Traditionally considered a subspecies of Trachemys scripta, recognised as full species by several authors, including Seidel (2002). Seidel (2002) placed two taxa as subspecies of T. gaigeae: T. gaigeae gaigeae (Hartweg, 1939), and T. gaigeae hartwegi (Legler, 1990).

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.

Trachemys gaigeae gaigeae: Upper Rio Grande and Rio Conchos basin of New Mexico-Texas, USA, and Chihuahua-Coahuila, Mexico.
Trachemys gaigeae hartwegi: Rio Nazas basin of Durango and adjacent Coahuila, Mexico (Iverson 1992, Seidel 2002).

Both gaigeae and hartwegi were hypothesized by Legler (1990) to have evolved in the endorrheic basins of northern Mexico and adjacent USA, before the Conchos and upper Rio Grande were captured by the Pecos-Grande system. The distribution of T. gaigeae gaigeae is parapatric to Pseudemys gorzugi and Trachemys scripta elegans.

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).

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).

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).

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.