Forty years of Projeto Lontra: Lessons learned and the future of otter-led estuarine conservation

Over four decades, Projeto Lontra has pioneered otter-led estuarine conservation in Brazil, generating one of the world’s longest continuous datasets on Lontra longicaudis and its habitats. This Expert View synthesizes eight foundational lessons distilled from 40 years of applied science, community engagement, and adaptive management across the Atlantic Forest, Pantanal, and Amazon. We demonstrate how 14-year monitoring (2003–2017) revealed a >90% decline in otter presence intensity—leading to a Critically Endangered classification for the Santa Catarina Island population—and how integrating emergy theory, non-invasive reproductive protocols (88% pup survival across 10 events, 2017–2024), and shared stewardship models transformed conservation practice. Critically, we show that the otter functions not merely as a bioindicator but as a high-transformity species (2.26 × 10²² seJ/J) whose presence quantifies estuarine integrity at systemic, energetic, and cultural levels. All protocols and datasets are released under CC0 1.0, supporting global replication. As Projeto Lontra enters its 40 th year, this article affirms a covenant—not of mastery, but of humility: conservation succeeds when science, technology, and relationship converge to reweave broken ecological and social threads.