Reptiles of North Carolina
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NC Records

Pantherophis alleghaniensis-quadrivittatus - Central/Eastern Ratsnake Complex


Photo: Steve Hall
Photo: Steve Hall
Photo: Jim Petranka
Taxonomy
Class: Reptilia Order: Serpentes Family: Colubridae Subfamily: Colubrinae Synonym: Pantherophis (o.) alleghaniensis/quadrivittatus complex Other Common Name(s): Rat Snake
Taxonomic Comments: Pantherophis, as currently considered, consists of 8 species of medium-to-large colubrid snakes native to the eastern United States, Midwest, and northern Mexico.

The taxonomy of the genus Pantherophis was in flux for many years, only stabilizing fairly recently. Initially, all North American ratsnakes and cornsnakes were included in a broader definition of the genus Elaphe, and many older texts (and some newer ones) retain this genus name. Utiger et al. (2002) revalidated Pantherophis and restricted Elaphe to the Eastern Hemisphere, but it took some time to gain consistent use. Further muddying the waters, an attempt to resurrect the name "Scotophis" for ratsnakes (by Collins and Taggart, 2008) was published, but not broadly accepted, though that name can be found in some field guides and occasionally in published literature. As it stands, all ratsnakes and cornsnakes native to North America are within the genus Pantherophis.

Species Comments: The Pantherophis alleghaniensis-quadrivittatus complex is one of two Pantherophis in North Carolina. The taxonomy of these Ratsnakes is easily one of the most contentious on-going nomenclatural debates in herpetology, and one riddled with confusion and numerous name changes after the advent of molecular systematics. Below, we summarize the recent taxonomic fluctuations of these snakes that have occurred since Palmer and Braswell (1995). In North Carolina, Ratsnakes are found essentially state-wide, though color and dorsal pattern vary considerably across the state.

For the purposes of this site, we record all Ratsnakes in North Carolina under "P. alleghaniensis-quadrivittatus", the Central/Eastern Ratsnake complex. We recognize that large areas of gene flow between populations may preclude more specific identification, and that this is a species complex where many individuals cannot be morphologically assigned with certainty. As such, this classification best reflects our current understanding of the evolutionary history (and therefore the taxonomy) of these populations. A detailed taxonomic history is available below.

The Eastern Ratsnake was previously classifed as the wide-ranging Elaphe obsoleta, with seven subspecies based primarily on color pattern and geographic location. Two of these, "E. o. obsoleta" and "E. o. quadrivittata" were considered to be in North Carolina. In a major revision of ratsnake taxonomy, Burbrink (2001) restricted "obsoleta" to the western clade of ratsnakes, elevating "E. spiloides" and "E. alleghaniensis" for the central and eastern ratsnakes, respectively (see also Burbrink et al., 2000). Burbrink (2001) noted a wide swath of taxonomic uncertainty that included most of the Mountain and Piedmont region of North Carolina, suggesting E. spiloides sensu stricto was only in the high mountains of the state, E. alleghaniensis sensu stricto only in the Coastal Plain, and the area in between was unknown due to hybridization. Utiger et al. (2002) changed the generic classification of these taxa (see above), leaving "Pantherophis alleghaniensis" and "Pantherophis spiloides".

For some time, it was understood that the area of taxonomic uncertainty would only really be delimited with greater sampling and better genomic techniques. In time, "P. alleghaniensis" came to be considered the taxon east of the Appalachian Mountains, with "P. spiloides" to the west, rendering the classification of the majority of ratsnakes in North Carolina as "P. alleghaniensis", and part of the "P. obsoletus complex".

Finally, Burbrink et al. (2021a) published a long-awaited follow up study using population genomic data from multiple samples across the range of the North American ratsnakes. This work showed that part of the confusion in delimiting these species arises from high levels of introgression between the "central" and "eastern" clades of these snakes. In this work, "P. alleghaniensis" was restricted to essentially only the Coastal Plain, and "P. spiloides" was known to cross the Appalachians down into the foothills and possibly Piedmont; the two species had introgressed in the middle portions of the state. Importantly, they noted that "migration rates between P. spiloides and P. alleghaniensis... may be high enough that they do not represent independent evolutionary trajectories"(23).

Despite this advance in understanding, the nomenclatural confusion continued due to a historic misunderstanding related to the type locality of the name "alleghaniensis". As noted by Hillis and Wuster (2021), the name "alleghaniensis" actually refers to the "central" clade of ratsnakes (called "spiloides" by Burbrink et al., 2021a), meaning that name should not be used for the "eastern" clade. An older name "quadrivittatus" instead had to be applied to the eastern clade, and "spiloides" was sunk into synonymy. They further suggested "alleghaniensis", "quadrivittatus", and "obsoletus" be considered subspecies under a larger species concept of P. obsoletus, due to the lack of reproductive isolation and broad areas of introgression between populations.

Burbrink et al. (2021b) corrected their taxonomy and published the most up-to-date rangemap of ratsnakes, noting that these taxa could not be subspecies as they are paraphyletic with respect to P. bairdi. Thus, they consider the eastern population P. quadrivittatus, the central popualtion P. alleghaniensis, and the western population P. obsoletus, without any subspecies. Hillis (2022) continued to argue for the use of subspecies.

To conclude, either 1) there are two species of Ratsnakes in North Carolina: P. quadrivittatus in the Coastal Plain and P. alleghaniensis in the western portion of the state, with a broad area of introgression across the middle of the state; or 2) there are two subspecies of a single Ratsnake species P. obsoletus in North Carolina: P. o. alleghaniensis and P. o. quadrivittatus following the distributions above. The "eastern" snakes typically are striped and have more greens and yellows in their coloration, while the "central" snakes have more browns and black with square blotches in their pattern. Areas of introgression result in many "intermediate" phenotypes, meaning that without molecular sequencing, individuals that are not right along the coast or just on the western, mountainous area of North Carolina are likely somewhere "in between" molecularly, with genes from both populations admixed.

The generic epithet Pantherophis is derived from the Greek panther, "panther", and ophis, "snake". The specific epithet alleghaniensis is in reference to the Allegheny Mountains. The specific epithet quadrivittatus is from quattuor, Latin for "four", and vittatus, Latin for "decorated or banded with ribbon", in reference to the dorsal stripes apparent on some individuals.

Taxonomic References: Burbrink et al. (2000); Burbrink (2001); Utiger et al. (2002); Burbrink et al. (2021a, b); Hillis and Wuster (2021); Pyron et al. (2021); Hillis (2022).
Identification
Description: Eastern Ratsnakes are moderately large snakes with heads distinct from the neck. Base dorsal coloration varies across their range. In North Carolina, adults in the southeastern Coastal Plain typically exhibit a green to greenish yellow dorsum with four black longitudinal stripes. The venter is cream to yellow and mottled with gray. Moving north and west, adults are black dorsally, with a prominent white chin; the venter may be white and mottled, becoming darker posteriorly. However, individuals may exhibit a range of intermediate phenotypes, especially as subadults transition out of juvenile coloration (see below). For example, snakes in the Piedmont may exhibit dark stripes more akin to Coastal populations, while Coastal snakes may exhibit blotching typically associated with the northern/western populations. This is a result of extensive introgression over time between the two forms as specified above, not necessarily the result of strict hybridization.

Juvenile ratsnakes are typically pale gray with multiple dark gray to black dorsal blotches, often with a noticeable intraocular stripe. As the snakes age, this pattern will typically fade into some combination of the adult color patterns mentioned above.
Morphological Features: Eastern Ratsnakes typically have 25-29 scale rows at midbody, usually decreasing to 19 posteriorly; middorsal scale rows are typically more noticeably keeled than those laterally. Ventral counts range from 218-258 (222-245 in NC specimens; Palmer and Braswell, 1995), with 46-102 (72-95) subcaudals and an anal plate that is typically divided. Head scale counts are typically as follows: 8 supralabials, 11 infralabials, 1 loreal, 2 nasals, 1 preocular, 2 postoculars, and 2+3-4 temporals. Palmer and Braswell (1995) noted variation in scalation across multiple specimens in NC.

Eastern Ratsnakes have a maximum recorded total length of 256.5 cm (101 inches). Palmer and Braswell (1995) reported a 226.0 cm male specimen from NC. Tail lengths account for approximately 14-20% of total length. Males reach larger sizes than females, have fewer ventrals and more subcaudals, and relatively longer tails than females. Palmer and Braswell (1995) also noted differences in the number of smooth lateral scale rows (more in males) and posterior scale rows (more in males).

Eastern Ratsnakes lack enlarged, grooved posterior teeth or Duvernoy's glands, meaning they are incapable of producing venom. Ratsnakes will typically "kink" their bodies when first spotted, and may rear up if threatened. They will occasionally strike and musk when handled, and though they may cause minor bleeding from bites, they are essentially harmless to humans and pets.
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: Eastern Ratsnakes are relatively common in North Carolina. They are semi-arboreal, and are often found climbing trees, shrubs, buildings, and birdhouses. They may also be found opportunistically on roads, or captured in drift fences.
Distribution in North Carolina
County Map: Clicking on a county returns the records for the species in that county.
Key Habitat Requirements
Habitat: Ratsnakes are adept climbers and spend much time up in trees, where they forage as well as seek shelter. Forested habitats, including hardwoods, pine stands, and cypress-gum swamps are all used. They also forage along forest edges and can be found well out into open areas. However, use of open habitats is probably more occasional and opportunistic than their use of forests and woodlands.
Life History and Autecology
Breeding and Courtship: Due to a complex taxonomic history, summaries of reproductive data for this species complex may include records that are not reflective of North Carolina populations. Per Ernst and Ernst (2003), obsoleta-complex Ratsnakes reach sexual maturity at snout-to-vent lengths greater than 80 cm. Mating occurs in the spring and early summer (April to July), with most North Carolina records in May.
Reproductive Mode: Ratsnakes are oviparous and typically lay eggs in summer (June to early August) that hatch in late spring and summer (late May to August). Clutches average 13–15 white, leathery, elongate, nonadherent eggs that average 46 mm long, but may reach lengths as long as 71 mm (Ernst and Ernst, 2003).

Hatchlings average 34 cm in total length, and weigh approximately 11 g (Palmer and Braswell, 1995; Ernst and Ernst, 2003). They are heavily patterned with lighter dorsal coloration and blotches (see “Description” above), which gradually fade as the snakes age.
Terrestrial Life History: Ratsnakes are primarily diurnal and crepuscular. They are agile climbers and as likely to be seen several meters off the ground as on it, leading to the herpetological maxim “If you look up and wonder ‘how did that snake get up there?’, it’s probably a Ratsnake”. They can also be found crawling on the ground and will cross roads between habitats. Hibernacula include rock crevices, hollow logs and stumps, mammal burrows, and man-made structures including crevices in old buildings and abandoned structures. Ratsnakes have been recorded year-round in North Carolina; most records are from May–July. Whether explicit behavioral differences exist between different genetic populations is not known.

Home range estimates are not known from North Carolina, and due to past (and continuing) taxonomic confusion, any published estimates may not be directly applicable to populations in the state. However, in populations most applicable to NC specimens, home ranges averaged 9.5 hectares (95,000 m2) in Maryland (Durner and Gates, 1993).
General Ecology
Adverse Environmental Impacts
Status in North Carolina
NHP State Rank: S5
Global Rank: G5

Photo Gallery for Pantherophis alleghaniensis-quadrivittatus - Central/Eastern Ratsnake Complex

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

Recorded by: David George, Jame Amoroso, John Amoroso, Meriel Goodwin, Jason Hollinger, Gary Perlmutter
Chatham Co.
Comment: 		Recorded by: Steve Hall and Meriel Goodwin
Chatham Co.
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Recorded by: Andrew W. Jones
Polk Co.
Comment: 		Recorded by: Andrew W. Jones
Polk Co.
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Recorded by: Tom Howard
Brunswick Co.
Comment: 		Recorded by: J. Reynolds
Rockingham Co.
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Recorded by: Salman Abdulali
Pitt Co.
Comment: 		Recorded by: Salman Abdulali
Pitt Co.
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Recorded by: Salman Abdulali
Pitt Co.
Comment: 		Recorded by: J. Mickey
Wilkes Co.
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Recorded by: J. Reynolds
Rockingham Co.
Comment: 		Recorded by: Erich Hofmann and CFCC BIO146 Students
Brunswick Co.
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Recorded by: R. Spainhour, M. Mabe, N. Bowman
Surry Co.
Comment: 		Recorded by: Caleb Garner
Wake Co.
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Recorded by: Caleb Garner
Wake Co.
Comment: 		Recorded by: Caleb Garner
Wake Co.
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Recorded by: Paul Hart, Mary Stevens
Harnett Co.
Comment: 		Recorded by: K. Sanford
Camden Co.
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Recorded by: K. Sanford
Camden Co.
Comment: 		Recorded by: Pat Momich
Madison Co.
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Recorded by: M.Windsor
Onslow Co.
Comment: HABE - bear island cart path		Recorded by: Erich Hofmann and Kayla Weinfurther
New Hanover Co.
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Recorded by: J. Mickey
Wilkes Co.
Comment: 		Recorded by: K. Sanford
Camden Co.
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Recorded by: K. Bischof
Transylvania Co.
Comment: 		Recorded by: C. Teague
Beaufort Co.
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Recorded by: Robert Russo
Caldwell Co.
Comment: 		Recorded by: Spainhour. R
Surry Co.
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Recorded by: Spainhour. R
Surry Co.
Comment: 		Recorded by: Erich Hofmann
New Hanover Co.
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