Behavioral correlates of tooth eruption in Madagascar lemurs

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Abstract
Observations on the sequence and timing of gingival tooth eruption are reported for six species of Madagascar lemurs. Complete sequences of eruption were obtained for the deciduous dentition, and partial to complete sequences were recorded for the permanent dentition. In Cheirogaleus medius and in four species of the genus Lemur, the deciduous teeth erupt in front‐to‐back sequence, with the toothcomb emerging near birth as an integrated complex. In Propithecus verreauxi the same pattern is exhibited, but the small peglike lower canine and dp3 erupt last. Eruption of the permanent dentition in Lemur species takes place in two distinct stages. In the first stage the upper incisors, toothcomb, and first two molars penetrate the gingiva. After an interval of 3 to 4 months, the remaining permanent teeth erupt.Deciduous premolars erupt when young animals are being weaned. The eruption of the deciduous toothcomb appears unrelated to feeding or grooming behavior. In L. catta and L. fulvus, the first stage of permanent tooth eruption occurs at approximately 6 months of age, when the growth rate slows down and (in wild populations) the rainy season is ending. This suggests that eruption of the anterior molars is timed to coincide with a shift from a more frugivorous to a more folivorous dietary regime, which occurs during the dry season. No further tooth eruption occurs until approximately 1 year of age, when the growth rate increases and the rainy season returns for wild populations. Thus, the second wave of permanent tooth eruption in these species again appears linked to changing climatic conditions which lead to a shift in dietary preferences.