Nutritional Ecology of Lactation in Franciscana Dolphins ( <i>Pontoporia blainvillei</i> ) From Argentina

ABSTRACT Milk production strategies, duration, and composition vary among mammals. Odontocete cetaceans exhibit a long lactation strategy characterized by high parental investment and prolonged nutritional dependence. Understanding the nutritional demands of these offspring during lactation is complex, particularly due to their aquatic lifestyle. This study examines the nutritional dynamics of endangered Franciscana dolphins ( Pontoporia blainvillei ) during their first year of life. Our findings indicate that Franciscana milk is energy‐rich, with proteins and lipids as primary energy sources, varying in proportion throughout lactation. Summer milk has a higher protein‐to‐lipid ratio and lower energy density, while winter milk is more energy‐dense, with a greater lipid proportion and increased variability in composition. Calves over 80 cm consume a combination of low protein‐to‐lipid ratio milk with high protein‐to‐lipid ratio prey. Artificial milk formulas used in rehabilitation closely resemble the macronutrient composition of wild milk. This study provides valuable insights into the critical life stage of this vulnerable species and contributes to developing nutritional protocols for rehabilitating live‐stranded individuals.