Telemetry System for Assessing Jaw-Muscle Function in Free-ranging Primates

Abstract

In vivo laboratory-based studies describing jaw-muscle activity and mandibular bone strain during mastication provide the empirical basis for most evolutionary hypotheses linking primate masticatory apparatus form to diet. However, the laboratory data pose a potential problem for testing predictions of these hypotheses because estimates of masticatory function and performance recorded in the laboratory may lack the appropriate ecological context for understanding adaptation and evolution. For example, in laboratory studies researchers elicit rhythmic chewing using foods that may differ significantly from the diets of wild primates. Because the textural and mechanical properties of foods influence jaw-muscle activity and the resulting strains, chewing behaviors studied in the laboratory may not adequately reflect chewing behaviors of primates feeding in their natural habitats. To circumvent this limitation of laboratory-based studies of primate mastication, we developed a system for recording jaw-muscle electromyograms Int J Primatol (2008) (EMGs) from free-ranging primates so that researchers can conduct studies of primate jaw-muscle function in vivo in the field. We used the system to record jawmuscle EMGs from mantled howlers (Alouatta palliata) at Hacienda La Pacifica, Costa Rica. These are the first EMGs recorded from a noncaptive primate feeding in its natural habitat. Further refinements of the system will allow long-term EMG data collection so that researchers can correlate jaw-muscle function with food mechanical properties and behavioral observations. In addition to furthering understanding of primate feeding biology, our work will foster improved adaptive hypotheses explaining the evolution of primate jaw form.29:1441-1453 DOI 10.1007/s10764-008-9292-

Methods for Studying the Ecological Physiology of Feeding in Free-Ranging Howlers (Alouatta palliata) at La Pacifica, Costa Rica

“…Previously, we reported on a telemetery system that transmitted EMG data to a digital compact flash recorder using an FM radio receiver (Williams et al 2008). Although this system continuously transmitted data in real time, we had no ability to power the system on or off to preserve battery life.…”

“…The available recording time limited our ability to study naturalistic feeding behaviors. Thus, we have modified the prototype telemetry unit described in Williams et al (2008) to extend battery life by allowing remote control of data recording.…”

“…To build on these studies of feeding behaviors and food properties, we are recording jaw-muscle activity during feeding in free-ranging mantled howlers (Williams et al 2008). By linking in vivo Fig.…”

“…Whereas researchers have collected telemetered data from unrestrained individuals (Kawai et al 2007;Langenbach 2011;Langenbach et al 2002Langenbach et al , 2004 and humans (Miyamoto et al 1996;Po et al 2011), the primate data were still collected in laboratory settings where subjects were fed and restrained. Previously, we acknowledged the benefits of these laboratory data for understanding masticatory physiology, but also highlighted the importance of collecting ecologically relevant data on jaw-muscle function from free-ranging primates in their natural habitats (Williams et al 2008). Specifically, we argued that naturalistic physiology data are integral for more accurately linking jaw-muscle EMGs to the evolution of primate cranial form and for placing the laboratory data in an appropriate adaptive context (Thompson et al 2011;Williams et al 2008).…”

“…Previously, we acknowledged the benefits of these laboratory data for understanding masticatory physiology, but also highlighted the importance of collecting ecologically relevant data on jaw-muscle function from free-ranging primates in their natural habitats (Williams et al 2008). Specifically, we argued that naturalistic physiology data are integral for more accurately linking jaw-muscle EMGs to the evolution of primate cranial form and for placing the laboratory data in an appropriate adaptive context (Thompson et al 2011;Williams et al 2008). By determining how the timing and relative magnitude of jaw-muscle recruitment during feeding varies with food mechanical properties and other ecological parameters in free-ranging primates, we gain a better understanding of how diets relate to masticatory function (Fig.…”