SMALL MAMMALS

Small mammals account for most of the land vertebrate faunal remains recovered from prehistoric San Diego sites. Two genera of lagomorphs (Lepus, hares; and Sylvilagus, rabbits) and at least eight genera of rodents (Dipodomys, kangaroo rats; Microtus, voles; Neotoma, wood rats; Perognathus and Peromyscus, mice; Sciurus, grey squirrels; Spermophilus, ground squirrels; and Thomomys, gophers) are represented with some frequency.

Interpretive possibilities that have been suggested for small mammal remains concern the reconstruction of paleoenvironments, settlement systems, procurement strategies, and processing methods, and the differentiation of cultural and natural remains:

-- Some small mammals are either confined to or found more frequently within particular biotic communities, and their presence or absence in archaeological deposit may support inferences about the site's prehistoric natural setting. Richard L. Reynolds noted an exceptionally high proportion of Sylvilagus bachmani (brush rabbit) bone in the faunal assemblage from SDM-W-143/146 in Carlsbad and concluded that "this indicates dense heavy brush near the site" (Cardenas and Robbins-Wade 1985:Appendix H).

-- Settlement size or stability may be indicated by the ratio of small mammal to large mammal remains and the diversity of small mammal remains. Discussing inland Luiseño sites, Georgie Waugh (1986:266) suggested that a more diverse microfauna in a site deposit may be "a function of increased procurement by more inhabitants. Alternatively, it may be an indication of increased sedentism rather than an increase in population...it is likely that with longer-term residency and the possibility of diminishing supply of larger fauna, procurement efforts would be directed towards smaller species...."

-- The social organization of procurement may be indicated by the ratios of different small mammal species. Lepus was procured, at least in part, by organized, communal drives, whereas Sylvilagus audubonii and rodents were probably procured through "encounter" hunting or by the use of traps. There is some question as to whether Sylvilagus bachmani was exploited by drives.

-- The season or seasons of site occupation may be inferable from the presence, absence, or relative abundance of remains from juvenile and subadult individuals of some small mammal genera, according to discussions by Reynolds (1980a, 1980b, 1987; Cardenas and Robbins-Wade 1985). Breeding seasons may have limited the presence of immature Lepus to the period between March and December, of Sylvilagus to between February and September, of Spermophilus to between May and September, of Thomomys perhaps to between December and August, and of Dipodomys perhaps to between May and October. Aestivation and hibernation may also have substantially reduced the availability of Spermophilus in July or August and from October or November through January. However, the existence of some of these proposed seasonal gaps specifically in the San Diego region has been questioned (cf. Laylander and Christenson 1988:96).

-- The ratios of rodent, lagomorph, and large mammal remains have been suggested as another set of site seasonality indicators. Reynolds (1987:E-9) cited a reported tendency for lagomorph drives to take place "in the fall and winter, when furs were good." Comparing two Late Prehistoric sites in the Peñasquitos area, he commented that "the ratio of rodents to lagomorphs in SDM-W-1339A is about 1 : 1 while in SDM-W-1337 it is 1 : 4. This significant difference, clearly a seasonal bias, demonstrates the importance to the Kumeyaay of lagomorphs as winter food when rodents (their preferred food) are scarce" (Reynolds 1980b:43). For southern California in general, he noted that "bone fragment ratios of [deer-size, rabbit-size, and rat-size] classes show distinctive seasonal shifts in numerical value. The deer : rabbit : rat ratio in warm weather (late spring to early fall) is approximately 1 : 4 : 20. In cold weather (late fall to early spring), this ratio approximates 1 : 4 : 4" (Reynolds 1987:E-41). (These specific ratios were apparently only intended to be applicable to assemblages recovered with 1/16-inch mesh screen.)

-- Waugh (1986:266) suggested that "a more successful or efficient hunting technology" may be indicated by a lower relative frequency of small mammal remains as against artiodactyl remains. Specifically, the bow and arrow might be a key example of enhanced hunting technology.

-- Michael W. Tuma (2004) reported a slightly higher proportion of lagomorph bone at site SDI-4608 in Poway within a component dated to ca. 1900-200 B.C. as compared with a component dated to ca. 4300-3900 B.C. He suggested that a greater reliance on rabbits and hares "may have been in response to an overharvest of deer, indicating intensification on terrestrial resources" (Tuma 2004:53).

-- Cultural preferences may also be reflected in small mammal species ratios. Discussing the predominance of Sylvilagus bachmani remains at SDM-W-143/146, Reynolds noted that brush rabbits "are quite small animals and difficult to procure....Since food was not in short supply, it seems likely that brushrabbit was a preferred food" (Cardenas and Robbins-Wade 1985:Appendix H).

-- Processing methods may be inferable from the condition of small mammal remains. For instance, highly fragmented small mammal bone may reflect pounding of whole animals in mortars. Burnt bone may indicate roasting or broiling rather than baking or boiling. For bone from SDM-W-143/146 and from Westwood Valley near Ranch Bernardo, Reynolds (1987; Cardenas and Robbins Wade 1985) used the burning patterns on specific anatomical elements and portions of elements to infer that lagomorphs had been skinned and then roasted whole above fire. On the other hand, burning patterns on the bones of rodents (including Dipodomys, Neotoma, Spermophilus, and Thomomys) indicated that these animals had been cooked, whole and unskinned, by broiling on top of or in coals. Lois Lippold (1983) concluded that the lagomorphs at Ystagua (SDI-4609) in Sorrento Valley had also been roasted, but suggested that the gophers at that site had been baked or boiled. Reynolds (1987:E-19) observed that certain lagomorph long bones (the humerus, radius, femur, and tibia) were "virtually never" encountered unbroken in archaeological sites; he inferred that, after being cooked, these bones were cracked open with the teeth in order to extract marrow.

-- In addition to the use as major food resources, lagomorphs were procured for their skins, to make capes or blankets, as well as for food use. Lynne E. Christenson (1990) sketched a linear programming model for Late Prehistoric resource requirements, which suggested that lagomorphs may have been one of the key Kumeyaay resources specifically because of this value. Lippold (1983) cited a high proportion of lagomorph foot bones recovered at Ystagua as evidence that hide preparation had occurred at the site.

-- The degree of contamination of the archaeological faunal assemblage by intrusive natural remains may be evaluated through consideration of the integrity of the bone, the proportion of burnt bone, and the proportion of bone from burrowing species such as gophers and ground squirrels.

PROSPECTS

Future archaeological investigations may be able to use evidence relating to small mammals to shed light on localized paleoenvironmental conditions, seasonality of site occupation, and prehistoric methods of procurement and processing. Identification of species and observations concerning age, anatomical element, and condition of specimens in archaeological collections are needed to achieve these objectives.


Taxon Common Name Range Archaeological
Occurrence
LAGOMORPHS
Lepus californicus black-tailed jackrabbit W, C, E common
Sylvilagus audubonii Audubon's cottontail W, C, E common
Sylvilagus bachmani brush rabbit W, C, E common
RODENTS
Amnospermophilus leucurus antelope ground squirrel E
Dipodomys agilis Pacific kangaroo rat W, C genus occasional
Dipodomys deserti desert kangaroo rat E
Dipodomys merriami Merriam's kangaroo rat C, E genus occasional
Dipodomys stephensi Stephens' kangaroo rat W, C genus occasional
Microtus californicus California vole W, C, E occasional
Neotoma albigula white-throated wood rat E
Neotoma fuscipes dusky-footed woodrat W, C, E genus common
Neotoma lepida desert wood rat W, C, E genus common
Onychomys torridus southern grasshopper mouse W, C, E
Perognathus baileyi Bailey's pocket mouse E --
Perognathus californicus California pocket mouse W, C genus occasional
Perognathus fallax San Diego pocket mouse W, C, E genus occasional
Perognathus formosus long-tailed pocket mouse E --
Perognathus longimembris little pocket mouse W, C, E genus occasional
Perognathus pencillatus desert pocket mouse E --
Perognathus spinatus spiny pocket mouse C, E --
Peromyscus boylii brush mouse W, C, E
Peromyscus californicus parasitic mouse W, C occasional
Peromyscus crinitus cañon mouse E
Peromyscus eremicus cactus mouse W, C, E
Peromyscus maniculatus deer mouse W, C, E
Peromyscus truei piñon mouse C
Reithrodontomys megalotis harvest mouse W, C, E
Sciurus griseus western gray squirrel W, C
Spermophilus beecheyi California ground squirrel W, C, E common
Spermophilus tereticaudus round-tailed ground squirrel E
Tamias merriami Merriam's chipmunk E
Tamias obscurus chaparral chipmunk C
Thomomys bottae Botta's pocket gopher W, C, E common
SHREWS and MOLES
Notiosorex crawfordi desert shrew W, C, E --
Sorex ornatus ornate shrew W, C --
Scapanus latimanus broad-footed mole W, C, E --
BATS
Antrozous pallidus pallid bat W, C, E --
Choeronycteris mexicana hog-nosed bat W, C, E --
Eptesicus fuscus big brown bat W, C, E --
Euderma maculatum spotted bat W, C, E --
Eumops perotis western mastiff bat W, C, E --
Lasiurus borealis red bat W, C, E --
Lasiurus cinereus hoary bat W, C, E --
Lasiurus ega western yellow bat E --
Macrotus californicus California leaf-nosed bat W, C, E --
Myotis californicus California bat W, C, E --
Myotis evotis long-eared bat W, C, E --
Myotis leibii small-footed bat W, C, E --
Myotis lucifugus little brown bat W, C, E --
Myotis thysandodes fringed bat W, C, E --
Myotis volans long-legged bat W, C, E --
Myotis yumanensis Yuma bat W, C, E --
Nyctinomops femorosaccus pocketed free-tailed bat W, C, E --
Pipistrellus hesperus western pipistrelle W, C, E --
Plecotus townsendii Townsend's long-eared bat W, C, E --
Tadarida brasiliensis guano bat W, C, E --
Modern distributions, based on Jameson and Peeters (1988): W = western San Diego County (coast, valleys); C = central San Diego County (mountains); E = eastern San Diego County (Colorado desert).