Stable isotope analysis in bone collagen reveals new insights into the feeding ecology of free-ranging manatees in the Mexican Caribbean

The greater Caribbean manatee Trichechus manatus manatus is a vital component of marine, estuarine, and freshwater ecosystems, relying on a diverse range of aquatic and semi-aquatic plants for sustenance. While early research inferred their diet through digestive tract and fecal analysis, a comprehensive understanding of their feeding habitats over time and across broader geographical scales in the Mexican Caribbean was lacking. This study aimed to address this gap by investigating spatial-temporal variations in the species’ trophic ecology. In Quintana Roo, Mexico, 68 bone collagen samples and 557 aquatic and semi-aquatic plant samples were collected and isotopically analyzed. Isotope ratios (δ 13 C and δ 15 N) of plants varied by type (algae, seagrass, mangrove, and other vascular plants) and environment (marine, estuarine, and freshwater). Manatee bone collagen δ 13 C and δ 15 N differed among locations but remained consistent across decades, sexes, and age classes, indicating a prevalent preference for seagrasses. Despite habitat modifications, no significant changes in manatee feeding habits over the past 30 yr were observed. Stable isotope analysis offers insights into the relative importance of aquatic vegetation types in the manatee’s diet, its feeding ecology, and the significance of different environments. This knowledge is critical for identifying and conserving essential habitats for the manatee population.