66
Chapter 6
RESULTS
This chapter presents results of the quantitative analyses applied to the faunal samples selected for
study. First, the taxonomic composition of each component is presented and statistical measures used in the
subsequent analyses are explained. Second, samples are divided between habitats and analyzed in terms of
site catchment. Both general subsistence patterns and taxonomic diversity are examined as part of the site
catchment analysis. Finally, the resulting subsistence economies for each habitat are discussed in terms of
foraging efficiency tempered by paleoenvironmental and technological changes.
The total number of identified vertebrate specimens examined in this study is 15,319 (Tables 6
through 8). Freshwater mussel weights are presented in Table 9. The Middle Period assemblage is
comprised of 6,219 specimens, while the Late Period sample contains 9,100 specimens.
Table 2. Diachronic Taxonomic Richness.
Taxa
Middle Period
Late Period
Difference
Mammals
16
21
31% increase
Birds
6
8
33% increase
Fish
11
11
No Change
Herpetofauna
3
7
133% increase
Total
36
47
31% increase
Richness was calculated for each site using the lowest taxonomic level of each taxon present. For
example, if no specimens could be identified to species, such as Canis latrans, then the sum of the
specimens identified to genus level, Canis, was used; if none could be identified to the genus level, then the
sum of the specimens at the level of family, Canidae, was used, etc. As a result, 36 taxa were identified in
the Middle Period and 47 taxa were identified in the Late Period, indicating a total increase of 31 percent in
taxonomic richness over time.
Common Name
Artiodactyls
Tule Elk
Black-tailed Deer
Pronghorn Antelope
Carnivores
American Black Bear
Canids
Raccoon
River Otter
Weasels and Minks
Mink
Spotted Skunk
Striped Skunk
Lagomorphs
Black-tailed Jack Rabbit
Cottontails
Squirrels
California Ground Squirrel
Grey Squirrel
Wood Rats
Botta's Pocket Gopher
Meadow Voles
California Meadow Vole
Deer Mice
Kangaroo Rats
Heermann's Kangaroo Rat
North American Beaver
Rodents
Badger
Mammal Richness
Table 3. Mammals NISP.
Scientific Name
SAC-67 SAC-133
Artiodactyla
34
42
Cervus elaphus nannodes
1
Odocoileus hemionus columbianus
7
Antilocapra americana
3
Carnivora
7
Ursus americanus
Canis sp.
9
Procyon lotor
2
Lutra canadensis
Mustela
Mustela vison
1
Spilogale putorius
Mephitis mephitis
Lagomorpha
Lepus californicus
7
45
Sylvilagus sp.
2
25
Sciuridae
12
Spermophilus beecheyi
10
17
Sciurus griseus
2
Neotoma sp.
Thomomys bottae
14
131
Microtus sp.
Microtus californicus
4
Peromyscus sp.
Dipodomys sp.
1
Dipodomys heermanni
1
Castor canadensis
Rodentia
26
Taxidea taxus
Totals
112
291
8
10
SAC-42
167
61
26
26
32
18
10
1
2
2
1
15
14
1
3
379
SAC-329
126
106
1
3
19
149
1
3
1
4
2
10
3
3
6
574
8
85
1104
SAC-267
36
29
2
1
2
1
1
1
2
7
50
39
32
25
7
15
3
4
204
461
SAC-29
207
201
41
22
1
24
42
1
1
3
4
40
3
6
596
Total
486
389
209
54
43
1
70
203
3
3
3
2
7
2
66
93
51
31
5
32
225
13
592
23
1
4
93
230
9
2943
13
16
15
12
21
67
67
8
1
Table 4. Birds NISP.
Scientific Name
SAC-67 SAC-133
Anseriformes
2
8
Cygnus columbianus
Anserinae
4
Branta canadensis
Anatinae/Aythyinae/Dendrocygninae/
24
21
Merginae/Oxyurinae
Mallard
Anas platyrhynchos
9
Northern Pintail
Anas acuta
Gadwall
Anas strepera
Ruddy Duck
Oxyura jamaicensis
American Coot
Fulica americana
1
Pie-billed Grebe
Podilymbus podiceps
Sandhill Crane
Grus canadensis
American Crow
Crovus brachyrhynchos
1
California Quail
Callipepla californica
1
Other (doves, perching birds, hawks, grouse, shorebirds)
2
Totals
39
34
Common Name
Waterfowl
Whistling Swan
Geese
Canada Goose
Ducks
Bird Richness
2
4
SAC-42
26
101
SAC-329
17
2
16
18
SAC-267
1
1
13
38
SAC-29
94
223
Total
27
1
127
29
425
45
19
1
2
6
200
4
15
16
8
96
2
4
8
67
76
4
35
432
11
4
15
16
122
19
8
2
3
59
868
6
4
4
4
11
Table 5. Herpetofauna NISP.
Common Name
Reptiles
Western Pond Turtle
Snakes
Scientific Name
Squamata
Actinemys marmorata
Serpentes
2
48
27
4
11
-
29
-
7
-
3
20
7
-
9
115
34
Garter Snake
Thamnophis sirtalis
2
-
-
1
-
-
3
Gopher Snake
Pituophis melanoleucus
-
-
-
1
-
-
1
Pit Vipers
Crotalinae
-
-
-
-
1
-
1
Frogs
North American Bullfrog
Western Toad
Salamander
Anura
Rana catesbeiana
Bufo boreas
Caudata
1
80
15
29
1
10
1
10
42
0
1
1
1
10
176
3
1
1
4
4
0
7
Totals
Herpetofauna Richness
68
8
1
Common Name
Sturgeon
Salmon
Chinook Salmon
Minnows & Suckers
Sacramento Sucker
Minnows
Hardhead
Sacramento Blackfish
Hitch
Sacramento Pikeminnow
Sacramento Splittail
Thicktail Chub
Sacramento Perch
Tule Perch
Scientific Name
Acipenser sp.
Salmonidae
Oncorhynchus tshawytscha
Cyprinidae/Catostomidae
Catostomus occidentalis
Cyprinidae
Mylopharodon conocephalus
Orthodon microlepidotus
Lavinia exilicauda
Ptychocheilus grandis
Pogonichthys macrolepidotus
Gila crassicauda
Archoplites interruptus
Hysterocarpus trask ii
Table 6. Fish NISP.
SAC-67 SAC-133
4
2
2
8
43
349
40
216
418
66
2
16
2
13
9
22
7
1
11
299
24
8
Totals
Fish Richness
SAC-42
20
19
286
1489
3
41
40
15
10
145
1390
20
SAC-329
13
4
103
57
50
100
79
50
221
865
78
SAC-267
8
34
1513
247
130
14
40
16
8
19
81
10
SAC-29
160
427
1444
6
154
5
62
22
29
6
128
109
-
Total
207
427
67
3349
898
2257
97
195
191
162
74
524
2768
116
856
706
3478
1620
2120
2552
11,332
10
8
11
10
11
10
11
Table 7. Invertebrates (weights in grams).
Common Name
Scientific Name
Freshwater Mussel
Unionoidea
-
-
-
4723.5
1634
163
6520.5
Western Pearlshell Mussel
Margaritifera falcata
Gonidea angulata
-
132.5
-
-
-
30
162.5
-
-
151.3
-
-
320
471.3
Anodonta nuttalliana
-
-
0.1
-
-
262
262.1
-
132.5
151.4
4723.5
1634
775
7416.4
Rocky Mtn Ridged Mussel
Nuttall's Anadon
Totals
69
8
1
70
However, taxonomic richness (i.e., the number of taxa present in an assemblage) is frequently a
function of sample size (Lyman 2008:180). Sample size can also affect taxonomic evenness, or how well
identified specimens are distributed among the assemblage. Given differences in sample sizes between the
sites analyzed, the Simpson’s Diversity Index was used to assess whether sample size influenced taxonomic
diversity. Simpson’s Diversity Index evaluates both the richness and evenness of a sample. As species
richness and evenness increase, so does diversity. The formula used to calculate Simpson’s D for a finite
population is:
∑ ni (ni -1)
D=
N(N-1)
ni = the total number of specimens of a particular species (NISPi)
N = the total number of specimens of all species (NISP total)
D= Simpson’s Index of dominance
(adapted from Lyman 2008)
When the reciprocal of D (1/D) is computed, the larger the value, the more evenly specimens are
distributed. Conversely, the lower the value of 1/D, the more an assemblage is dominated by one or a few
taxa (Lyman 2008:197).
The reciprocal of Simpson’s Diversity Index was applied to each of the site samples. The results
indicate an increase in diversity in all habitats over time.
Table 8. Diachronic Taxonomic Diversity.
Habitat
Richness
NISP
Site
Time
1/D
SAC-67
Middle Period
Freshwater
Marsh
23
499
2.65
SAC-329
Late Period
Freshwater
Marsh
34
2205
5.43
SAC-133
Middle Period
Grassland
25
570
4.75
SAC-267
Late Period
Grassland
38
762
7.39
SAC-42
Middle Period
Riparian
Woodland
31
2374
2.75
SAC-29
Late Period
Riparian
Woodland
26
1739
8.62
71
When a scatter plot is created comparing diversity with NISP (Figure 14), the best fit line shows there is no
relationship between NISP and diversity, indicating that the 31 percent increase in diversity/richness seen
between Middle Period and Late Period assemblages is not being driven by sample size.
10.00
CA-SAC-29
8.62
9.00
CA-SAC-267
7.39
8.00
7.00
CA-SAC-329
5.43
6.00
1/D
R² = 0.0006
5.00
CA-SAC-133
4.75
4.00
CA-SAC-42
2.75
3.00
2.00
CA-SAC-67
2.65
1.00
0.00
20
520
1020
1520
2020
2520
NISP
Figure 14. Scatter Plot of Diachronic Taxonomic Diversity (1/D) and NISP.
One of the problems in using NISP for the analysis of prehistoric diets is that it can differentially
exaggerate taxonomic abundance. For example, NISP does not control for the interdependence of
specimens which may be from one or many individuals. In an attempt to correct for the potential
overrepresentation of certain taxa, a variation of the chi-square test of independence, Cochran’s test of
linear trend, was applied to samples. Chi-square is calculated as follows:
𝛘2 = ∑
(observed – expected)2
expected
A percentage of significance or reliability is then applied to the result based on the number of data groups
(degrees of freedom) used in the calculation.
NISP totals were entered into a chi-square calculator macro for Excel created by M. Cannon
(Cannon 2012) and adjusted residuals were rounded to the hundredth. The results of the chi-square analyses
72
were compared by habitat type, because the restricted mobility assumed for both Middle and Late Period
populations would have limited foraging to site specific catchment areas.
Freshwater Marsh
The sites representing the freshwater marsh habitat are SAC-67 (Middle Period) and SAC-329
(Late Period). First, catchments areas for each site are described. Next, subsistence patterns and chi-square
analysis are compared. Last, results are interpreted in terms of site catchments and foraging efficiency.
Site catchments were reconstructed for SAC-67 and SAC-329 based on the paleoenvironmental
data used to create Figure 2 (see Chapter 2). The site catchment of SAC-67 indicates 59 percent of the
habitat within five kilometers (three miles) is grassland, 28 percent is freshwater marsh, and 13 percent is
riparian woodland. The catchment area of SAC-329 is 86 percent freshwater marsh and 14 percent riparian
woodland habitat. No grassland habitat was located within five kilometers (three miles) of SAC-329.
The SAC-67 faunal assemblage has an NISP of 1,087. Faunal diversity (richness) includes eight
mammals, two birds, ten fish, and three herpetofauna taxa. The faunal assemblage from SAC-329 has an
NISP of 2,690 and sample diversity includes 15 mammals, four birds, 11 fish, and four herpetofauna. Over
time, diversity in the freshwater marsh habitat increased by 48 percent.
Subsistence patterns were developed for each site using an arbitrary value system to measure
taxon attributes important to prey choice, e.g., taxa weight, habitat preference, and procurement method.
For fish, weight was replaced by standard length (length x girth). Taxon selection used the same criteria as
that used to calculate richness, i.e., only specimens from the lowest level of taxonomic rank were included
for analysis. A key showing values assigned to each taxon attribute and site specific calculation charts are
presented in Appendix C.
Freshwater marsh populations appear to have relied on medium sized animals primarily procured
by mass harvesting techniques from the freshwater marsh habitat (𝜒2=156.38, df=28, p <0.001). Large
slow-water fish, such as Sacramento perch, accounted for over 50 percent of the taxa targeted at both sites,
suggesting such fishes remained a dietary staple for freshwater marsh populations over time. In spite of this
consistency, changes in targeted taxa are apparent. First, the number of larger taxa incorporated in the diet
73
Figure 15. Freshwater Marsh Individual Site Catchments.
74
Figure 16. SAC-67 Middle Period Freshwater Marsh Subsistence Pattern.
Figure 17. SAC-329 Late Period Freshwater Marsh Subsistence Pattern.
75
increases in the Late Period. There is also a slight increase in the number of riparian woodland taxa
included in the diet. Finally, there is an increase in the number of taxa procured by single takes. The first
and third differences will be considered in the chi-square analysis presented below. The second difference
will be discussed in terms of site catchment area at the end of the freshwater marsh analysis.
In spite of this consistency, changes in targeted taxa are apparent. First, the number of larger taxa
incorporated in the diet increases in the Late Period. There is also a slight increase in the number of riparian
woodland taxa included in the diet. Finally, there is an increase in the number of taxa procured by single
takes. The first and third differences will be considered in the chi-square analysis presented below. The
second difference will be discussed in terms of site catchment area at the end of the freshwater marsh
analysis.
Chi-square analyses of the terrestrial taxa identified in freshwater marsh assemblages indicate
there is a significant increase in the amount of artiodactyl, carnivore (e.g., canids, raccoon, river otter,
mink, and skunks), and beaver remains in the Late Period (𝜒2=337.40, df =6, p <0.001). Significant
decreases are seen in lagomorphs, waterfowl, medium rodents (squirrels and gophers), and turtle.
Figure 18. Diachronic Freshwater Marsh Terrestrial Taxa.
76
Thus, the chi-square results for terrestrial taxa indicate that not only were more taxa incorporated in the
Late Period diet, but that more larger bodied taxa (e.g., artiodactyls, carnivores, and beavers) were being
procured at the expense of previously exploited smaller bodied animals (e.g., waterfowl, medium rodents,
and turtle). Further, as indicated in the subsistence pattern comparison, most of the animals which increase
in frequency are best procured via single takes (see Ugan 2005:77).
Figure 20 shows that fish NISP also increases over time, but it is not equally distributed across all
taxa (𝜒2=106.46, df=10, p <0.001). Due to the significant increases in other species, Sacramento perch
shows a decrease in abundance over time despite a nearly 200 percent increase in NISP. Similarly,
Sacramento sucker shows a decrease in abundance, despite a 157 percent increase in NISP. All other
resident fish show statistically significant increases, with the exception of Sacramento splittail, salmon, and
sturgeon. The largest increase is in thicktail chub, which is second in magnitude
Figure 19. Diachronic Freshwater Marsh Fish.
only to the decrease in the frequency of Sacramento perch. Thus, although Sacramento perch remains an
important constituent of the diet, a wider variety of fish was utilized by freshwater marsh occupants during
the Late Period.
77
One explanation for the increased variety of Late Period fish is that the SAC-329 catchment
contains approximately three times the amount of freshwater marsh habitat as SAC-67. This increased the
habitat for slow-water, i.e., freshwater marsh, species essentially, three-fold. On the one hand, mass
harvesting techniques likely procured a greater variety of fish simply because they were present. Support
for this conclusion can be found in the limited difference of NISP (no more than 50 specimens) between the
species intensified in presence during the Late Period. Such minor differences suggest that these species
were not specifically, but generically targeted.
On the other hand, it may be that the decrease in large bodied, slow-water fish indicates that
foraging efficiency was achieved in other ways. The significant increase in larger bodied terrestrial taxa in
the Late Period supports this conclusion as does the increase in single-take procurement. Many of the larger
bodied terrestrial species added to the diet were best procured individually and found primarily in the
riparian woodlands. These include carnivores and beaver, with deficiencies in the analysis of artiodactyl
remains from SAC-67 and SAC-329 making it difficult to assess which, if any, species significantly
increased over time. Scarcely any difference (one percent) in riparian woodland exists between the
catchments of the Middle and Late Period sites, so increased use of this habitat in the Late Period supports
a shift in prey choice.
Subsistence patterns for both sites also show that the grassland habitat was largely ignored during
both the Middle and Late periods. Grassland taxa account for less than one percent of each assemblage.
This is not surprising for SAC-329, because no grassland habitat was located within five kilometers (three
miles) of the site. However, 59 percent of SAC-67 catchment was grassland. One explanation for this
incongruity relates to the seasonal characteristics of study area grasslands. During late winter/spring
flooding, grasslands adjacent to the Cosumnes River (and other streams) became seasonal wetlands, leaving
SAC-67 an island. In fact, archaeologists working at the site needed boats to reach the site during these
seasons (J. Johnson 2010, personal communication). Thus, the formerly seasonal conversion of certain
grasslands to wetland habitats would have reduced the availability of grassland resources for nearly a
quarter of the year.
78
Grassland
The two grassland habitat sites are SAC-133 (Middle Period) and SAC-267 (Late Period). Both have nearly
identical catchments with 79 to 80 percent of the foraging radius in riparian woodland, 20-21 percent in
grassland, and less than one percent freshwater marsh.
Subsistence patterns reveal that exploitation of small to medium bodied freshwater marsh &
riparian woodland animals procured by mass capture is the dominant subsistence strategy at both sites
(𝜒2=92.34, df=29, p <0.001). This is largely reflected by the large abundance of Sacramento sucker in both
assemblages, where it appears to have been a dietary staple over time. Apart from that, little else is similar
between the two subsistence patterns.
The most significant differences between the two subsistence patterns are reflected in the decrease
of very small taxa (e.g., gopher), decrease in use of grassland & riparian woodland, and increase in the use
of freshwater marsh habitat in the Late Period. Decreases in the first two patterns are reflected by an 81
percent decrease in Late Period gopher remains, and ambiguity surrounding the squirrel remains from
Figure 20. SAC-133 Middle Period Grassland Subsistence Pattern.
79
Figure 21. Grassland Individual Site Catchments.
80
Figure 22. SAC-267 Late Period Grassland Subsistence Pattern.
SAC-267. Botta’s pocket gopher is attracted to mesic environments with a continuously growing root
system (Jameson and Peeters 2004:291). If root access is restricted due to prolonged flooding or habitat
loss, Botta’s pocket gophers will decrease in numbers. These preferences suggest pocket gophers would
have been most prevalent in riparian woodlands, but could also be found in moist areas of grassland.
Thirty-nine squirrel remains were documented in the SAC-267 assemblage, but none were
identified to species. This may be due to use of analysts from Arizona, who lacked familiarity with
California ground squirrel remains. If the squirrel remains had been assigned to species, use of either
grassland (California ground squirrel), or riparian woodland (grey squirrel), or both habitats may have
increased along with that of small animals during the Late Period. The increase in freshwater marsh taxa
relates primarily to waterfowl and slow-water fishes during the Late Period. The significance of other
changes is evident in the results of the chi-square analysis.
Chi-square analysis of terrestrial taxa (𝜒2=33.86, df=6, p <0.001) show significant increases in
artiodactyls, waterfowl, and beaver in grassland subsistence economies over time. Of note is the addition of
81
geese, primarily Canada goose, to Late Period diets. Geese can be found in both grassland and freshwater
marsh habitats, so travel beyond the catchment may have been unnecessary to procure geese. Significant
decreases are likewise apparent in carnivores and medium-size rodents, but the numerical decrease in
lagomorphs is not statistically significant.
Figure 23. Diachronic Grassland Terrestrial Taxa.
Figure 24. Diachronic Grassland Fish.
82
Figure 24 shows significant differences in grassland fish over time (𝜒2=100.62, df=10, p <0.001).
These differences included significant changes in salmon and all slow-water species. Salmon increases by
325 percent in the Late Period and slow-water fish by 638 percent. The extremely large increase in slowwater fish is amplified by the inclusion of three previously unidentified species: hitch, thicktail chub, and
tule perch.
In terms of site catchment, both the subsistence pattern and chi-square data indicate that habitats
within three kilometers (five miles) of the sites provided the bulk of faunal resources to occupants of
grassland environments over time. Although riparian woodland and grassland taxa provided the bulk of the
diet (e.g., lagomorphs, medium rodents, and Sacramento sucker), people living in grassland habitats were
exploiting habitats beyond their catchment to obtain freshwater marsh resources (e.g., waterfowl and
Sacramento perch). Intensification of this behavior during the Late Period is supported by a widening of
diet breadth to include three additional species of slow-water fish and an 83 percent increase in waterfowl
remains. At the same time, however, foraging efficiency also appears to increase, given a rise in large
bodied taxa. Most of these taxa (e.g., artiodactyls, beaver, Canada goose, and salmon) were previously
available in the site catchment, such that their increase implies improved success in encounter rates.
Riparian Woodland
The riparian woodland habitat is represented by SAC-42 and SAC-29. Both sites are located on
the east side of the Sacramento River. The SAC-42 catchment was composed of 75 percent freshwater
marsh and 25 percent riparian woodland, and the SAC-29 catchment was 75 percent freshwater marsh, 18
percent riparian woodland, and seven percent grassland (Figure 25).
The subsistence pattern derived from each of the riparian woodland faunal assemblages is
presented below. Despite similarities in catchment areas, significant differences exist between riparian
woodland subsistence patterns over time (𝜒2=213.41, df=26, p <0.001).
The Middle Period subsistence pattern indicates that inhabitants of SAC-42 practiced mass harvesting of
medium sized animals from freshwater marsh habitats. Most of these are Sacramento perch, a large, slowwater fish, that comprises nearly a third of the assemblage. The next most numerous taxa are Sacramento
83
Figure 25. Riparian Woodland Individual Site Catchments.
84
Figure 26. SAC-42 Middle Period Riparian Woodland Subsistence Pattern.
Figure 27. SAC-29 Late Period Riparian Woodland Subsistence Pattern.
85
sucker, artiodactyls, and waterfowl. Although no grassland habitat is present in the SAC-42 catchment,
limited numbers of grassland taxa (e.g., pronghorn, badger, and lagomorphs) were identified. These
indicate that inhabitants of SAC-42 probably ventured outside their catchment to supplement a fish based
diet, much like the people at SAC-133. Unlike the inhabitants of SAC-42, the Late Period people at SAC29 acquired a wide range of medium- and large-sized taxa from freshwater marsh and riparian woodland
habitats. These include large fish (e.g., salmon, Sacramento perch, and hardhead), large waterfowl (e.g.,
geese), and medium to large mammals (e.g., artiodactyls, canids, raccoon, badger, and beaver). Most of
these taxa were best procured by individual rather than mass capture techniques.
Both subsistence patterns include some grassland taxa (pronghorn and lagomorphs) despite the
lack of grassland habitat in the SAC-42 catchment and only seven percent in SAC-29 foraging radius. As
with the grassland habitats, inhabitants of the riparian woodland probably ventured outside their catchment
area to supplement a fish based diet. Other diachronic changes in subsistence are highlighted by the chisquare analysis. It shows that changes in the frequency of some terrestrial taxa are not significant
(𝜒2=60.73, df =6, p <0.001). Four of the seven taxa show no statistically significant changes in relative
frequency. A significant increase is seen in waterfowl, which increase by seven percent. Conversely,
carnivores and turtles exhibit a significant decrease over the same time.
Figure 28. Diachronic Riparian Woodland Terrestrial Taxa.
86
Despite significant increases in the frequency of identified fish, fish remains actually decrease in
the Late Period assemblage overall by 25 percent. This decrease is associated with a significant decline in
Sacramento perch, coupled with a significant increase in anadromous fast-water species over time.
(𝜒2=1732.08, df=10, p <0.001). As Figure 29 shows, Sacramento perch, staple of the Middle Period diet,
decrease by 92 percent and Sacramento sucker by 98 percent. These decreases are overshadowed, however,
by significant increases in the abundance of anadromous species (i.e., salmon and sturgeon). Salmon
increase in frequency by over 2,000 percent and sturgeon by 700 percent. Hardhead, another fast-water
species, shows a smaller yet still significant increase in frequency. The significant increase in all fast-water
species supports the increased use of riparian woodlands during the Late Period, whereas fish from other
settings show no consistent pattern.
When the subsistence patterns and chi-square analysis are compared to the site catchment for each
time period, several trends are apparent. First, although freshwater marsh is equally represented in both site
catchments, the use of this habitat decreased over time with increasing use of large bodied taxa from the
Figure 29. Diachronic Riparian Woodland Fish.
87
riparian woodland (i.e., salmon and sturgeon). Increases in the NISP of other large bodied riparian
woodland taxa such as black-tailed deer, raccoon, and beaver support this Late Period trend, although the
latter increases are not statistically significant (see Figure 29).
Second, the limited grassland taxa in either assemblage reflect the likely absence/near absence of
grassland habitat in both site catchments. Nevertheless, people in both time periods either foraged beyond
their immediate catchments or traded in order to procure grassland resources. Third, in contrast to previous
habitats, there is a decrease in diet breadth (richness decreases) and an increase in foraging efficiency
(amount and kind of large bodied game) within the riparian woodland during the Late Period. This, too, is
supported by the results of the reciprocal of Simpson’s Diversity Index presented in Table 11. It indicates
that the observed decrease in taxonomic diversity is not a function of sample size because NISP varies
independently. Lastly, the significant shift in procurement methods from group to individual hunting
techniques demonstrates that Late Period changes in hunting technologies increased success in encounter
rates with larger bodied taxa and, as a result, increased foraging efficiency.
Summary and Discussion
Quantitative analysis of diachronic faunal assemblages resulted in several conclusions relating to
changes in prehistoric subsistence patterns over time and space in the study area.
1.
A broad spectrum diet with fish serving as a staple supplemented by mammals and seasonal
waterfowl characterized regional subsistence patterns
Diversity among site samples ranges from 23 to 38 taxa. This includes between eight and 11 fish taxa,
which comprise 60 to 79 percent of the assemblages. The most numerous fish in all samples were either
Sacramento perch or Sacramento sucker. Sacramento perch was the largest minnow in the study area and
its remains account for a quarter of all fish bone examined. Sacramento sucker is a medium sized fish and
its remains account for eight percent of the fish bone. A total of 21 different mammals are represented in
study area assemblages. Artiodactyls and lagomorphs are found in every sample, with the quantity of
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medium rodents and carnivores varying. Although more than 11 bird taxa were identified, waterfowl
comprise the most numerous bird remains in every sample, with ducks accounting for 54 percent of all
identified birds.
2.
The freshwater marsh was the most targeted habitat during both the Middle and Late periods
The freshwater marsh habitat accounted for approximately 36 percent of the study area and 54 percent of
the taxa identified. Taxa which prefer a variety of habitats, including the freshwater marsh, account for an
additional 22 percent.
Figures 30 and 31 depict the subsistence patterns derived for the Middle and Late period
assemblages based on specimens from the lowest level of taxonomic rank (𝜒2=215.14, df=30, p <0.001).
Even when site catchments included less than one percent of this habitat (e.g., SAC-133 and SAC-267),
more than 50 percent of the taxa identified were associated with the freshwater marsh. While most taxa
procured from the freshwater marsh were fish, 29 percent represented terrestrial taxa, such as tule elk,
Figure 30. Study Area Middle Period Subsistence Pattern.
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Figure 31. Study Area Late Period Subsistence Pattern.
raccoon, beaver, ducks, and turtle. Conversely, grassland habitats, which comprised 52 percent of the study
area, never account for more than 10 percent of the taxa exploited, even when taxa preference includes a
grassland component.
3.
Artiodactyl remains increase over time
Artiodactyls are the largest taxa found in the study area and account for 39 percent of the mammals
identified. A significant increase in artiodactyl remains is exhibited in both the freshwater marsh and
grassland habitats. An increase in artiodactyls is also seen in the riparian woodland, although it is less
significant than changes in other terrestrial fauna.
Table 9. Diachronic Change in Artiodactyl Species.
Species
NISP
Adjusted Residual
Middle
Late
Tule Elk
62
327
2.44
Black-tailed Deer
33
176
1.44
Pronghorn
29
25
-6.78
90
The limited number of pronghorn in all assemblages most likely reflects the general lack of grassland
targeting, while the significant increases in tule elk and black-tailed deer are more likely related to the next
conclusion.
4.
Changes in hunting technology increased foraging efficiency in the Late Period
Although increases in taxonomic diversity were not identified in all habitats, increases in large prey are
seen in every study area habitat over time, regardless of site catchment. These large bodied taxa prefer
multiple habitats, and some were only seasonally present. Thus, increases in these animals cannot be
attributed to changes in environment alone. The aridity and droughts experienced in the Late Period during
the MCA appear to have precluded high water flows in the Sacramento River, which may have impacted
salmon runs and reduced primary production for herbivores. Nevertheless, this is exactly the time period
when both salmon and artiodactyl remains increase in assemblages.
Increased flooding during the LIA in the latter half of the Late Period, could have also impacted
primary production and reduced habitat for certain grassland species, such as lagomorphs and pronghorn,
by increasing the size and duration of seasonal wetlands. Despite this possibility, changes in lagomorph
frequency were typically not significant and the frequency of pronghorn specimens is currently impossible
to assess with the data available. Enlarged seasonal wetlands may have provided increased forage for
juvenile fish, increasing survivorship, and/or providing hunters with easy targets. Support for such a
scenario is reflected in fish increases in Late Period freshwater marsh and grassland assemblages, but
additional study (age grading) is needed before this scenario can be considered a direct influence on local
subsistence economies.
More certain, perhaps, is that the ubiquitous increase in Late Period artiodactyls, particularly tule
elk and black-tailed deer, implies that introduction of bow and arrow technology increased hunting success.
Corresponding conclusions have been proposed for the Bay Area in order to explain similar increases in
highly ranked mammalian prey species (Wake 2012:31). Increases in individually procured medium
mammals (i.e., canids, carnivores, and beaver) and geese, support the adoption of a more efficient hunting
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technology. Similarly, changes in fishing technology (e.g., the toggle harpoon) allowed large bodied
anadromous species to be exploited with greater success. Salmon and sturgeon were identified at all six
sites regardless of time period. It is not until when the toggle harpoon was introduced during the Late
Period that salmon and sturgeon surpass the stable dietary contribution of slow-water minnows and suckers.