Thursday, December 29, 2005

Zooarchaeology, Pokemon Archaeology and Climate Change

The above are pictures of pika's, small north american species related to rabbits and hares:

Pikas breed in March or April and have a litter of three or four young after a gestation period of about 30 days. Some females have a second litter. Like many mammals, pikas shed in late spring from their long winter coats to a shorter summer coat, then shed again in the fall. Because of the short warm season, the end of spring shedding can actually overlap the beginning of the fall shed so the animals look scruffy most of the summer.

Maximum life span is four to seven years. Predators of pikas include long-tailed weasels, ermines and martens. Coyotes and hawks probably take their toll as well, but pikas are fairly well protected from larger predators by their rocky habitat.

Additionally, Pikas are the inspiration for one of the characters in the popular children's show, Pokemon.

Zooarchaeology, on the other hand, is a subset of archaeology. Zooarchaeologists are a diverse lot who study the patterened distribution of animal remains in order to learn something about subsistence patterns of humans and their ancestors. Consequently, zooarchaeology covers a wide amount of territory. One aspect falls under the rubric of taphonomy - where zooarchaeologist study how critters become fossils. In particular, how fossils can be used to study and reconstruct past environments. Another example would be studying wild sheep and goats in order to make predictions about how these animals were first domesticated. A better example would be John Speth's Bison Kills and Bone Counts. The book is, primarily, an examination of a bison kill site. Along the way we learn about portability of bison parts based on nutrional value (and examine predictions this makes about the archaeological record - calculate sex ratios based on a variety of body elements, for example)and seasonal variation in nutrional value. He then examines various groups such as northern Native Americans and European fur trappers in light of the above (if your diet is primarily meat, make sure you have some fat in it).
One of the leading zooarchaeologists is D. K. Grayson - who's "Quantitative Zooarchaeology: Topics in the Analysis of Archaeological Faunas" is a classic. Grayson has recently been studying Pikas and the results are interesting:

New research indicates the small mammals, which are very sensitive to high temperatures, are being pushed upward in their mountain habitat and are running out of places to live. Climate change and human activities appear to be primary factors imperiling the pika, reports University of Washington archaeologist Donald Grayson in the current issue of the Journal of Biogeography.

Grayson's research which looks at a 40,000-year record of archaeological and paleontological sites, combined with yet unpublished work by several other researchers, paints a bleak future for the American pika (Ochotona princeps) in the Great Basin.


Grayson's analysis of 57 well-dated archaeological sites, dating as far back as 40,000 years, shows that pikas have been pushed to higher and higher elevations. During the late Pleistocene and early Holocene epochs, 40,000 to about 7,500 years ago, now-extinct populations of Great Basin pikas were found at an average elevation of l,750 meters (5741 feet). The average minimum elevation of 18 surviving Great Basin populations surveyed in 2003 by Erik Beever, now with the National Park Service, was 2,533 meters (8,310 feet). These populations are scattered across Nevada, eastern California and southern Oregon.

Nine populations of Pikas have become extinct, while the remaining populations have been pushed to higher elevations. Beever's recent (2004 - afarensis) research indicates:

...American pika (Ochotona princeps) populations were detected at only five out of seven re-surveyed sites that possessed pikas in Beever's research in the mid- to late-1990s. The original research documented local extinctions at seven of twenty-five sites in the Great Basin – the area between the Sierra Nevada and Rocky Mountains. The recent re-sampling brings the total number of sites at which American pika populations have suffered local extinction to nine out of twenty-five or 36 percent. Continued loss of populations raises concern, as does the fact that these results and other lines of evidence suggest that many of the losses have occurred towards the more recent end of the 14 to 91-year period since their scientific discovery.

Back to the Grayson article for the final word:

Beever recently discovered two more pika population extinctions in the Great Basin and another increase of 132 meters (433 feet) in the lower elevation range of the animals at the locations where populations still remain. Patton, who has been studying wildlife in Yosemite National Park, which is in the Sierra Nevada Mountains adjacent to the Great Basin, has reported a 1,700-foot upward increase in the range of pikas there over the past 90 years. Found as low as 7,800 feet in the first decade of the 20th century, the animals now can't be found below 9,500 feet in Yosemite.

"We might be staring pika extinction in the Great Basin, maybe in Yosemite, too, right in the face. Today, the Great Basin pika is totally isolated on separated mountain ranges and there is no way one of these populations can get to another," said Grayson. "They don't have much up-slope habitat left."

"Pikas are an iconic animal to people who like high elevations. They are part of the experience. What's happening to them is telling us something about the dramatic changes in climate happening in the Great Basin. Climate change will have a dramatic effect including important economic impacts, such as diminished water resources, on people.

So, studying the effects of climate change is another intersting facet of zooarchaeology...

The abstract to Grayson's article can be found here.
The absract to Beever et al's 2003 paper can be found here.

For additional info on zooarchaeology the following books are recommended:

Vertebrate Taphonomy by R. Lee Lyman
Bison Kills and Bone Counts by John D. Speth
Fossils in the Making: Vertebrate Taphonomy and Paleoecology by Behrensmeyer and Hill
Environment and Archaeology by Karl Butzer
The Grayson book mentioned above.