About Sierra San Luis

Sierra San Luis is situated on the continental divide, at the northern end of the Sierra Madre Occidental. It is part of the 70,000-square-mile Sky Islands region of southeastern Arizona, southwestern New Mexico, and northwestern Mexico. The sky islands are globally important

because of their rich diversity of species and habitats, including the last North American strongholds of such magnificent predators as the Mexican wolf and jaguar.

These mountain "islands," forested ranges separated by vast expanses of desert and grassland plains, are among the most diverse ecosystems in the world because of their great topographic complexity and unique location at the meeting point of several major desert and forest biological provinces. The region is a blend of tropical and temperate ecosystems, harboring well over half the bird species of North America, 29 bat species, over 3,000 species of plants, and 104 species of mammals--a diversity exceeding anywhere else in the U.S. This diversity is among the most threatened in North America by land development, climate change, livestock grazing, catastrophic wildfires, off-road vehicles, and resource extraction.

The Sierra San Luis is perhaps the most isolated Sky Island, with countless canyons so remote that they served as a stronghold for the Apache into at least the late 19th century. Our study site, Rancho Pan Duro, is situated on the Cajon Bonito, one of the few permanent streams in the entire Sky Island Region. This riparian system is what makes the site unique, leading to spectacular diversity in reptiles and amphibians

One project in which you will take part is a comprehensive inventory of reptiles and amphibians. This will involve extensive transects, time-area constrained searches, and monitoring funnel trap arrays. We will sample all habitats on Rancho Pan Duro, a former ranch where cattle have not been present for over a decade. Pan Duro is approximately 10,000 acres of rugged wilderness, with habitats ranging from deep wooded canyons to more open, grassy mesas.

Study Animals

There are at least two amphibians found on our study site, the Canyon Tree Frog (Hyla arenicolor) and the Tarahumara Tiger Salamander (Ambystoma rosaceum). These amphibians, as well as many across the globe, may be in danger of extinction by a fungal pathogen, Batrachytidrium dendrobatidis. It is not known if the amphibians of Sierra San Luis are infected with this pathogen, and part of our monitoring efforts will be to diagnose this disease in our study animals.

Another project focuses on the ecology of montane snakes, with an emphasis on the threatened New Mexico Ridge-nosed Rattlesnake (Crotalus willardi obscurus). This diminutive rattlesnake only occurs in three mountain ranges, and has been the subject of much concern due to potential negative effects of catastrophic wildfires. Where the snake occurs north of the border, fires have been suppressed for decades, increasing the possibility of damaging fires. However, in the Sierra San Luis, fires have been allowed to burn, which may have contributed to the relative abundance of rattlesnakes found there.  Besides ridge-nosed rattlesnakes, Pan Duro supports a host of other interesting herps, including Banded Rock Rattlesnakes (Crotalus lepidus klauberi), the Tarahumara Salamander (Ambystoma rosaceum), and a diverse lizard assemblage.