Case studies Central place foraging

1 case studies

1.1 central place foraging in non-human animals
1.2 archaeological case study: acorns , mussels in california
1.3 archaeological case study: silver miners , propaganda in colorado
1.4 ethnographic case study: shellfish in torres strait islands
1.5 ethnoarchaeological case study: pickleweed , piñon

case studies
central place foraging in non-human animals

orians , pearson (1979) found red-winged blackbirds in eastern washington state tend capture larger number of single species prey items per trip compared same species in costa rica, brought large, single insects. foraging specialization costa rican blackbirds attributed increased search , handling costs of nocturnal foraging, whereas birds in eastern washington forage diurnally prey lower search , handling costs. studies sea birds , seals have found load size tends increase foraging distance nest, predicted cpf. other central place foragers, such social insects, show support cpf theory. european honeybees increase nectar load travel time nectar sites hive increases. beavers have been found preferentially collect larger diameter trees distance lodge increases.

archaeological case study: acorns , mussels in california

to apply central place foraging model ethnographic , experimental archaeological data driven middle range theory, bettinger et al. (1997) simplify barlow , metcalf (1996) central place model explore archaeological implications of acorn (quercus kelloggii) , mussel (mytilus californianus) procurement , processing. model assumes foragers gathering resources @ distance central place goal of efficiently returning resource home. travel time expected determine degree foragers process resource in order increase utility prior returning foraging location central place. transport capabilities in aboriginal california established measuring volume of burden baskets , extrapolating load weight based on ethnographic data on basket use.

ethnographic , experimental data used estimate utility @ each possible stage of processing. examining ecology , procurement methods, central place foraging model used predict conditions in field processing of 2 species occur.

acorn: stages of acorn processing extremely time consuming marginally increase utility, therefore central place foraging model predicts acorns should dried prior transporting central place. further processing of acorns (cracking, shucking, , winnowing) increases efficiency when foragers’ 1 way travel time reaches 25 hours. corresponds approximately 124.75 km, exceeds territory size of native groups in california dependent on acorns.
mussels: when foragers employ plucking harvesting method, field processing expected short travel distances, shell meat ratio allows forager increase efficiency removing shell. stripping result in central place processing, rather field processing, harvesting method results in procurement of high percentage of small mussels high shell meat ratios.

an understanding of central place foraging has implications studying archaeological site formation. variability of remains @ sites can tell mobility – whether or not groups central place foragers, resource they’re mapping on to, , degree of mobility. based on central place foraging application processing of mussels , acorns, bettinger et al. (1997) make several predictions archaeological expectations. study shows procurement field processing more costly compared foraging , processing resources residentially. these results imply highly mobile foragers establish home base in close proximity staple resources, , processing of resources done residentially. less residentially mobile populations in turn mapped onto few resources, , expected field process non-local resources on logistical procurement forays @ greater distances central place. processing debris archaeological sites should reflect changes in mobility.

acorns: sites archaeobotanical remains dominated acorn can assumed seasonal sites of highly mobile foragers have mapped on acorns seasonal processing. sites have mix of archaeobotanical remains decreased abundance in acorn remains , plant material lost in stages of field processing interpreted less residentially mobile settlements characterized logistical procurement.
mussels: interpretation of archaeological mussel shell complicated because reliant on condition of mussel beds, distance mussel beds , type of harvest method being employed. in general, however, sites closer mussel beds should have larger mussel shell due plucking , residential consumption. sites far mussel procurement beds expected have mix of mussel shell sizes due stripping. presence of higher amounts of small mussel shell indicate , increase in resource intensification.

archaeological case study: silver miners , propaganda in colorado

glover (2009) used cpf model determine if late nineteenth century silver miners near gothic, colorado choosing mine locations efficiently given costs of transporting silver ore mill, value of silver, , amount of silver per kilogram of ore. estimates of costs associated transport obtained using research physiology determine energetically efficient load size. newspaper articles used determine hourly wage miner making if worked in town instead. newspapers used estimate value of silver @ time, , estimates of amount of silver per kilogram of ore obtained through records area silver mills, through newspapers. these differed, newspapers optimistically claiming silver deposits far more productive more accurate mill records demonstrated.

these estimates used determine optimal placement of mines. number of historic mining locations recorded using gps. these data used calculate least cost paths mines gothic, provided distances central place. results compared 2 different cpf models based on newspaper propaganda , more realistic mill records, respectively.

miners choosing locations further away feasible given value of silver , actual abundance. however, mines within distance predicted using optimistic newspaper estimates. glover suggested miners, being new area, used social learning strategies , based decisions on newspaper propaganda , rumors, rather individual experience. therefore, chose locations far away economically viable.

ethnographic case study: shellfish in torres strait islands

shellfish exemplify resources targeted cpf model – heavy, bulky, low utility component (e.g. shell) surrounding smaller, lighter high utility component (e.g. meat). if foragers differentially field process , transport shellfish prey items, analyses of midden composition may incorrectly estimate importance of species , relative contribution prehistoric diets. using foraging data meriam of australia, bird , bliege bird (1997) compare observed shellfish field acquisition shell deposition @ residential sites, , test hypotheses of cpf model.

the meriam inhabit torres strait islands of australia, of melanesian descent, , have strong cultural , historical ties new guinea. continue harvest marine resources such sea turtles, fishes, squid, , shellfish. bird , bliege bird conducted “focal individual foraging follows” of 33 children, 16 men , 42 women during intertidal foraging bouts on reef flats , rock shores. foraging technology includes 10- liter plastic buckets, long-blade knives, , hammers. foragers constrained time (2–4 hours @ low tide) , load size (10-liter bucket).

large clams (hippopus hippopus , tridacna spp.) collected on reef flat constitute on half of edible weight collected, since field processed shells make 10% of residential site deposition. in contrast, sunset clams (asaphis violascens) , nerites (nerita undata) processed residentially. large clams were, therefore, underrepresented while small clams , nerites overrepresented in reconstructed diet.

since reef flat , rocky shore foraging occurs @ multiple sites @ variable distances residential camp, authors calculated mean one-way travel distance processing threshold (




z

d
1




{\displaystyle z_{d1}}

, in meters) each species. cpf model accurately predicts field processing majority of reef flat foraging events bivalves. hippopus , tridacna have small processing threshold distances (




z

d
1




{\displaystyle z_{d1}}

= 74.6 , 137 respectively), , no shell returned camp @ distances beyond 150 meters. women’s fit nears 100%, children , men made optimal choice less because forage shellfish opportunistically, , therefore not carry appropriate processing technology.

for gastropods (lambis lambis,




z

d
1




{\displaystyle z_{d1}}

= 278.7), model accurately predicts processing 58-59% of time. in part due preference cooking species inside of shells (i.e. shell has utility), or because prey items prepared @ “dinner-time camps” rather residential camp. a. violascens , n. undata never field processed, consistent large processing threshold distances (2418.5 , 5355.7 respectively).

overall, prey types difficult or inefficient process and/or collected near residential or temporary camp not field processed. species required little processing time increase returns and/or collected far camp field processed. field processing predictions of cpf model might incorrect shellfish transported whole in order maintain freshness later consumption or trade, or shell valuable.

overall, prey types difficult or inefficient process and/or collected near residential or temporary camp not field processed. species required little processing time increase returns and/or collected far camp field processed. field processing predictions of cpf model might incorrect shellfish transported whole in order maintain freshness later consumption or trade, or shell valuable.

ethnoarchaeological case study: pickleweed , piñon

barlow , metcalfe (1996) address issues of field processing of plant materials. decisions of central place foragers may confound archaeological interpretations contribution plant material diet. 2 interrelated issues pertinent: location of central place, , field processing.

barlow , metcalfe study archaeological materials 2 sites, danger cave , hogup cave, in area of great salt lake. these sites contain evidence use of piñon pine (pinus monophylla) , pickleweed (allenrolfea occidentalis).

samples obtained experimental processing extant piñon groves , pickleweed patches in vicinity cave sites. piñon , pickleweed harvested , processed in timed , controlled stages. after each stage useful, i.e. edible, portion of remaining material weighed , recorded before proceeding next stage. stages consisted of: gathering, drying, , variety of processes (parching, hulling, winnowing, etc.) remove inedible constituents. caloric values of samples determined via laboratory analysis. these values, assumed load sizes 3 15 kg (based on ethnographic burden basket sizes) used generate field processing model predictions.

at distance of 15 kilometers central place, estimated net return rates field processing loads of piñon , pickleweed 3,000 , 190 calories per hour, respectively. since piñon has higher overall return rates, field processing produces higher rate of return. because pickleweed has lower rate of return, not worthwhile spend additional effort required field processing. therefore, central place situated closer pickleweed patches piñon in order more exploit lower-ranked resource.

these results imply archaeological evidence pickleweed @ cave may on estimate actual contribution diet. if foragers choose reside closer pickleweed patches , bring largely unprocessed plants, high density of pickleweed macrofossils incorporated site deposits. however, opposite true piñon, largely processed in field. thus, sites contain little macrofossil evidence of inedible portions of piñon later recovered archaeologists. such, relative abundance of macrofossils in cases not directly translate relative contribution of resources diet of central place foragers.