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The White Otters of the Aquidauana River: Mystery, Genetics, and Conservation

If someone told you there were “ghost” otters swimming in the Aquidauana River, in Mato Grosso do Sul, Brazil, would you believe it? Well, nature loves to surprise us! In March 2025, the G1 newspaper published an article about new sightings of these rare otters, and we were invited to share insights about these records.

Since 2019, photographic records and local reports have documented  Neotropical otters (Lontra longicaudis) in the Aquidauana region with unusually pale fur. These otters exhibit a phenomenon called leucism, a rare genetic mutation that reduces fur pigmentation but does not affect the eyes—unlike albinism. What began as an isolated case has become a true local phenomenon, and now we know: they are reproducing!

But how is this possible? Leucism is uncommon in nature because it can compromise an animal’s camouflage, making them  an easy target for predators. However, in the Aquidauana River, researchers have observed that this mutation has persisted for at least six years. In 2019, a single leucistic otter was spotted. Three years later, an entire family of leucistic otters was seen swimming in the area. And in 2024, new images revealed a leucistic pup alongside a normally colored adult. Far from disappearing,  the genetic trait appears to be growing more common in this population.

At the Giant Otter Project, we’ve proposed some hypotheses for this phenomenon. The first is genetics: leucism is a recessive trait, meaning it must be inherited from both parents. If the otter population  in the Aquidauana River is relatively small and isolated, the chance of two carriers of  the leucistic gene reproducing increases. This could explain why, in a short time, the number of otters with this trait has grown.

Another possibility involves the environment. Unlike in open areas, where light-colored animals are easily spotted, the otters’ habitat in the Aquidauana River offers some protection. The murky water and dense riverside vegetation may minimize the impact of their lack of camouflage. If there aren’t enough predators to make this mutation a disadvantage, the leucistic otters can live peacefully and continue passing on this genetic trait.

However, this story has two points of view. While it is not an immediate concern, the persistence of leucism could present challenges in the future. If this otter population remains small and inbreeding increases, genetic variability could decline. This might make the otters more vulnerable to diseases or less adaptable to environmental changes, such as climate change and habitat degradation.

For this reason, researchers and wildlife observers continue monitoring this unique population. Every new sighting helps us better understand the dynamics of these otters and the factors allowing leucism to persist in the region. This case also highlights the importance of preserving natural habitats and ensuring that these animals have clean rivers and healthy riparian forests to thrive. After all, regardless of color, otters are keystone species in aquatic ecosystems. And who knows, maybe in the future, the leucistic otters of the Aquidauana River will become a symbol of resilience of the Brazilian biodiversity?  One thing is certain: nature never stops surprising us!

Follow the Giant Otter Project for updates on this discovery and ways to support the conservation of these incredible semi-aquatic mammals.

Access the full article by clicking here!

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Giant Otter Conservation Fund – CNPJ: 38.005.209/0001-10

R. Presidente Vargas, 1319, Bairro Aimoré. CEP 95940-000,
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Jessika Albuquerque – graduated in Biological Sciences from the Universidade Estadual da Paraíba (UEPB, Campina Grande) and currently training as a Graphic Designer at the Centro de Capacitação Profissional InforQuality. She has experience in internships and volunteering in the areas of communication, with an emphasis on content production and social media management, science communication, environmental perception and education, experimental science teaching, and mammal conservation. At the Ariranhas Project, she works mainly in communication, managing and producing content for social media (Instagram, Threads, Facebook, LinkedIn, YouTube, and website), in addition to collaborating in the monitoring of giant otters in the Pantanal and in environmental awareness and education actions.

Greice Gonchoroski – Master’s student (CNPq scholarship) in the Postgraduate Program in Animal Biology (PPGBAN) – UFRGS. Veterinary from Centro Universitário Ritter dos Reis – UniRitter (PROUNI-MEC scholarship holder) working in the areas of Medicine and Conservation of Wild Animals, and Animal Parasitology. Collaborator in research projects in the area of ​​monitoring wild mammals and animal health at the Desidério Finamor Veterinary Research Institute – IPVDF.

Gabriela Duarte – Master in Biology from the University of São Paulo (USP), works in different areas of the Project, such as collecting and analyzing data on giant otters in the Southern Pantanal; carrying out educational/training activities that seek to increase information about otters and strengthen the public’s connection with this group of animals; and assistance to the team in administrative activities.

Gabriel Brutti – Founder of Projeto Dispersar, is a biologist, teacher and professional photographer. Graduated in Environmental Technician and Degree in Biological Sciences from the Instituto Federal Farroupilha (IFFar) Santa Rosa-RS campus, he worked as a scholarship holder and volunteer in research projects with birds in a set of extension projects focused on environmental education. He is currently a postgraduate student in Biodiversity and Conservation at the IFFar campus Panambi -RS and a member of the Giant Otter Project.

George Leandro – Biologist, Sanitarist. George has lived and worked professionally in some states in Brazil. He has experience with Conservation Parks management and with conservation of endangered species. He lived and worked with traditional populations in isolated areas, and he has participated with social projects and has worked in urban and rural areas.

Letícia Graciano – is illustrator and art educator, graduated in Visual Arts from the State University of Campinas. She researches childhood culture and she has worked in some NGOs in the state of São Paulo, providing artistic experiences for children and teenagers. Currently she is living with rural populations, and she has been engage with conservation projects in Brazil for a while.

Fernando Rodrigo Tortato – PhD in Ecology and Biodiversity Conservation. Fernando is associate researcher at the Panthera Foundation NGO and has been working for over 10 years on projects aimed at jaguar conservation. In his doctorate, he assessed how tourism can represent a tool for jaguar conservation in the Pantanal. In his field activities in the Pantanal the observation of giant otters is very frequent. Fernando is interested in understanding how tourism can affect the behavior and survival of this incredible mustelid. Fernando plays the role of collaborator of the Giant Otter Project, assisting in contacting with local leaders, logistical support and the dissemination of the actions developed by the project.

Nicole Duplaix – PhD in Ecology from the University of Paris, France. Nicole has studied otters for 45 years and is now focused on otter research and conservation in Asia and South America. She is the founder and co-chair of the IUCN-SSC otter expert group – the global otter conservation authority. She teaches Conservation Biology and Species Recovery Planning courses at Oregon State University.

Mariana Malzoni Furtado – Veterinary, graduated in 2002 from the University of São Paulo, with a doctorate in Science in 2010 from the Experimental Epidemiology Applied to Zoonoses Program at VPS/USP and a post-doctorate in Animal Epidemiology in 2014. She has worked for over 18 years in Wildlife Conservation in different Brazilian biomes such as Pantanal, Amazon, Cerrado and Caatinga, with emphasis on Conservation Medicine, Animal Epidemiology, Infectious Diseases and Interaction between domestic and wild animals. Researcher at Instituto Onça Pintada from 2003 to 2014, she has contributed to research projects in wildlife conservation, acting as a veterinarian and Conservation Medicine manager. She has experience with different methods of capturing wildlife, having anesthetized and managed more than 200 animals of different species, including jaguar, maned wolf, giant otter, ocelot, pampas cat, wild dog, peccary, giant armadillo, among others. Since 2007 she has been collaborating with giant otters’ research projects, performing captures and surgeries for implantation of radio transmitters and health assessment of the species. Always studying, publishing and contributing to the dissemination of Conservation Medicine and the importance of epidemiological wildlife studies.

Karen Arine Souza – Ecologist, Naturalist Tourism Guide for 10 years, she started guiding in the Pantanal and then moved to the Mato Grosso State. In 2020 she worked on the “Jaguar ID Project”, collecting data for the jaguars conservation and evaluating the jaguar population in the post-fire period. Karen currently participates in the Giant Otter Project actions envolving traditional communities in the Pantanal and helping to develop and apply good conduct practices in ecotourism aimed at giant otters. Karen is a founding member of the North Pantanal Tourism Association (Aecopan), being the administrative director from 2015 to 2017 and she currently is a member of the board. The AECOPAN aims to conserve the North Pantanal, using ecotourism as a social and environmental development tool, looking to develop a sustainable tourism.

Lívia Rodrigues de Almeida – Biologist and Environmental Analyst at the National Center for Research and Conservation of Carnivorous Mammals of ICMBio (ICMBio / CENAP). She began working with the ecology of otters in the state of Rio de Janeiro in 2002. Since 2011, Lívia has been working on the elaboration of conservation strategies for the endangered Brazilian fauna and the evaluation process of Brazilian carnivores extinction risk. She is also a member of the IUCN Otter Specialist Group.

Samara Almeida – Biologist and MSc in Biological Sciences. Samara has been working for the past 6 years with giant otters in the state of Tocantins, acting with conservation, monitoring, environmental education, communication and animal behavior. Currently Samara coordinates a research on acoustic communication of giant otters in the Cantão State Park, Tocantins, which is part of her PhD thesis.

Nathalie Foerster – Biologist and currently a PhD student at the Graduate Program in Ecology and Conservation at the Federal University of Mato Grosso do Sul. Nathalie has been developing her PhD thesis on behavioral and bioacoustic ecology of giant otters in the Miranda region of the Pantanal of Mato Grosso do Sul.

Grazielle Soresini – Veterinária, especialista em Clínica Médica e Cirúrgica de Animais Selvagens e mestre em Ciência Animal. Em 2019 Grazi finalizou seu doutorado em Ecologia e Conservação pela UFMS, realizando sua tese sobre genética e saúde de ariranhas. Atuou profissionalmente realizando atendimento veterinário clínico e cirúrgico em aves, répteis e mamíferos silvestres em diversas instituições. Sócia da Clínica Vida Livre – Medicina de Animais Selvagens (Curitiba/PR), primeira clínica veterinária do Brasil especializada em animais selvagens. Desde 2015 vem atuando em atividades de campo e monitoramento de grupos de ariranhas no Pantanal. É membro voluntário do Grupo de Especialistas em Lontras da IUCN (Otter Specialist Group) desde 2016.

Abigail Martin – American zoologist. In 2015 Abbie created the Jaguar Identification Project to instigate value to the world’s largest floodplain, the Pantanal. The Jaguar ID Project uses citizen science and camera traps to monitor the ecology and behavior of the jaguar population in the Encontro das Águas State Park and Porto Jofre region in the Northern Pantanal. Over the years watching jaguars along the region’s rivers, Abbie also follows the giant otter groups, contributing with information about the species and monitoring the groups that are focused by the project. Together her experience with the local community and the identification of jaguars has been contributing to the actions of the Giant Otter Project.

Caroline Leuchtenberger – Biologist. Coordinator and founder of the Giant Otter Project and professor at the Federal Farroupilha Institute. Since 2006 she has been conducting researches with the species that was the focal species for her master’s and doctorate. In 2013 she became the species coordinator of the International Union for Conservation of Nature (IUCN) of the otter expert group. Carol has also advised on the development of the National Action Plan for the Conservation of Giant Otters coordinated by the Brazilian Environmental Agency (ICMBio) and the Global Strategic Plan for the Conservation of Otters carried out by the IUCN. In addition, Carol participates of the giant otters reintroduction program coordinated by the Rewilding Argentina Foundation, held in Iberá, Argentina.