Indicators of Dental Health

The postcanine dentition is central for food processing, therefore, the patterns of dental pathology in premolars and molars are most often related to diet and the breakdown of food. This contrasts with patterns seen in the anterior teeth across primates, in which dental damage (often leading to disease) results from social behaviors, for example interindividual aggression (Lovell, 1990; Smith et al., 1977) or, in the case of ring-tailed lemurs at Beza Mahafaly, the possible impact of human activity and introduced foods (Sauther et al., 2006). As noted earlier, to date there is a paucity of information on lemur dental pathology, including patterns of wear (see Cuozzo and Sauther, 2004a,b, 2005, 2006, in press; Cuozzo et al., 2004; King et al., 2005; Sauther et al., 2002). Classic studies, such as the seminal work of Schultz (1935), and Miles and Grigson's (1990) revision of Colyer's work, present few if any examples of lemur dental health.

The lemur community at Beza Mahafaly, because of its long-term study (including the collection of skeletal remains from the reserve (Cuozzo and Sauther, 2004a, 2006, in press), allows for an initial understanding of dental health in wild lemurs, and provides important data for recognizing the role of ecology and the environment in dental pathology and tooth wear. Both ring-tailed lemurs and Verreaux's sifakas have been the focus of long-term dental study at Beza Mahafaly (e.g., Cuozzo and Sauther, 2004a,b, 2005, 2006, in press; Cuozzo et al., 2004; Lawler et al., 2005; Sauther et al., 2001, 2002, 2006; Yamashita, 1996, 1998a,b, 2000, 2002, 2003). Despite their sympatry, these taxa display quite different patterns of dental health and tooth wear. For example, while L. catta at Beza Mahafaly exhibits a high frequency of severe postcanine wear and antemortem tooth loss (Cuozzo and Sauther, 2004a,b, 2005, 2006, in press; Sauther et al., 2002), P. v. ver-reauxi does not (Cuozzo and Sauther, in press). In fact, in comparison to ring-tailed lemurs, in which 27% of the living individuals studied displayed antemortem tooth loss, most of which have been lost due to excessive wear (Cuozzo and Sauther, 2004a, 2006, in press), only 6% of the sifaka skeletal specimens at the reserve exhibit tooth loss (Cuozzo and Sauther, in press; Cuozzo, unpublished data). Among sifaka, most tooth loss results from dental pathology, not excessive wear (Cuozzo and Sauther, in press; Cuozzo, in preparation). In addition, the degree of tooth wear in the sifaka sample, while sometimes pronounced in older individuals relative to others in the sample (including the anterior dentition [Cuozzo and Sauther, in press; Cuozzo, unpublished data]), is far exceeded by ring-tailed lemurs, in which many teeth are worn down to the roots, and often completely lost, a condition seen in both living individuals and skeletal specimens (e.g., Cuozzo and Sauther, 2004a, 2005, 2006, in press; Sauther et al., 2002). A recent study of tooth wear in Propithecus edwardsi at Ranomafana National Park (King et al., 2005) illustrates that, although sifaka experience noticeable wear, even at advanced ages the degree of tooth wear is far less than that displayed by ring-tailed lemurs at Beza Mahafaly (Cuozzo and Sauther, in press).

The patterns of wear in this population of ring-tailed lemurs are clearly related to ecology, diet, and tooth use. In L. catta, the most frequently worn and missing teeth (P3, P4, and M1) are those used in the initial processing of tamarind fruit (Cuozzo and Sauther, 2004a, 2006, in press). This fruit (Tamarindus indica) is both hard and tough when ripe (Yamashita, 2000), and dominates the diet of ring-tailed lemurs living in gallery forest (Sauther, 1998; Simmen et al., in press), despite their opportunistic omnivory (e.g., Sauther et al., 1999). In contrast, P. v. verreauxi displays more excessive wear on P3, P4, and M3 (sifakas have only two premolars in each quadrant, see Table 1 [e.g., Swindler, 2002; Tattersall, 1982]), with M1 and M2 often retaining much of the original crown structure (Cuozzo and Sauther, in press; Cuozzo, unpublished data). The more limited wear and lower frequency of tooth loss in P. v. verreauxi at Beza Mahafaly when compared to L. catta likely reflects differences in diet, as well as tooth form. Although both taxa have relatively thin dental enamel (Table 2) (e.g., Godfrey et al., 2005), sifakas have very large molars relative to skull size (Godfrey et al., 2002), in addition to a specialized folivorous morphology (see comparisons of the molar morphologies of the lemurid Eulemur and indriid Propithecus in Figures 7 and 8) (Tattersall, 1982; Yamashita, 1998a,b). Sifakas at Beza Mahafaly do consume tamarind fruit, but most often eat the less tough, unripe fruits (e.g., Yamashita, 2002). As such, sifaka teeth are apparently a "better match" for their diet than seen in ring-tailed lemurs, which appear to represent an ecological "mismatch" between tooth structure and diet (Cuozzo and Sauther, 2005, in press). Understanding this relationship between ecology and dental health in living lemurs, in addition to aiding in our knowledge of lemur biology, provides an important context in which to understand lemur paleobiology and evolution (Cuozzo and Sauther, 2004b, in press), as seen in recent work on the subfossil lemurid Pachylemur, which displays noticeable tooth wear (Godfrey et al., this volume; Vasey et al., 2005).

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