Eastern foxsnake (Elaphe gloydi) (Carolinian)COSEWIC assessment and status report: chapter 5
Update
COSEWIC Status Report
on the
Eastern Foxsnake
Elaphe gloydi
Carolinian Population
Great Lakes/St. Lawrence Population
in Canada
2008
Species Information
Conant (1940) described the foxsnake throughout its range and concluded that specimens from eastern localities differed from the typical western variety in both habitat and colour pattern. As a result of these differences, and because the eastern and western forms were geographically separated, Conant (1940) described two subspecies: the Western Foxsnake (Elaphe vulpina vulpina) and the Eastern Foxsnake (E. v. gloydi). Morphologically, the only “distinguishing” feature is the number of dorsal blotches: the Western Foxsnake with 32–52 (mean = 41) and the Eastern Foxsnake with fewer and larger dorsal blotches, 28–43 (mean = 35) (Ernst and Barbour 1989, Harding 1997). However, there is no completely reliable morphological separation and the best distinction is simply that their ranges do not overlap (Harding, 1997).
The Latin name vulpina (= fox) has been reported by many authors to derive from the fox-like musk which the snake exudes when disturbed. However, this seems unlikely due to two factors. First, because the specimen originally described by Baird and Girard (1853) was preserved, and was collected by a Reverend Charles Fox, it is more probable that the species name was intended as a Latin translation of the collector’s name (Conant 1940, Rivard 1979, F. Cook pers. comm. 1998). Second, those familiar with both foxsnake and fox odours have commented that they bear little resemblance to each other (J. Wright pers. comm. 1997). The eastern form was named to honour the American herpetologist H. K. Gloyd.
Because the distributions of the Western and Eastern Foxsnakes are allopatric (likely since the end of the Wisconsin glaciation) with no evidence of gene exchange, and are distinct based on external morphology, Collins (1991) recommended that the Eastern Foxsnake be designated a full species, E. gloydi. This proposal was majority approved by a North American snake taxonomy group composed of John E. Cadle, Brian I. Crother, Harry W. Greene, L. Lee Grismer, James A. MacMahon, James R. McCranie, and Samuel S. Sweet. The taxonomic change was not without its detractors, however, as Cook (1991) suggested that splitting the western and eastern forms into two distinct species would obscure important zoogeographic relationships. Nevertheless, this taxonomic change (Eastern Foxsnake = E. gloydi) was recognized in Crother (2001), which standardized names for North American herpetofauna, and has been adopted by federal and provincial agencies in Canada. The taxonomic designation of the Foxsnake remains unsettled, however, both on the specific level (see Genetic Description), and on the generic level. For example, given the recent phylogenetic examinations of Utiger et al. (2002) and Burbrink and Lawson (2007), it seems clear that North American Elaphe (new world ratsnakes), as formerly classified, would comprise a paraphyletic genus. Consequently, reclassification schemes are being examined. Utiger et al. (2002) argued that the Eastern Foxsnake should be called Pantherophis gloydi. However, according to the rationale detailed in Burbrink and Lawson (2007 p.186), the Eastern Foxsnake would most correctly be called Pituophis gloydi.
The Eastern Foxsnake commonly attains lengths of 91–137 cm, and large individuals have measured up to 179 cm SVL (Conant and Collins 1991). Adults usually lack any kind of distinct head pattern or conspicuous markings, and head colouration varies from brown to reddish. The dorsum is patterned with bold, dark brown or black blotches on a yellowish background that alternate with smaller, dark blotches on the sides. The ventral scutes are most often yellow and strongly checkered with black. The scales are weakly keeled and the anal scale is divided. Juveniles have a lighter ground colour (commonly grey), lighter blotches bordered in black, a transverse line anterior to the eyes, and a dark line extending from the eye to angle of jaw on each side (Johnson 1989, Conant and Collins 1991). The dark lines on the head of the juveniles fade with age, and are usually quite faint in adults. Although extremely rare, leucistic specimens are occasionally discovered in wild populations. A melanistic individual was reported from an industrial area in Ohio (Kraus and Schuett 1983).
Elaphe gloydi has many common names which vary by locality. The species has been called timber snake in Ohio, hardwood rattler in parts of Ontario (Johnson 1989), womper in southwestern (SW) Ontario, marsh womper on Pelee Island, and, unfortunately, foxsnakes are also commonly referred to as copperheads due to their reddish head colouration. In Ontario, E. gloydi may be confused with several blotched snake species. These include Massasauga (Sistrurus catenatus), Milksnake (Lampropeltis triangulum), Eastern Hog-nosed Snake (Heterodon platirhinos), Northern Watersnake (Nerodia sipedon), juvenile Blue Racer (Coluber constrictor foxii), and juvenile Gray Ratsnake (Elaphe spiloides). However, Massasaugas have a darker ground colouration with lighter brown or black blotches, a vertical eye pupil, heat-sensitive facial pit, and a distinct rattle at the tip of the tail. Milksnakes are similar in colouration but have smooth scales, undivided anal plates, and a conspicuous head pattern (Y- or V-shaped blotch). Eastern Hog-nosed Snakes have a distinctive upturned snout; watersnakes have a banded, rather than blotched, dorsal pattern; and juvenile Blue Racers have similar blotching patterns but have smooth scales, different colouration on the ventral scutes, and lack the stripe extending from the eye to angle of the jaw in the foxsnake (Harding 1997). Juvenile Gray Ratsnakes can be distinguished from juvenile Eastern Foxsnakes (both are dorsally blotched) by counting ventral scutes: Gray Ratsnakes have 221 or more and Eastern Foxsnakes have 216 or fewer (Conant and Collins 1991).
The foxsnake is heavier and stouter than its congeners (Froom 1972) and while the species is an adept climber, it is probably the least arboreal of the North American Elaphe. The Eastern Foxsnake is a proficient swimmer and will take to the water and swim long distances across bays and between islands (Froom 1972, M. Villeneuve unpubl. data, MacKinnon 2005, Lawson 2005). The foxsnake is one of the most inoffensive of ratsnakes (Staszko and Walls 1994); however, it is particularly prone to ejecting a foul-smelling glandular secretion from the cloacal scent glands when initially disturbed.
Based on analyses of genetic samples collected from Eastern and Western Foxsnake populations, Corey et al. (2005) found that the current species designations (E. gloydi and E. vulpina)--as distinguished by differences in morphological characters and geographical distributions--do not reflect fundamental underlying patterns of genetic differentiation. Specifically, the haplotype “that is found in most E. gloydi individuals is widely shared with at least some E. vulpina individuals, suggesting that E. gloydi, as currently defined, is not a genetically distinct clade within fox snakes as a whole.” (Corey et al. 2005). With further improvements to our understanding of these genetic relationships, it is important to examine whether E. gloydi is sufficiently distinct from E. vulpina to warrant specific status, as this would have implications for estimates of the proportion of the species’ range in Canada. Work currently being conducted by Row and Lougheed (2006, 2007) will help to expand and clarify the findings of Corey et al. (2005), as well as examine the genetic relationships among the foxsnake populations in Ontario. This work is in its second season and is part of the PhD. research of Jeffrey Row.
One of the most interesting results of Row and Lougheed’s work thus far is that populations along Georgian Bay appear to be severely genetically depauperate relative to those in SW Ontario; this pattern is suggestive of a bottleneck or founder effect (Row and Lougheed 2006). Analysis of molecular variance (AMOVA) revealed that a large and significant amount of the total genetic variation could be attributed to differentiation between regional populations (~24%, p < 0.001). Similarly, a significant proportion of the variation could also be attributed to differentiation between local sub-populations (~13%, p < 0.001). At the regional level all pairwise FST and RST comparisons were significant (mean FST = 0.25; mean RST = 0.25 p<0.001 in all pairwise comparisons).
More recent research by Row and Lougheed (2007) indicates that there is much more genetic population structure in the Essex-Kent region than in Haldimand-Norfolk. In brief, Row and Lougheed (2007) genotyped ~250 individuals for ~10 microsatellite loci and estimated the number of genetic populations across southwest Ontario using a program that combines genotypic data and geographic locations. Both ecological and genetic data indicated significant fragmentation of habitat and populations at a fine scale. Overall, there were five Bayesian clusters or “populations”, four in Essex-Kent and one in Haldiman-Norfolk. There was no evidence of recent gene flow among any of these populations. Although, the data indicated less fragmentation in Haldiman-Norfolk, there were fewer samples and more work needs to be done to verify this result (Row and Lougheed, 2007).
Eastern Foxsnakes occupy two Faunal Provinces: Carolinian (Essex-Kent populations and Haldimand-Norfolk populations) and Great Lakes/St. Lawrence (Georgian Bay Coast populations). There are large genetic differences among the three regional populations (Row and Lougheed, 2006, 2007, Jeff Row, e-mail communication Feb 10, 2008). However, mtDNA indicates that the separation was not pre-glacial (Corey et al., 2005). Two DUs (Great Lakes/St. Lawrence (Georgian Bay Coast population) and Carolinian) are justified according to the following points;
- There are significant genetic differences (DNA microsatellies) between the Georgian Bay Coast populations and those of Essex-Kent or Haldimand-Norfolk
- There is no gene flow between Georgian Bay Coast populations and the other regions nor is there likely to be in the future.
- Although there are no known morphological differences between the two regions, there are large behavioural differences (see Biology section). These may be expressions of phenotypic plasticity, but they also could represent adaptive genetic variation.
- The Georgian Bay Coast populations occupy a clearly disjunct and separate Faunal Province from the other two regional populations (Essex-Kent and Haldimand-Norfolk). This separation has likely been longstanding and movement between the two Faunal Provinces will not occur in the foreseeable future. Furthermore, this disjunction is likely to lead to evolution of different local adaptations if indeed it has not already done so.
- Persistence of the two putative DUs is likely to lead to local adaptations given the distinct differences in ecological setting.
- Loss of either DU would result in a large gap in the range of the foxsnake in Canada.
- It can be asserted that the Great Lakes/St. Lawrence populations represent a unique natural occurrence of this species globally given this DUs unique habitat and behaviour/ecology.
Page details
- Date modified: