Thirteen of the 38 species of amphibians that inhabit Chihuahua are endemic to Mexico, one of them (Lithobates lemosespinali) is restricted to a small area in the Sierra Madre Occidental of Chihuahua, and another (Isthmura sierraoccidentalis) is found only in an isolated population in the Sierra Madre Occidental of Sonora and Chihuahua. Eleven more are distributed in western Mexico (Ambystoma rosaceum, A. silvense, Anaxyrus mexicanus, Incilius mazatlanensis, I. mccoyi, Craugastor tarahumaraensis [Fig. 2], Eleutherodactylus interorbitalis, Agalychnis dacnicolor, Tlalocohyla smithii, Lithobates magnaocularis, and L. pustulosus). Three more species are widely distributed from southern Canada to northern Mexico (Ambystoma mavortium, Anaxyrus cognatus, and Spea bombifrons). One species (Lithobates forreri) is widely distributed from northern Mexico to Central America, with a range that extends from central western Sonora through the Pacific Coast to Costa Rica. Another sixteen species occur from central or southern United States to northern, central or southern Mexico (Anaxyrus debilis, A. punctatus, A. speciosus, A. woodhousii, Incilius alvarius, Craugastor augusti, Eleutherodactylus marnockii, Hyla arenicolor, H. wrightorum, Gastrophryne mazatlanensis, G. olivacea, Lithobates chiricahuensis, L. tarahumarae, L. yavapaiensis, Scaphiopus couchii, and Spea multiplicata). Four more occur from eastern and/or southeastern United States to South America (Rhinella horribilis, Smilisca baudinii, Hypopachus variolosus, and Lithobates berlandieri), this last species with isolated populations in the Sierra Madre Occidental. Only one of the amphibian species that currently inhabit Chihuahua was introduced to the state (Lithobates catesbeianus).

Figure 2. 

Craugastor tarahumaraensis. Ocampo, Chihuahua. Photo courtesy of Peter Heimes.

Five of the 13 species of turtles that inhabit Chihuahua are endemic to Mexico, two of them to the Bolsón de Mapimí, a small area in southeastern Chihuahua, southwestern Coahuila, and northeastern Durango (Kinosternon durangoense and Gopherus flavomarginatus), two more to western Mexico (Terrapene nelsoni and Kinosternon integrum), and one more to the subtropics of southeastern Sonora, southwestern Chihuahua, and northern Sinaloa (Gopherus evgoodei). Six more species occur from central or southern United States to northern (Terrapene ornata [Fig. 3], Trachemys gaigeae, Kinosternon flavescens, and K. sonoriense) or central or southern Mexico (Kinosternon hirtipesand Apalone spinifera). The remaining two species of turtles are widely distributed from southern Canada to northern Mexico (Chrysemys picta) and from southeastern Sonora, through the Pacific Coast, to Costa Rica (Rhinoclemmys pulcherrima).

Figure 3. 

Terrapene ornata. Rancho de Flores Magón, Buenaventura, Chihuahua. Photo by Julio Lemos Espinal.

Fifteen of the 51 species of lizards that occur in Chihuahua are endemic to Mexico, two of them to the state of Chihuahua (Barisia levicollis [Fig. 4] and Plestiodon multilineatus), one of the remaining 13 endemics is limited to the Bolsón de Mapimí (Uma paraphygas), one more to a small area in eastern Sonora and western Chihuahua (Sceloporus lemosespinali), another one to the temperate forests of western Chihuahua and northern Durango (Plestiodon bilineatus), one more to the Chihuahua Desert from northern Chihuahua to central Mexico (Holbrookia approximans), two others occupy areas in the Sierra Madre Occidental and the Sierra Madre Oriental (Barisia ciliaris), and even the Transvolcanic Belt (Phrynosoma orbiculare). The remaining seven endemic species are distributed mainly along the Pacific Coast of Mexico (Anolis nebulosus, Ctenosaura macrolopha, Sceloporus albiventris, S. nelsoni, Urosaurus bicarinatus, Plestiodon parviauriculatus, and Aspidoscelis costata).

Figure 4. 

Barisia levicollis (female). Sierra del Nido, Chihuahua. Photo courtesy of Marisa Ishimatsu.

The remaining 36 lizard species are not endemic to Mexico, one of them is distributed from southern Canada to northern Mexico (Phrynosoma hernandesi), and two more range from Mexico to northern Guatemala (Heloderma horridum) or to Costa Rica (Phyllodactylus tuberculosus) mainly on the Pacific Coast. Another 32 are distributed in the United States and Mexico, most of them are species characteristic of the Chihuahua Desert or woodlands of the Sierra Madre Occidental (Elgaria kingii, Gerrhonotus infernalis, Crotaphytus collaris, Gambelia wislizenii, Coleonyx brevis, Cophosaurus texanus, Holbrookia elegans, H. maculata, Phrynosoma cornutum, P. modestum, Sceloporus bimaculosus, S. clarkii, S. consobrinus, S. cowlesi, S. jarrovii, S. merriami, S. poinsettii, S. slevini, S. virgatus, Urosaurus ornatus, Uta stansburiana, Plestiodon callicephalus, P. multivirgatus, P. obsoletus, P. tetragrammus, Aspidoscelis exsanguis, A. gularis, A. inornata, A. marmorata, A. sonorae, A. tesselata, and A. uniparens). Only one of the 51 lizard species that occur in Chihuahua is an introduced species (Hemidactylus turcicus).

Twenty-one of the 73 species of snakes are endemic to Mexico (Conopsis nasus, Leptophis diplotropis, Mastigodryas cliftoni, Pituophis deppei, Salvadora bairdii, Sonora aemula, Sympholis lippiens, Trimorphodon tau, Geophis dugesii, Lampropeltis polyzona, Leptodeira splendida, Rhadinaea hesperia, R. laureata, Tropidodipsas repleta, Micrurus distans, Storeria storerioides, Thamnophis errans, T. melanogaster, T. unilabialis, T. validus, and Crotalus basiliscus). Thirty-seven snake species that are found in Chihuahua are distributed from the United States to Mexico (Arizona elegans, Bogertophis subocularis, Gyalopion canum, G. quadrangulare, Lampropeltis getula, L. knoblochi, Masticophis bilineatus, M. flagellum, M. taeniatus, Pantherophis emoryi, Rhinocheilus lecontei, Salvadora deserticola, S. grahamiae, Sonora semiannulata, Tantilla hobartsmithi, T. nigriceps, T. wilcoxi, T. yaquia, Trimorphodon vilkinsonii, Heterodon kennerlyi, Hypsiglena chlorophaea, H. jani, Micruroides euryxanthus, Rena dissecta, R. humilis, R. segrega, Nerodia erythrogaster, Thamnophis eques, Agkistrodon contortrix, Crotalus atrox, C. lepidus, C. molossus, C. ornatus, C. pricei, C. scutulatus, C. viridis, and C. willardi [Fig. 5]). Another four species range from northern Mexico to Central or even South America (Boa sigma, Masticophis mentovarius, Imantodes gemmistratus, and Agkistrodon bilineatus). Six more species are found from central or southern United States to Central or South America (Drymarchon melanurus, Drymobius margaritiferus, Oxybelis aeneus, Senticolis triaspis, Thamnophis cyrtopsis, and T. marcianus). Five more range from Canada to northern or central Mexico (Opheodrys vernalis, Pituophis catenifer, Diadophis punctatus, Thamnophis elegans, and T. sirtalis).

Figure 5. 

Crotalus willardi. Sierra del Nido, Chihuahua. Photo courtesy of Robert Bryson.

In terms of habitat types, 47 species are found in the temperate forests of the Sierra Madre Occidental. Forty-four are found in the subtropical canyons of the Sierra Madre Occidental. Fifty-eight species are found in the Chihuahuan Desert. One species is found in SON. Twenty-five species occupy more than one habitat type (i.e., are generalists).

There are several additional species that are likely to occur in Chihuahua, but that have not been recorded within the state. Three species of anurans might occur in the deep canyons and lowlands of the extreme southwestern part of the state. The Pacific Stream Frog (Craugastor vocalis) was recorded by Hardy and McDiarmid (1969) in extreme northeastern Sinaloa, 16 km NNE Choix, 520 m, near the state line with Chihuahua. The Sabinal Frog (Leptodactylus melanonotus) was recorded by Bogert and Oliver (1945) from Güirocoba and Álamos, Sonora, only about 25 and 35km respectively from the Chihuahua border, and by Smith et al. (2005) from the Río Mayo at the gates of Presa Mocuzari, Sonora. Hardy and McDiarmid (1969) mapped localities for this species (as L. occidentalis, a junior synonym) from throughout the lowlands of Sinaloa, including a locality in the extreme northeastern corner. The Lowland Burrowing Treefrog (Smilisca fodiens) has been recorded close to Chihuahua by Hardy and McDiarmid (1969) for Sinaloa, Bogert and Oliver (1945) for Sonora, and Trueb (1969) and Duellman (2001) for both states. Another anuran species likely to occur in extreme northeastern Chihuahua is the Gulf Coast Toad (Incilius nebulifer). This species of toad is represented by isolated populations at the southern extremity of the Big Bend region of Texas, adjacent to Coahuila (Conant and Collins 1998).

It is likely that at least four other turtle species occur in Chihuahua. Three species have been taken close to the state line with Sonora and Sinaloa, in the extreme southwestern part of the state. Kinosternon alamosae has been taken in the vicinity of Álamos, Sonora, about 35 km from the Chihuahua border. Trachemys hiltoni has been recorded from Güirocoba, ~25 km from Chihuahua, and from extreme northern Sinaloa (Hardy and McDiarmid 1969). Seidel (2002) mapped its range into Chihuahua, but only conjecturally. Legler and Webb (1970) stated that the species is limited to the Río El Fuerte drainage. These last authors stated that Trachemys yaquia is limited to the drainages of the Río Mayo, Río Sonora and Río Yaqui, however, Seidel (2002) conjectured that the range of this species extended into Chihuahua. In addition, the Common Snapping Turtle (Chelydra serpentina) occurs in the Río Grande at least in New Mexico (Degenhardt et al. 1996), and may well occur farther south in extreme northeastern Chihuahua, where little turtle trapping has been done.

There are at least nine lizard species not yet recorded in the state of Chihuahua that are likely to occur in it; four of them in the deep canyons and lowlands of extreme southwestern Chihuahua; three in the extreme northeastern part of the state; and two in the extreme northwestern part. The Zebra-tailed Lizard (Callisaurus draconoides) was recorded by Bogert and Oliver (1945) from Güirocoba and Álamos, Sonora (~25 and 35 km respectively from the Chihuahua border), and Hardy and McDiarmid (1969) spotted it at several localities in extreme northeastern Sinaloa. The Black Banded Gecko (Coleonyx fasciatus) has been recorded from five localities along the foothills of the Sierra Madre Occidental of eastern Sonora, three of these localities are in the Álamos region, one fairly close to Chihuahua. Its habitat suggests that it might occur in some of the deep canyons of southwestern Chihuahua. The Regal Horned Lizard (Phrynosoma solare) ranges from southern Arizona through almost all of Sonora, into northern Sinaloa. Hardy and McDiamid (1969) and Bogert and Oliver (1945) recorded it near Chihuahua in both Sinaloa and Sonora. It is a species of arid and semiarid habitats on plains, hills, and low mountain slopes. The Desert Spiny Lizard (Sceloporus magister) shows a range similar to that of the preceding species. East of the Sea of Cortés, it is the western representative of the eastern S. bimaculosus.

In northeastern Chihuahua the presence of three additional lizard species is likely. Wright (1971) indicated that the New Mexico Whiptail (Aspidoscelis neomexicana) is known from only central New Mexico and extreme southwestern Texas; almost all records are from near the Río Grande. He projected its range into Chihuahua along the Río Grande; although there are no records, its occurrence is highly likely there. Conant and Collins (1998) depicted the southern part of the Big Bend region of Texas as part of the range of the Reticulate Banded Gecko (Coleonyx reticulatus). It may be expected in adjacent parts of Chihuahua. Also Conant and Collins (1998) projected the range of the Texas Alligator Lizard (Gerrhonotus infernalis) to include the southern part of the Big Bend region of Texas, southward through eastern Chihuahua, most of Coahuila and other states to the south. In northwestern Chihuahua the presence of the Western Banded Gecko (Coleonyx variegatus) is expected. As indicated in Stebbins (2003) and Degenhardt et al. (1996), this species occurs in extreme southwestern New Mexico, and probably also in adjacent northwestern Chihuahua. The Gila Monster (Heloderma suspectum) is also expected to occur in this part of the state. The known occurrence of this species in Sonora, Arizona, and New Mexico close to the Chihuahua border indicates that occurrence in Chihuahua is likely.

It is highly likely that nine more snake species occur within the state of Chihuahua. Two of them in southwestern Chihuahua (Phyllorhynchus browni and Pseudoficimia frontalis); four in northeastern Chihuahua (Coluber constrictor, Lampropeltis alterna, Pantherophis bairdi, Tantilla cucullata); two in the northwestern part of the state (Crotalus tigris, Sistrurus catenatus); and one in extreme southeastern Chihuahua (Tantilla atriceps). The Saddled Leaf-nosed Snake (Phyllorhynchus browni) was recorded by Bogert and Oliver (1945) from Alamos, ~35 km from the Chihuahua border; Hardy (1972) reviewed the distribution of The False Ficimia (Pseudoficimia frontalis), citing specimens from near Álamos and Güirocoba, Sonora, ~35 and 25 km from the Chihuahua border, respectively. The North American Racer (Coluber constrictor) is rare in Mexico, with only three records. Two are from Coahuila, including one from the extreme northwestern corner, in the Sierra del Carmen (Wilson 1966). Occurrence in Chihuahua seems likely. The Gray-banded Kingsnake (Lampropeltis alterna) is well known in the Big Bend of Texas, and elsewhere in that state, as well as in Coahuila and other adjacent states in Mexico, but it has never been found in Chihuahua, although it almost certainly occurs there. Baird´s Ratsnake (Pantherophis bairdi) occurs in western Texas, including the Big Bend region, as well as northern Coahuila (Conant and Collins 1998); it is highly likely to occur in adjacent Chihuahua. The Trans-Pecos Blackheaded Snake (Tantilla cucullata) is known only in Texas, in the Big Bend and immediate vicinity (Dixon et al. 2000); occurrence in adjacent Coahuila and Chihuahua is to be expected. In northwestern Chihuahua the occurrence of the Tiger Rattlesnake (Crotalus tigris) is expected. Stebbins (2003) indicates occurrence of this species in the extreme southeastern corner of Arizona, and in eastern Sonora near the Chihuahua border. An inhabitant of arid and semiarid foothills deserts, it may enter the latter state in some of its semiarid valleys. Another rattlesnake, the Massasagua (Sistrurus catenatus), is known from southern New Mexico (Degenhardt et al. 1996) and southeastern Arizona (Brennan and Holycross 2006); it likely occurs in adjacent Chihuahua. In extreme southeastern Chihuahua the occurrence of the Mexican Black-headed Snake (Tantilla atriceps) is expected. The known range of this species comes close to the southeastern corner of the state (Cole and Hardy 1981, Conant and Collins 1998).

Some amphibian and reptile species are known to occur in Chihuahua from only a few records, including the Sonoran Desert Toad (Incilius alvarius) recorded by Santos-Barrera et al. (2006) in the municipality of Janos; the Spectacled Chirping Frog (Eleutherodactylus interorbitalis) recorded by Lemos-Espinal et al. (2006) in Cumbre del Caballo, Chínipas; the Cliff Chirping Frog (Eleutherodactylus marnockii) recorded by Lemos-Espinal et al. (2001) in the Grutas de Coyame; the Many-lined Skink (Plestiodon multivirgatus) recorded only by Van Devender and Van Devender (1975) at Ojo de Galeana; the Smooth Green Snake (Opheodrys vernalis) recorded only by Van Devender and Lowe (1977) at 38.4 km SE of Guerrero; the Crowned Graceful Brown Snake (Rhadinaea laureata) recorded by Villa et al. (2012) near km 86 on Hwy 25 N of Creel, Bocoyna, and 1 km N of Baborigame, Guadalupe y Calvo; the Banded Blacksnake (Tropidodipsas repleta) recorded by H. Smith and Lemos-Espinal (2006) at km 36 road Temoris-Chínipas, Guazapares; and the Plain-bellied Watersnake (Nerodia erythrogaster) recorded by Uriarte-Garzón and García-Vázquez (2014) in the municipality of Ojinaga.

Overall, the species of amphibians and reptiles in Chihuahua represent just over 37% of the total pool of species from Chihuahua and its neighboring states (Tables 3, 4). Species of reptiles from Chihuahua make up even more of the total pool of species, especially the Squamata, and more specifically Anguids and Snakes. Chihuahuan amphibians make up less of the species pool, especially salamanders. Chihuahua has a good proportion of the region’s Ambystomatid salamanders, but is very depauperate in Plethodontids.

Overall, Chihuahua shares the highest proportion of its species with Sonora followed by Durango (Table 4). This is particularly evident in amphibians, with over 80% of Chihuahuan amphibians shared with Sonora. For reptiles, Chihuahua shares nearly 77% of its species with Durango and 66% with Sonora. Chihuahua generally shares the least number of species with Coahuila, Sinaloa, and Texas. These patterns of shared species are likely a function of the extent to which these states share habitat types. For example, Chihuahua, Sonora, and Durango all have extensive desert habitats whereas Texas, for example, has a much more diverse range of habitats than Chihuahua. In addition, Sonora and Chihuahua share the habitats and species found in the Sierra Madre Occidental. Our results considering Chihuahua and all of its neighboring states parallels the results of an analysis of the states along the US-Mexico border using Jaccard hierarchical clustering analyses (Smith and Lemos-Espinal 2015).

Most of the herpetofauna of Chihuahua falls in the IUCNs least concern category (119 of 132 [does not include DD species]; 90%), and as not listed by SEMARNAT (105 of 172; 61%) (Table 2). These percentages are similar to those from other recently compiled tallies of conservation statuses for Mexican states (Coahuila: Lemos-Espinal and G. Smith 2016, Hidalgo: Lemos-Espinal and G. Smith 2015, Nayarit: Woolrich-Piña et al. 2016, Nuevo León: Lemos-Espinal et al. 2016). However, there are species of conservation concern in Chihuahua. For example, turtles and tortoises in Chihuahua appear to be a group of particular conservation concern with nearly half considered Vulnerable or Near Threatened by IUCN and more than half listed as Pr or A by SEMARNAT. Emydidae and Testudinae are the families of most conservation concern. Indeed, turtles account for 4 of the 13 species (31%) of the Chihuahuan herpetofauna that are categorized as Vulnerable, Near Threatened, or Endangered by the IUCN, even though they make up only 7% of the species in Chihuahua. We also found that turtles as a group also have the highest mean Environmental Vulnerability Score (EVS), especially Emydidae, Testudinidae, and Trionychidae. We therefore encourage additional emphasis be placed on better understanding the ecology and conservation status of turtle and tortoise populations in Chihuahua.

In addition, even though there are relatively few reptiles and amphibians placed on conservation lists in Chihuahua, this does not mean they are safe. Indeed, there are species, such as Craugastor tarahumaraensis, Ctenosaura macrolopha, Uma paraphygas, and Tropidodipsas repleta that are of great conservation concern based on their EVS values (Wilson et al. 2013a, b). In addition, the more locally appropriate EVS assessments (see Wilson et al. 2013a,b) also suggest that conservation concern should exist for the amphibian families Ambystomatidae, Craugastoridae, and Eleutherodactylidae; and the non-turtle reptile families Anguidae, Eublepharidae, Iguanidae, Scincidae, Teiidae, and Elapidae.

Even beyond these species and families, the environment and habitats of Chihuahua are subject to anthropogenic change, such as construction of border fences (Lasky et al. 2011), increased urbanization (Biggs et al. 2010), and changes in precipitation and increased drying associated with climate change (Seager and Vecchi 2010). Indeed, the distribution of species at high risk according to the EVS assessment (≥ 14; Wilson et al. 2013a,b) is not the same across habitat types. Nearly 40% of species (18/47) in the temperate forests of the Sierra Madre Occidental is at risk according to the EVS, and nearly a third of species in the Chihuahuan Desert (19/58). Just over 20% (10/44) of species in subtropical canyons of the Sierra Madre Occidental are at high risk. Generalist species (those that use more than one habitat type) are the least at risk (2 of 25 species). These results suggest that particular conservation attention should be paid to the Sierra Madre Occidental and the Chihuahuan Desert habitat types in Chihuahua. We thus again emphasize that continued and increased study of the herpetofauna of Chihuahua is needed to monitor the possible effects of any environmental changes.