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Manatees (Trichechus spp.) are herbivorous aquatic mammals found in tropical and subtropical waters. At maturity, they possess only supernumerary molars (SM), with 5-8 in occlusion at each quadrant. Manatees exhibit a dental replacement system in which they shed old teeth anteriorly and erupt new teeth posteriorly. This adaptation is thought to have arisen to deal with abrasive foods. Mesowear (facet development on occlusal surfaces of teeth) increases from posterior (younger) to anterior (older) molars. Tooth functionality is linked to level of mesowear, with increased amounts resulting in decreased food-processing ability. Less functional teeth can result in an increase in feeding time, potentially decreasing fitness. Domning (1982) noted that Florida manatees (T. manatus latirostris) appeared to experience greater levels of mesowear compared to other manatee populations, however, he did not quantify the difference. To address this, we examined museum specimens from all manatee taxa: Florida (n=64), Antillean T. m. manatus (n=49), Amazonian T. inunguis (n=121) and African T. senegalensis (n=4) manatees. Photographs of the dental arcade (upper and lower) were taken and analyzed. Each SM in occlusion was numbered (posterior to anterior) per quadrant and classified into one of five discrete wear categories (level 5, extreme, being considered as non-functional). Total number of teeth (TNTQ) and total number of functional teeth (TNFTQ) per quadrant were counted including missing teeth (evidenced by dental alveoli). Florida manatees had significantly fewer mean TNTQ (H=130.03, p<0.001) than other taxa except Antillean manatees, and fewer mean TNFTQ (H=362.21, p<0.001) than all other manatee taxa. In addition, except for SM1, Florida manatees had greater mean levels of mesowear (SM2-SM6) compared to all other taxa. Florida is not only a marginal habitat for manatees because of seasonally cooler water, but also because of the additional dental burden: it appears they are wearing down their teeth faster than the replacement process.
Woodard, Nina, "Are Florida Manatees (Trichechus Manatus Latirostris) Wearing their Teeth Beyond Functionality? Interspecific and Intraspecific Mesowear in Manatees" (2020). Honors Theses. 233.
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