Ring-Tailed Ground Squirrels (Notocitellus annulatus): Mexican Mammal Drawn by Jean-Jacques Audubon

Jean-Jacques depicted the specimen in his mammalian masterpiece, The Quadrupeds of North America. The publication evidenced the naturalist’s passion for all wildlife -- not just the avian representatives in The Birds of North America. He and his collaborator, Reverend John Bachman (February 4, 1790 – February 24, 1874), found the pelt attractively colored, with a dark body and head and with a tail banding black over a black, buff, and pink background. They found the sciurid intermediately sized between bigger, ground-based marmots and prairie dogs in the Marmotini tribe and:

• Ground-based “chipping squirrels” – chipmunks -- in the Tamiina subtribe;
• Tree-based flying and tree squirrels in the respective Pteromyini and Sciurini tribes.

They named it annulated marmot squirrel (Spermophilus annulatus).

Scientific nomenclature accedes to inquiring minds, scientific breakthroughs, and technological advances. Categories based upon appearance and habitat currently answer to phylogenetic analyses of molecules and morphology. Scientists nowadays appreciate finely differentiated relationships between -- and structures within -- organisms because of sub-cellular investigations. Ground squirrels are among the beneficiaries of research into mitochondria, the cellular sub-units that change specialized chemical energy from food into generalized energy -- adenosine triphosphate (ATP) -- for cells. Analysis of cytochrome b’s role in respiratory complex III’s generating ATP indeed contributes to Mammals Department Curator Kristofer M. Helgen and fellow Smithsonian National Museum of Natural History scientists -- F. Russell Cole, Lauren E. Helgen, and Don E. Wilson -- re-organizing the Spermophilus genus.

Ring-tailed ground squirrels now belong to the genus Notocitellus.  The name combines the Greek adjective noto (“black”) and the Latin noun citellus (“ground squirrel”). The genus divides into two species. Ring-tailed and tropical ground squirrels function as respective common names for the annulatus and adocetus species. Each species gets divided into subspecies. Membership goes according to distribution along western coastal Mexico. Scientists identify ring-tailed ground squirrels as:

• Notocitellus annulatus annulatus in Manzanillo, state of Colima;
• N.a. goldmani in Santiago and Tepic, Nayarit.

They indicate tropical ground squirrels in Michoacán as:

• Notocitellus adocetus adocetus in La Salada, about 40 miles (64.37 kilometers) south of Uruapan;
• N.a. infernatus in an area 8.5-8.75 miles (13.68-14.08 kilometers) south of El Infiernillo.

All species and subspecies appear grizzled black and tan because of darkly- and palely-flecked fur. The individual hairs are coarse-looking but marmot-like in their softness. The coat becomes brighter during the dry-season breeding months of December through June. The body conveys slenderness while the 15-ringed, tree squirrel-like tail expresses length. The mature head-and-body and tail lengths respectively hover around 11.3 - 18.75 inches (28.7 - 47.6 centimeters) and 5.0 - 9.37 inches (12.7 - 23.8 centimeters). The female -- who is larger-skulled than the male -- imitates marmots in possessing three sets of mammary glands despite all other ground squirrels typically having four to six pairs. One set is at the front limbs’ juncture with the body. Two sets locate at the rear limbs’ union with the posterior.

Small molars and stout incisors aid in digesting:

• Fronds, especially prickly pear cactus (Opuntia spp);
• Fruits, especially figs (Ficus spp) and plums (Prunus mexicana);
• Insects, especially ants, grasshoppers and termites;
• Nuts and seeds, especially calabash (Crescentia alata) and mesquite (Prosopis spp).

Thumbs at the ends of the front limbs’ long, narrow feet bring food into internal, large cheek pouches directly behind small premolars. Broad auditory bullae and rounded ears catch the slightest sounds from such predators as:

• Coyotes;
• Hawks;
• Snakes.

The omnivorous carnivore counter-attacks by:

• Balancing on haunches and tail;
• Chirping warnings and whistling alarms differentiating predatory presences from range breaches;
• Navigating undergrowth;
• Scaling trees, with the tail curved tree squirrel-like over the back;
• Sneaking into burrows.

Burrows are constructed with entrances, hallways, and rooms. The entrances can be built as gently sloping horizontal or straight up-and-down vertical entries. The hallways give corridor access to such rooms as:

• Chambers, in which mating, playing and sleeping take place;
• Nests, from which annual litters of four to six newborns are thought to emerge after maternal gestations of about 30 days;  
• Pantries of stored food, to which residents retire if above-ground supplies are scarce or when the morning or midday sun is too hot.

The rooms have grass-lined ceilings, floors, and walls. They house the changing family of parents and progeny. Males may be short-lived since they disperse soon after weaning at one-to-two months. Females remain in their birth-ranges.

In birth- and dispersal-ranges, ringtails build cavities under:

• Dense vines growing from tropical forest floors up large trees;
• Fallen leaves in oil palm groves;  
• Thorn-riddled trunks of catclaw (Senegalis greggii) and mesquite.

In home- and relocation-ranges, tropical ground squirrels burrow under:

• Drought-tolerant undergrowth on open ground;
• Rocks along canyon sides and small ravines;
• Roots of calabash, mesquite and plum trees.

Ringtails and tropicals additionally construct homes along the wildland-urban interface. They dwell in a coastal mini-strip that is attracting farmers and ranchers. They have one of two reactions to the growing agro-industrial presence:

• Build under the natural hedges and stone walls of cultivated fields or within the corrals of grazing pastures;
• Retreat to their area’s arid plateaus.

The two species come face-to-face with agro-industry in the northern part of the southwest Mexican state of Guerrero. Ring-tailed and tropical ground squirrel populations only confront one another in Guerrero. Otherwise, ringtails enjoy predominantly humid environments -- at altitudes from sea level to 3,937 feet (1,200 meters) -- in the lowland plains and tropical deciduous forests of:

• Colima;
• Nayarit.

Their smaller counterparts otherwise favor seasonally arid habitats – at elevations from sea level to 9,842.52 feet (3,000 meters) -- in the overgrown mesquite woodlands, tropical deciduous forests, and upland desert shrubs of:

• Jalisco;
• Michoacán.

Tropical ground squirrels nevertheless have the survival advantage over their ring-tailed counterparts. Their homeland includes such protected areas as:

• Infiernillo;
• Pico Tancitaro National Park.

Thirty-nine (39) years distance scientific knowledge of the first-known peddled specimen of the ring-tailed ground squirrel in 1838 from the second-known in 1877. One-hundred-fifty-eight (158) years divide the depiction of the ring-tail in The Quadrupeds of North America of 1851 and the re-organization of temperate ecozone-dwelling ground squirrels in “Generic Revision in the Holarctic Ground Squirrel Genus Spermophilus” of 2009. The reclusiveness of the sciurid’s behavior and the remoteness of their natural habitats -- within territory just 35 miles (156.33 kilometers) wide by 200 miles (321.87 kilometers) long -- discourage interactions. But the steady expansion of farms, ranches, and vacation homes into the semi-arboreal, semi-terrestrial’s isolated ranges does result in leaps in familiarity unknown to 19th- and 20th-century time-dwellers.

Squirrels amaze humankind with their acrobatics, aesthetics, and amiability. Does a bad fur day or photo opportunity ever cross a squirrel’s path? As with their specifically arboreal or strictly terrestrial counterparts, ring-tailed and tropical ground squirrels enchant with their upbeat reactions to range invasions. They enjoy:

• Bread;
• Lettuce;
• Meat;
• Tortillas.

They entertain locals with agile feats and friendly inquisitiveness. They keep insect pests out of barns and outbuildings. But they keep on:

• Burrowing, to combat claw overgrowth;
• Chewing, to halt teeth overgrowth;
• Devouring field corn and sorghum, garden beans, and orchard fruits, to maintain healthy diets.

Domestication and protection promise these obligate seed-dispersers sustainability. Domesticators and scientists nevertheless will need flashlights when night-strolling through ground squirrel-burrowed grounds!

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Spencer Fullerton Baird: 1850 daguerrotype portrait: Smithsonian Institution Archives, No restrictions, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:Spencer_Fullerton_Baird_-_1850.jpg; No restrictions, via Smithsonian Institution Archives @ https://siarchives.si.edu/collections/siris_sic_9863

National Portrait Gallery, Washington DC: Cliff (cliff1066™), CC BY 2.0, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:John_James_Audubon_painting.jpg

Mitochondrial cytochrome bc1 complex: Andrei Lomize, CC BY-SA 3.0, via Wikimedia Commons @ https://en.wikipedia.org/wiki/File:1l0l_opm.gif

A.W. Howell, North American Fauna 56 (1938), Plate 31, Figure D, opposite page 245: via Biodiversity Heritage Library @ https://www.biodiversitylibrary.org/page/25806655

A.H. Howell, North American Fauna 56 (1938), Plate 26, Figure D, opposite page 240: via Biodiversity Heritage Library @ https://www.biodiversitylibrary.org/page/25806646

A.H. Howell, Revision of the North American Ground Squirrels (1938), Plate 9, opposite page 28: North American Fauna 56, via Biodiversity Heritage Library @ https://www.biodiversitylibrary.org/page/25806395

A.H. Howell, Revision of the North American Ground Squirrels (1938), page 163: North American Fauna 56, via Biodiversity Heritage Library @ https://www.biodiversitylibrary.org/page/25806556

Laguna La María, State of Colima, west central Mexico: wendolyne78, CC BY-SA 2.0, via Flickr @ https://www.flickr.com/photos/66947169@N04/6121446887

Plate LXXIX, No. 16, opposite page 212, J.J. Audubon, The Quadrupeds of North America, vol. II (MDCCCLI [1851]): via Internet Archive @ https://archive.org/details/quadrupedsofnort02audu/page/n276/mode/1up; via Biodiversity Heritage Library @ https://www.biodiversitylibrary.org/page/34896757

en el palmar: palm grove, Colima, Mexico: Ana Rodríguez Carrington (Ani Carrington), CC BY 2.0, via Flickr @ https://www.flickr.com/photos/35506817@N00/5797558262

C.L. Bachman, John Bachman The Pastor of St. John's Lutheran Church Charleston (1888), frontispiece: Not in copyright, via Biodiversity Heritage Library @ http://biodiversitylibrary.org/page/23769091

panorama of San Blas: Vic0 at en.wikipedia, CC BY SA 3.0, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:San_Blas_(Mexico).JPG

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