Academic journal article Southeastern Archaeology

Using Fluorescence of Bones and Teeth to Detect Remains of the Eastern Fox Squirrel (Sciurus Niger) in Archaeological Deposits

Academic journal article Southeastern Archaeology

Using Fluorescence of Bones and Teeth to Detect Remains of the Eastern Fox Squirrel (Sciurus Niger) in Archaeological Deposits

Article excerpt

The skeletal remains of the eastern fox squirrel, hereafter fox squirrel (Sciurus niger), and the eastern gray squirrel, hereafter gray squirrel (S. carolinensis), are common in faunal deposits at archaeological sites in the eastern United States (Barfield and Barber 1992; Carder et al. 2004; Holm 2002; O'Brien and Kuttruff 2012; Smith 2011; VanDerwarker 2001). These archaeological remains are an underused, but potentially very valuable, resource for analyses of environmental conditions associated with archeological deposits and studies of the ecology and evolution of fox squirrels and gray squirrels during the Holocene and late Pleistocene. However, assignment of remains as either fox squirrel or gray squirrel can be extremely challenging, because the overall skeletal morphology of tree squirrels (genus Sciurus) is quite conservative, with very few differences between species (Emry and Thorington 1982). Living fox squirrels and gray squirrels are easily distinguished using differences in pelage color (Edwards et al. 2003); also, teeth and skeletal elements of the fox squirrel are often larger than those of the gray squirrel (Hall 1981). However, there is overlap in the size ranges in modern specimens of these species. The body mass of adult gray squirrels ranges from approximately 300 g to approximately 700 g, whereas adult fox squirrels range in body mass from approximately 500 g to approximately 1,300 g (Koprowski 1994a, 1994b). Furthermore, modern populations of both species currently occur in most temperate forests east of the Rocky Mountains (Hall 1981), and they often coexist in the same local habitats (Edwards et al. 2003).

These factors complicate, or prevent, researchers from definitively assigning many elements of Sciurus in archaeological deposits in eastern North America to the species level. As a result, many bones, bone fragments, and isolated teeth at archaeological sites can be identified as remains of animals that are in the genus Sciurus, but the species cannot be assigned unless the elements are from especially large individuals, or unless particular features are preserved (the gray squirrel has a tiny, peglike upper premolar tooth [P3] that is absent in the fox squirrel [Figure 1A; Hall 1981]). Thus, many studies of archaeological sites in the southeastern United States report individual elements as Sciurus sp., indicating that the authors are confident that the element is from an animal in the genus Sciurus but cannot assign the element to S. niger or S, carolinensis.

We recently demonstrated a method to definitively assign fossils to S. niger using 7,000-year-old specimens of the fox squirrel from a sinkhole deposit in Florida (Dooley and Moncrief 2012). This method takes advantage of the fact that modern populations of S. niger include individuals that display some characteristics of a condition called congenital erythropoietic porphyria (CEP; Levin and Flyger 1971). CEP is caused by mutations in the genes that code for enzymes in the biosynthetic pathway that produces heme, which is an important component of hemoglobin, the red pigment in vertebrate blood that allows effective delivery of oxygen to tissues (van Tuyll van Serooskerken et al. 2010).

CEP has been reported in at least eight mammalian species besides S. niger (Richard et al. 2008; Rivera and Leung 2008; Samman 1991; van Tuyll van Serooskerken et al. 2010). Symptoms of CEP (also known as Günther's disease when it affects humans) (Richard et al. 2008) usually include anemia, cutaneous photosensitivity, and/or acute neurological attacks (van Tuyll van Serooskerken et al. 2010). Surprisingly, fox squirrels do not display any of these debilitating symptoms of CEP (Levin and Flyger 1973).

CEP is an atypical condition in most species, because it is usually the result of rare, spontaneous mutations (van Tuyll van Serooskerken et al. 2010). However, in S. niger, the condition exists in most or all individuals (Flyger and Levin 1977; Spradling et al. …

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