Tortuga de la Sierra Madre
My encounter with a cryptic and elusive turtle
Near the end of a weeklong biological reconnaissance in 2012 I encountered one of North America’s least known chelonians on the eastern bank of the Río Yaqui. A short film about my adventure can be seen here: https://vimeo.com/49623630. This includes the only video of the Spotted Box Turtle in the wild.
This is an expanded version of an article appearing in The Tortoise magazine. Your purchase will support turtle conservation around the world. Turtle Conservancy is dedicated to protecting the most endangered turtles and tortoises and their habitats worldwide.
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©Robert Anthony Villa
México, lindo, querido
“Just as all plant life springs from the soil, so from it come also the souls of men.”
-J. Frank Dobie, Tongues of the Monte
Dorstenia drakena, a primitive fig at the northern limit of its ocurrence. ©Robert Anthony Villa
After graduating from high school, I made my first journey beyond the border town of Nogales. As we drove south into the state of Sonora where the Sonoran Desertscrub receives more annual rainfall, I experienced Mexican “speed bumps” rarely visible until hit with full force, Crested Caracaras, and clusters of Mexican Bird of Paradise (tabachín: Caesalpinia pulcherrima) in full bloom growing as roadside weeds. I first encountered the Sinaloan form of the Desert Tortoise (Gopherus morafkai) under the first canopies of the Tropical Deciduous Forest on Mexico 16 as a woman in her Volkswagen beetle stopped to whisk it away. Stopping at the Río Yaqui bridge, I imagined all the mysterious verdant canyons descending from the wild Sierra Madre. How many Beaded Lizards (Heloderma horridum) had I passed by in this slot canyon I had walked up? As we approached the magical land surrounding the town of Álamos in all of her tropical splendor, I was awestruck. I’ll never forget the smell of the forest as we drove by: intense green tea mixed with rich damp soil. We walked through a mango orchard enjoying its sweet fruit and hoping for the holy grail of any herpetological endeavor to Álamos: the pichecuate (Cantil: Agkistrodon bilineatus). Soon I held my first escropión (Beaded Lizard), babatuco (Indigo Snake: Drymarchon melanurus), corúa (Boa constrictor), coralillo falso (Sinaloan Milksnake: Lampropeltis triangulum sinaloae), Thornscrub Hook-nosed Snake (Gyalopion quadrangulare). The list of fantastic and exotic beauty goes on.
Tabachín. ©Robert Anthony Villa
All this plays vividly as I remember my first trip into the Mexican interior; a country I had previously experienced only books and television. I needed more. By the time of this writing I have ventured into the rural and wild places of Sonora many times to document its relatively neglected flora and fauna under the auspices of various bi-national conservation organizations.
“During the revolution Martín Luis Guzmán rode the train through Navojoa and looked over at the sierra and felt what we all do when we see its green folds rising up off the desert. We all wonder what is up there and in some part of us, that rich part where our mind plays beyond our commands, we all dread and lust for what is up there.”
-Charles Bowden, The Secret Forest
©Robert Anthony Villa
The Setting
Around 23 million years ago the Sierra Madre Occidental (SMO) cordillera was lifted by tectonic and volcanic force from tropical lowlands, creating the physio-climactic setting for Sonora’s biodiversity. Around five to eight million years ago, various ice ages expanded and contracted the various biomes, becoming defined by increasingly seasonal precipitation. The biota in the adjacent Pacific lowlands perished, or retreated south with the tropics, and/or adapted to the newly established desert, and/or migrated and adapted to the new temperate woodlands of the SMO and adjacent ranges (Van Devender 2002).
Sierra Madre Occidental from MX-16. ©Robert Anthony Villa
So like a Humboldt Current, the modern Sonoran biota is a smörgåsbord of predominantly tropical affinity, including at least four other biomes intermixing in southern Arizona and the entire state of Sonora. Most notable are the tropical and temperate species converging at their distributional limits via biotic corridors on and along the SMO and the adjacent lowlands. These corridors are deep, north-south canyons or barrancos that act as tropical shelters from seasonally cold temperatures in more exposed terrain; and temperate isolated mountain ranges associated with the SMO surrounded by lowlands (sky islands). While winters become increasingly mild to the south, the odd freeze acts as a “pruning” factor for many tropical species in this giant transition zone between northern temperate and southern tropical biota. This ocurrs between 28º and 31º north in east-central Sonora (Van Devender 2002). Indeed the upper regions of the SMO regularly freeze and snow during the winter months (Burquez et al. 1992).
At Sonora’s tropical southern tip you have a few desert biota at their southern limits such as Tiger Rattlesnakes (Crotalus tigris), Gila Monsters (Heloderma suspectum), and Saguaro cactus (Carnegia gigantea) amongst the northernmost tropical taxa: Mexican Leaf Frogs (Pachymedusa dacnicolor), Potamonid (semi terrestrial) crabs (Pseudothelphusa sonorensis), Amazon Parrots (Amazona sp.), Margays (Leopardus weidii), pichecuates, tlacuachínes (Murine Opossums: Tlacuatzin canescens), Blunt-headed Treesnakes (Imantodes gemmistratus), coralillos (West Mexican Coralsnakes: Micrurus distans), and Ant Hill Snakes (Sympholis lippiens) (Robichaux and Yetman 2000). Maybe even a Jaguarundi (Herpailurus yagouaroundi)…
©Robert Anthony Villa
For the cheloniaphile it should be noted that several species from distinct families may be encountered in this relatively small geographic area (all but the second tortoise are endemic to Mexico and/or Sonora): The “Sinaloan type” Desert Tortoise, Mexican Wood Turtles (Rhinoclemmys pulcherrima), Sonoran Slider (Trachemys nebulosa hiltoni), Alamos, and Mexican Mud Turtles (Kinosternon alamosae, K. integrum). Slightly farther north reside Yaqui Sliders (Trachemys yaquia) and the “Sonoran type” Desert Tortoise. And of course throughout the southern and eastern portion of Sonora resides one of the most elusive New World chelonians: the Spotted Box Turtle (Terrapene nelsoni)
At around 95 kilometers south of the international border, one can see the northernmost population of B. constrictor amongst Saguaros, oaks (Quercus sp.), and palms (Brahea nitida) (Felger and Joyal 1999). Further at 161-201 kilometers one can see maple trees (Acer grandidentatum) next to palms in the higher elevations. Lower in elevation are the northernmost Kapok (Ceiba and Pseudobombax sp.) and Morning Glory Trees (Ipomea arborescens)*, terrestrial bromeliads (Hechtia montana), and breeding populations of: Military Macaws (Ara militaris), Neotropical River Otters (Lontra longicaudis), and the largest, most powerful cat in the new world, the Jaguar (Panthera onca) (Felger and Joyal 1999; Felger et al. 2001; O’Brien 2006). It was in this region, on a biological expedition of the Río Aros and Yaqui that I encountered one of the least known New World chelonians in its habitat: a Northern Spotted Box Turtle (Terrapene nelsoni klauberi).
©Robert Anthony Villa
* Palo santo: holy tree - “A spectacular tree 7-10 m. high, with smooth, white-gray bark like the hide of a hippopotamus. It flowers in winter when leafless, holding a high, thin spread of white corollas like stars against the morning sky. These stars soon fall upon the ground, where the deer eat them. With the summer rains the tree forms a dense foliage, which on the characteristically recurved branches is somewhat plumelike, especially from a distance. It deciduates during late September or early October.”
-Howard Scott Gentry, Rio Mayo Plants
Entrada
In July of 2012 I had the pleasure of assisting with a biological rafting expedition of the Río Aros and surrounding wilderness. The purpose was to help monitor a large preserve, and surrounding properties for possible acquisition, that are flanked by the Aros. Rafting is the only practical route of entry to the extremities of these large properties. The particularly lush Foothills Thornscrub we were entering led me to entertain the hope of establishing new records expanding the known range of Beaded Lizards, and other tropical herps (amphibians and reptiles). More importantly on my mind were populations of Northern Spotted Box Turtles reported on previous rafting trips to this region. Since learning of this secretive creature, I knew I had to find this precious gem among North American chelonians in the Mexican back of beyond.
©Robert Anthony Villa
The launch site was at Natora, two days drive from Tucson with the second day taken up by driving 100 kilometers over mountainous dirt road from the nearest town. This little village is the last outpost before entering some of the most wild and inaccessible terrain in the Sonoran region. In the chaotic assembly of the rafts, gear, and supplies we were drenched by a chubasco (monsoonal downpour) and shivering in the middle of July. The locals had more ammunition for the theory that gringos are crazy (and as the river rose I began to agree). Among the gathering crowd I managed to buy a liter of home-distilled bacanora from a very inebriated man. This regional mezcal (Agave liquor) made from the Narrow-leaved Agave (Agave angustifolia) would be a most appreciated purchase later on. It was getting late and the spectators now included young men hoping we could get them and/or their clandestine goods to el otro lado (the other side [of the border]) if we hired them as helpers. They offered us anything we wanted within their recreational pharmacopeia. We launched without them and landed just a few kilometers downstream before dark.
Hintonia latiflora, a tropical tree at its northernmost occurrence along the Río Aros. ©Robert Anthony Villa
©Robert Anthony Villa
Beauty and Fracaso
“The real Sierra Madre…the wondrous cruelty of those mountains.”
-J. P. S. Brown, The Mulatos River Journal [IN The Cinnamon Colt and Other Stories]
©Robert Anthony Villa
My desire to participate in such an expedition grew from poring over online photo albums by whitewater runners on the great rivers and gorges of northwestern Mexico, including the Aros and Yaqui. My expectations were met as we passed through steep, deep canyons covered with Octopus Agave (A. vilmoriniana), so named for their curvy, spineless leaves. Beside them were various cacti, and some of the northernmost terrestrial bromeliads, frangipani (Plumeria rubra), and Rock Figs (nacapule/tescalama; Ficus petiolaris) whose exposed roots clung beautifully to the walls. These frost-sensitive plants could be indicators of specifically tropical herpetofauna! So on a midday hike when I was called over to look at Gila Monster, I hoped it would actually be a Beaded Lizard. Yaqui Sliders and otters left us only tracks on the sandbars to evidence their presence.
©Robert Anthony Villa
One day approaching camp the paddler of the large raft I was on drifted beyond timely return while swimming. Quickly fatiguing, I was barely able to avert disaster from rapids and large debris. I was mad, ashamed, and high on endorphins. One fracaso leads to another….
Large boulders and debris. ©Robert Anthony Villa
Another day we began to hear what could only be the raucous cacophony of large parrots. We were approaching the northernmost roost of Military Macaws, a spectacle beyond description. An hour of observation from shore allowed us to determine there were about nine of these marvelous birds on the cliff wall. We were also close to the three largest and most difficult rapids and were pausing to assess running them. I couldn’t help but wonder if the macaws were a figurative offering from the universe before what would turn out to be a test of mental, technical, and physical fortitude.
In Mexican fashion I called them Las Tres Marias, or The Three Marias, after the saint of that name with which many people in Mexico pray to in dire straits. The first rapid was actually named for the canyon in the vicinity: La Morita (Little Mulberry). An oxymoron! We were all humbled as we observed from shore one of the most impressive forces of nature I had ever seen.
Before returning to our respective crafts we noticed one of the kayaks sans paddler headed down river. He didn’t tie off his kayak, not realizing that the river in fact rises and falls imperceptibly throughout the day due to distant storms in the watershed. This was to set off the next set of fracasos before the end of the day. I never again want to be in such a fearful situation that I have to encourage another (eyes wild with fear), who quite literally holds my life in their hands, to extract us from between a rock and a hard place (quite literally). As the paddler I was riding with negotiated large waves and giant boulders, we scarcely skirted a massive whirlpool I’m sure would have flipped the twelve-foot raft we were on. By the end of the day we had tested our wits and friendships against the worst of the river. Sweet, hard bacanora….
Large boulders and debris. ©Robert Anthony Villa
We had reached the point of the trip where the Aros meets the Bavispe to form the Yaqui. It was all smooth sailing from here they said, and I was relieved, since I had enough whitewater by this point! But I was admittedly dismayed not to have seen the more impressive herps known from this river including Indigo Snakes and Spotted Box Turtles. Every day we’d awake early to explore canyons in search of biota before breaking camp. I should have seen something new by now…
Río Aros. ©Robert Anthony Villa.
Tortuga de Chispitas
“First you just look,
later you will find, find.
First you just look,
later you will find, find.
Over there, I, in an opening,
in the flower-covered grove,
I went out,
then you will find, find”
First you just look,
later you will find, find.”
-Maso Bwikam [Yaqui Deer Song]
We were nearing the end of the trip and I was beginning to question my abilities to find herps. Another lunchtime hike. The hummingbirds were many, sipping from the uvalama (Tree Verbena, Vitex mollis). It was a lovely canyon with seeps from which we filtered drinking water. Going to the raft for a tool, I noticed a log at the mouth of the canyon I hadn’t seen previously. Searching for amphibians and reptiles, logs must be flipped, even if half-heartedly. Hot and somewhat depressed I lifted it, and realizing it was heavier than I thought, dropped it on my foot, scraping off a gnarly bit of skin.
PUTA MADRE! Cursing my rookie move I looked up and became instantly joyous. There in her quizzical silence a Spotted Box Turtle beheld a most peculiar ape. The ape was bleeding, in pain, and dancing. I had found one of North America’s most secretive and unknown chelonians. Photos were taken (gratuitous and documentary) and all was good.
Terrapene nelsoni klauberi. ©Robert Anthony Villa
In the thrill of the moment I neglected my duty as a naturalist to observe anything of importance relating to the animal in its natural setting.
Tortuga de Monte
Like other box turtles, T. nelsoni is active during the summer rainy season (July to September), aestivates (dry season dormancy) and seems to be most active/common following drenching rains (Buskirk and Ponce-Campos 2011). The apparent difficulty in finding specimens may have to do with their densely vegetated habitat, and effective camouflage. It has been found in a variety of habitats and corresponding elevational gradients including Foothills Thornscrub, Tropical Deciduous Forest, Oak Woodland, Pine-oak Woodland, and Mixed Conifer Forest (Buskirk and Ponce-Campos 2011).
©Robert Anthony Villa
T. nelsoni has been documented to eat beetles (Lemos-Espinal 2005), the fruit of columnar cacti (pitahaya) and/or Prickly Pear (túna: Opuntia sp.) as evidenced by crimson juice-stained beaks (O’Brien et al. 2006). Likely to be as opportunistic as other box turtles, one can surmise that they will eat carrion, bird eggs and nestlings, other fruits, scavenge through scat, and even eat their own offspring as observed in captive Desert Box Turtles (Terrapene ornata luteola; author observation).
Mating has been observed on 7 July at ca. 09:30 hrs in the tropical deciduous forest of southern Sonora – well within the rainy season (Lozano and Sauceda, pers. comm.). Mating and egg laying is likely opportunistic. Eggs laid during the end of the rainy season likely undergo diapause during the winter and dry season and resume development the next year until hatching. during spring or summer. Female turtles are known to retain sperm and produce fertile eggs years from being copulated. This species develops between one and four eggs (Milstead and Tinkle 1967). There is a single recorded observation of a juvenile Spotted Box Turtle from Chihuahua state (Ponce-Campos and Buskirk 2011).
The relation of T. nelsoni to T. ornata (Ornate Box Turtle) has been strongly supported on the basis of osteology, historical biogeography (Milstead and Tinkle 1967; Dodd 2001), and phylogeny (Martin et al. 2013). It would seem likely that the two species descended from a common ancestor and assimilated into their modern adjoining habitats during the biotic modifications within the five to eight million years (Van Devender 2002).
Most of the range of T. nelsoni lies within mountainous regions with poor access and socially volatile, clandestine activities, thus explaining the paucity of specimens and the great hiatuses between them. However, within the last few years, new records of T. nelsoni have augmented its poorly known distribution. T. nelsoni is recorded in the states of Chihuahua, Jalisco, Nayarit, Sinaloa, and Sonora (Buskirk and Ponce-Campos 2011). It likely occurs in neighboring states of the pacific slope of the Sierra Madre Occidental.
Sierra Madre Occidental from MX-16. ©Robert Anthony Villa
The Range of the Spotted Box Turtle. Triangles: range limits. Circles: areas of possible occurrence. White circles: Ornate Box Turtle locales. ©Robert Anthony Villa
Probably the first specimen of T. nelsoni collected for science was collected on the Nelson-Goldman expedition of the Smithsonian Institution/US National Museum of Natural History (USNM) in 1897 (Buskirk and Ponce-Campos 2011). Over the course of 14 years, Dr. W. E. Nelson and C. A. Goldman led the epic expedition that spanned every corner of the Mexican Republic. No greater and more thorough accumulation and synthesis of biotic information of such a massive and biotically diverse country had been undertaken; moreover by only two people. While it was indeed a golden age of exploration, Mexico will continue to hold her secrets, a steadfast allure to the romantic, intrepid adventurer. Not included in the published summary of the expedition, are 150 amphibians and reptiles collected during the expedition, including some new to science.
Much later Leonhard Stejneger described T. nelsoni in 1925 from the very specimen collected on this expedition (the holotype: USNM 46252) at Pablo Pedro in the state of Nayarit (type locality) and named it after Nelson.
French geologist/naturalist Léon Diguet collected possibly an earlier specimen in Nayarit; but a report on reptiles collected by him in western México only provides the date 1896 to 1897. It was presented to the Muséum National d’Histoire Naturelle of France in Paris in 1898 (Mocquard 1899). It wasn’t referenced in the literature until 1979.
Had this specimen been used to describe the species, Charles Bogert (American Museum of Natural History) wouldn’t have had such confusion describing the Spotted Box Turtles he encountered from Sonora 610 kilometers north of the Nayarit specimens previously the only ones known.
Eighteen years from the description of T. nelsoni, Bogert described Terrapene klauberi (=Terrapene nelsoni klauberi) from four female specimens collected at Rancho Güirocoba near Álamos, Sonora.
Bogert’s description as a distinct species was due in part to the reversing of labels of photographs of the holotypes of the Mexican Box Turtle (Terrapene goldmani [= T. carolina mexicana]) and Spotted Box Turtle (T. nelsoni) in a review of the North American Box Turtles by Ditmars in 1934. The animals likely were confused because both virtually lack carapace markings, the latter a result of advanced age (Shaw 1952; see above). Ideally he would have examined the specimens, but wartime restrictions prevented shipping them to him.
Despite only having a photograph of the single uncharacteristic spotless Spotted Box Turtle specimen at his disposal, Bogert was perceptive enough to note the morphological and biogeographic similarities between the holotype and his specimens.
After several reassignments between species and subspecies, Bogert’s taxon was ultimately classified as subspecific to T. nelsoni (Milstead and Tinkle 1967), as Bogert (1943) had originally predicted pending the collection of additional specimens. However, the physical characters used to distinguish the subspecies from each other are vague and unreliable. Martin et al. (2013) do not support the current subspecies status based on genetic markers. However, a greater sample size is needed and may elucidate more viable anatomical and genetic distinctions between populations across a large range.
Common names given to T. nelsoni are caja/cajita pintada (spotted box/little spotted box), casco/casquita pintada (spotted casque/little spotted casque), tortuga de bisagra (hinge turtle), and tortuga manchada (stained turtle). But one that stands out is from southern Sonora near Álamos where some elders refer to it tortuga de chispitas (turtle of little sparks) in reference to the many yellow spots on the shell and skin of the species (Buskirk, pers. obs.). Indeed sparks will fly whenever I lay my eyes on this chelonian.
In some parts of Sonora it’s thought that this turtle is a hybrid between a local chelonian and a Gila monster. Sadly in Jalisco and much of México it’s belived that the blood of this and other (non-sea) turtles is a remedy for asthma, stomach inflamation, and malnutrition and its associated lack of appetite (ética).
México, lindo, y que herido, que Dios te lleve…
“Everywhere I look this night I hear the distant thunder of the Twentieth Century’s rush into the desert, the last pocket of space left in the idea of the frontier.”
-Charles Bowden, Blue Desert
© Robert Anthony Villa
A variety of threats face T. nelsoni and its home in Sonora. Most directly is slashing and burning its habitat to plant Buffel Grass (Pennisetum ciliare) for cattle. Northern Mexico shares the deep-rooted romanticism for cattle and the cowboy with the U.S. So it’s not surprising that in 2003 government figures showed cattle (largely subsidized by the government) occupied 83 percent of the state of Sonora, and contributed approximately four percent to its $226 million gross domestic product that year (Ibarra-Flores et al. 2009). Holy cow! Holy $#!%
Furthermore, 71 percent of the Sonoran region we speak of occurs in the state of Sonora, only five and a half percent of which is actually designated as wilderness preserves. In 2006 it was determined that 80 percent of these preserves remained intact (Ibarra-Flores et al. 2009). T. nelsoni is found in four protected wilderness areas in Mexico, and protected by the country’s laws (Buskirk and Ponce-Campos 2011). Logging, agricultural, urban and highway expansion, climate change, and poaching for the exotic pet trade constitute other threats to T. nelsoni throughout its range.
“Of what avail are forty freedoms without a blank spot on the map?”
-Aldo Leopold, A Sand County Almanac
©Robert Anthony Villa
If the sky is indeed falling, maybe we should at least have the faith of turtles and other living things who become displaced, persecuted, and sense global climate shifts far more than we do, and yet carry on in the face of whatever life offers.
©Robert Anthony Villa
“It has never occurred to me to speak with elegant animals: I am not curious about the opinion of wasps or of racing mares. Let them settle matters while flying, let them win decorations while running! I want to speak with flies, with the cur that has recently littered, and to converse with snakes. … I want to speak with many things and I will not leave this world without knowing what I came to find, without solving this affair, and people are not enough. I have to go much farther and I have to go much closer.”
-Pablo Neruda, Bestiary
Caterpillar with metallic horns. ©Robert Anthony Villa
Gracias
Thanks to those who revised prior drafts of this article for grammatical and factual errors, especially James Buskirk, Randy Babb, Taylor Edwards, Kaitlyn Foley, Eric Goode, John Iverson, Sky Jacobs, James Juvik, Ross Kiester, Eric Kroll, Pablo A. Lavín-Murcio, Lee Oler, Ted Papenfuss, Todd Pierson, John and Susy Pint, Paulino Ponce-Campos, Jesus Rodríguez-Campos, and Philip C. Rosen, and Ryan Schoek. For information on museum specimens, thanks goes to Jeremy F. Jacobs and Kenneth Tighe (Amphibians and Reptiles Staff at Smithsonian/USNM) for providing information on the box turtles of the Nelson-Goldman expedition, and to Carol L. Spencer (Staff Curator, Museum of Vertebrate Zoology, University of California, Berkeley) and James Merzbacher.
Tabachín. ©Robert Anthony Villa
Bibliography and Suggested Reading
Bogert, C. M. 1943. A New Box Turtle from Southeastern Sonora, Mexico. American Museum Novitates No. 1226, American Musuem of Natural History, New York, New York. http://digitallibrary.amnh.org/dspace/handle/2246/4799
Bogert, C. M. and J. A. Oliver. 1945. A Preliminary Analysis of the Herpetofauna of Sonora. Bulletin of the American Museum of Natural History 83(6):297-426. American Museum of Natural History, New York, New York. http://digitallibrary.amnh.org/dspace/handle/2246/333
Brown, D. E. and C. A. Lopez Gonzalez. 2001. Borderland Jaguars | Tigres de la Frontera. University of Utah Press, Salt Lake City, Utah.
Burkhalter, D. 1998. La Vida Norteña: Photographs of Sonora, México. The Southwest Center Series, University of Arizona Press, Tucson, Arizona.
Burquez, A., A. Martínez-Yrízar, and P. S. Martin. 1992. From the high Sierra Madre to the coast: Changes in vegetation along Highway 16, Maycoba-Hermosillo. Pp. 239-252 IN K. F. Clark, J. Roldán-Quintana, and R. H. Smith [Eds.] Geology and Mineral Resources of Northern Sierra Madre, Mexico. El Paso Geological Survey, El Paso, Texas.
Buskirk, J. R. and P. Ponce-Campos. 2011. Terrapene nelsoni Stejneger 1925 — Spotted Box Turtle, Tortuga de Chispitas, Tortuga de Monte. Pp. 60.1-60.8 IN Rhodin, A. G. J, P. C. H. Pritchard, P. P. van Dijk, R. A. Saumure, K. A. Buhlman, J. B. Iverson, and R. A. Mittermeier [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, Chelonian Research Foundation. http://www.iucn-tftsg.org/wpcontent/uploads/file/Accounts/crm_5_060_nelsoni_v1_2011.pdf
Ditmars, R. L.. 1934. A Review of the Box Turtles. Zoologica 17(1):1-44.
Dobie, J. F.. 1985. Apache Gold and Yaqui Silver. University of Texas Press, Austin, Texas.
Dodd, C. K.. 2001. North American Box Turtles — A Natural History. Animal Natural History No. 6. University of Oklahoma Press, Norman, Oklahoma.
Felger, R. S., M. B. Johnson, and M. F. Wilson. 2001. The Trees of Sonora, Mexico. Oxford University Press, New York, New York.
Felger, R. S. and E. Joyal. 1999. The Palms (Areaceae) of Sonora, Mexico. Aliso 18(1):1-18.
Franklin, C. J. and D. C. Killpack. 2009. The Complete North American Box Turtle. ECO Herpetological Publishing & Distribution, Rodeo, New Mexico.
Gentry, H. S. 1963. The Warihio Indians of Sonora-Chihuahua: An Ethnographic Survey. Anthropological Papers, No. 63, Bureau of American Ethnology Bulletin 186: 61-144, pls. 28-38. United States Printing Office, Washington, District of Columbia.
Goldman, E. A. 1951. Biological Investigations in México. Smithsonian Miscellaneous Publications Volume 115 (whole volume), Publication 4017, Smithsonian Institution, Washington, District of Columbia.
Hilton, J. W. 1947. Sonora Sketchbook. Macmillan, New York, New York.
Ibarra-Flores, F. A., M. H. Martín-Rivera, F. G. Denogean-Ballesteros, and R. Aguirre-Murrieta. 2009. Buffelgrass, Cattle, and the Sonoran Desert. Pp. 375-381 in T. R. Van Devender, F. J. Espinosa-García, B. L. Harper-Lore, and T. Hubbard [Eds.] Invasive Plants on the Move: Controlling Them in North America. Based on Presentations from Weeds Across Borders 2006 Conference, Hermosillo, Sonora, Mexico, May 25th through 29th, 2006. Arizona-Sonora Desert Museum, Tucson, Arizona and U. S. Department of Transportation, Washington, D. C.
Johnson, Jr., R. 2005. The Quiet Mountains: A Ten-Year Search for the Last Wild Trout of Mexico’s Sierra Madre Occidental. The Southwest Center Series, University of New Mexico Press, Albuquerque, New Mexico.
Lemos-Espinal, J. A.. 2005. Anfibios y Reptiles de la Sierra Tarahumara. Informe final: SNIB-CONABIO proyecto X004. Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México.
Martin, B. T., N. P. Bernstein, R. D. Birkhead, J. F. Koukl, S. M. Mussmann, J. S. Placyk, Jr. 2013. Sequence-based molecular phylogenetics and phylogeography ofthe American box turtles (Terrapene spp.) with support from DNA barcoding. Molecular Phylogenetics and Evolution 68(1):119-134.
Milstead, W. W. and D. W. Tinkle. 1967. Terrapene of Western Mexico, with Comments on the Species Groups in the Genus. Copeia 1967(1): 180-187.
Mocquard, M. F. 1899. Reptiles et Batrachiens Recueillis au Mexique par M. Léon Diguet en 1896 et 1897. Bulletin de la Société Philomatique 9(1)4:154-169.
Montes-Ontiveros, O. and P. Ponce-Campos. 2006. Terrapene nelsoni nelsoni (Southern Spotted Box Turtle). Geographic Distribution. Herpetological Review 37(2): 239.
Northern Jaguar Project: http://www.northernjaguarproject.org.
Robichaux, R. H. and D. A. Yetman [Eds.] 2000. The Tropical Deciduous Forest of Alamos: Biodiversity of a Threatened Ecoystem in Mexico. University of Arizona Press, Tucson, Arizona.
Shaw, C. E. 1952. Sexual Dimorphism in Terrapene klauberi and the Relationship of T. nelsoni to T. klauberi. Copeia 1952(2): 39-41.
Stejneger, L. H. 1925. New Species and Subspecies of North American Turtles. Journal of the Washington Academy of Sciences 15(2): 462-463. http://www.biodiversitylibrary.org/pdf4/011943300123269.pdf
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