Herpetofauna of the Peloncillo Region: Legendary Diversity
More species of amphibians and reptiles live in the Peloncillo Mountains than in any other single mountain range in New Mexico—at least 89 species, which is 72% of the 123 species known to occur throughout the entire state of New Mexico. Even more impressive is the fact that these comprise almost a third of the amphibian and reptile species of the Western United States.2 And just one small pass in the Peloncillos —the 4,265-foot Antelope Pass, between the towns of Animas and Rodeo in Hidalgo County, New Mexico—has the highest lizard diversity of any comparable-sized place in the United States.
Outstanding Features:
These facts underscore the contribution of these mountains to the overall U.S. and global biodiversity. Set in a narrow, north- south row, the arid Peloncillo Mountains run parallel to the New Mexico/Arizona border for approximately 100 miles and continue a short distance into Chihuahua and Sonora, Mexico. Geographic Scope. For the purposes of this chapter, discussions are split into two geographic areas: the Peloncillo Mountains and the Sierra San Luis. The eastern border of the Peloncillo Mountains is the Animas Valley; the western border is the San Bernardino Valley and the San Simon Valley. The higher (1,300-2,520 meters; 4,265 – 8,268’ feet) and wetter Sierra San Luis run north-south in Sonora and Chihuahua, Mexico (31º05’ - 31º19’N, 108º40’30” - 108º58’W).
Overview of Geographic Placement & Significance
The herpetological diversity of the Peloncillo region is impressive. At least 89 species of amphibians and reptiles are known from the region, which is 72% of the 123 species known to occur throughout the entire state of New Mexico. The Peloncillo region also includes about a third of the 186 taxa (161 species and 15 additional subspecies3) reported from the much more tropical state of Chihuahua, sharing 32% of taxa at the subspecies level and 42% at the species level. The large number of species from the region may be surprising in view of the overall aridity and remoteness from tropical regions. However, the geographical position of the area, located at the intersection of six major biomes—including the Chihuahuan Desert, Great Plains, Great Basin, Rocky Mountains, Sierra Madre, and Sonoran Desert—results in high species diversity.
Although relatively little is known about the herpetofauna of the Sierra San Luis in Mexico, the diversity of flora and fauna prompted the government of Mexico to declare the Sierra San Luis a Zona de Protección de la Flora y la Fauna Silvestres ye Acuáticas. (http://www.cideson.mx/conserv/sanpes/sanluis.html). This area is characterized by temperate pine-oak, pinyon-juniper, and riparian gallery forests. Douglas -fir and Arizona cypress occurs at the higher elevations. Three major biotic provinces —the Chihuahuan Desert, Sierra Madre Occidental, and Southern Rocky Mountains—influence distribution of the floral and faunal elements of this region. The geographic position, and the great variety of habitats, makes this area an important biological corridor between the Sierra Madre and the Southwestern United States.
Important complex transitional areas, or filter barriers, exist in the region. The most complex and best known of these is the Cochise Filter Barrier of Cochise and Santa Cruz counties, Arizona, Hidalgo County, New Mexico, the northeastern tip of Sonora and extreme northwestern Chihuahua. Physiographically, the Cochise Filter Barrier is a 60 – 120 mile (100 - 200 km) gap between the Sierra Madre Occidental and the Colorado Plateau. It is about 120 miles (200 km) east-west as well. It is a broad, 5,000-foot (1,500 meter) plain disrupted by steep but discontinuous north-south ranges (Chiricahua, Huachuca, and Peloncillo Mountains), up to 9,800 feet (3,000 meters) at their peaks. It is the only physiographic portal along the western wall of the desert. High species diversity in this region is due both to the ecotonal nature of the region and its geographical/physiographical accessibility.
A bibliography of New Mexico herpetology exists at http://www.unm.edu/~msbherp/. This site, maintained by James N. Stuart, provides an updated, annotated bibliography of New Mexico herpetology. A companion to Degenhardt et al., this bibliography includes all pertinent literature (journal articles, books, unpublished agency and contract reports, and Internet publications) not cited in Amphibians and Reptiles of New Mexico. This supplemental bibliography is a work in progress and is continuously updated as new literature is published and older literature is located. It is the most valuable resource that exists when investigating the diversity of the amphibians and reptiles that exist in the borderlands area of New Mexico and Arizona.
A review of many of these borderland species already exists (e.g., Degenhardt et al.). Therefore, only those species, species assemblages, or specific habitat areas identified as special conservation concerns (Peloncillo Region Science Workshop, Herpetofauna Group, Feb. 5 – 6, 2003, Willcox, AZ) are covered in further detail in this report.
Discussion by Taxon
Amphibians
Primarily due to the overall xeric nature of the habitat, amphibian diversity in this region is limited. There are 14 native and one introduced species of amphibians—including two salamanders and 13 toads and frogs—known to occur in this region (Appendix D). This is 58% of the 26 amphibian species known to occur in New Mexico, and 32% of the species reported for Chihuahua. Many (e.g., Bufo, Scaphiopus , Spea) are well-adapted to the arid conditions, being “explosive” breeders with short-duration, high-density breeding aggregations that form in ephemeral pools during periods of summer thundershowers. Others (e.g., Ambystoma, Hyla , Rana) rely upon semi-permanent or permanent streams or stock tanks for breeding. Two native species of true frogs (Ranidae) occur in this region. Both are experiencing significant population declines in the Arizona and New Mexico and neighboring states, as a result of a combination of factors. Both require permanent to semi-permanent water for breeding and refugia during long-term drought, although both use temporary stock tanks and may disperse considerable distances along aquatic corridors. Fritts et al. reviewed these species in New Mexico.
Chiricahua leopard frog (Rana chiricahuensis)
This leopard frog occurs in Arizona, New Mexico and Sonora and Chihuahua, Mexico. The distribution is discontinuous. Populations in the northern part of the range are essentially confined to montane habitats of the Mogollon Rim country of central and eastern Arizona, and the montane areas of adjacent western New Mexico. This portion of the range is separated from populations along the southern borders of Arizona and New Mexico by an intervening expanse of scrub desert with elevations below 3,281 feet (1000 meters). Another series of populations are distributed southward in Chihuahua along the eastern base of the Sierra Madre Occidental. The species occurs from 3,281 to 8,530 feet (1,000 to 2,600 meters) in a variety of aquatic habitats, including montane streams, lakes, marshes, and at intermediate elevations, stock tanks and plunge pools of canyon streams. The species was reviewed by Platz and Mecham.
The Chiricahua leopard frog is federally listed as Threatened, primarily due to habitat alteration, destruction and fragmentation, predation by non-native organisms, and disease. Detailed information on the current status and threats to this species is found in USFWS (2002).
The newly described chytrid fungus, Batrachochytrium dendrobatidis is often implicated in the die-off of populations of ranid frogs in the Southwestern US. The Declining Amphibian Populations Task Force (DAPTF) has developed guidelines to aid in the efforts to prevent the spread of this little understood fungi. These guidelines can be reviewed at <http://www.fws.gov/ventura/es/protocols/dafta.pdf>. Guidelines are also summarized below in the Conservation Targets section.
Lowland leopard frog (Rana yavapaiensis)
This leopard frog currently occurs in extreme southwestern New Mexico, southern Arizona, and presumably in adjacent parts of northern Sonora, Mexico although its distribution in Mexico is poorly known. Most populations occupy ponds, streams, and river pools at elevations below
3,281 feet (1,000 meters) in scrub desert localities. Some populations in central Arizona may reach 5,577 feet (1,700 meters) where they are occasionally sympatric with R. chiricahuensis. Platz reviewed this species in 1988.
Populations of R. yavapaiensis in the Peloncillo Mountains of New Mexico have never been common and breeding has not been documented to occur in the state. Since a single individual was observed in Guadalupe Canyon during 1985, the species was not observed again until an additional specimen was identified there during August 2000. In New Mexico the species is listed as Endangered; in Arizona, it is a Candidate species. Threats include low population levels and innumerable human uses of its aquatic habitat, as well as introduced predaceous crawfish, fishes, and bullfrogs.
Reptiles
Overall reptile diversity within the study area is very high, with at least 74 forms known, including three turtles, 34 lizards, and 37 snakes (Appendix D). That is 76% of the 97 reptile species known to occur in New Mexico.
Hotspot: Antelope Pass
Antelope Pass is a low pass through the Peloncillo Mountains between Animas and Rodeo, Hidalgo County, New Mexico. The landscape of the area surrounding Antelope Pass is Chihuahuan Desert desertscrub with steep rocky hills and associated bajadas and arroyos; elevation range is 4,265 to 4,921 feet (1,300 to 1,500 meters). The soils vary, being rocky, gravelly, or sand loam depending upon elevation, slope, and aspect. Dominant vegetation includes creosotebush (Larrea tridentata) and tarbush (Flourensia cernua), with occasional shrubby clumps of mesquite (Prosopis glandulosa ), allthorn (Koeberlinia spinosa ), and Mormon tea (Ephedra spp.). Small clumps of prickly pear ( Opuntia) and cholla (Cylindropuntia ) are common. Sandy areas associated with the barren, rocky arroyos are dominated by Apache plume (Fallugia paradoxa), desert willow (Chilopsis linearis), littleleaf sumac ( Rhus microphylla), fourwing saltbush (Atriplex canescens ), and desert hackberry (Celtis pallida). Dwarf desert -holly (Perezia nana), snakeweed ( Gutierrezia sarothrae), and zinna ( Zinnia acerosa) are common perennial herbs. Grass cover is sparse, with muhly grass (Muhlenbergia sp.) and tobosa grass (Hilaria mutica) most abundant. Antelope Pass is characterized by summer rainfall, with over half of the annual precipitation received during thundershowers from May-September. Mean annual precipitation is 10.4” (26.4 cm) at Lordsburg and 10.6” (26.9 cm) at Animas.
Sias and Painter reported on data collected by NMDGF during pitfall studies at Antelope Pass conducted between 1987-93.16 During that time pitfall traps with and without drift fences were operated for 417,366 trap days and caught 8,554 reptiles and amphibians of 45 species. The total catch consisted of 8,288 lizards of 18 species, 177 snakes of 21 species, and 89 amphibians of six species. This catch represented a sampling of the herpetofauna from an area of 3.48 mi2 (9 km2 ). Thus the herpetofaunal assemblage (lizards and snakes) at Antelope Pass may be the most diverse of any comparable-sized area within the United States. At least 19 species of lizards and 22 species of snakes are known to occur at Antelope Pass (Sceloporus poinsetti and Tantilla yaquia have been collected at Antelope Pass since completion of the pitfall trapping), while at least 32 species of lizards and 32 species of snakes are known to occur with a 50-mile (80.5 km) radius. Lizard species not collected at Antelope Pass yet known to occur within a 50-mile radius
Herpetofauna of the Peloncillo Region: Legendary Diversity & Specific Threats 86 include Callisaurus draconoides , Sceloporus jarrovii, S. magister, S. slevini , S. virgatus, Phrynosoma hernandesi, P. solare, Cnemidophorus burti, C. exsanguis, C. inornatus, C. flagellicaudus, C. neomexicanus, and Eumeces callicephalus . Snake species not collected at Antelope Pass yet known to occur within a 80.5 km radius include Lampropeltis pyromelana, L. triangulum, Masticophis taeniatus, Salvadora grahamiae, Senticolis triaspis, Trimorphodon biscutatus, Crotalus lepidus, C. pricei, C. willardi, and Sistrurus catenatus.
Lizards
Whiptail Lizards (Cnemidophorus spp.)
The first modern synopsis of the “most difficult” genus Cnemidophorus was by E.D. Cope. After years of study Cope had concluded: “The discrimination of the North American species of this genus is the most difficult problem in our herpetology.18” Throughout the distribution of the genus, which includes much of the drier regions in the New World, there are roughly 45 described species. These range from the prairie form Cnemidophorus sexlineatus occurring as far north as southeastern Minnesota, to the tropical C. lemniscatus group which ranges to Patagonia in southern Argentina, South America.
At least nine species of the widespread teiid genus Cnemidophorus occur in the Peloncillo region. [A tenth species, C. flagellicaudus, the Gila spotted whiptail, is reported by Stebbins as occurring in the area although the origin of these specimens is unknown. Degenhardt et al. reported the species only as far south as the Gila River in extreme northern Hidalgo County20 , which is not included in this region.] According to Pianka, lizards as a group partition resources in three different ways: by being active at different times, by foraging in different places, and by feeding on different prey. Numerous investigations of resource partitioning in Cnemidophorus reveal that all sympatric species are essentially active at the same time of day, eat very similar foods, and possess similar foraging habitats. The major factor preventing competition appears to be the choice of different microhabitats or different areas, although there is extensive overlap in this choice as well.
Schall studied interactions between nine Cnemidophorus species occurring in the “Trans Pecos” region of west Texas22 (i.e., that area between the Pecos River and the Río Grande). These whiptails represent a guild of widely foraging, rapidly moving insectivorous lizards. All species studied overlapped greatly in food taxa consumed and the four largest species had no significant difference in prey sizes. There was no evidence of a difference between the all-female and bisexual species in patterns of diet, but the smallest species may use a different size range of prey items. Comparing the bisexual and all-female species revealed the two parthenogenetic species have the broadest microhabitat niche breaths. Activity times and presumed preferred body temperatures were similar for all species. It seems there is little actual competition between the species within this group.
However, the generalized habitat chosen by parthenogenetic species is broader and tends to be in disturbed zones where population sizes of lizards may not have reached their carrying capacities. Wright and Lowe hypothesized that the hybrid, highly heterozygous nature of the all-female whiptails allows them to exploit ecotonal zones. These unisexual species are found over geographic regions that have been most severely altered by changing climatic patterns. Despite the wider range of macrohabitat occupied by parthenogenetic Cnemidophorus species, their geographical ranges are rather restricted compared to other lizards.
Slevin’s Bunchgrass Lizard (Sceloporus slevini)
Sceloporus slevini occurs from southeastern Arizona and extreme southwestern New Mexico south to northern Durango, west into eastern Sonora, and east to Nuevo León.24 In New Mexico, this small lizard is active throughout the year in the intermountain Animas Valley of the border region. Sias and Painter reported year-round activity with captures dates ranging from 4 Jan – 22 Dec. Lizards were most active in the spring and fall. The species was the third most abundant lizard reported (only Cnemidophorus uniparens and C. exsanguis were more abundant) from the grassland habitat sampled and accounted for ca. 17% of the total lizards captured. Cnemidophorus uniparens and C. exsanguis accounted for ca. 29% and 23%. Populations in Mexico are poorly known.
Population declines of this species have been reported from high-elevation sites in the Chiricahua Mountains, Cochise County, Arizona, by Ballinger and Congdon, and Tomberlin and Sherbrooke. Overgrazing in high-elevation bunchgrass habitat was implicated in these reported declines. Bock et al. suggested that the apparent restriction of S. slevini to montane meadows might be a historic artifact associated with chronic and ubiquitous grazing of lower-elevation perennial grasslands. They further suggest that S. slevini may be one of the best indicators of habitat degradation by grazing.
Turtles
The turtle fauna of the Peloncillo Mountains and the Sierra San Luis mountains is limited to only three species: the terrestrial desert box turtle (Terrapene ornata luteola), and two aquatic mud turtles (Kinosternon flavescens and K. sonoriense). Although the subspecies occurs throughout much of this region, few life history data are available for the desert box turtle. In many areas it is primarily a prairie grassland species, although the desert subspecies is also found in rocky, xeric habitats and along riparian corridors. The mud turtles occupy perennial or temporary stock tanks or small woodland streams.
Although most species of Kinosternon are known for their capacity for terrestrial activity, K. sonoriense has long been thought to hibernate underwater. However, Stone studying an intermittent stream in the Peloncillo Mountains reported that during drought periods the entire population likely estivated on land.28 He also reported movement data for 13 individuals that moved >1km overland, as well as densities that exceeded 3,000 individuals/ha at Blackwater Hole in the Peloncillo Mountains, Hidalgo County, New Mexico. This is among the highest densities ever reported for a freshwater turtle.
Snakes
There are 37 species of snakes that are known from this region. That is 80% of the 46 snake species known to occur in New Mexico; 70% of 53 snake species known to occur in Arizona29; 58% of the 62 snake species from Chihuahua (and 39% of the state’s 79 subspecies); and even includes 51% of 72 snake species known from Texas.
Northern Mexican Gartersnake (Thamnophis eques megalops).
The subspecies Thamnophis eques megalops, occurs in the Chihuahuan Desert region. It is state listed as Endangered in New Mexico where it is very rare or perhaps extirpated, likely as a result of long-term drought and water depletion. In Arizona it is a Candidate species and is restricted to a few wetlands in the southeast corner of the state; and in Mexico where it is listed as Threatened, the status throughout much of its range is unknown.31 In 2003 Conant reviewed this species in the transvolcanic belt of southern Mexico.32 In his treatment of the species, he described seven new subspecies, each found in a different lake or remnant of a once-larger lake. Many of these new forms were originally described as T. e. eques or T. e. megalops.
Northern Green Ratsnake (Senticolis triaspis intermedia).
The northern green ratsnake reaches the northern edge of the species range in the southern Peloncillo Mountains. The species has a broad geographic distribution, ranging from southeastern Arizona and southwestern New Mexico and southern Tamaulipas southward through Mexico and much of Central America to Costa Rica. The elevational range is from near sea level to over 7,218 feet (2,200 meters). Price reviewed the species in 1991. The green ratsnake is suspected to be common in the Sierra San Luis, although it is reliably represented by only three records from the Peloncillo Mountains of New Mexico (Guadalupe Canyon and Post Office Canyon). Sight records for the Animas Mountains in Hidalgo County have not been verified. The species is highly sought after in the commercial pet trade.
The natural history of the green ratsnake is poorly known. Most individuals have been taken in montane mesophytic forests along the slopes of the Mexican highlands. In western and southern Mexico, it is also found in more xeric thorn forests (Price 1991). In New Mexico, Senticolis has been encountered in rocky riparian areas grown to cottonwood, sycamore, oaks, ash, and mesquite. These snakes are secretive but not uncommon along Cave Creek in the Chiricahua Mountains in Cochise County, Arizona.
New Mexico Ridge-nosed Rattlesnake (Crotalus willardi obscurus).
The ridgenose rattlesnake occurs mostly within the highlands of the Sierra Madre Occidental and associated ranges of northwest Mexico. In the United States it occurs in a few isolated mountain ranges in southeast Arizona and southwest New Mexico. The federally Threatened subspecies, Crotalus willardi obscurus is known only from the Animas and Peloncillo Mountains, Hidalgo County, New Mexico and Cochise County, Arizona, and from the Sierra San Luis, Chihuahua and Sonora, Mexico. Elevational range in the U.S. is 5,970 to 8,500 feet (1,820 to 2,591 meters) (Animas Mountains) and 5,600 to 6,200 feet (1,707 – 1,890 meters) (Peloncillo Mountains). Diet of this species was studied by Holycross et al35; reproduction was studied by Holycross and Goldberg.36 Populations in the Sierra San Luis are relatively little -studied, thus the elevational limits in this mountain range is unknown. This montane form is generally restricted to rocky hillsides, canyon bottoms, and talus slopes in Madrean woodlands. Dominant vegetation in the habitat includes various oaks (Quercus spp.), Apache pine (Pinus engelmannii), Chihuahua pine (P. leiophylla var. chihuahuana), alligator juniper (Juniperus deppeana), Manzanita (Arctostaphylos sp.), and various grasses.
Knowledge Gaps
Lizards
Little is known of the population status and distribution of Sceloporus slevini in Mexico, and further study of this declining species could determine if S. slevini is an important indicator of habitat degradation by over-grazing.
Turtles
Although the desert box turtle (Terrapene ornata luteola) occurs throughout much of the Peloncillo region, few life history data are available for the desert box turtle. Additionally it is not known how local collecting events affect this species, and further study is warranted.
Snakes
Little is known of the status of the northern Mexican gartersnake (Thamnophis eques megalops) in Mexico, where it is listed as Threatened.
The northern green ratsnake (Senticolis triaspis intermedia) has a broad geographic distribution, but its status and presence in the Peloncillo region is poorly documented. Further study is needed, including its natural history. Additional research programs, including the use of radio telemetry should be initiated.
The population in the Sierra San Luis of the ridgenose rattlesnake (Crotalus willardi obscurus) is little known. More study is needed, especially given its restricted distribution and endangered status.
Conservation Targets
Leopard Frogs
The newly described chytrid fungus, Batrachochytrium dendrobatidis, (Longcore et al. 1999) is often implicated in the die-off of populations of ranid frogs in the arid regions of North America. This and other pathogens and parasites can easily be transferred between habitats on equipment or footgear of fieldworkers, spreading organisms to new locations containing species that have little or no resistance to the agents. Therefore it is vitally important for anyone involved in amphibian research and other types of wetland studies, including those on fish, bats, invertebrates, and plants, to take steps to prevent the introduction of disease agents and parasites. Protocols for helping to stem the spread of this and other diseases are at: http://www.fws.gov/ventura/es/protocols/dafta.pdf. These guidelines emphasize sterilizing boots, nets, traps, and other gear between aquatic sites; preventing cross -contamination of animals caught at different sites; and quarantine and disease screening of any animals to be released back into the habitat. All resource and land management agencies, as well as researchers, are encouraged to follow this or a similar protocol to prevent or reduce the spread of amphibian and other aquatic borne diseases. For further DAPTF information see http://www.open.ac.uk/daptf/index.htm.
Proper management of the bullfrog is also an important consideration in the conservation of R. chiricahuensis. Bullfrogs are well known as large, voracious, aquatic predators that have been implicated in the decline of certain native frogs throughout western North America.37 The expansion of bullfrog populations and the presence of large numbers of these frogs in western North America are a result of intentional introductions and the creation of naturally rare favorable habitats. Prior to settlement by Europeans, permanent ponds and lakes were scarce in the arid parts of this continent. Now however, there are thousands of these aquatic habitats created in response to agricultural, domestic, and recreational needs, and for flood control.38 Bullfrogs have successfully colonized these habitats and have been an important agent in the disappearance of native leopard frogs through direct competition and consumption.
As important conservation considerations and given that bullfrogs are not native to this area, intentional introductions should be halted. The possession of live bullfrogs (either larvae or adults), by private or commercial interests, intended for bait, pets, or consumption should be strictly controlled or banned. Elimination of bullfrogs, through harvest, dewatering, or other means should be attempted at all occupied sites.
Non-native fishes, especially trout, sunfishes, and catfishes, have also been implicated in the decline of native frogs in the Southwestern US and elsewhere. For example, in the San Rafael Valley, Arizona, R. chiricahuensis were found only at sites that lacked non-native fishes, and Sredl and Howland noted that these frogs are nearly always absent from sites supporting bullfrogs and non-native predatory fishes, including mosquitofish, trout, and catfish. Intentional stocking of these species by wildlife management agencies should be halted anywhere near where native leopard frogs are know to occur. The fact that state fish hatcheries and stocking programs are supplemented by federal tax revenues distributed by USFWS–the same agency ultimately responsible for protection of endangered species in the US–emphasized the conservation value of coordinating actions by the many arms of public land and wildlife management agencies.
Maintenance of healthy stock tanks is also important in the conservation of R. chiricahuensis. Since many of the remaining populations are located in stock tanks, USFWS proposed a special rule to exempt operation and maintenance of stock tanks on non-federal lands from the Section 9 take prohibitions of the Endangered Species Act. This special rule was designed to encourage private landowners and ranchers to continue to maintain stock tanks.
Lizards
Populations of the state-listed Sceloporus slevini should be routinely monitored to investigate current status. These studies should be conducted for an entire year, as populations tend to fluctuate widely during the year. Overgrazing in high-elevation bunchgrass habitat was implicated in declines of Sceloporus slevini. Bock et al. suggested that the apparent restriction of S. slevini to montane meadows might be an artifact of over-grazing of lower-elevation perennial grasslands42; further study could determine if S. slevini is an important indicator of habitat degradation by grazing.
Turtles
One of the main threats to turtle populations in the region comes from human collecting, especially for the pet trade and for “turtle racing” events. In Texas during 1999, for example, 865 Kinosternon flavescens and 528 Terrapene ornata were reported to be collected by resident or non-resident nongame permit holders. Most of these 1,396 turtles were likely sold into the pet trade. During the “Annual Turtle Race” held each year [since 2000] in Clovis, New Mexico, box turtles are collected and allowed to “race” for a cash prize. These turtles are then liberated “en masse” by fair officials at one or two localities, often considerable distances from the original point of capture. During 2000, there were 150 turtles collected for this race; during 2001, 247 turtles; and during 2002, 109 turtles. This suggests these species are commonly encountered and are therefore often collected for the pet trade industry. To further aid in the conservation of these species in the Chihuahuan Desert region, detailed life history studies should be initiated to investigate population status. Collecting permits should be required by wildlife management agencies and monitoring of the take should continue. When the turtles are displaced from their original home ranges, these turtle “races” should be discontinued.
Snakes
The subspecies of the Mexican gartersnake (Thamnophis eques megalops ) is state listed as Endangered in New Mexico where it is very rare or perhaps extirpated, likely as a result of long- term drought and water depletion. In Arizona it is a Candidate species and is restricted to a few wetlands in the southeast corner of the state; and in Mexico where it is listed as Threatened, the status throughout much of its range is unknown. This highly aquatic garter snake should be protected from take throughout its range in the U.S. In Mexico, further distribution studies should be conducted. [Conant conducted most of the fieldwork for his recent review paper46 during the mid 1960s. Therefore, the current status of the habitat and many of the populations of T. eques is unknown, although it is likely that much of the habitat has been dewatered and the populations likely extirpated.]
The northern green ratsnake (Senticolis triaspis intermedia) is highly sought after in the commercial pet trade. Its natural history is poorly known, as is its distribution in the region. This species should be protected from take except by qualified researchers investigating various aspects of its life history. Riparian areas should be protected from catastrophic fire, whether management-ignited or naturally occurring.
The ridgenose rattlesnake (Crotalus willardi obscurus) is threatened by catastrophic wildfire. In modern times fire frequency within the habitat of C. willardi obscurus has decreased greatly as a result of active fire suppression and reduction of fine fuels by livestock grazing. After nearly a century of suppression, fuel loads are greatly elevated above “natural” levels, thus increasing the potential for catastrophic fires. Reintroduction of fire into these habitats is essential in maintaining a mosaic of habitats. However, prior to the reintroduction of large-scale summer fires, consideration should be given to reducing artificially high fuel loads to preserve habitat and reduce mortality of the New Mexico ridgenose rattlesnake.
Section Authors:
REPTILES AND AMPHIBIANS - Charles W. Painter. Herpetologist, New Mexico Department of Game and Fish Endangered Species Program. Charles has worked in New Mexico herpetology since 1976 and is coauthor of Amphibians and Reptiles of New Mexico. His current research includes conservation biology of the New Mexico ridge-nosed rattlesnake, sand dune lizard, and Jemez Mountains salamander.
