Heat increment of feeding in the common bottlenose dolphin (Tursiops truncatus) contributes moderately to field metabolic rate estimates.

Digestion elevates metabolism through the heat increment of feeding (HIF) - the energy expended on mechanical and biochemical processes after eating. Quantifying this cost is essential for bioenergetic models that predict energy flow and prey requirements in populations. Using breath-by-breath respirometry, we measured oxygen consumption (V̇O2) in eight common bottlenose dolphins (Tursiops truncatus) before and after feeding standardized meals (1659-2658 kcal of capelin and herring). Metabolic rate rose by ∼37% above resting levels, peaking 60 min after feeding before returning to baseline within 2 h. When scaled across the day, digestion increased daily metabolic needs by ∼8.2% of basal metabolism, similar to values reported for Steller sea lions (Eumetopias jubatus) and harbour seals (Phoca vitulina), where HIF contributes 4-10% of daily energy expenditure. This study provides the first multi-individual estimate of HIF in dolphins and suggests that the energetic cost of digestion is a moderate contribution to overall daily metabolism, refining energetic models and improving prey requirement estimates for cetaceans in the wild.