The Giant Otter

The Giant Otter

The “Giant Otter Project” was founded with the objective of strengthening the conservation of the species and its ecosystem, seeking to improve human coexistence with the giant otter and the engagement of stakeholders in conservation actions and decisions

The species

The giant otter belongs to the otter subfamily (Lutrinae) and is the largest of the 13 extant otter species.
The scientific name of the otter is Pteronura brasiliensis (Ptero = wing, nura = tail), due to the flattened shape of its tail, which resembles a wing or an oar. The first giant otter was discovered in Brazil, which is why its scientific name is also a tribute to the country, which still has the largest distribution area of the species.
Otters only occur in South America and feed mainly on fish, but they can also consume crabs, frogs, snakes, lizards, caimans and other vertebrates.


Giant otters live in groups of 2 to 20 individuals, consisting of a breeding pair and several young individuals of different ages, who help in raising the small cubs.
Their dens are built along the banks of rivers and bays and are used for protection, resting, reproduction and care of the young.

In addition, the group uses latrines, which are a kind of collective bathroom, which serves to mark the territory with its characteristic smell.
The territories of the groups measure a linear average of 10 km along water bodies and the banks are scent-marked daily by the members of the group. During the rainy season, when the level of the river rises, territories can increase up to 3 times or more.
Scent-marking is one of the ways that giant otters communicate and that helps groups to organize the limits of their territories along the water bodies.
Encounters between rival groups often end in violent and noisy fights.

Otters use a vocal repertoire with up to 15 different sounds to communicate.

To learn more about the species, read our publications.


Giant otters are considered globally endangered (IUCN Red List) and need your help.

Until the beginning of the 1990s, hunting for the commercialization of pelts drastically reduced the population of giant otters along all the species distribution. In Brazil, viable populations of the species occur in some regions of the Amazon Basin and in the Pantanal. In the Cerrado, a giant otter population seems to be limited to the Tocantins River basin.
The Pantanal population is at the southern limit of the species’ distribution and, in addition, has the lowest genetic diversity.

Habitat loss and degradation, mainly due to human activities is today the greatest threat to the species. Throughout their entire range, giant otter populations are being decimated by contamination of rivers and destruction of riparian forest caused by gold mining, agriculture and other human activities. Hydroelectric dams can isolate populations and degrade the environment, changing the availability of resources. Human conflicts with the species are also common and are often motivated by the simplistic idea that the species is dangerous or a competitor for fish.
Poorly-managed tourism is also a threat. Traffic and the approach of vessels can scare away the group or even affect the survival of cubs.

Behaviors and Sounds

Have the experience of hearing some of the sounds of giant otters.

Cub care / Sounds: hum’s, coo’s, pur’s and high-pitched coo’s

In a group of giant otters, only the dominant pair reproduces, but all other individuals help in the care of the offspring. After the third week of life, the adults begin to carry the cubs out of the den, to receive their first baths and swimming lessons. Some adults are clumsier than others, but this learning is critical to the success of cubs. During activities, it is common to hear pur’s and discreet hum’s, interspersed with high-pitched coo’s vocalized by adults, which can intensify if the cubs do not obey. Cubs, in turn, whimper and vocalize high-pitched squeaks during baths. But it’s during the fishing lesson that the adults have the harder work, especially when the litter is hungry. Cubs receive small and alive fish near the shores to learn how to capture them, but the capture is not always successful and the cubs vocalizes even more strident screams until it satiates its hunger.

Food defense / Sound: growl

Despite performing most of the activities together, giant otters do not share their food with the other members of the group. When an otter approaches another, who is devouring a delicious fish, it will hear an intimidating growl that can get louder and louder if he continues to approach.

Agonism, fight / Sound: snorts, high-pitched screams and calls

When an intruding individual or group of giant otters is detected by the resident group, a dispute can ensue. It’s what biologists call an “agonistic encounter,” and it can take the form of long chases and even violent physical confrontations, accompanied by a chorus of screams and high-pitched calls, interspersed with snorts. Giant otters can be seriously injured in these fights and some can even die from their injuries.

Scent-Marking: purring and humming

Giant otters are territorial, what means that they defend the stretch of river where they live with determination. The groups patrol their territory daily and choose specific places along the banks to leave their scent and to signal their property to other giant otter intruders. During territory demarcation, all individuals defecate and urinate in latrines (collective toilets located on the banks), purring while spreading the smell around the place. The purring can intensify and be interspersed with more acute sounds such as “hum’s” and “high-pitched coo’s”, which are even louder.

Call/Sound: adult call

The giant otter group is very cohesive, what means that the members of the group perform almost all activities together. When an individual moves away from the group and feels lost, it vocalizes with high-pitched screams or “adult calls” , calling the others.

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.