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

Abstract

The greater Caribbean manatee Trichechus manatus manatus is a vital component ofmarine, 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 andfecal analysis, a comprehensive understanding of their feeding habitats over time and acrossbroader geographical scales in the Mexican Caribbean was lacking. This study aimed to addressthis gap by investigating spatial–temporal variations in the species’ trophic ecology. In QuintanaRoo, Mexico, 68 bone collagen samples and 557 aquatic and semi-aquatic plant samples were col-lected and isotopically analyzed. Isotope ratios (δ13C and δ15N) of plants varied by type (algae, sea-grass, mangrove, and other vascular plants) and environment (marine, estuarine, and freshwater).Manatee bone collagen δ13C and δ15N differed among locations but remained consistent acrossdecades, sexes, and age classes, indicating a prevalent preference for seagrasses. Despite habitatmodifications, 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 inthe manatee’s diet, its feeding ecology, and the significance of different environments. This knowl-edge is critical for identifying and conserving essential habitats for the manatee population.