How important is this discovery?<\/h2>\n
In the Amazon, seed dispersal and plant distribution are intrinsically linked to rivers\u2019 flood-and-drought cycles. Piedade explains that, during floods, water is the main disperser in floodplains and igap\u00f3s (blackwater-flooded forests), especially of aquatic and semiaquatic plants.<\/p>\n
\u201cThe plants bear fruit, and their seeds fall into the water. Then fish eat them and take them to other habitats located upstream or in nearby areas,\u201d she explains, referring to studies that have found seeds in the digestive tracts of fish.<\/p>\n
But knowing that the manatee plays a similar role is significant. Weighing up to 550 kilograms (1,200 pounds), manatees eat up to 40 kg (88 lbs) of aquatic plants per day and have been recorded traveling up to 115 kilometers (71 miles) between lakes Aman\u00e3 and Mamirau\u00e1. With a long digestive tract, seeds can remain in their intestines for up to a week, increasing their potential as seed dispersers. \u201cIn addition, they deliver the seeds with natural fertilizer, a real gardening kit,\u201d Piedade comments humorously.<\/p>\n
The manatee\u2019s migratory patterns suggest that it plays a vital role in dispersing seeds between fertile habitats such as river floodplains and nutrient-poor areas such as igap\u00f3s. \u201cDuring floods, the manatee stays in the floodplains, where food is abundant,\u201d explains Miriam Marmontel, an aquatic mammal expert at the Mamirau\u00e1 Institute for Sustainable Development. \u201cWhen river levels drop, they seek refuge in lakes and flooded areas,\u201d she adds.<\/p>\n
While river floodplains are productive areas with some 400 species of plants, the swamp forests known as igap\u00f3s, with more acidic waters and poor soils, are home to only 10% of those. Therefore, it is possible to assume that manatees transport seeds between these areas, increasing the biodiversity of these environments and securing their own food source for the next drought.<\/p>\n A native of Porto Alegre, Michelle Guterres has extensive experience with the Amazon and manatees. Her first stay in the Amazon municipality of Tef\u00e9 lasted 10 years, from 2000-10, when she worked at the Mamirau\u00e1 Institute.<\/p>\n In 2012, she published her first work on seed ingestion by manatees. At the time, with more than 200 samples collected, all the seeds found were nonviable \u2014 they had no embryos \u2014 which led to the conclusion that the manatee was not a disperser.<\/p>\n Other researchers have also investigated this possibility. A 2020 study about manatees in the Caribbean found no viable seeds in their feces. Previous research, such as that of biologist Robin C. Best\u2019s study conducted in the 1980s, had speculated about this role but had no proof.<\/p>\n After moving to Florian\u00f3polis and having a break from her career to take care of her children, Guterres resumed her research work in 2019 and during the pandemic, and returned to Lake Aman\u00e3. \u201cThat question never left my mind,\u201d she says. \u201cBut this result was totally unexpected and came from field experience. The Amazon allows you to find things that no one would ever imagine.\u201d<\/p>\n Currently, the manatee is listed as a vulnerable species by IUCN, the International Union for Conservation of Nature. Its greatest risk of extinction comes from illegal hunting.<\/p>\n In the first half of the 20th century, when fishing was legal and booming, around 19,000 manatees were killed for leather, which was used in rubber production. Their meat is also appreciated by riverine communities. Hunting was banned in 1967, but it is still practiced in some areas.<\/p>\n Published in 2019, a study with riverine populations indicates that hunting is still the main cause of death for manatees in the Amazon. That was confirmed by 62% of respondents interviewed in the Anavilhanas area and by 52% in the Tapaj\u00f3s area.<\/p>\n Severe droughts such as those experienced in 2023 and 2024 also facilitate the capture of these animals. In general, the dry season lasts about three months, during which they remain in the lakes, where they are more easily killed. However, prolonged droughts also extend this period of greater vulnerability.<\/p>\n \u201cDroughts worsened by climate change also affect manatees\u2019 diet,\u201d Marmontel points out. \u201cThey feed on organic matter at the bottom of the lakes but end up ingesting mud and sand, which may harm their digestive system. A longer dry season increases the chances of this outcome.\u201d<\/p>\n Guterres sees her finding as yet another argument for manatee conservation. \u201cWe always emphasize environmental education to raise awareness about the importance of manatees for the Amazon, including the health and well-being of communities that depend on river, floodplain and forest waters.\u201d<\/p>\n Piedade adds: \u201cBy fertilizing the waters and transporting seeds, manatees contribute to biodiversity. Protecting this species means protecting the ecosystem and the populations that depend on it.\u201d<\/p>\n Gil Guterres-Pazin, M., Lopes, A., Fernando Volpato Pazin, V., Garcia de Santana, D., Marmontel, M., & Teresa Fernandez Piedade, M. (2024). A giant gardener of the floodplains: The Amazonian manatee. Journal for Nature Conservation, 82, 126708. doi:10.1016\/j.jnc.2024.126708<\/p>\n Guterres-Pazin, M. (2012). Short note: Ingestion of invertebrates, seeds, and plastic by the Amazonian manatee (Trichechus inunguis) (Mammalia, sirenia). Aquatic Mammals, 38(3), 322-324. doi:10.1578\/am.38.3.2012.322<\/p>\n Best, R. C. (1981). Foods and feeding habits of wild and captive sirenia. Mammal Review, 11(1), 3-29. doi:10.1111\/j.1365-2907.1981.tb00243.x<\/p>\n Crema, L. C., Da Silva, V. M., & Piedade, M. T. (2019). Riverine people\u2019s knowledge of the vulnerable Amazonian manatee Trichechus inunguis in contrasting protected areas. Oryx, 54(4), 529-538. doi:10.1017\/s0030605318000686<\/p>\nA decades-long debate<\/h2>\n
Urgent need for conservation<\/h2>\n
Citations:<\/h2>\n