Methods for Studying the Ecological Physiology of Feeding in Free-Ranging Howlers (Alouatta palliata) at La Pacifica, Costa Rica
adductor muscle force; fecal cortisol-levels; Feeding ecology; in-vivo; Jaw-muscle physiology; lemurs lemur-catta; macaca-fascicularis; mandibular function; mastication; mechanical defenses; postorbital septum; Research methods; symphyseal fusion; telemetry system; Zoology
We lack a general understanding of how primates perform physiologically during feeding to cope with the challenges of their natural environments. We here discuss several methods for studying the ecological physiology of feeding in mantled howlers (Alouatta palliata) at La Pacifica, Costa Rica. Our initial physiological effort focuses on recording electromyographic activity (EMG) from the jaw muscles in free-ranging howlers while they feed in their natural forest habitat. We integrate these EMG data with measurements of food material properties, dental wear rates, as well as spatial analyses of resource use and food distribution. Future work will focus on incorporating physiological measures of bone deformation, i.e., bone strain; temperatures; food nutritional data; and hormonal analyses. Collectively, these efforts will help us to better understand the challenges that howlers face in their environment and the physiological mechanisms they employ during feeding. Our initial efforts provide a proof of concept demonstrating the methodological feasibility of studying the physiology of feeding in free-ranging primates. Although howlers offer certain advantages to in vivo field research, many of the approaches described here can be applied to other primates in natural habitats. By collecting physiological data simultaneously with ecological and behavioral data, we will promote a more synthetic understanding of primate feeding and its evolutionary history.
Vinyard C J; Glander K E; Teaford M F; Thompson C L; Deffenbaugh M; Williams S H
International Journal of Primatology
2012
2012-06
Journal Article
<a href="http://doi.org/10.1007/s10764-012-9579-2" target="_blank" rel="noreferrer noopener">10.1007/s10764-012-9579-2</a>
Accessing foods can exert multiple distinct, and potentially competing, selective pressures on feeding in common marmoset monkeys
apparatus; behavior; Callithrix; callithrix-jacchus-jacchus; enamel thickness; evolution; feeding adaptations; food; food choice; Food mechanical properties; food selection; hardness; masticatory; mechanical defenses; morphology; prey size; processing; red deer; resource acquisition; tree gouging; Zoology
Animals must overcome the physical properties protecting foods to obtain nutrition. While animals can experience selection for traits that facilitate resource exploitation, specific feeding behaviors may entail multiple, different mechanical challenges with each potentially eliciting distinct selection pressures. Tree gouging by common marmosets (Primates: Callithrix jacchus) provides an illustrative case for studying these distinct mechanical challenges and their correlated behaviors and morphologies. We test the hypothesis that marmosets respond differently to three sequential mechanical stages of bark removal: (1) indentation; (2) crack initiation; (3) crack propagation. By surveying trees gouged by free-ranging marmosets in Pernambuco, Brazil, we found that mechanical variables related to crack initiation (fracture toughness, critical strain energy release rate and elastic modulus) were inversely correlated with measures of gouging intensity, with less mechanically challenging trees being gouged more intensely. Because crack initiation is likely the most mechanically challenging aspect of tree gouging, behavioral preference for less challenging resources likely allows marmosets to reduce costs and potential risks associated with accessing exudates. Variables related to bark indentation (hardness and friction) showed no relationship to the intensity of gouging behavior. Contrary to our prediction, trees with greater mechanical challenges for crack propagation (work to peel) were gouged more intensely. We attribute this pattern of gouging trees requiring greater effort in crack propagation to an inverse correlation between work to peel and fracture toughness in our tree sample. Importantly, marmosets exhibit morphological specializations of the feeding apparatus that facilitate indentation and crack propagation, potentially mitigating the need for behavioral choice. Here we show that extracting a single food resource can exert a series of distinct, potentially competing, selective forces during resource acquisition. This study illustrates how animals combine behaviors and morphological specializations to competently overcome distinct mechanical challenges, emphasizing the need for holistic approaches in understanding feeding adaptations.
Thompson C L; Valenca-Montenegro M M; Melo Lcdo; Valle Y B M; Oliveira Mabd; Lucas P W; Vinyard C J
Journal of Zoology
2014
2014-11
Journal Article
<a href="http://doi.org/10.1111/jzo.12164" target="_blank" rel="noreferrer noopener">10.1111/jzo.12164</a>