The hunt for the giant otter

They’re large and they hunt in packs, so giant otters ought to be easy to study. Sophie Stafford put her tracking skills to the test in Brazil’s Pantanal.

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Giant otter article

They’re large and they hunt in packs, so giant otters ought to be easy to study. BBC Wildlife editor Sophie Stafford put her tracking skills to the test in the Brazilian Pantanal. 

There’s nothing to fear in the Pantanal,” announced field co-ordinator Ellen Wang at our orientation meeting. “Apart from the peccaries, which will bite you given half a chance (so make sure your tree-climbing abilities are up to scratch), the piranhas and stingrays lurking in the cold, deep waters of the river (so shuffle, don’t walk), the pit vipers that may climb into your boots if you leave them outside (so don’t), and two species of blood-sucking bat, which don’t normally bite humans.”

With these words of encouragement, I arrived in Brazil’s Pantanal, the world’s largest wetland and home to the greatest concentration of – mainly benign – wildlife in South America. I was joining a research project, run by environmental charity Earthwatch, studying the ecology of the giant otter Pteronura brasiliensis and its smaller cousin, the neotropical river otter Lontra longicaudis.
 
For the past four years, researchers Miguel Rico and Helen Waldemarin have been studying the giant otter families that live along a 26km stretch of the Rio Negro, a tributary of the Paraguay River. With the assistance of teams of Earthwatch volunteers, the researchers are building a complete picture of the otters’ natural history. Their aim is to develop management plans for both species, taking account of the pressure of human activities in the Pantanal, and evaluate the potential impact of increasing ecotourism in the area.
 
“The giants are a great attraction for tourists,” explains Miguel. “They are active during the day and very sociable, moving around in large groups of up to 20 individuals (though groups average about five individuals around here). They are also incredibly playful and inquisitive, so they often actively approach tourist boats.” But studies have shown that the otters are sensitive to human disturbance, including poorly managed ecotourism, which can affect their reproductive success.
 
The researchers, therefore, aim to provide policy-makers with information about the biology of the Pantanal’s otters, which will enable them to formulate appropriate, scientifically founded regulations for local ecotourism. First, though, they need to get to know the local otters intimately.
 
Messing about on the river
 
As otters spend most of their time in the water, the majority of the research is conducted from canoes and motorised boats. In a canoe, the researchers can locate, approach and watch the otters without disturbing them.

The Rio Negro is a broad and seemingly sluggish river, but as we volunteers soon found out, the water has a powerful current that makes itself known when you’re paddling back upstream after a long day on the river, and when your canoe refuses to go in the direction you intend.
 
Dense forest crowds the banks, and every meander is edged by a small beach, studded with basking Jacaré caimans. There are apparently 30 million of these small crocs living in the Pantanal, and they proved to be our constant companions while on the river. Sometimes they joined us when we were nowhere near the water (during the dry season, they walk for miles across land in search of a new territory, so you often stumble across them in unexpected places). And somehow there always seem to be caimans sunbathing exactly where you need to beach your canoe.
 
It was time to put one of Ellen’s convictions to the test. “The caimans are more scared of you than you are of them,” Ellen said breezily. “They won’t bother you at all. Just don’t grab them by the tail.” As if! So one morning, soon after my arrival, I decide to tiptoe up on a recumbent reptile to see just how close I could get before his nerve gave out.
 
He was brave – maybe because he had back-up in the form of 13 pairs of eyes watching me suspiciously from the safety of the water. I got to within about 10 paces before he lunged off the bank with a splash. Score one to Ellen Wang. After that, beaching the canoe was less a battle of nerve and more a matter of trying to avoid hitting the lazier caimans with the prow.
 
Every day, Helen, Miguel and research assistant Manoel canoe up and down the Rio Negro in search of their study species. The neotropical otters are rarely difficult to spot. Before we’ve even pushed our canoes off the beach, we can see them among the knotty roots of the bankside trees and hear their enthusiastic crunching of tiny fish. For such small animals, they eat incredibly noisily, with much smacking of lips, snapping of tiny sharp teeth and cracking of bones.
 
Whipping out our clipboards and GPS (Global Positioning System), we note what each animal is doing at one minute intervals, twisting and turning in our seats to keep them in view as our canoes drift unhelpfully in circles downstream. The otters appear unafraid of us, often diving and surfacing right by the prow of the boat with an inquisitive ‘huff’ before vanishing beneath the surface again. 
 
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