An analysis of chewed food particle size and its relationship to molar structure in the primates Cheirogaleus medius and Galago senegalensis and the insectivoran Tupaia glis

The chewed food particle size and shearing capacity of the lower molars of two primate species, the fat‐tailed dwarf lemur, Cheirogaleus medius and the bushbaby Galago senegalensis , and an insectivoran, the tree shrew, Tupaia glis , were compared. Differences in the shearing design of the lower molars correlate strongly with the chewed food particle size in these species: the greater the shearing capacity, the smaller the chewed food particles. These three species are of comparable size but differ greatly in diet in the wild. C. medius primarily eats fruit and nectar, while G. senegalensis and T. glis are largely insect‐eaters. The lower molars of G. senegalensis and T. glis show a much greater shearing capacity than do those of C. medius. The average length of chewed food particles of C. medius is significantly larger than that of G. senegalensis , while that of T. glis is intermediate between the two primates but is closer to that of G. senegalensis. Our findings that insect‐eating species grind their food more finely than do fruit‐ and resin‐eating species can be correlated with digestibility of foods: finely chewing foods such as fruits which are low in relatively undigestible cell wall components would not greatly improve their digestibility, so a highly efficient food processing apparatus would be less important to the animal's survival. Insect‐eaters much more finely chew their foods, implying that there is some constituent of insect bodies difficult to digest, and that grinding increases its digestibility. We suggest that this constituent is chitin.