ANSWERING QUESTIONS ABOUT DESERT TORTOISES
A GUIDE FOR PEOPLE WHO WORK WITH THE PUBLIC
Kristin H. Berry & Timothy Duck
APPENDIX 3

CHAPTER 1
CHAPTER 2
CHAPTER 3
CHAPTER 4
CHAPTER 5
CHAPTER 6
CHAPTER 7
APPENDIX 1
APPENDIX 2
APPENDIX 3

Appendix 3: Turtles And Tortoises That May be Mistaken For Desert Tortoises

by Michael J. Connor
Agency officials are often contacted by members of the public regarding a desert tortoise they may have seen or found.  For an official to offer the appropriate advise, the identification of the animal must be confirmed.  This is particularly important if unusual characteristics are reported such as large size or aberrant coloration or behavior.  Many species of turtles and tortoises are kept as pets and may be mistaken for desert tortoises.  The table below lists some of the species that have been reported as desert tortoises by members of the public and are commonly kept in captivity based on statistics maintained by the California Turtle and Tortoise Club (CTTC).  These species may be encountered in the field as escapees or after being deliberately released.
 
Using the table:
Carapace
N Nuchal (Cervical)
M Marginal
P Parietal
C Central (Vertebral)
S Supracaudal		Plastron
I Intergular
G Gular
H Humeral
P Pectoral
Ax Axillary
The "description" includes adult straight line carapace length. Approximate straight line carapace length can be measured by standing the tortoise over a ruler. The "diagnostic" indicates key differences from desert tortoises. Agency officials should be aware that turtles and tortoises raised in captivity often show shell abnormalities.  This often takes the form of unusually flattened shells or abnormal "pyramiding" of the scutes and underlying bone that affects their appearance. Other indicators of captivity include tethers and holes in the shell to hold a tether. The nuchal (or cervical) scute present in the desert tortoise is absent from the carapace of several of the more confusing species. Detailed dichotomous keys can be found in the references cited below.  "Captive status" indicates the abundance of the species in captivity categorized as Rare (<0.1%), Frequent (0.1% to 1.0%), Common (1% to 5%), and Abundant (>5%) based on adoption and rescue statistics for 2005 maintained by CTTC.  Desert tortoises are in the abundant category and accounted for 30.4% of the 2,070 animals reported in 2005.  "Desert survivorship" is an indication of their likely long-term survival after release in U.S. deserts. Click on the images to see larger images.

 

Gopherus berlandieri, Texas Tortoise


Origin: Southern Texas through eastern Coahuila to Tamaulipas, Mexico. Description: Small tortoises, to 22 cm (8.5 in).
Diagnostic: The Texas tortoise has a rougher and broader or more squared-off shell; more pointed, triangular head; paired axillary scutes; often found with a reduced or lost nuchal scute.		 Hybridization: Known to hybridize with G. agassizii. 
Disease: May harbor Mycoplasma.
Desert Survivorship: Possible?
 

 

 Captive Status: Frequent. Accounted for 0.68% of chelonians placed by CTTC in 2005.

This species has been seen in desert tortoise habitat and removed from the wild.
 

Geochelone sulcata, African Spurred Tortoise


Origin: Southern perimeter of the Sahara Desert from Ethiopia west to Senegal. Description: Robust, large tortoises to frequently misidentified as desert tortoises. The largest species of mainland tortoise, to 80 cm (32 in).
Diagnostics: Nuchal scute absent; large prefrontal scales on head; large spurs on hind limbs.		 Hybridization: Unlikely with G. agassizii.
Disease: known to carry Mycoplasma and may have Herpes.
Desert Survivorship: A low frost tolerance limits their long term survival chances in most U.S. deserts.		 Captive Status: Common. Accounted for 4% of chelonians placed by CTTC in 2005.  The number has increased 4 fold over the last 5 years. 

This species has been seen in desert tortoise habitat and removed from the wild.
 

Geochelone pardalis, Leopard Tortoise


Origin: Southern Sudan south through eastern Africa to South Africa. Description: Medium to large tortoises, to 68 cm (27 in) (most are smaller).
Diagnostic: Nuchal scute absent; typically high domed; 2 large prefrontal scales on head; straw colored, patterned shell with contrast decreasing with age and size.		 Hybridization: Unlikely with G. agassizii.
Disease: May harbor Mycoplasma, Herpes and ticks.
Desert Survivorship: Considered low; most captive stock are from tropical populations.		 Captive Status: Frequent. Accounted for 0.24% of chelonians placed by CTTC in 2005.
 

Testudo horsfieldii, Russian or Steppe Tortoise


Origin: Caspian Sea area southeast through to Pakistan. Description: Small tortoises, to 22 cm (8 in).
Diagnostic: Typically flat rounded shells almost as broad as long; 4 claws on front feet; plastron black with yellow seams; tail ends in a horny "nail". 		Hybridization: Unlikely with G. agassizii.
Disease: May harbor Mycoplasma and Herpes.
Desert Survivorship: possible?		 Captive Status: Common.  Accounted for 3% of chelonians placed by CTTC in 2005. Common in the commercial pet trade.
 

Testudo graeca, Mediterranean Spur-thighed tortoise


Origin: Southern Spain, coastal north Africa to Israel and Syria and from northern Greece eastwards through Turkey to Iran. Description: Small to medium sized tortoises, to 30 cm (12 in).
Diagnostic: Domed shells, highest behind the center; gulars are short and do not extend beyond the carapace; each thigh bears a tubercle or "wart".		 Hybridization: Unlikely with G. agassizii.
Disease: May harbor Mycoplasma agassizii and other species of Mycoplasma from Europe, as well as Herpes.
Desert Survivorship: Low. Generally does well in a Mediterranean climate.		 Captive Status: Frequent.  Accounted for 0.1% of chelonians placed by CTTC in 2005. Formerly common in the commercial pet trade.
 

Trachemys scripta elegans, Red-eared slider


Origin: Mississippi Valley from Illinois to the Gulf of Mexico. Description: Medium sized water turtles, to 28 cm (11 in).
Diagnostic: Flattened shells; webbed hind feet; often colored markings on skin of head and limbs; markings on shell and plastron; note peeling of scute outer lamellae is a normal process in this species.		 Hybridization: No.
Disease: May harbor Salmonella.
Desert Survivorship: no.		 Captive Status: Abundant.  Accounted for 51% of chelonians placed by CTTC in 2005. Trachemys are the commonest of all captive turtles. Tens of millions of hatchlings are produced each year for commercial trade.

Attempted release intercepted at the DTNA.
 

Actinemys (Clemmys) marmorata, Pacific or Western pond turtle

Origin: North America west of the Cascade-Sierra Crest. Description: Small water turtles, to 19 cm (7.5 in).
Diagnostic: Flat shell; webbed feet; long tail.		 Hybridization: No.
Disease: ?
Desert Survivorship: Occurs naturally in a few riparian areas within desert tortoise habitat.		 Captive Status: Common. Accounted for 1% of chelonians handled by the CTTC Adoption program in 2005. Note, there is a zero "bag limit" for this species in California and these turtles are not placed with the public. 
 

Terrapene species, Box turtles
Ornate box turtle showing carapace
Ornate box turtle showing plastron
Origin: North America. Description: Small to medium sized, to 20 cm (7.5 in), semi-terrestrial turtles.
Diagnostic: Webbing on rear feet; hinged plastron (under shell) that allows them to close up; often with pigmented areas of skin (white, red, yellow, orange, green, blue) on the head and forelimbs; may have elaborately patterned shells.		 Hybridization: No.
Disease: May harbor Mycoplasma.
Desert Survivorship: low for the common captive species. T. mexicana and T. ornata luteola occur in desert areas.		 Captive Status: Abundant. Accounted for 6% of chelonians placed by CTTC in 2005.

A dead box turtle was removed from the DTNA.
 

Manouria emys, Burmese brown or Mountain Tortoise


This is the largest species of Asian tortoise, to 60 cm (24 in).  It is not a commonly seen captive and is unlikely to be reported to agency officials.  It is included in this table as an example of incorrect identification in a published paper where a specimen was reported as the largest desert tortoise on record. Hybridization: No.
Disease: ?
Desert Survivorship: low.		 Captive Status: Rare. Accounted for less than 0.1% of chelonians placed by CTTC in 2005.
 
Photocredits: M. J. Connor, D. Gatti, J. Buskirk, S. McKeown.

 

References

Ernst, C. H. and Barbour, R. W. 1989 Turtles of the World. Smithsonian Institution Press, Washington, D.C., 313 pp.

Ernst, C. H., Lovich, J. E. and Barbour, R. W. 1994 Turtles of the United States and Canada. Smithsonian Institution Press, Washington, D.C., 578 pp.

 

[ INDEX ] [ CHAPTER 1 ] [ CHAPTER 2 ] [ CHAPTER 3 ] [ CHAPTER 4 ] [ CHAPTER 5 ] [ CHAPTER 6 ] [ CHAPTER 7 ] [ APPENDIX 1 ] [ APPENDIX 2 ] [ APPENDIX 3 ]