Giant Otters in the Water? Jaguars Think Twice11/14/18
by Fernando Tortato, Ph.D., Ailton Lara and Rafael Hoogesteijn, MS, DVM
Editor’s Note: This is Part One in a series about the surprising interactions between jaguars and giant otters. Read Part Two here. Rafael Hoogesteijn is Conflict Program Director for Panthera’s Jaguar Program in the Brazilian Pantanal. Fernando Tortato is a Panthera Research Associate there. Ailton Lara is Director of wildlife tour company Pantanal Nature.
The Brazilian Pantanal, one of the largest floodplains in the world, has the highest population densities of jaguars in the species’ entire range. In the Porto Jofre region in the north, Panthera Brasil owns the 10,000-hectare Jofre Velho Ranch, dedicated to wildlife conservation and research, jaguar conflict resolution, and community education.
Here, we have the incredible opportunity to observe this great feline and discover behaviors that are often undetectable through conventional research methods like camera-trapping and radio collars. It’s easy to see jaguars during the dry season resting or prowling on the riverbanks. Jaguar social behavior is also frequently documented: females caring for cubs, couples mating, and even adult males sharing a sunny beach on the banks of the Cuiabá and São Lourenço rivers.
But observing them hunting or interacting with other jaguars or other species can be difficult. Some of the most surprising encounters are between jaguars and giant otters (Pteronura brasiliensis).
Giant otters are carnivorous, formidable, and extremely agile aquatic predators (to the extent that they are called the “aquatic jaguar” by some local indigenous tribes) and are always in social groups taking care of their territory and one other. The most suitable period for their breeding is when the waters of the Pantanal are low—because they can easily find fish and build predator-proof lairs out of exposed riverbanks, gullies, and roots.
The water weasels demarcate their territories by defecating and urinating at the entrance of their dens, compressing mud with feet and tails, and creating layers of latrines. When the water level is low, the otters need to adjust or change their den location—lest they and their young become vulnerable to attacks by jaguars.
This male giant otter confronted two jaguars with head movements, calls, and occasional jumps.
Even the jaguar—a versatile feline that climbs trees, moves imperceptibly through forests, and does not see the water as a barrier—thinks twice before entering a river when otters are nearby. Drinking water near them can become an arduous, worrying, and challenging task.
In October, at the end of the dry season, the waters of rivers and lagoons are low, with trunks and dead tree branches more exposed on the banks of rivers and corixos (seasonal water-streams). This past fall, we had the privilege of watching two jaguar sisters (both with surprisingly light coats) being challenged by a dominant male giant otter that fiercely defended its aquatic territory.
The jaguars, who were initially resting on a dry trunk on the banks of Corixo Negro in the heat of the afternoon, decided to go down the trunk to the water line to quench their thirst. But even before drinking the water, they were confronted by the audacious otter, who, with quick dives between the submerged branches, always surprised the sisters.
With the characteristic vocalizations of giant otters, this male made clear who dominated the submerged realm of the Pantanal. The sisters were left with expressions that seemed a mixture of surprise and curiosity.
The jaguar sisters—named Medrosa and Jaju by local guides—are between 2 to 3 years old. Young jaguars primarily hunt prey through lessons learned from their mother. The sisters’ mother, Patricia, is an excellent caiman hunter, but we have no record of her standing against giant otters. So the young females may have feared the otter because of never seeing their mother face its kind before.
The otter, realizing the two sisters were scared, was emboldened to protect one of his favorite tree trunks in this fish-productive water-stream. His group had their den nearby and used this trunk daily as a basking place and a nice feeding station.
So, after about 15 minutes of action, the jaguars retreated, patrolling the banks of the corixo in search of an inattentive caiman or capybara. We were among about 20 privileged witnesses of this agonistic interaction of these incredible carnivores, and we all smiled and celebrated the incredible experience we saw, photographed, and filmed. In this case, it was a happy ending for both parties.
In a semi-aquatic world like the Pantanal, encounters between jaguars and giant otters are inevitable. But the otter is not part of the jaguar’s natural staple diet, which consists mostly of capybaras and caimans.
A 2016 article described three agonistic encounters between giant otters and jaguars in the Pantanal. The result of these encounters was similar to the ones we have observed—the jaguars were repelled twice by a group of giant otters and once by a solitary otter.
But otters do not always rule the situation. Ramalheira and collaborators registered the first predation of giant otters by jaguars. The event took place on the Balbina Hydroelectric Dam in the Brazilian Amazon, where a solitary otter, which had been monitored by a radio-collar, was found killed by a jaguar in a burrow below a log on the banks of the lake. Out of the water, the otter loses all its agility and becomes vulnerable prey for an attentive jaguar.
This rare occurrence was only documented because of the otter’s collar. Giant otters can walk a few meters into the ravines of their dens, making it virtually impossible to observe what is happening inside.
From the comfort of our boats, researchers like us are lucky to observe encounters like these between two worlds, terrestrial and aquatic, where jaguars and otters recognize their strengths and limitations.
And so, we enjoy the life of these incredible Pantanal predators, who are both vital for the maintenance of the ecosystems in which they survive.
To learn more about Panthera’s work in the Pantanal and across jaguar range, click here.
To hear and read the legendary Dr. Alan Rabinowitz narrate an action-packed sequence of one of the “pale sisters” dragging a dead caiman out of the river for her dinner, click here.