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Native Californian, biologist, wildlife conservation consultant, retired Smithsonian scientist, father of two daughters, grandfather of 4 small primates. INTJ. Believes nature is infinitely more interesting than shopping malls. Born 100 years too late.

Friday, August 24, 2007

A chipmunk between two worlds

I believe this is a lodgepole chipmunk (Tamias speciosus), but I am not certain. The old addage, "if it looks like a duck and sounds like a duck. . ." may apply to chipmunks in general, but it doesn't apply to species of chipmunks. Some chipmunk species are remarkably similar in coat color and size, and only diligent study reveals their true identify. This one, photographed at Lassen National Park among the Jeffrey pines, could also be the yellow pine chipmunk (T. amoenus).

Californians proudly boast 13 species of chipmunks. (Well, they should anyway.) Yes, 50% of the world's species of chipmunks live in the golden state. Most of the other species live in the intermontane parts of the western US, Canada, and Mexico.

Chipmunks are basically mini-tree squirrels with racing stripes. They occur from sea level to treeline, and fill an ecological niche between the terrestrial world of ground squirrels and the largely arboreal world of tree squirrels.

The sexes show variable dimorphism in body size. In more extreme habitats females tend to be larger than males, while males are the larger sex in other areas. This infers that big female chipmunks have certain advantages, perhaps in energetics and reproduction--though the subject needs more study. Their best known trait is their internal cheek pouches, which allow them to haul food from feeding areas to hoards and nests.

The two most widespread species, the eastern chipmunk (Tamias striatus) and the Siberian chipmunk (T. sibiricus) have the largest geographic ranges. They also have more generalized traits, so mammalogists believe they are a bit closer to the ancestral chipmunk. The hotbed of chipmunk evolution is western North America. Here where the forces of nature have created a quiltwork of habitats they have evolved into many forms.

The debate isn't settled on where exactly chipmunks came from--Eurasia, North America, or perhaps somewhere in between, like Beringia. If the ancestral chipmunk was Eurasian or North American, however, it had to cross the Bering land bridge, like a lot of other mammals in the past.

Contrary to popular belief, the word chipmunk does not owe its derivation to the resemblance of these rodents to cheerful Jesuit monks, or men of any particular monastic order. The word comes from the Algonquian "achitamon" for "one who descends trees headlong". In other words, chipmunks can rotate their hindlegs and climb down tree trunks headfirst. They share this trait with tree squirrels. Their small size gives them advantage when it comes to negotiating shrubby vegetation that bears nutlets, berries, and drupes. Thus they get around much better in the brushlands, chaparral and forest understory than ground squirrels and tree squirrels.

Like ground squirrels, they nest and hibernate in burrows, but apparently some species, like the lodgepole chipmunk, make tree nests in cavities or exposed on a limb close to the trunk. These are used by mother and young after the munklets develop their climbing skills. This practice of using both subterranean and arboreal nests is just another example of how chipmunks live between two worlds.

Best, T.L., R.G. Clawson, and J.A. Clawson. 1994. Tamias speciosus. Mammalian Species, No. 478:1-9.

Broadbooks, H.E. 1974. Tree nests of chipmunks with comments on associated behavior and ecology. Journal of Mammalogy, 55(3):630-639.

Levenson, H. 1990. Sexual size dimorphism in chipmunks. Journal of Mammalogy, 71(2):161-170.

Levenson, H., R.S. Hoffmann, C.F. Nadler, L. Deutsch, and S.D. Freeman. 1985. Systematics of the Holarctic chipmunks (Tamias). Journal of Mammalogy, 66(1):219-242.

Ralls, K. 1976. Mammals in which females are larger than males. The Quarterly Review of Biology, 51:245-276.

Sutton, D. A. and D.B. Patterson. 2000. Geogrpahic variation of the western chipmunks Tamias senes and T. siskiyou, with two new subspecies from California. Journal of Mammalogy, 81(2):299-316.

Wilson, D.E. and D. M Reeder. 1993. Mammal species of the world, a taxonomic and geographic reference. Smithsonian Institution Press, Wasgington D.C. and London.


Anonymous said...

Looks to me that you have a lodgepole chipmunk. The abundant y-p chipmunks up here have a yellowish fringe along their tail and less of the dark spot at the end. According to Ingles, and Kays and Wilson the lodgepole generally lacks the dark stripe under the outer light stripe, and the
sides are rusty.
Fascinating genus. I have a ton of good chipmunk data from my flying squirrel study that I have yet to dig into. It actually is a better dataset than for squirrels - more captures give better demographic data.
The interesting thing here is that we are on the edge of Townsend's chipmunk range - they spill over the Cascades and are in the closed canopy
patches vs. the open patches where we catch y-p chipmunks. In our trapping grids you could predict with high certainty what species you'd find in a trap depending on the canopy openness, even if the patchiness was less than a ha or so.

Anonymous said...

Great post, as always!

Anonymous said...

Nice essay. We have least and pine chipmunks here in NE New Mexico. The least runs with its tail straight up and the pine runs with its tail extended straight back.

Steve Bodio said...

What are the ecological differences between the species with larger females and with larger males? I am thinking about the sexual differences in raptorial birds, where the dichotomy is greater in the more active predators, but the female is always bigger.

Unknown said...
This comment has been removed by the author.
Unknown said...

Hi! I would like to know where I can buy these cameras trap. I am Brazilian biologist.

Ann Downer-Hazell said...

Hey, I'm so glad to have found this blog...I am a science editor, mother of a chipmunk-adoring 7 year old, and ambitious to build a camera trap for our suburban Boston yard. Nice to meetcha!

Camera Trap Codger said...

Steve, Your question is a good one, but one I cannot answer. It would make a good topic for a PH D dissertation. The differing selection pressures in "extreme" and less extreme habitats and how they act on the sexes is an intriguing topic. (I'm just too old to take it on myself -- LOL).

Elizandra, Check out Calelas on-line catalogue to get an idea of that is commercially available in camera traps. Then look up the Pixcontroller. com website and see what they have to offer.

Hi Ann, Glad you like this stuff. It's always good to hear about parents who encourage their children's interest in wildlife.

Anonymous said...

Hi Chris,
I am not an expert at identifying chipmunks, but I agree with your identification of the one in your picture as speciosus. It is definitely not amoenus which has a distinct blackish stripe lateral to the the lateral-most white stripes. This gives it a five dark stripe appearance as opposed to three in speciosus. As I understand it, the other chipmunk in the Lassen areas is senex which is much duskier in appearance, i.e, grayish instead of white stripes and little or no white behind the ears.
I appreciate your on-going saga of photographic adventures.

Camera Trap Codger said...

Thanks a lot Bill: I was hoping to get confirmation or correction from the mammalogists out there.

Betsy Seeton said...

I live at 10,000 feet in the Rocky Mountains of Colorado and have many wild pets that I've known year after year. Chippy is a golden mantled ground squirrel going on her fifth summer around my cabin. She comes when I call as do her offspring and several chipmunks and all feed from my hand. I also have birds who come when I whistle and feed from my hand. Check out my photos of these lovely creatures. I also have a website dedicated to animals rights and ending abuse/trafficking of animals and humans. i have a page called Chippy and the Crew about life in the woods with all the animals. My blog also mentions them.



Look forward to hearing from you.