Oral presentation- Open Session 12th International Mammalogical Congress

Merycism in western grey (Macropus fuliginosus) and red (Macropus rufus) kangaroos (#255)

Catharina Vendl 1 , Adam Munn 1 , Keith Leggett 2 , Marcus Clauss 3
  1. School of Biological, Earth and Environmental Sciences, The University of New South Wales, Sydney, New South Wales, Australia
  2. Fowlers Gap Arid Zone Research Station, School of Biological, Earth and Environmental Sciences, University of New South Wales, via Broken Hill NSW 2880, New South Wales, Australia
  3. Clinic for Zoo Animals, Exotic Pets and Wildlife, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland

Kangaroos occasionally regurgitate and re-chew digesta. This so-called 'merycism' is distinct from rumination, being non-essential for digestive activity, significantly varying in frequency, and causing seeming discomfort. Triggering mechanisms and benefits remain unknown. Although often reported, detailed descriptions are lacking. We performed a systematic evaluation of 17 anecdotal observations of six kangaroos (M. fuliginosus, M. rufus) in captive feeding situations (14 videos with lucerne pellets and 3 with chopped lucerne hay feeding, covering 4.38 h with more than 55 regurgitation events). A characteristic merycism sequence consisted of retreat from feeding trough, pumping abdominal contractions, slurping, re-chewing and re-swallowing. In some individuals variations occurred, e.g. instead of re-swallowing digesta, it was spilled (35 % of cases). We hypothesize that the purpose of merycism is grinding of non-sufficiently chewed food particles that trigger contractions of the forestomach beyond voluntary control. The numerically higher frequency of this behaviour during pellet compared to hay feeding supports this hypothesis, as pellets were often gobbled hastily. In accord with observations in the literature, we hypothesize that merycism happens more frequently in captivity, as the type of food, fixed feeding times and limited feeding spots make gobbling of food more likely.