Stable isotope analysis of dog, fox, and human diets at a Late Holocene Chumash village (CA-SRI-2) on Santa Rosa Island, California

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Abstract

Stable carbon (δ13C) and nitrogen (δ15N) isotope analyses of dog (Canis familiaris), island fox (Urocyon littoralis), and human bone collagen from CA-SRI-2 (AD 130–1830) on Santa Rosa Island, California provide a proxy of diet and the relationships between humans and these animals. Carbon isotopic signatures indicate that Native Americans and their dogs at CA-SRI-2 subsisted almost exclusively on marine resources, while the island fox ate primarily terrestrial foods. Nitrogen isotopes and archaeofaunal remains indicate that humans and dogs also ate higher trophic level foods, including finfishes, marine mammals, and seabirds with smaller amounts of shellfish. The CA-SRI-2 island foxes appear to have eaten higher amounts of terrestrial foods, similar to the diets observed in modern fox populations. These data generally confirm the commensal relationship assumed to exist between domesticated dogs and people, but the carbon isotopic composition of dogs is enriched ∼2‰ compared to humans. We hypothesize that the difference in carbon isotopes between dogs and humans may have resulted from a higher consumption of C3 plants with lower δ13C values by humans, or less likely from the ingestion by dogs of significant amounts of bone collagen, which is enriched by ∼4‰ over associated muscle.

Highlights

► Stable isotope analysis of dog, fox, and human remains provides insight into ancient diets and human animal relationships. ► Dogs and humans appear to have eaten generally higher trophic level marine foods, while foxes primarily ate terrestrial foods. ► Stable isotope analysis of dog remains can be used as a proxy for human diets. ► δ13C values in dogs may be enriched relative to humans because people consumed more terrestrial plants than dogs, or perhaps dogs consumed significant amounts of bone collagen that enriched their carbon isotopic signature.

Introduction

Stable isotope analyses of archaeological materials provide an important technique for investigating a variety of cultural and environmental issues. Studies of ancient carbon (δ13C) and nitrogen (δ15N) isotopes in human and animal bone collagen, hair, and other tissues are particularly useful for documenting trends in diet, health, and resource exploitation (Ambrose and DeNiro, 1986, Ambrose and Norr, 1993, Cannon et al., 1999, Choy and Richards, 2009, Hedges and Reynard, 2007, Katzenberg et al., 1993, Lee-Thorp, 2008, Newsome et al., 2004, Schwarcz, 1991, Walker and DeNiro, 1986). For archaeologists working in coastal regions, stable isotope analysis of human remains provides a means to evaluate the relative contribution of marine and terrestrial resources in human diets, as well as associated cultural and environmental developments (Clutton-Brock and Noe-Nygaard, 1990, Fischer et al., 2007, Newsome et al., 2004, Walker and DeNiro, 1986). A number of studies over the last decade or so also have used stable isotopes as a tool to investigate domestic dog (Canis familiaris) diets and the interactions between dogs, humans (Homo sapiens), and local ecosystems (Allen and Craig, 2009, Allitt et al., 2008, Cannon et al., 1999, Clutton-Brock and Noe-Nygaard, 1990, Fischer et al., 2007, Germonpre et al., 2009, Schulting and Richards, 2002, Schulting and Richards, 2009, Tankersley and Koster, 2009, White et al., 2001, White et al., 2004).

Stable isotope analysis requires the removal and destruction of skeletal remains, and can be objectionable to some Native North Americans and museum curators concerned with the destruction of human remains. Acknowledging these concerns, Cannon et al. (1999) proposed that analyzing stable carbon and nitrogen isotopes from archaeological dog remains may serve as a proxy for reconstructing human diet. Domesticated dogs have been a key companion of anatomically modern humans for millennia, and their subsistence base can generally be expected to largely mirror human diet because they are either provisioned by their owners or they scavenge in kitchen middens/refuse heaps and consume human feces. At the site of Namu (British Columbia), Cannon et al. (1999) observed that changes in dog stable isotopes, indicating a diet heavy in marine foods, tracked changes in the composition of the archaeofaunal remains from the site. This suggests the potential for dog bones to serve as a proxy for human dietary reconstruction.

Following Cannon et al., 1999, Allitt et al., 2008 analyzed stable isotopes from three dog bones from coastal New Jersey and Pennsylvania, suggesting dogs, and possibly people, consumed maize. Based on the analysis of stable isotope data for 51 dogs (5 archaeological and 46 contemporary/ethnoarchaeological) and five archaeological humans associated with one of the dogs, Tankersley and Koster (2009) argued that dogs and humans had essentially the same isotopic signature. In the Old World, stable isotope data from Mesolithic Europe (Fischer et al., 2007) and South Korea (Choy and Richards, 2009) lend general support to the similarity of human and dog diets. Since dogs are known to eat human feces and prey on other resources (see Allitt et al., 2008, Cannon et al., 1999, Rick et al., 2008), questions remain about the comparability of human, dog, and other animal diets. Consequently, additional data are needed to refine our understanding of the similarities and differences between ancient dog and human diets.

In this paper, we present stable carbon and nitrogen isotope values from Late Holocene (AD 130–1830) domestic dog, island fox (Urocyon littoralis), and human remains from CA-SRI-2, a large Chumash village on Santa Rosa Island, California (Fig. 1). When compared to faunal remains from the site these data provide a framework with which to interpret the dietary patterns of these animals and the relationships between humans and canids on the Channel Islands.

Section snippets

The Channel Islands and CA-SRI-2

California’s Channel Islands are composed of eight islands (San Miguel, Santa Rosa, Santa Cruz, Anacapa, San Nicolas, Santa Barbara, Santa Catalina, and San Clemente). Santa Rosa Island, located about 44 km from the mainland coast is about 217 km2 in area and has a number of relatively well-watered streams. Terrestrial ecosystems on the islands are generally diminished in flora and fauna compared to the adjacent mainland. For example, the diminutive island fox currently found on six islands and

Archaeological materials

Orr (1968) recovered the remains of as many as seven dogs and nine foxes at CA-SRI-2 (Collins, 1991a, Collins, 1991b, Rick et al., 2008, Rick et al., 2009). Rick also excavated a partially eroded dog burial at CA-SRI-2 in 2003. In this study, we analyzed bone collagen extracted from mandibles because they were generally better preserved and we could ensure that we were not sampling the same individual twice. Five dog and three fox mandibles were available for this analysis.

Orr (1968) also

Results

Analysis of stable isotopes from 5 dogs, 3 island foxes, and 15 humans from CA-SRI-2 provides insight into the diets of the three largest Holocene terrestrial mammals on the Channel Islands (Table 3). As depicted in Fig. 3, human and dog stable isotopes are highly enriched compared to foxes: human δ13C = −12.4 to −14.7‰, δ15N = 15.1–21.2‰; dog δ13C = −10.7 to −12.9‰, δ15N = 17.1–18.6‰; fox δ13C = −17.8 to −18.9‰, δ15N = 7.7–11.4‰ (Fig. 3). This indicates that human and dog diets were heavily

Discussion

The dog, fox, and human isotope data presented here provide insight into Late Holocene diets of the three largest Holocene mammals on the Channel Islands. Our analysis suggests that dogs were primarily scavenging the refuse of foods leftover from human consumption and processing and/or were being fed many of the same types of foods that people were eating. Given the dearth of terrestrial foods available on the Channel Islands, not surprisingly these data demonstrate that people and their dog

Conclusions

Our analyses of dog, fox, and human isotopes add to a growing body of literature that illustrates the utility of isotope analyses for enhancing our understanding of ancient human environmental dynamics (e.g., Cannon et al., 1999, Choy and Richards, 2009, Fischer et al., 2007, Schulting and Richards, 2002, Schulting and Richards, 2009, White et al., 2001, White et al., 2004). In the case of Santa Rosa Island, dogs and humans were clearly living in close proximity to one another and subsisting

Acknowledgments

This paper is dedicated to the late Phil C. Orr who collected most of the human, dog, and fox remains analyzed in this study in the 1940s and 1950s. Funds for this project were provided by the Smithsonian Institution, University of Oregon, and Channel Islands National Park (Cooperative Agreement #1443CA8120-00-007). We thank Ann Huston and Kelly Minas of Channel Islands National Park for supporting our research. Finally we thank Seth Newsome, anonymous reviewers, Richard Klein, and the

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