Overview

Brief Summary

Summary

The Big Bend slider, Trachemys gaigeae (Family Emydidae), is a medium-sized freshwater turtle (carapace length to 308 mm) that is limited to riverine areas of the desert southwestern United States and northern Mexico. Two allopatric subspecies are currently recognized, T. g. gaigeae and T. g. hartwegi, which might represent distinct species. Degradation and fragmentation of riverine habitat is likely the most significant threat to T. gaigeae in both the United States and Mexico. Overcollecting for the pet trade or as food and hybridization with introduced Trachemys scripta are also of concern, although more information is needed. Commercial collection is prohibited in the United States but otherwise this slider receives little protection, except where it occurs on public lands. The species uses reservoirs and artificial ponds in New Mexico, suggesting some adaptability to human-modified environments. The status and ecology of this species in the United States has been little studied until recently and even less is known about populations in Mexico.
  • Stuart, J.N. and Ward, J.P. 2009. Trachemys gaigeae (Hartweg 1939) – Big Bend slider, Mexican Plateau slider, jicotea de la Meseta Mexicana. In: Rhodin, A.G.J., Pritchard, P.C.H., van Dijk, P.P., Saumure, R.A., Buhlmann, K.A., Iverson, J.B., and Mittermeier, R.A. (Eds.). Conservation Biology of Freshwater Turtles and Tortoises: A Compilation Project of the IUCN/SSC Tortoise and Freshwater Turtle Specialist Group. Chelonian Research Monographs No. 5, pp. 032.1-032.12, doi:10.3854/crm.5.032.gaigeae.v1.2009, http://www.iucn-tftsg.org/cbftt
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Distribution

occurs (regularly, as a native taxon) in multiple nations

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National Distribution

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

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Global Range: (20,000-200,000 square km (about 8000-80,000 square miles)) Rio Grande and Rio Nazas drainage systems of southern New Mexico, Texas, and northeastern Mexico (Chihuahua, Coahuila, and Durango) (Stuart and Ernst 2004). Most records in the Rio Grande along the border of the United States and Mexico are downstream of the Rio Conchos confluence; only a couple documented localities between New Mexico and the Rio Conchos (Stuart and Ernst 2004). Current distribution in New Mexico is limited to the Rio Grande from Caballo Dam upstream to at least the Bosque del Apache Refuge (Stuart 1997).

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Mexico, USA. Occurs in the Rio Grande (= Río Bravo del Norte) drainage from south-central New Mexico downstream to western Texas and northwestern Coahuila, the Río Conchos in Mexico from southern Chihuahua downstream to the confluence with the Rio Grande, and the Río Nazas closed basin of Durango and Coahuila, Mexico.
  • Stuart, J.N. and Ward, J.P. 2009. Trachemys gaigeae (Hartweg 1939) – Big Bend slider, Mexican Plateau slider, jicotea de la Meseta Mexicana. In: Rhodin, A.G.J., Pritchard, P.C.H., van Dijk, P.P., Saumure, R.A., Buhlmann, K.A., Iverson, J.B., and Mittermeier, R.A. (Eds.). Conservation Biology of Freshwater Turtles and Tortoises: A Compilation Project of the IUCN/SSC Tortoise and Freshwater Turtle Specialist Group. Chelonian Research Monographs No. 5, pp. 032.1-032.12, doi:10.3854/crm.5.032.gaigeae.v1.2009, http://www.iucn-tftsg.org/cbftt
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Continent: Middle-America North-America
Distribution: USA (S New Mexico,SW Texas), Mexico (Rio Conchos system in Chihuahua, Coahuila)  gaigeae: Mexico (Chihuahua, Coahuila), USA (New Mexico;
Type locality: “Boquillas, Rio Grande River, Brewster County, Texas.”  hartwegi: Mexico (NE Durango, SW Coahuila)
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
Trachemys gaigeae gaigea inhabits mainly pools and backwaters in the main Rio Grande and Conchos valleys, rarely moving inland away from the main river. It has also been recorded from reservoirs (Ernst et al. 1994). Subspecies hartwegi apparently inhabits the main channel of the Rio Nazas. Wild animals of ssp. gaigeae are apparently nearly exclusively herbivorous (Legler 1960), although captives readily fed on fish (Ernst et al. 1994).

Males of ssp. gaigeae become sexually mature at carapace length (CL) of about 11 cm and reach a maximum CL of 17 cm, while females reach sexual maturity at about 17 cm CL and can reach a maximum size of 22 cm. Females produce clutches of 6-11 eggs (Legler 1960). A dissected large female of ssp. hartwegi would likely have produced three clutches totaling 48 eggs (Legler 1990).

Systems
  • Terrestrial
  • Freshwater
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Comments: Rivers with permanent water (at least permanent pools); ponds, impoundments, and stock tanks along the Rio Grande; basks on shore, logs, vegetation mats, or at water surface (Bartlett and Bartlett 1999). A nest in New Mexico was on level sandy ground among forbs, 25 m from a large shallow pond (Morjan and Stuart 2001).

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Migration

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

A marked female in New Mexico was found nesting in 1999 about 2.2 km from a pond in which she had been found in 1998 and 1994; the areas were linked by a canal, and a pond was present near the nesting site (Morjan and Stuart 2001).

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Trophic Strategy

Comments: A female in New Mexico defecated remains of filamentous algae, Potamogeton, and crayfish (Morjan and Stuart 2001).

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Population Biology

Number of Occurrences

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 6 - 20

Comments: Stuart and Ernst (2004) mapped 28 localities concentrated in three areas; these may represent perhaps a dozen or more distinct occurrences. Degenhardt et al. (1996) mapped 6 locality records in New Mexico (one extirpated).

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Global Abundance

2500 - 100,000 individuals

Comments: Common within range, but not abundant (A. Price, pers. comm., 1997). Common along many stretches of the Rio Grande in Texas (Bartlett and Bartlett 1999). Monitored for past 20 years during float trips on the Rio Grande, Texas; approximately 5-6 turtles/mile (D. Miller, pers. comm., 1997). Fairly common in canals and ponds in the Bosque del Apache National Wildlife Refuge, New Mexico (New Mexico Department of Game and Fish 1996). May regularly move among waterbodies (i.e., unit ponds), thus complicating any efforts to determine population densities at a given site (Stuart 1997).

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Life History and Behavior

Reproduction

Nesting has been observed on May 31 in New Mexico; clutch size is 6-29; hatchlings overwinter in the nest (see Morjan and Stuart 1999).

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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Trachemys gaigeae

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 1
Species With Barcodes: 1
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
VU
Vulnerable

Red List Criteria
A2ce+4ce

Version
3.1

Year Assessed
2013

Assessor/s
van Dijk, P.P.

Reviewer/s
Horne, B.D., Mittermeier, R.A., Philippen, H.-D., Quinn, H.R., Rhodin, A.G.J., Shaffer, H.B. & Vogt, R.C

Contributor/s

Justification

Both subspecies of Trachemys gaigeae are restricted to relatively limited sections of main river valleys subject to major hydrological management and engineering works, with pollution and hybridisation as additional potential threats; available population data indicate a common to uncommon species declining in abundance, and hartwegi specifically going extinct across substantial areas of occurrence. Subspecies hartwegi qualifies for Endangered A2bc A4bc B2a+b(i,ii,iii,iv,v).

Trachemys gaigeae is currently listed as Vulnerable.


History
  • 1996
    Vulnerable
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National NatureServe Conservation Status

United States

Rounded National Status Rank: N2 - Imperiled

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NatureServe Conservation Status

Rounded Global Status Rank: G3 - Vulnerable

Reasons: Small range in Rio Grande drainage of Texas, New Mexico, and Mexico; trend may be stable or declining; threats include stream flow alterations and shooting; hybridizing uncommonly with introduced T. SCRIPTA.

Intrinsic Vulnerability: Highly to moderately vulnerable.

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Status

IUCN 2009 Red List: Vulnerable (VU A1c,D2) (assessed 1996, needs updating); CITES: Not Listed; US ESA: Not Listed; New Mexico: Species of Greatest Conservation Need.
  • Stuart, J.N. and Ward, J.P. 2009. Trachemys gaigeae (Hartweg 1939) – Big Bend slider, Mexican Plateau slider, jicotea de la Meseta Mexicana. In: Rhodin, A.G.J., Pritchard, P.C.H., van Dijk, P.P., Saumure, R.A., Buhlmann, K.A., Iverson, J.B., and Mittermeier, R.A. (Eds.). Conservation Biology of Freshwater Turtles and Tortoises: A Compilation Project of the IUCN/SSC Tortoise and Freshwater Turtle Specialist Group. Chelonian Research Monographs No. 5, pp. 032.1-032.12, doi:10.3854/crm.5.032.gaigeae.v1.2009, http://www.iucn-tftsg.org/cbftt
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Population

Population
Very little information is available; based on distribution records it appears that T.g. gaigeae is fragmented into a number of isolated subpopulations along the upper Grande and Conchos; where monitored, most of these subpopulations appear reasonably stable. Price (1997, in Clausen and Hammerson 2005) considered ssp. gaigeae ‘common within range but not abundant’, and Miller (idem) monitored the species during 20 years of float trips on the Rio Grande, recording three to four turtles per km. Surveys in New Mexico in the 1990s indicated some shrinking populations (NM DGF, in Clausen and Hammerson 2005). Subspecies gaigeae is rated Vulnerable in New Mexico and Imperiled in Texas (Clausen and Hammerson 2005).

Concerning the ssp. hartwegi, Legler (1990) wrote of ‘tail waters below the dam’ and that the population in the vicinity of San Pedro de las Colonias may be nearing extinction, and elsewhere (ibid, p. 96) that ‘Aridity and increased use of water for irrigation may have placed hartwegi populations in danger everywhere except in the immediate region of the Presa El Palmito’. The subspecies became extinct in the Laguna Viesca since 1960 (Legler 1990).

Population Trend
Unknown
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Global Short Term Trend: Relatively stable to decline of 30%

Comments: In Texas, declining to stable, long-lived and difficult-to-observe population over a short period (A. Price, pers. comm., 1997). Rio Grande populations associated with the Big Bend region are stable (C. Lieb and D. Miller, pes. comm., 1997). Common at Elephant Butte Lake (A. Price, pers. comm., 1997). Recent surveys in New Mexico indicate the population may be shrinking (New Mexico Department of Game and Fish 1996). Existing populations in the Rio Grande of New Mexico appear to be stable, although restricted in geographic area (Stuart 1997). May have been extirpated or experienced a decline at the La Joya State Waterfowl Area in recent decades; evidence for an established population at this site at any time in history is scant (Stuart 1997).

Global Long Term Trend: Relatively stable to decline of 50%

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Threats

Major Threats
Pollution, hydrological projects, and other forms of habitat degradation, mortality from shooting target practice ('plinking'), past collection for pet trade and subsistence consumption, and occasional hybridisation with T. scripta elegans, are recorded threats (Clausen and Hammerson 2005).
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Degree of Threat: Medium

Comments: Evidently hybridizing uncommonly with introduced TRACHEMYS SCRIPTA in New Mexico (Stuart 1995, Herpetological Review 26:107). Threatened by stream flow alteration in the Rio Grande, Texas (A. Price, pers. comm., 1997) and deliberate take by recreationists for target practice (New Mexico Department of Game and Fish 1996). At present, no clearly defined threats in the Rio Grande, New Mexico: unknown if current water management practices have an impact; however, dewatering at La Joya site could have a great impact on aquatic turtles; maintenance of deepwater marsh and pond sites is necessary for persistence in nonreservoir reaches of the river; reduction of surface water in the La Joya-Elephant Butte reach would likely have an adverse impact; commercial collecting apparently is not a current threat; shooting was not seen during 1992-1996 surveys, but monitoring is required to evaluate this potential threat and additional unknown future threats (Stuart 1997). Readily leaves basking sites when disturbed, but the impact of human prescence is negligible; a constant human prescence could cause abandonment of basking and nesting sites (J. Stuart, pers. comm., 1997).

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Management

Conservation Actions

Conservation Actions

Turtles in general are protected from exploitation under Mexican wildlife and natural resource legislation. Trachemys gaigeae gaigeae inhabits a number of protected areas, including being fairly common in the Bosque del Apache NWR (Clausen and Hammerson 2005) and occurring in the Canon de Santa Elena FFPA - Big Bend NP - Maderas del Carmen FFPA - Rio Grande National Scenic River cluster of protected areas. It appears that there are no protected areas located within the range of T. g. hartwegi.

Much more information on population status, natural history and conservation status are urgently needed, particularly for the subspecies hartwegi. Based on study results, the species may warrant specific legal protection in the USA.

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Biological Research Needs: Clarify taxonomic status and determine relationship with TRACHEMYS SCRIPTA; further investigate life history (Degenhardt et al. 1996). Determine sensitivity to disturbance at localities with high abundance at Bosque del Apache and Elephant Butte in New Mexico (J. Stuart, pers. comm., 1997). Determine potential affects of water management practices and killing.

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Global Protection: Few (1-3) occurrences appropriately protected and managed

Comments: Occurs in Bosque del Apache National Wildlife Refuge and other federal lands; other than restrictions on take, limited protection is afforded (New Mexico Department of Game and Fish 1996).

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Wikipedia

Big bend slider

The Big Bend Slider (Trachemys gaigeae) is a species of aquatic turtle native to the United States in the states of New Mexico and Texas, and northern Mexico in the state of Chihuahua. It is found primarily in the Rio Grande and Rio Conchos river systems. The epithet gaigeae is in honor of the American herpetologist, Helen Beulah Thompson Gaige, who collected the first specimen in the Big Bend region of Texas in 1928.[1] The species was first described by professor of zoology at the University of Michigan, Dr. Norman Edouard Hartweg in 1939. It was for a time considered to be a species of Cooter, genus Pseudemys, and then a subspecies of the Pond Slider, Trachemys scripta, but it was granted full species status, though many sources still refer to it by its various synonyms.

Behavior[edit]

Primarily aquatic, they are often seen basking on rocks or logs in the water, and when approached quickly dive to the bottom. They only time they spend a large amount of time on land is when the females emerge to lay their eggs. They are an omnivorous species, with younger animals being more carnivorous, and progressively becoming more herbivorous as they age, with older adults being nearly entirely herbivorous. Adults 5 to 11 inches long.

Subspecies[edit]

References[edit]

  1. ^ Fritz Uwe; Peter Havaš (2007). "Checklist of Chelonians of the World". Vertebrate Zoology 57 (2): 205. Archived from the original on 2010-12-17. Retrieved 29 May 2012. 
  • Stebbins RC (2003) Western Reptiles and Amphibians, Peterson Field Guides
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Names and Taxonomy

Taxonomy

Comments: Trachemys gaigeae has been regarded as a subspecies of Trachemys scripta or T. nebulosa. Ernst (1992) and Seidel et al. (1999) reviewed the taxonomic history and justification for species status. Seidel (2002) concurred that T. gaigeae warrants species status.

Trachemys gaigeae hartwegi formerly was regraded as a subspecies of Trachemys scripta. Seidel (2002) and Stuart and Ernst (2004) recognized hartwegi as a subspecies of T. gaigeae but noted that further study may prove that gaigeae and hartwegi are distinct species. Crother et al. (2003) and Stuart and Ernst (2004) updated the common name of T. gaigeae to Mexican Plateau Slider.

Based on morphological and hemoglobin data, Seidel et al. (1999) concluded that T. scripta cataspila is a species distinct from Trachemys scripta, but appropriate nomenclature for the proposed new species must await a broader phylogenetic analysis of all forms in the complex.

See Jackson (1988) for review of fossil record in relation to taxonomic status of genus Trachemys.

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Subspecies

Two currently recognized: Trachemys gaigeae gaigeae (Big Bend Slider, Jicotea de Gaige) and Trachemys gaigeae hartwegi (Nazas Slider, Jicotea del Nazas) (synonymy: Pseudemys scripta hartwegi Legler 1990, Chrysemys scripta hartwegi, Trachemys scripta hartwegi, Trachemys nebulosa hartwegi, Trachemys ornata hartwegi, Trachemys hartwegi).
  • Stuart, J.N. and Ward, J.P. 2009. Trachemys gaigeae (Hartweg 1939) – Big Bend slider, Mexican Plateau slider, jicotea de la Meseta Mexicana. In: Rhodin, A.G.J., Pritchard, P.C.H., van Dijk, P.P., Saumure, R.A., Buhlmann, K.A., Iverson, J.B., and Mittermeier, R.A. (Eds.). Conservation Biology of Freshwater Turtles and Tortoises: A Compilation Project of the IUCN/SSC Tortoise and Freshwater Turtle Specialist Group. Chelonian Research Monographs No. 5, pp. 032.1-032.12, doi:10.3854/crm.5.032.gaigeae.v1.2009, http://www.iucn-tftsg.org/cbftt
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