Members of the Family Rodentia
If you plan to be a renowned authority on Panamint chipmunks, you’ll have to figure out first how to know one when you see one. That may come harder than it sounds.
How Will I Know a Panamint Chipmunk When I See One?
The Panamint chipmunk named for a Death Valley National Park mountain range it inhabits belongs to the order of Rodentia, making it a rodent. Rodents account for more than 40 percent of the world’s 5,419 known mammals, according to the Smithsonian’s National Museum of Natural History Internet site. In the United States, its Rodentia relatives include porcupines, beavers, prairie dogs, gophers, rats, mice, marmots, tree and ground squirrels, and more than 20 other chipmunk species. All the rodents, according to the Zoology Museum Internet site, have a “long pair of chisel-like incisor teeth (with enamel on the front surface only) projecting from each jaw at the front of the mouth; these teeth grow continuously and if for any reason they are not worn down by gnawing, the tips may grow past each other and perforate the palate.”
Most of the time, as far as I can tell, the Panamint chipmunk doesn’t look a whole lot like most of the porcupines or beavers I know, but it sure can look something like a ground squirrel, for instance, a thirteen-lined ground squirrel or, especially, a golden-mantled ground squirrel.
Fortunately, it doesn’t share a range with the thirteen-lined ground squirrel. Otherwise, it might have to stand side-by-side with the squirrel so we could distinguish between the species by counting and comparing the stripes down their backs.
On the other hand, the Panamint chipmunk does share a limited range with the golden-mantled ground squirrel, and both species have certain similar characteristics. Both measure several inches in length. Both weigh only a few ounces. Both have highly elastic cheek pouches for carrying food to their burrows. Both have striped bodies. Both will try, perfectly brazenly, to con you out of treats.
However, according to William H. Burt and Richard P. Grossenheider, A Field Guide to the Mammals of America North of Mexico, the typical Panamint chipmunk measures about eight to nine inches in length from the tip of its nose to the tip of its tail while the golden mantled ground squirrel measures about 10 or 11 inches. The chipmunk weighs two to four ounces; the squirrel, about twice as much. The chipmunk has alternating dark and light stripes from the base of its tail to the tip of its nose. The squirrel has a white stripe bordered with black on each side of its body, from the base of its tail to the back of its head, with no stripes on its face. The chipmunk runs with its tail held erect, like a miniature pennant on the back fender of a low rider. The squirrel runs with its tail held horizontally, almost seeming to float along behind its body. The chipmunk caches food in and around its burrow, feeding on its stores during its periods of semi-hibernation. The squirrel puts on considerable body fat, which sustains the animal during its deep hibernation.
The Panamint chipmunk resembles some of its brethren western chipmunk species much more closely. As George D. Baumgardner said in “Nevada State Museum Newsletter,” August 2003, “Individual chipmunks can, presumably, recognize fellow members of their own species; however, it can be very difficult for people to tell them apart. Even trained and experienced biologists can have a hard time identifying the different chipmunk species using external characteristics.”
The Panamint and its fellow chipmunk species, specifically the males, do, however, offer important clues to the identity of their species in their particular bacula, which looks something like micro-miniature back-scratchers. One species may have a comparatively long and thin baculum; another, a short and stout baculum; and still another, a variable-dimensioned baculum. Female chipmunks regard this issue as an important distinction because a baculum is a penis bone, which is found in most mammals (although it is absent in humans, kangaroos and hyenas), and lady chipmunks have developed more skill than most trained biologists in identifying the males of their species.
(I can tell you an easy way to distinguish between Chip ‘n Dale, Walt Disney’s two beloved cartoon chipmunks and Donald Duck’s most exasperating adversaries: Chip has a black nose, and Dale, a red nose. That probably won’t help much, though, in identifying real chipmunks in the field.)
Anatomy of the Panamint Chipmunk
The Panamint chipmunk, first reported by the famed naturalist Clinton Hart Merriam in 1893, has a brightly colored coat, with yellowish brown, or tawny, color along its sides and back, grayish patches on its head and rump, and alternating light and dark stripes along its back and face. It dresses in its brightest coat in the summertime, “whereas in the winter the fur is long and silky, with yellowish coloration and faded markings,” according to the University of Michigan Museum of Zoology Animal Diversity Web site. Typically, its two- to four-ounce body, from nose tip to rump, averages about four to five inches in length. Its tail averages roughly one-half to three-quarters of an inch shorter than its body. Its baculum, you will be pleased to discover, has a comparatively small keel and short shaft with distinct ridges on either side of the tip, according to Troy L. Best, Robin G. Clawson, and Joseph A. Clawson, writing about the Panamint chipmunk for Mammalian Species.
Range, Habitat, Diet
The Panamint chipmunk primarily occupies the piñon pine- and juniper-covered mountain flanks of various ranges in the southwestern Great Basin region, in southeastern California and southwestern Nevada, according to Best, Clawson and Clawson. It favors rocky outcrops, using fissures for shelter, nesting and food caches.
Typically, a Panamint chipmunk population lives in a “habitat island,” isolated by surrounding desert environments, said Baumgardner. Presumably, during the Ice Ages, before the piñon pine, juniper and other coniferous trees disappeared from the lower elevations, the chipmunks lived in the basins as well as on the mountain flanks. As the region grew drier and warmer, the coniferous trees, with the Panamint chipmunk, retreated to the higher and wetter and cooler elevations. Together they became confined to the more restricted ranges.
The opportunistic chipmunk forages primarily on piñon nuts and juniper seeds, but it will also feed on other seeds as well as fruits, fresh green vegetation, insects, spiders, carrion, bark and even lichen, said the Animal Diversity Web site. Absent a water source, the Panamint chipmunk can get the moisture it requires from its food sources, but it will drink water, given the opportunity.
Generally, a chipmunk is a classic glutton. Given a chance, it caches far more food than it can possibly use. “I recorded one chipmunk that carried off thirty-four to thirty-eight sunflower seeds [from a bird feeder] to its burrow and made a round trip every seven minutes,” said Leonard Lee Rue, Vivid Light Photography Internet site. “It did this for hours on end…”
“One chipmunk that I examined , that had been killed by a car on the highway, had four hundred thirteen little grass and weed seeds stuffed into its pouches.”
The Panamint chipmunk chattering with delight mates during the spring months, the primary time for social gatherings of the species. The female emerges from her burrow, chirping, to announce that she is prepared to consider potential mates. The male emerges from his burrow to contest other males for her paw. After mating, which she will do but once during the course of the year, the female retreats to her intricate and carefully camouflaged burrow to prepare for her coming young. The male, encouraged by his conquest, goes on his way in search of more good fortune.
A little more than a month later, the female delivers a litter of three to nine (usually four to six) hairless and squeaking young in a nest, or birthing chamber, within her burrow. “In newborn Panamint chipmunks,” said Best, Clawson and Clawson, “the skin is pink and semi-transparent. Organ movements and white areas containing milk can be seen immediately after nursing... Eyes of newborn chipmunks bulge and appear dark through the transparent covering of skin. Pinnae [the exterior portions] of the ears are folded against the sides of the head... Toes, although formed at birth, are united by a membranous covering and have minute claws.”
For the next five weeks, the Panamint chipmunk mother, with no help from the lusty father, nurses and protects her youngsters. Their eyes begin to open within about four days, becoming fully open within 29 or 30 days. The pinnae of their ears open within a few days and the external opening of the auditory canal opens within about four weeks. Their hair begins to grow within a week to 10 days, with their stripes first appearing within 12 to 13 days. Their toes began to separate some 10 days after their birth, with clearly distinguishable claws forming within 21 days. Their incisors the signature feature of rodents begin to erupt within about two weeks and continue emerging, developing and growing for another three weeks. Between feedings, “...the babies sleep with their forepaws held over the face, with the body and tail curled in a ball,” said Best, Clawson and Clawson.
Weaned about five weeks after their birth, the rapidly developing young soon venture outside their burrow, still under the watchful eye and nurturing care of their mother. They graduate to solid Panamint chipmunk food. They play among the rocks surrounding their burrow. They learn survival skills, taking refuge in rocky shelters when alarmed. With the onset of autumn and falling temperatures, each youngster, now an adult in size, leaves home, establishes its own burrow, and begins an independent life. The Panamint chipmunk may live for several years if it can avoid becoming a tasty snack for a predator.
The Panamint chipmunk makes its home almost exclusively within rocky outcrops, especially those within growths of piñon pine and juniper trees, said Best, Clawson and Clawson. Active throughout the day, but especially during the early morning and late afternoon, it scurries over stony surfaces, perches on rocky overlooks, and forages over the ground and in lower tree branches. It stays close to rock piles and fallen branches, which offer a quick refuge in the event of a threat. Where it pauses, it may leave a small pile of shells from seeds that it has cracked open to get at the meat. If it ventures briefly into open areas, for instance, to drink at a spring or a pond, it stops frequently, checking for danger. When the sun falls, it returns to its burrow for the night.
Like all chipmunks, the Panamint chipmunk produces a variety of sounds, including “chucks, chatterings, whistles, chips, chipperings, bursts and sweeps,” according to the Animal Diversity Internet site, and, presumably, like other chipmunks, the Panamint chipmunk communicates visually with tail positioning and body posture and tactically with mating and courtship stroking and nuzzling.
Come winter, the Panamint chipmunk becomes less active, staying in its burrow and, presumably, sleeping in semi-hibernation and feeding on its food stores during cold cloudy days. Irrepressible, however, it emerges on clear days, even cold windy ones, remaining active to some degree throughout the season. As Best, Clawson and Clawson put it, “The Panamint chipmunk has an annual rhythm with flexibility in phasing that enables adjustment to environmental variation among years.”
If the Panamint chipmunk can charm, or con, us humans, with not a baculum among us, into feeding it fruit and nuts, it behaves like a pugnacious fussbudget among its baculum-endowed peers. Generally solitary and highly territorial, it guards its burrow and the immediately surrounding area. It protects its food caches. The males squabble over females during the annual breeding season.
The Panamint chipmunk serves as an example of how even a small creature has a place in the environmental health of its range. As prey, it (unintentionally, I’m sure) makes up part of the diet of birds such as the raptors as well as animals such as coyotes, foxes and bobcats. In its sometimes forgotten food caches, it has effectively planted the seeds for new piñon pines, juniper and other plants, repaying the favor of its provisioning and helping insure the health of the forest.
How the Chipmunk Got Its Stripes
If you still plan to be a renowned authority on Panamint chipmunks, and its various rodent cousins, you need to know, of course, how they got their stripes, an event that unfolded a long time ago in a land far, far away.
It happened about 1000 years B.C., when the legendary Indian King Rama, according to the ancient Indian poem, Ramayana, led an epic quest to recapture his beloved wife Sita, who had been taken hostage by the evil tyrant Ravana. Rama’s search was interrupted when he came to the impassible Palk Strait, between India and Sri Lanka, and he found help from an army of holy monkeys, who cast stones into the sea to build a bridge. Rama discovered that chipmunk-like animals, sympathizing with his suffering and distress, carried stones to the water’s edge to help, as best they could, supply the monkeys with materials for the enterprise.
Touched, Rama stroked the length of the small creatures’ backs with his fingers. Finally, with the bridge finished, he marched across to defeat Ravana and recover his love, leaving his tiny allies with permanent stripes along their backs, where he had stroked them.
By Jay W. Sharp
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