Game and Wildlife Science, Vol. 20 (4), March 2004, p. 1-19 ISSN 1622-7662 MONITORING JAW MOVEMENTS: A CUE TO FEEDING ACTIVITY Y.ROPERT-COUDERT (*), A. KATO (*), N. LIEBSCH (**), R.P. WILSON (**), G. MÜLLER (**) and E. BAUBET (***) (*) National Institute of Polar Research, 1-9-10 Kaga, Itabashi Tokyo 173-8515, Japan. E-mail: yan@nipr.ac.jp (**) Institut für Meereskunde Düsternbrooker, Weg 20, D-24105 Kiel, Germany. (***) Office national de la chasse et de la faune sauvage, CNERA Cervidés-Sanglier, 1 place Exelmans, F-55000 Bar-le-Duc, France. KEY WORDS: Carnivore, herbivore, mammal, bird, turtle, jaw movement, data logger, food quality, ingestion event. ABSTRACT We investigated the potential of a recently-developed data logger that monitors jaw movements using a magnet/Hall sensor combination to identify features that characterize prey ingestion. Experiments were conducted on eleven captive animal species of mammals, birds and turtles, with carnivorous and herbivorous feed- ing habits, exploiting either marine or terrestrial environments. Following calibra- tion, the timing of prey ingestion was accurately detected in all instances but food manipulation prior to swallowing led to a large interspecific variability in jaw opening angle over time. Pros and cons of the system are given together with an assessment of the applicability of such a tool for ecological studies on free-ran- ging animals. Overall, the system proved promising for estimation of the quanti- ty and quality of the food. I. INTRODUCTION Assessment of the feeding activity of free-ranging animals is important for modelling energy flux in ecosystems (ELTON, 1927). For example, assess- ments of the attributes of ruminant diets are necessary to fully understand pasture–animal relationships and to manage grassland systems (COATES and PENNING, 2000). However, for many species, feeding behaviour cannot be observed directly or cannot be quantified by direct measurements. This is especially true in the case of free-ranging individuals foraging in ecosys- tems that are difficult to access such as marine environments (KOOYMAN et al., 1992), deserts (MEYERS, 1996), forests, as well as for nocturnal feeders.