MANAUS, Amazonas, Brazil — Positioned close to the confluence of the Solimões and Japurá rivers, Lake Amanã, which implies “the trail of the rain,” is called the house of the Amazonian manatee (Trichechus inunguis). Through the dry season, when river ranges drop, this mammal finds refuge and meals there. It was on the seashores of the Amanã that biologist Michelle Guterres made a shocking discovery: manatee feces with strands of germinating grass. This remark was an vital step towards confirming a speculation that to this point had been solely speculated about: the manatee is able to dispersing seeds, thus serving to crops migrate between totally different habitats.
“I do not forget that, firstly of the analysis, my adviser insisted that the manatee was not a seed disperser,” Guterres says, recalling earlier research that had not discovered viable seeds in fecal samples. “And I informed her: not that we all know.”
Guterres collected 96 fecal samples, 19 of which had crops germinating in them. One of many main challenges within the analysis was discovering a big quantity of feces. As quickly as a manatee defecates, its feces both dissolve within the water or are eaten by fish. That’s the reason these animals had been already recognized for fertilizing the waters, however their position as seed dispersers was a groundbreaking discovery.
The acute drought of 2023 made it simpler to gather the samples, which had been discovered on the seashores fashioned by low water ranges. In October, Lake Amanã was solely 20 centimeters (8 inches) deep.
After that, the samples needed to be damaged up with tweezers, attributable to their fibrous texture. In complete, 2,033 seeds had been discovered, 556 of which had been viable with embryos. “That’s a formidable quantity,” says Maria Tereza Piedade, a researcher on the Nationwide Institute for Amazonian Analysis. “It’s greater than sufficient to substantiate that the manatee is a seed disperser.”
How vital is that this discovery?
Within the Amazon, seed dispersal and plant distribution are intrinsically linked to rivers’ flood-and-drought cycles. Piedade explains that, throughout floods, water is the principle disperser in floodplains and igapós (blackwater-flooded forests), particularly of aquatic and semiaquatic crops.
“The crops bear fruit, and their seeds fall into the water. Then fish eat them and take them to different habitats positioned upstream or in close by areas,” she explains, referring to research which have discovered seeds within the digestive tracts of fish.
However realizing that the manatee performs the same position is critical. Weighing as much as 550 kilograms (1,200 kilos), manatees eat as much as 40 kg (88 lbs) of aquatic crops per day and have been recorded touring as much as 115 kilometers (71 miles) between lakes Amanã and Mamirauá. With a protracted digestive tract, seeds can stay of their intestines for as much as per week, rising their potential as seed dispersers. “As well as, they ship the seeds with pure fertilizer, an actual gardening package,” Piedade feedback humorously.
The manatee’s migratory patterns counsel that it performs an important position in dispersing seeds between fertile habitats corresponding to river floodplains and nutrient-poor areas corresponding to igapós. “Throughout floods, the manatee stays within the floodplains, the place meals is ample,” explains Miriam Marmontel, an aquatic mammal skilled on the Mamirauá Institute for Sustainable Growth. “When river ranges drop, they search refuge in lakes and flooded areas,” she provides.
Whereas river floodplains are productive areas with some 400 species of crops, the swamp forests often known as igapós, with extra acidic waters and poor soils, are residence to solely 10% of these. Subsequently, it’s attainable to imagine that manatees transport seeds between these areas, rising the biodiversity of those environments and securing their very own meals supply for the subsequent drought.
A decades-long debate
A local of Porto Alegre, Michelle Guterres has in depth expertise with the Amazon and manatees. Her first keep within the Amazon municipality of Tefé lasted 10 years, from 2000-10, when she labored on the Mamirauá Institute.
In 2012, she revealed her first work on seed ingestion by manatees. On the time, with greater than 200 samples collected, all of the seeds discovered had been nonviable — they’d no embryos — which led to the conclusion that the manatee was not a disperser.
Different researchers have additionally investigated this risk. A 2020 examine about manatees within the Caribbean discovered no viable seeds of their feces. Earlier analysis, corresponding to that of biologist Robin C. Finest’s examine carried out within the Nineteen Eighties, had speculated about this position however had no proof.
After transferring to Florianópolis and having a break from her profession to deal with her youngsters, Guterres resumed her analysis work in 2019 and in the course of the pandemic, and returned to Lake Amanã. “That query by no means left my thoughts,” she says. “However this consequence was completely surprising and got here from subject expertise. The Amazon lets you discover issues that nobody would ever think about.”
Pressing want for conservation
Presently, the manatee is listed as a susceptible species by IUCN, the Worldwide Union for Conservation of Nature. Its biggest danger of extinction comes from unlawful searching.
Within the first half of the twentieth century, when fishing was authorized and booming, round 19,000 manatees had been killed for leather-based, which was utilized in rubber manufacturing. Their meat can be appreciated by riverine communities. Searching was banned in 1967, however it’s nonetheless practiced in some areas.
Printed in 2019, a examine with riverine populations signifies that searching remains to be the principle reason behind loss of life for manatees within the Amazon. That was confirmed by 62% of respondents interviewed within the Anavilhanas space and by 52% within the Tapajós space.
Extreme droughts corresponding to these skilled in 2023 and 2024 additionally facilitate the seize of those animals. Typically, the dry season lasts about three months, throughout which they continue to be within the lakes, the place they’re extra simply killed. Nevertheless, extended droughts additionally prolong this era of higher vulnerability.
“Droughts worsened by local weather change additionally have an effect on manatees’ food plan,” Marmontel factors out. “They feed on natural matter on the backside of the lakes however find yourself ingesting mud and sand, which can hurt their digestive system. An extended dry season will increase the possibilities of this consequence.”
Guterres sees her discovering as yet one more argument for manatee conservation. “We at all times emphasize environmental training to lift consciousness concerning the significance of manatees for the Amazon, together with the well being and well-being of communities that rely on river, floodplain and forest waters.”
Piedade provides: “By fertilizing the waters and transporting seeds, manatees contribute to biodiversity. Defending this species means defending the ecosystem and the populations that rely on it.”
Citations:
Gil Guterres-Pazin, M., Lopes, A., Fernando Volpato Pazin, V., Garcia de Santana, D., Marmontel, M., & Teresa Fernandez Piedade, M. (2024). A large gardener of the floodplains: The Amazonian manatee. Journal for Nature Conservation, 82, 126708. doi:10.1016/j.jnc.2024.126708
Guterres-Pazin, M. (2012). Quick word: 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
Finest, R. C. (1981). Meals and feeding habits of untamed and captive sirenia. Mammal Assessment, 11(1), 3-29. doi:10.1111/j.1365-2907.1981.tb00243.x
Crema, L. C., Da Silva, V. M., & Piedade, M. T. (2019). Riverine folks’s information of the susceptible Amazonian manatee Trichechus inunguis in contrasting protected areas. Oryx, 54(4), 529-538. doi:10.1017/s0030605318000686
This article by Tiago Mota e Silva was first revealed by Mongabay.com on 25 November 2024. Lead Picture: Amazonian manatee (Trichechus inunguis). Picture courtesy of André Dib.
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