Lodgepole chipmunk

Sexual Dimorphism & Phenotype Characteristics

Sexual dimorphism can be witnessed in the Lodgepole Chipmunk as females are known to be larger in size than males. Female Lodgepole Chipmunks have an average body weight of 55-69 grams whereas males on average are 50-60 grams in total weight. Along with weight, females can be observed having a body length ranging from 197–229 mm (7 3/4 - 9 inches), while males typically exhibit an average body length of 200–222 mm (7.8 - 8.7 inches). Body patterns remain consistent in both sexes as they exhibit characteristic white dorsal and facial stripes, where the central dorsal stripes are known to be less prominent and closer to yellow-white than that of the lateral white stripes. In comparison to other close relatives, this species can be identified by examination of the darker and more broad facial stripes. Other notable body patterns include dark black dorsal stripes, a lack of a black stripe underneath the prominent white lateral stripe, bright orange color on sides and orange-gray coloring on the shoulders, a gray under-belly, and a gray rump. The top of the head, the crown, is known to be brown with some gray interspersed. The tail, lengthier in females, ranges from 13–22 mm (0.5 - 0.87 inches) and is characterized by its black tip and cinnamon body.

Range & Habitat

The Lodgepole Chipmunk spans from the high Sierra Nevada, San Jacinto, San Bernardino, and San Gabriel Mountain ranges of California into the Lake Tahoe region of the west central corner of Nevada. This species lives in subalpine coniferous forests made primarily of several species of pines (Lodgepole, Jeffrey, Ponderosa, and Sugar) and firs (Douglas, white and red). They can be observed foraging around and on top of rocks and fallen logs, which make up the forest floor. In 1978, a removal experiment based on observations was conducted by Mark A. Chappell which took four different species of chipmunk into account. This experiment was to detail the process of removal by the different species. In the experiment, it was noted that the four different species were allopatric, meaning they formed non-overlapping borders in their Sierra Nevada habitat. Each species (T. alpinus, T. speciosus, T. amoenus, and T. minimus) was noted to live at different zones making up the Sierra Nevada. The Lodgepole Chipmunk (T. speciosus) was observed living from 2400–3000 meters in the lodgepole pine zone, between the alpine zone (3000+ meters) and the Piñon pine/mountain mahogany zone (1900–2400 meters). This ecological competition for different zones of a single area is determined by physiological and environmental limits, where each species is limited specifically to a zone that best fit each species' habitat preferences. The effects of burning and mechanical thinning were investigated from 1999-2000 and 2002-2003 in the southern Sierra Nevada Mountains. This experiment was conducted through captures of Lodgepole Chipmunks and the results indicated that over a short-term period, forest management techniques such as burning and mechanical thinning do not have a significant impact on the species in respect to capture rate or population number. However, the experiment did indicate that body mass of these chipmunks decreased because forest structure changed, limiting food availability provided by the cones of trees.

Predators

Being a small rodent, the Lodgepole Chipmunk has larger predators it must be on the look out for. Natural predators of this chipmunk include coyotes, foxes (primarily the gray fox), hawks (Cooper's and Red-Tailed), bobcats, and martens. To avoid such threats, the Lodgepole Chipmunk is capable of climbing trees in order to seek safety and also minimize open exposure by utilizing the color patterns and markings of its fur to blend in to its surroundings, providing camouflage against the environment.

Behavior & Communication

Several different vocalizations are used by the Lodgepole Chipmunk during both courtship and when frightened by a predator. During courtship, visual displays can be shown through the action of tail flipping and body postures of both sexes. Alongside visual displays, during courtship males and females utilize chips and whistles. When frightened or alerting others, the Lodgepole Chipmunk produces a high pitched "whisk", a shrill "tsew", as well as the series "pst-pst-pst-a-ku" in a rapid and repeated manner. After caching food throughout the spring and summer months, hibernation begins at the end of October and lasts until early to mid April, a five-six month span.

Diet & Ecological Role

The Lodgepole Chipmunk is an omnivore, feeding on a multiple of both animal (mammals, birds, bird eggs, small invertebrates arthropods, and insects) and plant matter (leaves, flowers, pollen, forbs, fungi, and seeds). Like most rodents, this chipmunk engages in the foraging behavior of caching and storing food in order to survive the long winter hibernation. The Lodgepole Chipmunk is also known to serve two main ecological roles. Through its diet, this chipmunk ingests seeds, which are not broken down through the digestive process, and the seeds are then defecated and dispersed throughout its habitat, spreading variation and enhancing the range o f the seed-producing plant. Similarly, the Lodgepole Chipmunk also disperses ectomycorrhizal fungi. This kind of fungi is important to forests, allowing for trees to subsist by increasing their water and nutrient gains. By dispersing spores, seeds, and pollen, the Lodgepole Chipmunk plays an important role in the maintenance of the forest and mountain ecosystem.

Reproduction

Through visual displays and vocalizations, both males and females engage in courtship. When the scrotum turns black and the testes are loosely relaxed, the male is ready to mate. Once per year Lodgepole Chipmunks breed during May to early June, three to six young (pups) are born in early June after a one-month gestation period. Lactation provided by the mother allows nourishment to poorly developed pups, lasting for approximately one month, and then the young are independent by Fall. Young reach sexual maturity the following Spring. Though not known, it is expected that like other relatives, the Lodgepole Chipmunk exhibit a polygynous system of mating. Also, parental investment rests solely on the mother as the father of the litter does not provide parental care to his offspring.