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Pituophis ruthveni

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA REPTILIA SQUAMATA COLUBRIDAE

Scientific Name: Pituophis ruthveni
Species Authority: Stull, 1929
Common Name(s):
English Louisiana Pinesnake, Louisiana Pine Snake
Taxonomic Notes: Pituophis ruthveni formerly was included in P. melanoleucus. In recent years many authors have regarded the gopher snakes and bullsnake as a species (P. catenifer) distinct from the Pine Snake (P. melanoleucus) and Louisiana Pine Snake (P. ruthveni). This classification, though not unequivocally supported by available data, has been adopted in this database.

Reichling's (1995) analysis led him to concur that ruthveni is phenetically distinct and is a valid evolutionary species, though he referred to it consistently as P. m. ruthveni, probably in acknowledgment that the status of the nominal Pituophis subspecies still need further study.

Rodriguez-Robles and De Jesus-Escobar (2000) examined rangewide mtDNA variation in Pituophis and found two divergent, allopatric segments: (1) the lodingi-melanoleucus-mugitus eastern pinesnake clade and (2) the affinis-annectens-bimaris-catenifer-deserticola-sayi-ruthveni-vertebralis clade. These two clades were recognized as distinct species (P. melanoleucus and P. catenifer). The taxon ruthveni was also recognized as a distinct species because it is a diagnosable allopatric entity. However, it has strong genetic affinities to sayi - some ruthveni are more closely related to sayi than to other ruthveni. Thus P. ruthveni may not be monophyletic, which calls into question its status as a distinct species. Nevertheless, Crother et al. (2000) and Collins and Taggart (2002) accepted P. ruthveni as a distinct species. In contrast, Ernst and Ernst (2003) treated ruthveni as a subspecies of P. catenifer, emphasizing the closer relationship between ruthveni and catenifer than between ruthveni and P. melanoleucus.

Assessment Information [top]

Red List Category & Criteria: Endangered B2ab(iii) ver 3.1
Year Published: 2007
Date Assessed: 2007-03-01
Assessor(s): Hammerson, G.A.
Reviewer(s): Cox, N., Chanson, J.S. & Stuart, S.N. (Global Reptile Assessment Coordinating Team)
Justification:
Listed as Endangered because the known area of occupancy is estimated to encompass less than 500 km², it is experiencing a continuing decline, and populations are severely fragmented. Additionally, population size may be fewer than 10,000 adults, and no subpopulation is estimated to contain more than 1,000 mature individuals (qualifies it as Vulnerable under C2a(i)).

Geographic Range [top]

Range Description: The Louisiana Pine Snake historically occurred in portions of west-central Louisiana and extreme east-central Texas (Jennings and Fritts 1983, Dundee and Rossman 1989, Conant and Collins 199, Rudolph in litt. 1999, Werler and Dixon 2000). This area roughly coincides with a disjunct portion of the longleaf pine ecosystem situated west of the Mississippi River. The species is currently extant in a small portion of the historical range (Rudolph et al. 2006).
Countries:
Native:
United States
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: This species is represented by a small number of occurrences (subpopulations). Based on recent range-wide surveys, Rudolph et al. (2006) mapped the extant distribution as comprising six small patches, plus two additional locations represented by single individuals in areas lacking significant amounts of suitable habitat. Only three areas (Fort Polk Military Reservation and the adjacent unit of the Kisatchie National Forest, Peason Ridge Military Reservation in Louisiana, and the southern portion of the Angelina National Forest in Texas) have extensive areas of suitable, frequently burned longleaf pine habitat that is not currently subject to extensive change in management intensity (Rudolph et al. 2006). The adult population size is unknown but relatively small and presumably at least a few thousand. This snake is uncommon to rare (Rudolph et al. 2006). Rudolph et al. (2006) conducted extensive trapping in several areas of Louisiana and Texas identified as having most of the best remaining habitat for Louisiana pine snakes. Only 26 pine snakes were trapped in over 100,000 trap days. Surveys documenting the current condition of the fire climax longleaf pine forests, and results of Louisiana pine snake trapping and radio-telemetry, suggest that the species has declined in geographic distribution and possibly in local abundance during the last 50 to 80 years (Rudolph et al. 2006). Louisiana pine snakes originally occurred in at least 9 Louisiana parishes and 15 Texas counties; recent surveys indicate that the species now occurs in only four Louisiana parishes and six Texas counties (Rudolph et al. 2006). Both the quantity and quality of Longleaf Pine savanna have declined sharply in Louisiana and Texas. Virtually all remaining virgin timber in the south was cut during intensive logging from 1870 to 1920 (Frost 1993). In the 1920s, foresters began converting unmanaged woodlands to pine plantations (Frost 1993). Wahlenberg (1946) estimated that in 1935, 1.2 million ha (approximately 3 million acres) of Longleaf Pine type forests remained in southwest Louisiana and southeast Texas. However, 43% of these Longleaf Pine types consisted of clear-cuts and only 2.9% were uncut old-growth stands. Bridges and Orzell (1989) used published data from the 1980s to make more current estimates of the natural Longleaf Pine forests remaining in Louisiana and Texas. They estimated that in Louisiana only 15%, and in Texas only 7.5% of the 1935 acreages remained. A habitat assessment of known historical localities found that only 34% were still considered capable of supporting a viable population of pine snakes. Its area of occupancy, number of subpopulations, and population size are probably still declining, but the rate of decline is unknown.
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: Habitat consists of longleaf pine savanna with sandy, well-drained soils and substantial herbaceous ground cover (Reichling 1990, Rudolph and Burgdorf 1997). Recent records of this snake are primarily from isolated patches of habitat where the influence of fire has been most effective in maintaining well-developed herbaceous understorey conditions (Rudolph et al. 2006). In Texas, these snakes occur in longleaf pine-oak sandhills interspersed with moist bottomlands; sometimes in adjacent blackjack oak woodlands and in sandy areas of short-leaf pine/post oak forest; the snake prefers openly wooded areas over dense forest; it is frequently found in fields, farmland, and tracts of second-growth timber (Werler and Dixon 2000). In Texas, Mitchell and Tinkle (1960) reported observing P. ruthveni foraging in a seasonally dry, acid bog, where the vegetation consisted of loblolly pine (Pinus taeda) and shortleaf pine (Pinus echinata) with a dense sweetbay (Magnolia virginiana) and cyrilla (Cyrilla racemiflora) understorey. In Louisiana, P. ruthveni is restricted to longleaf pine forests and second growth longleaf pine-blackjack oak (Quercus marilandica) associations (Fugler 1955, Walker 1965). Pocket gophers (Geomys breviceps) are an essential component of this habitat. They create burrow systems where the snakes are most frequently found and are a major source of food for the species (Rudolph and Conner 1996, Rudolph in litt. 1997). Movement patterns of pine snakes are typically from one pocket gopher burrow system to another (Rudolph in litt. 1997).
Systems: Terrestrial

Threats [top]

Major Threat(s): The primary factors leading to degradation of P. ruthveni habitat are intensive pine silviculture and alteration of the pre-European fire regime (Rudolph et al. 2006). Intensive silviculture and reduction in fire frequency eliminate or reduce the microhabitat conditions needed by pine snakes and also may result in declines of Geomys breviceps (Baird's Pocket Gopher), a primary prey of P. ruthveni (Rudolph et al. 2006). Vehicle mortality, both on state roads and off-road trails, may cause significant impacts to the Louisiana Pine Snake's population numbers and community structure. Roads with moderate to high traffic levels can cause significant reductions in the populations of large snake species (see Rudolph et al. 2006). Most existing pine snake habitat is within 500 m of currently existing roads (Rudolph et al. 2006). Take of Louisiana pine snakes for commercial, recreational, scientific, or educational purposes is not currently considered to be a threat. However, the low number of Louisiana pine snakes makes them vulnerable to unscrupulous collectors should locality data become available. Disease and predation are not currently considered to be significant threats.

Conservation Actions [top]

Conservation Actions: In March of 2004, a Candidate Conservation Agreement was developed and approved in order to identify and establish management protection for the pine snake on Federal land by protecting known populations and habitat, reducing threats to its survival, maintaining its ecosystem, and restoring degraded habitat. This agreement was intended to establish a framework for cooperation and participation in the pine snake's protection, conservation, and management within the boundaries of the Angelina and Sabine National Forests of Texas, Kisatchie National Forest in Louisiana, and Fort Polk Military Reservation in Louisiana. This agreement was implemented by the USDA Forest Service; Fort Polk, US Army, Department of Defense (Fort Polk); Region 2 and 4 of the US Fish and Wildlife Service; Texas Parks and Wildlife Department; and Louisiana Department of Wildlife and Fisheries. Restoration measures will include prescribed burning, thinning, and replanting of long-leaf pine forest.

Citation: Hammerson, G.A. 2007. Pituophis ruthveni. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 24 July 2014.
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