A giant river otter with a fish in its mouth. Photo by: Frank Hajek.
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Lobo de río, or river wolf, is the very evocative Spanish name for one of the Amazon's most spectacular mammals: the giant river otter (Pteronura brasiliensis).
This highly intelligent, deeply social, and simply charming freshwater predator almost vanished entirely due to a relentless fur trade in the 20th Century.
But decades after the trade in giant river otter pelts was outlawed, the species is making a comeback—at least in well-managed protected areas.
A new study in PLOS ONE finds that the species' population has recovered to full capacity in most of its habitat in Manu National Park in Peru.
The first year of the study, the survey area had 49 individuals, which dropped to a nadir of 42 in 1994.
However, the population rose significantly after that: in 2004 it hit 88 individuals, before dropping to 81 in 2006, the last year of the study.
"When we initiated our study in 1991, it appears that the population in the floodplain of Manu National Park was still in a process of recovery from the impact of decades of hunting for the pelt trade," lead author Jessica Groenendijk, the Education and Outreach Coordinator for Cocha Cashu Biological Station, told mongabay.com.
She added that the current "results suggest a return to carrying capacity after the hunting decades, since the environmental capacity has not increased (the area has been protected since 1973 when the Park was established)."
Groenendijk says the species' recovery is due to three measures.
The first was that Peru banned commercial hunting of giant river otters in 1973 coupled with the CITES decision in 1975 to list the species as an Appendix I animal, essentially banning international trade.
Giant river otter footprints. Photo by: Frank Hajek.
"Next came the establishment of large protected areas that contained remnant giant otter populations, including Manu," said Groenendijk.
"These areas, resulting from conservation and land use planning decisions at the national level, have been crucial in stabilizing populations."
Finally she says more recent zoning and management plans of giant river otter habitat have helped populations bounce back.
The study looked at the bulk of the giant river otters' best habitat in the park, including all of the oxbow lakes, which are the otters' favorite habitat.
Groenendijk said the park's total population of otters is probably around 100 to 130, comprised of about 22 family groups.
But even as the surveyed populations have seen a hopeful rise in this one area, it doesn't mean the species is out of the woods yet.
The giant river otter, the longest member of the Mustelidae family (even longer than marine otters), is currently listed as Endangered by the IUCN Red List.
While the species is found north to the Guiana Shield and south to Brazil's Pantanal, it remains hugely threatened by deforestation.
In all, the IUCN estimates that there are only 1,000-5,000 giant river otters left on the planet.
Groenendijk said that even in Manu National Park, the species is not safe from human activities.
Manu National Park lies in Peru's Madre de Dios, which has seen an influx of people working to exploit's the area's rich natural resources, such as gold and timber.
Giant river otter portrait. Photo by: Frank Hajek.
"The average rate of human population growth between 2002 and 2012 was 3 percent [in the Madre de Dios], the highest in the country.
It is estimated that 40 percent of this population consists of recent immigrants attracted by land availability and job opportunities," Groenendijk pointed out.
Given that giant river otters survive entirely on fish and live their whole lives in freshwater habitats, one of the most worrisome threats to the species; survival is mercury poisoning from an epidemic of gold mining in the region.
"The extent of gold mining in the Madre de Dios region increased from less than 10,000 hectares in 1999 to more than 50,000 hectares in 2012," Groenendijk said, pointing to a recent study that found that "total mercury levels in 68 percent of fish muscles [in Peru] exceeded the tolerable level for the European otter (Lutra lutra) and 17.6 percent exceeded...the common standard for human consumption."
Such a run for commodities has also taken a particular toll on the region’s giant river otter habitat.
“Thirty percent of riverine forests in Madre de Dios (this figure includes those in Protected Areas) have already been destroyed,” Groenendijk said.
“If Protected Areas are excluded from the analysis, the situation is much worse.”
Giant river otter family group. Photo by: Frank Hajek.
If we are to ensure a long-term future for giant river otters and maintain genetic diversity, Groenendijk said there needs to be a population of at least 500 individuals somewhere in its range.
The Madre de Dios region may be the best bet, according to the conservationist.
“The Madre de Dios River itself, twice as wide as the Manu River, provides the highest quality habitat for the species; its large oxbow lakes and wetlands could support large giant otter groups with high reproductive output and, potentially, the largest sub-population of the watershed,” Groenendijk noted.
. “The Madre de Dios floodplain is also a natural corridor through which giant otters of the Manu, Los Amigos, Heath and other tributaries could disperse.”
In order to move the species behind recovery to safe, Groenendijk suggests the creation of “an aquatic habitat conservation corridor…along the Madre de Dios River,” adding that, “effective Protected Area design and broader wetland landscape management initiatives are therefore critical for the long term conservation of the species in Madre de Dios.”
A young otter sniffing an oar. This individual is in the process of leaving his family on Cocha Salvador. Photo by: Frank Hajek.
Otters on a latrine. Photo by: Frank Hajek.
Giant river otter in a typical landscape in beautiful Manu National Park. Photo by: Frank Hajek.
Giant river otter carrying a cub back to the den. Photo by: Frank Hajek.
Giant river otter sleeping in the sun. Photo by: Frank Hajek.
Groenendijk J, Hajek F, Johnson PJ, Macdonald DW, Calvimontes J, et al. (2014)
Demography of the Giant Otter (Pteronura brasiliensis) in Manu National Park, South-Eastern Peru: Implications for Conservation. PLoS ONE 9(8): e106202. doi:10.1371/journal.pone.0106202
Saving the world’s biggest river otter
Charismatic, vocal, unpredictable, domestic, and playful are all adjectives that aptly describe the giant river otter (Pteronura brasiliensis), one of the Amazon's most spectacular big mammals. As its name suggest, this otter is the longest member of the weasel family: from tip of the nose to tail's end the otter can measure 6 feet (1.8 meters) long. Living in closely-knit family groups, sporting a complex range of behavior, and displaying almost human-like capricious moods, the giant river otter has captured a number of researchers and conservationists' hearts, including Dutch conservationist Jessica Groenendijk.
The giant river otter. Photo by: Frank Hajek.
Behavior and conservation of the Amazon’s giant river otter.
“Otters have always had tremendous appeal for me, ever since reading Gavin Maxwell’s Ring of Bright Water, and the idea of a ‘giant’ otter was entrancing,” Groenendijk told mongabay.com in an interview.
After obtaining a Masters degree in Aquatic Resource Management from King’s College, London, Groenendijk was recruited to become Project Leader of the Frankfurt Zoological Society Giant Otter Conservation Program.
“I was very fortunate. Our first encounter with a giant otter family was a deeply impressive experience and I was hooked. This was the start of what I believe, and hope, will be a life-long commitment to the giant otter.”
This was the start of what I believe, and hope, will be a life-long commitment to the giant otter.”
Researchers are just beginning to untangle some of the complex familial relations in giant river otter communities, who live together in related groups of around a dozen individuals.
These family groups are overseen by one breeding couple, but do pretty much everything together.
“Groups are highly cohesive: they hunt, mark their territories, sunbathe, and sleep together, with bonds constantly reinforced by mutual grooming and play,” explains Groenendijk, adding that “a giant otter family has much in common with a human family, which is why observing them over many years has something of the soap opera about it.
There’s drama, bickering, unity in the face of a caiman threat, babysitting and shared feeding of the cubs, and, finally, offspring leaving home.
If fate is kind, a breeding pair may stay together for up to 10 years.”
Jessica Groenendijk walking up a stream in the hope of filming a transient giant otter. Photo courtesy of Jessica Groenendijk.
Researchers have found that these family groups practice alloparenting, which means non-parents also participate in raising cubs, not unlike many human communities.
In addition, a recent observation found young otters purposefully feeding an aged matriarch, who likely had difficulty hunting for herself.
. Even with such insights, Groenendijk says there is much scientists don’t yet know about the private lives of giant river otters.
“We know almost nothing of the dynamics of transient animals once they have left their families.
Where do they go, how far do they travel, what threats do they face, how are new groups formed?
Unfortunately, telemetry in the rainforest is hampered by local conditions: we need to devise innovative ways of radio tracking giant otters.”
In addition, researchers are trying to figure out the natural causes behind giant river otter mortality: for example they believe infant mortality is high, but have had difficulty collecting data on it in the absence of bodies.
Mating behavior and predator/prey relationships also remain largely obscure.
But even as scientists are making strides in uncovering giant river otter behavior, there is a sense that they are racing against time as the Amazon ecosystem faces changes from deforestation, mining, roads, and climate change.
Although the giant river otter is found in ten Amazonian nations, it remains endangered.
Almost driven to extinction by the pelt trade, which was banned in 1975, the giant river otter today faces a number of new and rising direct threats that have held back a full recovery.
A surge in gold mining, habitat destruction, pollution, conflict between humans and otters over fish resources, and even poorly-managed tourism have all injured giant river otter populations.
“Artisanal gold mining is out of control in the Department of Madre de Dios, with all the devastation this implies.
The increase in gold-mining activity along the Madre de Dios, Malinowski, and Inambari Rivers has resulted in near local extinction of the species with giant otters only surviving in tributaries and lakes where there is no mining activity,”
Groenendijk says, adding that this raises the question of mercury pollution from gold mining possibly “bio-accumulating in giant otters and affecting their reproductive health and survival.”
Conflict between fishermen and giant river otters is another problem unique to the species.