Terrapene nelsoni, Stejneger 1925 (spotted box turtle)

Known from only a handful of localities in the Sierra Madre Occidental of western Mexico, the Spotted Box Turtle, Terrapene nelsoni (Family Emydidae), remains one of the least known chelonian species of North America. Only at the type locality and at one site in Chihuahua have more than four specimens been recorded, most other records consisting of incidental finds or acquisition of solitary specimens. Population density, natural history, and reproductive parameters are thus not understood, and even the favored microhabitat of the species is uncertain. Often the habitat is of difficult access, precipitous, and the turtles themselves seem to have a short activity season, coinciding with the summer monsoon. Most literature on the species is limited to physical description of specimens, on the basis of which two subspecies have been recognized. Based on comparisons of 32 morphological features, the most recent phylogenetic analysis of genus Terra- pene has confirmed the close relationship of T. nelsoni to T. ornata, to which it is parapatric in the northern portion of its range. No threats to the species are currently known, and it is classified as Data Deficient on the IUCN Red List. Monitoring for the possibility of an international pet trade developing would be advisable.

Distribution – Mexico. Records exist from five Mexican states: Chihuahua, Jalisco, Nayarit, Sinaloa, and Sonora, with those from the latter outnumbering all the others combined. All locali- ties are restricted to the Pacific versant of the Sierra Madre Occidental in montane regions from approximately 450 m to at least 1640 m. It is the only Terrapene species found to the west of the Cordillera. More than 200 km separate the southernmost record for the species (near Guachi- nango, Jalisco) from the type locality (Pedro Pablo, Nayarit), which in turn lies more than 600 km southeast of the nearest confirmed locality to the north (near Terreros, Sinaloa) suggesting that the species is either more widespread than documented, or that its range is fragmented.

Subspecies – Two subspecies are currently recognized: Terrapene nelsoni nelsoni (Southern Spot- ted Box Turtle) (distribution: Nayarit, Jalisco, and southern Sinaloa, Mexico) and Terrapene nelsoni klauberi (Northern Spotted Box Turtle) (synonymy: Terrapene klauberi Bogert 1943) (distribution: Sonora, Chihuahua, and northern Sinaloa, Mexico).

Synonymy – Terrapene nelsoni Stejneger 1925.

Status – IUCN 2011 Red List: Data Deficient (DD, assessed 1996, needs updating); CITES: Appendix II, as Terrapene spp.; Mexico: Pr (2.2.4., Subject to Special Protection).