MANAUS, Amazonas, Brazil — Situated close to the confluence of the Solimões and Japurá rivers, Lake Amanã, which suggests “the trail of the rain,” is named the house of the Amazonian manatee (Trichechus inunguis). In the course of 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 stunning discovery: manatee feces with strands of germinating grass. This commentary was an vital step towards confirming a speculation that up to now had been solely speculated about: the manatee is able to dispersing seeds, thus serving to crops migrate between totally different habitats.
“I keep in mind 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 instructed 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 major 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 function 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, on account of 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 situated 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 an identical function is important. 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 an extended 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 equipment,” Piedade feedback humorously.
The manatee’s migratory patterns counsel that it performs an important function in dispersing seeds between fertile habitats akin to river floodplains and nutrient-poor areas akin to igapós. “Throughout floods, the manatee stays within the floodplains, the place meals is plentiful,” explains Miriam Marmontel, an aquatic mammal skilled on the Mamirauá Institute for Sustainable Improvement. “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 referred to as igapós, with extra acidic waters and poor soils, are residence to solely 10% of these. Due to this fact, 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 following 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 printed 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 chance. A 2020 research about manatees within the Caribbean discovered no viable seeds of their feces. Earlier analysis, akin to that of biologist Robin C. Finest’s research carried out within the Eighties, had speculated about this function 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 throughout the pandemic, and returned to Lake Amanã. “That query by no means left my thoughts,” she says. “However this outcome was completely sudden and got here from subject expertise. The Amazon means that you can discover issues that nobody would ever think about.”
Pressing want for conservation
At the moment, the manatee is listed as a susceptible species by IUCN, the Worldwide Union for Conservation of Nature. Its best 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. Looking was banned in 1967, however it’s nonetheless practiced in some areas.
Revealed in 2019, a research with riverine populations signifies that searching continues to be the principle reason for demise 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 akin to these skilled in 2023 and 2024 additionally facilitate the seize of those animals. Usually, 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 larger vulnerability.
“Droughts worsened by local weather change additionally have an effect on manatees’ weight-reduction 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 final result.”
Guterres sees her discovering as one more argument for manatee conservation. “We at all times emphasize environmental schooling 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). An enormous 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 observe: 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 Evaluate, 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 individuals’s data 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 printed by Mongabay.com on 25 November 2024. Lead Picture: Amazonian manatee (Trichechus inunguis). Picture courtesy of André Dib.
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