Rock Squirrel (Spermophilus variegatus)

About Rock Squirrel (Spermophilus variegatus)

• Kingdom: Animals
• Phylum: Chordates
• Class: Mammals
• Order: Rodents
• Family: Squirrels

This taxon is found in the Sierra Madre Occidental pine-oak forests ecoregion, which boasts some of the richest biodiversity anywhere in North America, and contains about two thirds of the standing timber in Mexico. Twenty-three different species of pine and about 200 species of oak reside within the Sierra Madre Occidental pine-oak forests ecoregion.

Pine-oak forests here typically grow on elevations between approximately 1500 and 3300 meters, and occur as isolated habitat islands in northern areas within the Chihuahuan Desert. Soils are typically deep, where the incline allows soil build-up and derived from igneous material, although metamorphic rocks also form part of the soils in the west and northwest portions of the sierra. Steep-sloped mountains have shaped some portions of the Sierra, while others are dominated by their deep valleys, tall canyons and cliffs. These steep-sided cliffs have thinner soils limiting vegetation to chaparral types; characterized by dense clumps of Mexican Manzanita (Arctostaphylos pungens), Quercus potosina and Netleaf Oak (Q. rugosa). There are also zones of natural pasture, with grasses from the genera Arisitida, Panicum, Bromus and Stevis.

The pine-oak forests gradually transform into an oak-grassland vegetative association. Such communities represent an ecological transition between pine-oak forests and desert grasslands..  Here, species such as Chihuahuan Oak (Quercus chihuahuensis), Shin Oak (Q. grisea),  Q. striatula and Emory Oak (Q. emoryi), mark a transition zone between temperate and arid environments, growing in a sparse fashion and with a well-developed herbaceous stratum resembling xeric scrub. Cacti are also part of these transition communities extending well into the woodlands. Some cacti species such as the Little Nipple Cactus (Mammillaria heyderi macdougalii), Greenflower Nipple Cactus (M. viridiflora), Mojave Mound Cactus (Echinocereus triglochidiatus), and Leding's Hedgehog Cactus (E. fendleri var. ledingii) are chiefly centered in these biotic communities. The dominant vegetation in the northernmost part of the ecoregion in the Madrean Sky Islands includes Chihuahua Pine (Pinus leiophylla), Mexican Pinyon (P. cembroides), Arizona Pine (P. arizonica), Silverleaf Oak (Quercus hypoleucoides), Arizona White Oak (Q. arizonica), Emory Oak (Q. emoryi), Netleaf Oak (Q. rugosa), Alligator Juniper (Juniperus deppeana), and Mexican Manzanita (Arctostaphylos pungens).

This ecoregion is an important area for bird richness and bird endemism. Likewise, virtually all of the ecoregion is included in the Sierra Madre Occidental and trans-mexican range Endemic Bird Area. Endemic bird species include the Thick-billed Parrot (Rhynchopsitta pachyrhyncha EN) which is in danger of extinction, with population estimates as low as 500 pairs; the Tufted Jay (Cyanocorax dickeyi NT), Eared Quetzal (Euptilptis neoxenus NT) and the Green-striped Brush Finch (Buarremon virenticeps). Temperate and tropical influences converge in this ecoregion, forming a unique and rich complex of flora and fauna. Many other birds are found in this ecoregion including the Green Parakeet (Aratinga holochlora), Eared Trogon (Euptilotis neoxenus NT), Coppery-tailed Trogon (Trogon elegans), Grey-breasted Jay (Aphelocoma ultramarina), Violet-crowned Hummingbird (Amazilia violiceps), Spotted Owl (Strix occidentalis NT), and Golden Eagle (Aguila chryaetos).  Some species found only in higher montane areas are the Gould's Wild Turkey (Meleagris gallopavo mexicana), Band-tailed Pigeon (Patagioenas fasciata), Mexican Chickadee (Poecile sclateri) and Hepatic Tanager (Piranga flava).

The Sierra Madre Mantled Ground Squirrel (Spermophilus madrensis NT) is an endemic to the Sierra Madre Occidental pine-oak forests, restricted to southwestern Chihuahua, Mexico. The Mexican Gray Wolf (Canis lupus baileyi) and Mexican Grizzly Bear (Ursus horribilis), although considered by most to be extinct from this ecoregion, once roamed these mountains. Mammals also present include White-tailed Deer (Odocoileus virginianus), American Black Bear (Ursus americanus), Buller’s Chipmunk (Tamias bulleri), endemic Zacatecan Deer Mouse (Peromyscus difficilis), rock Squirrel (Spernophilis variegatus), Zacatecas Harvest Mouse (Reithrodontomys zacatecae) and Coati (Nasua nasua), to set forth a subset of mammals present.

Reptiles are also numerous in this ecoregion. Fox´s Mountain Meadow Snake (Adelophis foxi) is an endemic taxon to the ecoregion, only observed at the type locality at four kilometers east of  Mil Diez, about  3.2 kilometers west of El Salto, in southwestern Durango, Mexico. There are at least six species of rattlesnakes including the Mexican Dusky Rattlesnake (Crotalis triseriatus), Mojave Rattlesnake (C. scutulatus), Rock Rattlesnake (C. lepidus), Western Diamondback Rattlesnake (C. atrox), Twin-spotted Rattlesnake (C. pricei), and Ridgenose Rattlesnakes (C. willardi).  Clark's Spiny Lizard (Sceloporus clarkii) and Yarrow's Spiny Lizard (S. jarrovii), Bunchgrass Lizard (S. scalaris), and Striped Plateau Lizard (S. virgatus) are several of the lizards found in the Sierra Madre Occidental pine-oak forests.

Along springs and streams the Western Barking Frog (Craugastor augusti) and the Tarahumara Frog (Rana tamahumarae) are two anuran taxa occurring in the ecoregion. Other anuran taxa found here include: Bigfoot Leopard Frog (Lithobates megapoda), Northwest Mexico Leopard Frog (Lithobates magnaocularis) and the Blunt-toed Chirping Frog (Eleutherodactylus modestus VU). The Sacramento Mountains Salamander (Aneides hardii) is an endemic salamander found in the Sierra Madre Occidental pine-oak forests, restricted to the Sacramento Mountains, Capitan Mountains, and Sierra Blanca in Lincoln and Otero Counties within southern New Mexico, USA.

World Wildlife Fund & C. Michael Hogan