Table 1. Mean values for mandibular peak-strain data in mammals (available only for rabbits and primates) recorded while processing various experimental foods, with corresponding mean food mechanical properties and fragmentation indicesa.
| Species | Food | W–S corpus shear strainb (γ) | Elastic modulusc (E, MPa) | Toughnessd (R, Jm−2) | Stress-limited indexe ([E∗R]0.5) | Displacement- limited indexe ([R/E]0.5) |
|---|---|---|---|---|---|---|
| Rabbit | Hay (wet/dry) | 604 | 227.8/3,335.6 | 1,759.2/2,759.8 | 633.0/3,034.1 | 2.8/0.9 |
| (Oryctolagus) | Pellet | 590 | 29.2 | 1,030.6 | 173.5 | 5.9 |
| Carrot | 297 | 6.9 | 343.9 | 48.7 | 7.1 | |
| Galago | Monkey chow | 1,459 | 50.4 | 1,030.6 | 228.0 | 4.5 |
| (Otolemur) | Gummy bear | 1,140 | 0.1 | 1,709.7 | 10.9 | 156.3 |
| Prune | 565 | 0.5 | 345.7 | 12.8 | 27.1 | |
| Raisin | 494 | 0.2 | 306.6 | 8.2 | 37.3 | |
| Owl monkey | Gummy bear | 1,107 | 0.1 | 1,709.7 | 10.9 | 156.3 |
| (Aotus) | Prune | 1,063 | 0.5 | 345.7 | 12.8 | 27.1 |
| Apple skin | 733 | 12.9 | 662.9 | 92.4 | 7.2 | |
| Macaque | Monkey chow | 775 | 50.4 | 1,030.6 | 228.0 | 4.5 |
| (Macaca) | Popcorn kernel | 705 | 325.4 | 2,978.8 | 984.5 | 3.0 |
| Apple skin | 509 | 12.9 | 662.89 | 92.4 | 7.2 |
Notes.
By definition, stiff items exhibit a high elastic modulus (E). Because such food items experience little strain at high stresses, they influence oral fragmentation in a particular way characterized as stress-limited (Lucas, 2004; Williams et al., 2005). In contrast, when a food item exhibits greater toughness (R) and thus requires higher strains to fragment, oral breakdown of the bolus is displacement-limited. Fragmentation indices for displacement-limited ([R/E]0.5) and stress-limited ([E∗R]0.5) foods reflect the toughness and stiffness, respectively, of an item.
Rabbit data for the working-side (W-S) mandibular corpus are from Weijs & De Jongh (1977), while similar data for primates are from Hylander et al. (1998).
Data for hay and pellets are from Ravosa et al. (2007), while the remaining data are from Williams et al. (2005).
Data for hay are from Ravosa et al. (2007), whereas the remaining data are from Williams et al. (2005). Data for monkey chow are used to represent toughness for pellets.
Data are calculated based on mean values for stiffness and toughness presented in this table.