5.8 KiB
| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Central place foraging | 2/4 | https://en.wikipedia.org/wiki/Central_place_foraging | reference | science, encyclopedia | 2026-05-05T14:59:49.572605+00:00 | kb-cron |
=== Archaeological case study: silver miners and propaganda in Colorado === Glover (2009) used a CPF model to determine if late nineteenth century silver miners near Gothic, Colorado were choosing mine locations efficiently given the costs of transporting silver ore to the mill, the value of silver, and the amount of silver per kilogram of ore. Estimates of the costs associated with transport were obtained using research from physiology to determine the most energetically efficient load size. Newspaper articles were used to determine the hourly wage that a miner could be making if they worked in town instead. Newspapers were also used to estimate the value of silver at that time, and estimates of the amount of silver per kilogram of ore were obtained through records from area silver mills, as well as through newspapers. These differed, with the newspapers optimistically claiming that silver deposits were far more productive than the more accurate mill records demonstrated. These estimates were used to determine the optimal placement of mines. A number of historic mining locations were recorded using GPS. These data were used to calculate least cost paths from the mines to Gothic, which provided the distances to the central place. The results were compared to two different CPF models based on newspaper propaganda and the more realistic mill records, respectively. Miners were choosing locations that were much farther away than feasible given the value of silver and its actual abundance. However, the mines were within the distance predicted using the optimistic newspaper estimates. Glover suggested that miners, being new to the area, used social learning strategies and based their decisions on newspaper propaganda and rumors, rather than individual experience. Therefore, they chose locations that were too far away to be economically viable.
=== Ethnographic case study: shellfish in Torres Strait Islands === Shellfish exemplify the resources targeted by the CPF model – those with a heavy, bulky, low utility component (e.g. shell) surrounding a smaller, lighter high utility component (e.g. meat). If foragers differentially field process and transport shellfish prey items, analyses of midden composition may incorrectly estimate the importance of some species and their relative contribution to prehistoric diets. Using foraging data from the Meriam of Australia, Bird and Bliege Bird (1997) compare observed shellfish field acquisition to shell deposition at residential sites, and test the hypotheses of the CPF model. The Meriam inhabit Torres Strait Islands of Australia, are of Melanesian descent, and have strong cultural and historical ties to New Guinea. They continue to harvest marine resources such as sea turtles, fishes, squid, and shellfish. Bird and Bliege Bird conducted “focal individual foraging follows” of 33 children, 16 men and 42 women during intertidal foraging bouts on reef flats and rock shores. Foraging technology includes 10- liter plastic buckets, long-blade knives, and hammers. Foragers are constrained by time (2–4 hours at low tide) and load size (10-liter bucket). Large clams (Hippopus hippopus and Tridacna spp.) collected on the reef flat constitute over half of the edible weight collected, but since they are almost always field processed their shells make up only 10% of the residential site deposition. In contrast, sunset clams (Asaphis violascens) and nerites (Nerita undata) are usually processed residentially. Large clams were, therefore, underrepresented while small clams and nerites were overrepresented in the reconstructed diet. Since reef flat and rocky shore foraging occurs at multiple sites at variable distances from the residential camp, the authors calculated the mean one-way travel distance processing threshold (
z
d
1
{\displaystyle z_{d1}}
, in meters) for each species. The CPF model accurately predicts field processing for the majority of reef flat foraging events for bivalves. Hippopus and Tridacna have small processing threshold distances (
z
d
1
{\displaystyle z_{d1}}
= 74.6 and 137 respectively), and no shell is returned to camp at distances beyond 150 meters. Women’s fit nears 100%, but children and men made the optimal choice less frequently because they usually forage for shellfish opportunistically, and therefore do not always carry the appropriate processing technology. For gastropods (Lambis lambis,
z
d
1
{\displaystyle z_{d1}}
= 278.7), the model accurately predicts processing only 58-59% of the time. This could in part be due to a preference for cooking some species inside of their shells (i.e. the shell has some utility), or also because some prey items are prepared at “dinner-time camps” rather than the residential camp. A. violascens and N. undata are never field processed, consistent with their large processing threshold distances (2418.5 and 5355.7 respectively). Overall, prey types that were difficult or inefficient to process and/or were collected near the residential or temporary camp were not field processed. Species that required little processing time to increase returns and/or were collected far from camp were field processed. The field processing predictions of the CPF model might be incorrect where shellfish are transported whole in order to maintain freshness for later consumption or trade, or where the shell itself is valuable.