In vivo bone strain in the mandibular corpus of Sapajus during a range of oral food processing behaviors

Abstract

It has been hypothesized that mandibular corpus morphology of primates is related to the material properties of the foods that they chew. However, chewing foods with different material properties is accompanied by low levels of variation in mandibular strain patterns in macaques. We hypothesized that if variation in primate mandible form reflects adaptations to feeding on foods with different material and geometric properties, then this variation will be driven primarily by differences in oral food processing behavior rather than differences in chewing per se. To test this hypothesis, we recorded in vivo bone strain data from the lateral and medial surfaces of the mandibular corpus during complete feeding sequences in three adult male Sapajus as they fed on foods with a range of sizes and material properties. We assessed whether variation in mandibular corpus strain regimes is associated with variation in feeding behaviors and/or chewing on different foods, and we quantified the relative variation in mandibular corpus strain regimes associated with chewing on foods of different material properties versus a range of oral food processing behaviors (incisor, premolar, and molar biting; pulling on incisors; mastication). Feeding behavior had a significant effect on mandibular corpus strain regimes, as did chewing side and the cycle number in a feeding sequence. However, food type had weaker effects and usually only through interaction effects with chewing side and/or cycle type. Strain regimes varied most across different chew sides, then across different behaviors, and lastly between mastication cycles on different foods. Strain magnitudes associated with premolar, molar, and incisor biting were larger than those recorded during mastication. These data suggest that intra- and inter-specific variation in mandible morphology is a trade-off between performance requirements of different oral food processing behaviors and of variation in chewing side, with direct effects of food type being less important.

The dental microwear of hard‐object feeding in laboratory Sapajus apella and its implications for dental microwear formation

“…All animals had been used previously for other research, the three UChicago capuchins for analyses of jaw kinematics (Iriarte‐Diaz, Reed, & Ross, ; Reed & Ross, ; Ross & Iriarte‐Diaz, ; Ross, Iriarte‐Diaz, & Nunn, ; Ross, Iriarte‐Diaz, Reed, Stewart, & Taylor, ), and the two NEOMED capuchins for analyses of craniofacial bone strain and EMG activity (Thompson, Jackson, Stimpson, Horne, & Vinyard, ; Vinyard, Thompson, Doherty, & Robl, ). While some of the equipment from this previous work allowed us to capture cineradiographic recordings and to monitor chewing cycles, these procedures have been shown to have no measurable effect on the feeding (especially chewing) behavior of the animals used in this study (Ross et al, ).…”

Taking a big bite: Working together to better understand the evolution of feeding in primates

“…It has provided a powerful perspective—ineffable knowledge sensu Polanyi ()—on the lives of wild primates. In vivo laboratory studies come with an array of ethical trade‐offs related to housing and research methods that responsible animal researchers have to acknowledge (Fish, ; Ross, ; Ross et al, ; Thompson et al, ). The study of primates in the wild forces a profound confrontation with those trade‐offs.…”

Bite force and cranial bone strain in four species of lizards

“…Perhaps the most difficult strain data to collect in vivo are those associated with infrequent traumatic events, such as blows or bites during predation or intraspecific agonistic interactions, which have been hypothesized to be important determinants of skull design in primates (Carrier, 2011;Hylander and Johnson, 1997;Hylander et al, 1991b;Hylander and Ravosa, 1992). In the absence of in vivo strain data across the complete range of animal behaviors, and estimates of their frequency and ecological importance (Ross et al, 2016), some progress can be made by assuming that behaviors associated with relatively high strain magnitudes are likely to impose greater demands on skeletal design than behaviors associated with lower strain magnitudesbone size and shape are expected to be more closely adapted to resist high strain than low strain magnitude loading regimes. This expectation applies not only across behaviorsdifferent gaits (Biewener et al, 1983a, b;Blob and Biewener, 1999); biting versus chewing, licking and yawning (Hylander, 1981;Ross et al, 2016) but also between different phases of the same behavior.…”

“…In the absence of in vivo strain data across the complete range of animal behaviors, and estimates of their frequency and ecological importance (Ross et al, 2016), some progress can be made by assuming that behaviors associated with relatively high strain magnitudes are likely to impose greater demands on skeletal design than behaviors associated with lower strain magnitudesbone size and shape are expected to be more closely adapted to resist high strain than low strain magnitude loading regimes. This expectation applies not only across behaviorsdifferent gaits (Biewener et al, 1983a, b;Blob and Biewener, 1999); biting versus chewing, licking and yawning (Hylander, 1981;Ross et al, 2016) but also between different phases of the same behavior. For example, the shapes of limb bones are expected to be more closely adapted to dissipating forces associated with stance phase than swing phase of the gait cycle (Biewener, 2003), and mandible shape is expected to be adapted more to dissipating forces associated with the power stroke than with the opening phases of the gape cycle (Hylander et al, 1987).…”