reach lengths as long as 50 mm (Ernst and Ernst, 2003).

Hatchlings are approximately 24 cm in total length, and weigh approximately 6 g (Palmer and Braswell, 1995). They are heavily patterned with blotches (see “Description” above), which gradually fades as the snakes age.
Terrestrial Life History: Racers are diurnal, active snakes; at night they typically stay put under cover objects. Though primarily terrestrial, they can be found in small bushes and shrubs. They are commonly encountered actively moving through habitat, as well as basking in the sun or under cover objects. They have been recorded in North Carolina during every month of the year, but most activity occurs from April to June. In colder climates they will hibernate in mammal burrows, rock outcrops and crevices, or in rotting stumps and logs, usually with high site fidelity and often shared with other species.

Home range estimates are not known from North Carolina, but in South Carolina this species has been reported to have an average home range greater than 12 hectares (~120,000 m2; Plummer and Congdon, 1994). They will move great distances from hibernacula.
General Ecology
Adverse Environmental Impacts
Status in North Carolina
NHP State Rank: S5
Global Rank: G5

Photo Gallery for Coluber constrictor - North American Racer

106 photos are available. Only the most recent 30 are shown.

Recorded by: J. Mickey
Wilkes Co.
Comment: 		Recorded by: Caleb Garner
Wake Co.
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Recorded by: Erich Hofmann and Kayla Weinfurther
Brunswick Co.
Comment: 		Recorded by: Andrew W. Jones
Polk Co.
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Recorded by: Andrew W. Jones
Polk Co.
Comment: 		Recorded by: J. Mickey
Wilkes Co.
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Recorded by: J. Mickey
Wilkes Co.
Comment: 		Recorded by: K. Bischof, S. Hill, M. Briley
Transylvania Co.
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Recorded by: J. Mickey
Wilkes Co.
Comment: 		Recorded by: J. Mickey
Wilkes Co.
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Recorded by: A. Ledford
Wake Co.
Comment: 		Recorded by: Erich Hofmann
Columbus Co.
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Recorded by: Erich Hofmann
New Hanover Co.
Comment: 		Recorded by: K. Williams, D. Wallace
Surry Co.
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Recorded by: L. Eckart
Carteret Co.
Comment: 		Recorded by: Travis McLain
Cabarrus Co.
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Recorded by: Mark Shields
Onslow Co.
Comment: 		Recorded by: Robert Russo
Tyrrell Co.
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Recorded by: Robert Russo
Tyrrell Co.
Comment: 		Recorded by: Erich Hofmann and Kayla Weinfurther
Columbus Co.
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Recorded by: L. Eckart, M.Meyers
Carteret Co.
Comment: 		Recorded by: J. Mickey
Wilkes Co.
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Recorded by: Erich P. Hofmann and Kayla Weinfurther
Columbus Co.
Comment: 		Recorded by: Erich Hofmann
Columbus Co.
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Recorded by: Z. Lunn
Moore Co.
Comment: 		Recorded by: J. Mickey
Wilkes Co.
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Recorded by: Erich Hofmann
New Hanover Co.
Comment: 		Recorded by: J. Mickey
Stokes Co.
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Recorded by: J. Mickey
Wilkes Co.
Comment: 		Recorded by: Erich Hofmann and Kayla Weinfurther
Columbus Co.
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