Potential energetic implications of emesis in the house musk shrew (Suncus murinus)

During the course of studies investigating novel anti-emetic therapies we serendipitously observed a previously unreported behaviour related to emesis in the house musk shrew. This behaviour consisted of spontaneous ingestion of vomit in about half of the animals (males and females) in which emesis was induced by either nicotine (4 mg kg-1 sc.) or horizontal motion (1 Hz, 4 cm, 10 min). Analysis of vomit samples and gastric contents revealed that in a "typical" individual the gastric contents would be voided by as few as 3 vomits. Energetic calculations of the metabolisable energy of food, gastric contents, vomit and field metabolic rate (FMR) predict that a male weighing 60 g would lose 17.3% of its hourly energy requirement for FMR if it vomited once. A 40 g female, however, would experience an hourly energy loss of approximately 22.8%. The possible energetic consequences and resulting ecological implications of this unusual behaviour are discussed.