Eastern yellow-bellied racer Coluber flaviventris, copyright Peter Paplanus.

Belongs within: Colubrinae.

Coluber, the racers, is a genus of large non-venomous snakes that has been variously treated as included a range of Holarctic species or restricted to the North American Coluber constrictor.

The race of racers
Published 9 October 2021

Snakes are, for the most part, fairly retiring animals, little seen even in areas where they may be abundant. In much of North America, however, one of the most commonly encountered snake species is the racer Coluber constrictor. This moderately large non-venomous snake, with the largest individuals approaching two metres in length, is a widespread inhabitant of open habitats such fields, brushland or open woodlands. Its distribution is centred over much of the continental United States, being found in most regions except much of the arid south-west. Outside the United States, it has a very patchy distribution in southernmost Canada, Mexico and northern Central America. Most recent authors treat it as the sole species in the genus Coluber; other species historically assigned to this genus from across the Holarctic region now being treated as separate. These include the North American whip snakes of the genus Masticophis, believed to the closest relatives of the racer (Myers et al. 2017).

Southern black racer Coluber constrictor priapus, copyright Peter Paplanus.

Adult racers are generally uniformly dark in coloration dorsally, with a lighter-coloured venter, though juveniles have a blotchy checkered pattern (Fitch 1963). The exact shade varies across the species’ range and a number of subspecies have been recognised such as the blue racer Coluber constrictor foxii and the northern black racer C. c. constrictor. In general, individuals are darker towards the east and north, and lighter towards the west and south. Wilson (1978) listed eleven subspecies of C. constrictor whereas a phylogeographic study of the species by Burbrink et al. (2008) identified six major lineages. As well as coloration, members of these lineages may differ in factors such as behaviour or genital morphology, and future studies may see them elevated to the rank of separate species.

Blue racer Coluber constrictor foxii, copyright Peter Paplanus.

The natural history of Coluber constrictor was reviewed in detail by Fitch (1963). As the vernacular name of ‘racer’ suggests, Coluber constrictor is a fast mover. Its diet contains a mixture of small vertebrates, such as frogs, lizards and small mammals, and large invertebrates such as grasshoppers, crickets and caterpillars. Foraging individuals often hold the front end of the body raised above the ground. Despite their species name, racers do not kill their prey by constriction. Instead, they mostly capture prey by darting forward quickly and grabbing it, often swallowing prey live. Fitch recorded one occasion when he observed a racer in the process of subduing a large skink. While the snake was swallowing its prey, Fitch attempted to capture it. The racer disgorged the skink, and both snake and lizard escaped the scene. Diet may vary with size, with smaller individuals taking a higher proportion of invertebrates, but also varies with range. Populations in the west may primarily feed on insects whereas others may almost exclusively take vertebrates. The northern black racer of the northeastern United States is the most inclined of the subspecies to feed on other snakes. Cannibalism is not unknown; at least one author recorded observing it among broods raised in captivity. In one case, two young racers latched onto a single lizard. One of them successfully downed the lizard, and then also continued on to devour the snake attached to the other end, despite the swallowed snake being nearly as large as its swallower.

Eastern yellow-bellied racer Coluber constrictor flaviventris, copyright David Sledge.

During winter, racers hibernate in crevices and hollows among rocks. Preferred hibernation locations are often at the top of hills, away from their usual hunting sites. Mating and egg-laying occurs shortly after emergence with the peak of egg-laying being in early June (Rosen 1991). Racers, particularly the large northern black, may become more aggressive during this period. Eggs are buried shallowly, in loose soil or under litter, though females may take advantage of abandoned mammal burrows to provide a more secure location. As with other snakes, laying seems to be a matter of pump and dump; I didn’t come across any references to females protecting clutches. After hatching, males take about a year to reach sexual maturity whereas the larger females take about two years. Fitch (1963) reports encountering the same individuals over the course of several years (recognisable by their bearing the scars of prior collection of scale samples). Nevertheless, the majority of racer hatchlings do not survive their first summer. Few get the opportunity to seek out shelter for their winter’s sleep.

Systematics of Coluber
<==Coluber Linnaeus 1758RB05
    |--C. aesculapii Linnaeus 1758L58
    |--C. agilis Linnaeus 1758L58
    |--C. ahaetulla Linnaeus 1758L58
    |--C. albus Linnaeus 1758L58
    |--C. alidras Linnaeus 1758L58
    |--C. ammodytes Linnaeus 1758L58
    |--C. angulatus Linnaeus 1758L58
    |--C. annulatus Linnaeus 1758L58
    |--C. arges Linnaeus 1758L58
    |--C. aspis Linnaeus 1758L58
    |--C. atropos Linnaeus 1758L58
    |--C. atrox Linnaeus 1758L58
    |--C. aulicus Linnaeus 1758L58
    |--C. aurora Linnaeus 1758L58
    |--C. buccatus Linnaeus 1758L58
    |--C. cadurci Rage 1974B93
    |--C. caerulescens Linnaeus 1758L58
    |--C. caeruleus Linnaeus 1758L58
    |--C. calamarius Linnaeus 1758L58
    |--C. candidus Linnaeus 1758L58
    |--C. canus Linnaeus 1758L58
    |--C. carinatus Linnaeus 1758L58
    |--C. caspioides Szyndlar & Schleich 1993RB05
    |--C. cenchoa Linnaeus 1758L58
    |--C. cerastes Linnaeus 1758L58
    |--C. chersca Linnaeus 1758L58
    |--C. cinereus Linnaeus 1758L58
    |--C. cobella Linnaeus 1758L58
    |--C. collaris (Müller 1878) (see below for synonymy)SBM01
    |--C. conspicillatusW06
    |--C. constrictor Linnaeus 1758L58
    |--C. corallinus Linnaeus 1758L58
    |--C. cyaneus Linnaeus 1758L58
    |--C. dione Pallas 1773M01
    |--C. dipsas Linnaeus 1758L58
    |--C. dolnicensis Szyndlar 1987RB05
    |--C. domicella Linnaeus 1758L58
    |--C. exoletus Linnaeus 1758L58
    |--C. filiformis Linnaeus 1758L58
    |--C. flagellumF15
    |--C. flaviventris Say in James 1823J23
    |--C. fuscus Linnaeus 1758L58
    |--C. gemonensisK08
    |--C. haje Linnaeus 1758L58
    |--C. heterodonJ23
    |--C. hippocrepis Linnaeus 1758L58
    |--C. jugularis Linnaeus 1758L58
    |    |--C. j. jugularisK08
    |    `--C. j. caspius [=Hierophis caspius, Zamenis jugularis caspius]K08
    |--C. lacteus Linnaeus 1758L58
    |--C. laticaudatus Linnaeus 1758L58
    |--C. leberis Linnaeus 1758L58
    |--C. lebetinus Linnaeus 1758L58
    |--C. lemniscatus Linnaeus 1758L58
    |--C. lineatus Linnaeus 1758L58
    |--C. longissimusW06
    |--C. lutrix Linnaeus 1758L58
    |--C. maurus Linnaeus 1758L58
    |--C. melanocephalus Linnaeus 1758L58
    |--C. miliaris Linnaeus 1758L58
    |--C. minervae Linnaeus 1758L58
    |--C. molurus Linnaeus 1758L58
    |--C. monilis Linnaeus 1758L58
    |--C. mucosus Linnaeus 1758L58
    |--C. mycterizans Linnaeus 1758L58
    |--C. naja Linnaeus 1758L58
    |--C. najadum (Eichwald 1831) (see below for synonymy)SBM01
    |--C. nebulatus Linnaeus 1758L58
    |--C. niveus Linnaeus 1758L58
    |--C. obsoletus Say in James 1823J23
    |--C. ordinatusJ23
    |--C. ovivorus Linnaeus 1758L58
    |--C. padera Linnaeus 1758L58
    |--C. pallidus Linnaeus 1758L58
    |--C. parietalis Say in James 1823J23
    |--C. pelias Linnaeus 1758L58
    |--C. petola Linnaeus 1758L58
    |--C. petolarius Linnaeus 1758L58
    |--C. plicatilis Linnaeus 1758L58
    |--C. pouchetii (Rochebrune 1880) [=Tamnophis pouchetii, Sansanosaurus pouchetii]RB05
    |--C. proximus Say in James 1823J23
    |--C. pullatus Linnaeus 1758L58
    |--C. ravergieriWA05
    |--C. reginae Linnaeus 1758L58
    |--C. rhombeatus Linnaeus 1758L58
    |--C. rodorachisB03 [=Platyceps rhodorachisSBM01]
    |--C. rubricepsLK03
    |--C. rufodorsatusW06
    |--C. saturninus Linnaeus 1758L58
    |--C. sauritaJ23
    |--C. scaber Linnaeus 1758L58
    |--C. schrenckiW06
    |--C. severus Linnaeus 1758L58
    |--C. sibilans Linnaeus 1758L58
    |--C. sibon Linnaeus 1758L58
    |--C. sipedon Linnaeus 1758L58
    |--C. sirtalis Linnaeus 1758L58
    |--C. situla Linnaeus 1758L58
    |--C. stolatus Linnaeus 1758L58
    |--C. suevicus (Fraas 1870)RB05
    |--C. taeniurusW06
    |--C. triscalis Linnaeus 1758L58
    |--C. typhlus Linnaeus 1758L58
    |--C. tyria Linnaeus 1758L58
    |--C. ventromaculatusLK03 [incl. *Platyceps subfasciatus Blyth 1860SBM01]
    |--C. vipera Linnaeus 1758L58
    |--C. viridiflavus (Lacepède 1789)BB03 [=Zamenis viridiflavusK08]
    |    |--C. v. viridiflavusM55
    |    `--C. v. carbonariusM55
    |--C. viridissimus Linnaeus 1758L58
    `--C. vittatus Linnaeus 1758L58

Coluber collaris (Müller 1878) [=Zamenis dahlii var. collaris non C. collaris Ménétries 1832 (not preoc. if in dif. gen.), C. najadum collaris; incl. Z. dahlii var. rubriceps Venzmer 1919, C. najadum rubriceps, C. rubriceps thracius Rehák 1985]SBM01

Coluber najadum (Eichwald 1831) [incl. C. dahlii Schinz 1835, Haemorrhois najadum dahli, Psammophis dahlii, Tyria dahlii, Zamenis dahlii Schinz 1835]SBM01

*Type species of generic name indicated


[B03] Babocsay, G. 2003. Geographic variation in Echis coloratus (Viperidae, Ophidia) in the Levant with the description of a new subspecies. Zoology in the Middle East 29: 13–32.

[B93] Benton, M. J. 1993. Reptilia. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 681–715. Chapman & Hall: London.

[BB03] Blain, H.-A., & S. Bailon. 2003. Les amphibiens et les reptiles des couches du Pléistocène supérieur ancien du gisement d’Artenac (Charente, France). Quaternaire 14 (1): 85–95.

Burbrink, F. T., F. Fontanella, R. A. Pyron, T. J. Guiher & C. Jimenez. 2008. Phylogeography across a continent: the evolutionary and demographic history of the North American racer (Serpentes: Colubridae: Coluber constrictor). Molecular Phylogenetics and Evolution 47: 274–288.

Fitch, H. S. 1963. Natural history of the racer Coluber constrictor. University of Kansas Publications, Museum of Natural History 15 (8): 351–468.

[F15] Fowler, H. W. 1915. Cold-blooded vertebrates from Florida, the West Indies, Costa Rica, and eastern Brazil. Proceedings of the Academy of Natural Sciences of Philadelphia 67 (2): 244–269.

[J23] James, E. 1823. Account of an Expedition from Pittsburgh to the Rocky Mountains, performed in the years 1819 and ’20, by order of the Hon. J. C. Calhoun, sec’y of war: under the command of Major Stephen H. Long. From the notes of Major Long, Mr. T. Say, and other gentlemen of the exploring party vol. 1. H. C. Carey & I. Lea: Philadelphia.

[K08] Korsós, Z. 2008. History of the Herpetological Collection of the Hungarian Natural History Museum. Annales Historico-Naturales Musei Nationalis Hungarici 100: 37–93.

[L58] Linnaeus, C. 1758. Systema Naturae per Regna Tria Naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata. Laurentii Salvii: Holmiae.

[LK03] Lymberakis, P., & A. Kalionzopoulou. 2003. Additions to the herpetofauna of Syria. Zoology in the Middle East 29: 33–39.

[M01] Méhely, L. 1901. Csúszómászók és kétéltűek [Reptilien und Amphibien]. In: Horváth, G. (ed.) Zichy Jenő Gróf Harmadik Ázsiai Utazása [Dritte Asiatische Forschungsreise des Grafen Eugen Zichy] vol 2. Zichy Jenő Gróf Harmadik Ázsiai Utazásának Állattani Eredményei [Zoologische Ergebnisse der Dritten Asiatischen Forschungsreise des Grafen Eugen Zichy] pp. 41–68. Victor Hornyánszky: Budapest, and Karl W. Hierseman: Leipzig.

[M55] Mertens, R. 1955. Die Mauereidechsen der Liparischen Inseln, gesammelt von Dr. Antonino Trischitta. Senckenbergiana Biologica 36 (1–2): 25–40.

Myers, E. A., J. L. Burgoon, J. M. Ray, J. E. Martínez-Gómez, N. Matías-Ferrer, D. G. Mulcahy & F. T. Burbrink. 2017. Coalescent species tree inference of Coluber and Masticophis. Copeia 105 (4): 640–648.

[RB05] Rage, J.-C., & S. Bailon. 2005. Amphibians and squamate reptiles from the late early Miocene (MN 4) of Béon 1 (Montréal-du-Gers, southwestern France). Geodiversitas 27 (3): 413–441.

[SBM01] Schätti, B., I. Baran & P. Maunoir. 2001. Taxonomie, Morphologie und Verbreitung der Masken-Schlanknatter Coluber (s. l.) collaris (Müller, 1878). Revue Suisse de Zoologie 108 (1): 11–30.

[WA05] Wasserberg, G., Z. Abramsky, N. Valdivia & B. P. Kotler. 2005. The role of vegetation characteristics and foraging substrate in organizing a centrifugal gerbil community. Journal of Mammalogy 86 (5): 1009–1014.

[W06] Werner, F. 1906. Die nördlichsten Reptilien und Batrachier. In: Römer, F., & F. Schaudinn (eds) Fauna Arctica. Eine Zusammenstellun der arktischen Tierformen, mit besonder Berücksichtigung des Spitzbergen-Gebietes auf Grund der Ergebnisse der Deutschen Expedition in das Nördliche Eismeer im Jahre 1898 vol. 4 pp. 527–544. Gustav Fischer: Jena.

Wilson, L. D. 1978. Coluber constrictor Linnaeus. Catalogue of American Amphibians and Reptiles 218: 1–4.

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