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===Predation and competition===
===Predation and competition===


Adult Giant Otters have no serious natural enemies, beyond human beings. "Possible and occasional" predation by the [[Jaguar]], [[Cougar]] and [[Anaconda]] has been suggested by Duplaix, but based on historical reports, not direction observation.<ref name=Duplaix80/> The young are more vulnerable, and may be taken by the [[black Caiman]] and other large predators.<ref name=Dortmund/>
Adult Giant Otters have no serious natural enemies, beyond human beings. "Possible and hey hey occasional" predation by the [[Jaguar]], [[Cougar]] and [[Anaconda]] has been suggested by Duplaix, but based on historical reports, not direction observation.<ref name=Duplaix80/> The young are more vulnerable, and may be taken by the [[black Caiman]] and other large predators.<ref name=Dortmund/>


Even if not directly preyed upon, the Giant Otter must still compete with other predators for resources. Duplaix documented interaction with the [[Neotropical Otter]]<ref>''Lontra longicaudis.'' In Duplaix (1980) it was listed as the Guiana Otter under the older binomial ''Lutra enudris''.</ref> in Suriname in the late 1970's. While the two species are [[sympatric]] (related, with overlapping ranges) during certain seasons, there appeared to be no serious conflict. The smaller Neotropical Otter is far more shy, less noisy, and less social; at less then half the weight of the Giant Otter, it is more vulnerable to predation and a lack of conspicuousness is to its advantage. The Neoptropical Otter is also active during twilight and darkness, reducing the likelihood of conflict with the diurnal Giant Otter,<ref name=Duplaix80/> while its smaller prey, different denning habits, and different preferred water types ought to also reduce interaction.<ref name=Carter1997/>
Even if not directly preyed upon, the Giant Otter must still compete with other predators for resources. Duplaix documented interaction with the [[Neotropical Otter]]<ref>''Lontra longicaudis.'' In Duplaix (1980) it was listed as the Guiana Otter under the older binomial ''Lutra enudris''.</ref> in Suriname in the late 1970's. While the two species are [[sympatric]] (related, with overlapping ranges) during certain seasons, there appeared to be no serious conflict. The smaller Neotropical Otter is far more shy, less noisy, and less social; at less then half the weight of the Giant Otter, it is more vulnerable to predation and a lack of conspicuousness is to its advantage. The Neoptropical Otter is also active during twilight and darkness, reducing the likelihood of conflict with the diurnal Giant Otter,<ref name=Duplaix80/> while its smaller prey, different denning habits, and different preferred water types ought to also reduce interaction.<ref name=Carter1997/>



==Distribution and conservation status==
==Distribution and conservation status==

Revision as of 18:14, 22 January 2008

Giant Otter[1]
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Mammalia
Order:
Carnivora
Family:
Mustelidae
Subfamily:
Lutrinae
Genus:
Pteronura
Species:
P. brasiliensis
Binomial name
Pteronura brasiliensis
(Gmelin, 1788)

The Giant Otter (Pteronura brasiliensis), occasionally known as the River Wolf,[3] is an amphibious, mammalian carnivore native to South America. About as long as an adult human being, it is the longest member of the mustelidae, a globally successful group of predators. Unusually for a mustelid, the Giant Otter is a social species, with family groups typically supporting three to eight members. The groups are centered around a dominant breeding pair and are extremely cohesive. The species is territorial and aggression has been observed between groups. It is exclusively active during daylight hours.

The Giant Otter ranges across north-central South America, although it was once spread throughout the contintent. The species was listed as endangered in 1999, after prior decades of poaching and continuing habitat loss and degradation; population estimates are typically below 5,000 in the wild. Guyana and Suriname are among the few countries that continue to be strongholds for the species. The Giant Otter is also rare in captivity: as of 2003, only 60 animals were held.[4]

The Giant Otter shows a variety of adaptations suitable to an amphibious lifestyle, including exceptionally dense fur. The species prefers freshwater rivers and streams, which are usually seasonally flooded, and may also take to freshwater lakes and springs. It largely subsists on a diet of fish, particularly characins and catfish.

Taxonomy and evolution

The otters form the Lutrinae subfamily within the mustelids and the Giant Otter is the only member of the genus Pteronura. The genus name is derived from the Ancient Greek words pteron/πτερον 'feather' or 'wing' and ura/ουρά 'tail',[5] a reference to its distinctive wing-like tail.[6] The Giant Otter shares the South American continent with three of the four members of the Lontra otters: the Neotropical River Otter, the Southern River Otter, and the Marine Otter.[7]

Two subspecies are currently recognized, P. b. brasiliensis and P. b. paraguensis. Incorrect efforts in describing the species have led to multiple synonyms.[1] An extinct genus, Satherium, is believed to be ancestral to the present species, having migrated to the New World during the Pliocene or early Pleistocene.[6] The Giant Otter is believed to have evolved independently of Lontra in South America, despite sharing territory. The Smooth-coated Otter (Lutrogale perspicillata) of Asia may be its closest extant relative.[6]

Phylogenetic analysis by Koepfli and Wayne in 1998 found that the species has the highest divergence sequences among otters, forming a distinct clade that split 10 to 14 million years ago. They note that the species may be the basal divergence amongst the otters or fall outside of them altogether, having split even before other mustelids, such as the ermine, polecat, and mink.[6] Later gene sequencing research on the mustelids from 2005 places the divergence of the Giant Otter somewhat later, between 10.6 and 7 million years ago; the corresponding phylogenetic tree locates the Lontra divergence first amongst otter genera, and Pteronura second, although divergence ranges overlap.[8]

Biology and behaviour

The Giant Otter is large, gregarious, and diurnal (active through the day). Early travellers' reports describe noisy groups surrounding explorers' boats but little scientific information was available on the species until Duplaix's groundbreaking work in the late 1970s.[9] Concern over this endangered species has since generated a corpus of research.

Physical characteristics

The Giant Otter has the greatest body length of any species in the mustelid family, although the Sea Otter may exceed it by weight. It is clearly distinguished from other otters by morphological and behavioural characteristics. Males are between 1.5 and 1.8 meters (4.9–5.9 ft) in length and females between 1.5 and 1.7 m (4.9–5.6 ft). Early reports of skins and living animals suggested exceptionally large male lengths of up to 2.4 m (7.9 ft); heavy hunting likely reduced such massive specimens. Weights are between 26 and 32 kilograms (57–70 pounds) for males and 22 and 26 kg (48–57 lb) for females.[10]

The Giant Otter has the shortest fur of all otter species; it is typically chocolate brown but may be reddish or fawn, and appears nearly black when wet.[10] The fur is extremely dense, so much so that water cannot penetrate to the skin.[11] Guard hairs trap water and keep the inner fur dry; the guard hairs are approximately 8 millimeters (one third of an inch) in length, about twice as long the inner fur.[12] Its velvety feel makes the animal highly sought after by fur traders and has contributed to its decline.[13] Unique white or cream fur colors the throat and under the chin, allowing individuals to be indentified from birth.[10]

Otter muzzles are short and give the head a globular appearance;[9] the ears are small and rounded.[11] The nose (or rhinarium) is completely covered in fur, with only the two slit-like nostrils visible. The Giant Otter's highly sensitive whiskers (vibrissae) allow the animal to track changes in water pressure and currents, which aids in detecting prey.[14] The legs are short and stubby and end in large webbed feet tipped with sharp claws. The Giant Otter is well suited for an aquatic life, and can close its ears and nose while underwater.[15]

As of Carter and Rosas' writing, vision had not been directly studied, although in other otter species it is generally normal or slightly myopic, both on land and in water.[10] The fact that it is exclusively active during the day suggests its eyesight should be strong to aid in hunting. Giant Otter hearing is acute and its sense of smell excellent.[9]

Social structure

Giant Otters at the Philadelphia Zoo. The species is extremely social, a rarity amongst Mustelids.

The Giant Otter is a highly social animal and lives in extended family groups. Group sizes are anywhere from two to twenty members but likely average between three and eight.[16] (The largest figure may reflect two or three family groups temporarily feeding together.)[17] The groups are strongly cohesive: the otters sleep, play, travel, and feed together.

Group members share roles, structured around the dominant breeding pair. The species is territorial, with groups marking their ranges with latrines, gland secretions, and vocalizations.[18] At least one case of a change in alpha relationship has been reported, with a new male taking over the role of a previous animal; the mechanics of the transition were not determined.[19] Duplaix suggests a division between residents, who are established within groups and territories, and nomadic and solitary transients; the categories do not seem rigid, and both may be a normal part of the Giant Otter life cycle.[9] One tentative theory for the development of sociality in Mustelids is that locally abundant but unpredictably dispersed prey causes groups to form.[20]

Aggression within the species ("intraspecific" conflict) has been documented amongst Giant Otters. Defence against intruding animals appears to be cooperative: while adult males typically lead in aggressive encounters, cases of alpha females guarding groups has been reported.[19] One fight was directly observed in the Brazilian Pantanal in which three animals violently engaged with a single individual near a range boundary.[18] In another instance in Brazil, a carcass was found with clear indications of violent assault from other otters, including bites to the snout and genitals, an attack pattern similar to that found in captive animals.[21] While not rare amongst large predators in general, intraspecific aggression is uncommon amongst otter species; Ribas and Mourão suggest a correlation to the animal's sociability, which is also rare in other otters.[18]

Reproduction and lifecycle

Captive Giant Otters have provided much of the research on the species' reproduction and lifecycle.

Details of Giant Otter reproduction and lifecycle are scarce, and captive animals have provided much of it. Females appear to give birth year round, although in the wild births may peak during the dry season. The estrous cycle is 21-days, with females receptive to sexual advance between three and 10 days.[10] Captive research has found that only males initiate copulation.[4] At Tierpark Hagenbeck in Germany, long term pair bonding and individualized mate selection were seen, with copulation most frequent in water.[22] The Giant Otter is the only species of mustelid that is monogamous.[23] Females have a gestation period of 65 to 70 days, giving birth to one to five pups, with an average of two.[22][10] Research over five years on a breeding pair at the Cali Zoo in Columbia found that the average interval between litters was six to seven months, but as short as 77 days where the previous litter did not survive.[4] Other sources have found greater intervals, with as much as 21 to 33 months suggested for the wild.[10]

Mothers give birth in an underground den near the river shore and fishing sites.[9] Males actively participate in rearing cubs and family cohesion is strong;[9] older, juvenile siblings also participate in rearing, although in the weeks immediately after birth they may temporarily leave the group.[10] Pups open their eyes in their fourth week, begin walking in their fifth, and are able to swim confidently between 12 and 14 weeks.[4] They are weaned by nine months and begin hunting successfully soon after.[10] The animal reaches sexual maturity at about two years of age and both male and female cubs leave the group permanently between two and three years.[22][10] They then search for new territory to begin a family of their own.[24]

The Giant Otter is very sensitive to human activity in rearing its young. No institution, for example, has successfully raised Giant Otter cubs unless parents were provided sufficient privacy measures; the stress caused by human visual and acoustic interference can lead to neglect, abuse and infanticide, and decreased lactation. In the wild, it's been suggested, although not systematically confirmed, that tourists cause similar stress: disrupted lactation and denning, reduced hunting, and habitat abandonment are all dangers.[24] This sensitivity is matched by a strong protectiveness over young. All group members may aggressively charge intruders, including human boats.[9]

The oldest documented Giant Otter lifespan in the wild is eight years. In captivity this may increase to 17, with an unconfirmed record of 19. The animal is susceptible to a variety of diseases, including the Parvovirosis that also affects domestic dogs. Parasites, such as the larvea of flies and a variety of intestinal worms, also afflict the Giant Otter.[24] Other causes of death include accidents, gastroenteritis, consumption of young, and epileptic seizures.[10]

Hunting and diet

The Giant Otter is an apex predator and its population status reflects the overall health of riverine ecosystems.[25] It feeds mainly on fish, including characins (such as piranha), catfish, and perch; if fish are unavailable it will also take crabs, snakes, and even small caimans and anacondas.[26] It can hunt both in groups and alone, tending to head towards the deeper waters while in groups. It consumes up to 10 lb (4.5 kg) of food each day, using mostly its eyesight to locate its prey.[citation needed]

Ecology

Habitat

An amphibious species, the Giant Otter is found in freshwater rivers and streams, which are generally seasonally flooded. Areas adjacent to rivers are used for the construction dens, campsites, and latrines.[27] Other habitats include marshes and bogs, freshwater springs, and permanent freshwater lakes.[2] Duplaix identifies two critical factors in habitat selection: food abundance, which appears to positively correlate to shallow water, and low sloping banks with good cover and easy access to preferred water types. The Giant Otter seems to choose black waters with rocky or sandy bottoms over silty, saline, and white waters.[9]

Giant Otters clear significant amounts of vegetation in constructing their campsites. One report suggests areas 28 m long and 15 m wide, well-marked by scent glands, urine, and feces to signal territory.[7] Carter and Rosas, however, note areas a third this size. Communal latrines are adopted adjacent to the campsites, and dens with a handful of entrances are dug, typically under root systems or fallen trees. One report found between three and eight campsites, clustered around feeding areas.[10]

Research is generally carried on in the dry season and an understanding of the species' overall habitat use remains partial. Dry season range size analysis of three otter groups in Ecuador found areas between 0.45 km and 2.79 km². Habitat requirements and availability were presumed to be dramatically different in the rainy season: range sizes of 1.98 to as much as 19.55 km² were estimated for the groups.[27] Other researchers suggest approximately 7 km² and note a strong inverse correlation between sociality and home range size; the highly social Giant Otter has smaller home range sizes than would be expected for a species of its mass.[20]

Predation and competition

Adult Giant Otters have no serious natural enemies, beyond human beings. "Possible and hey hey occasional" predation by the Jaguar, Cougar and Anaconda has been suggested by Duplaix, but based on historical reports, not direction observation.[9] The young are more vulnerable, and may be taken by the black Caiman and other large predators.[24]

Even if not directly preyed upon, the Giant Otter must still compete with other predators for resources. Duplaix documented interaction with the Neotropical Otter[28] in Suriname in the late 1970's. While the two species are sympatric (related, with overlapping ranges) during certain seasons, there appeared to be no serious conflict. The smaller Neotropical Otter is far more shy, less noisy, and less social; at less then half the weight of the Giant Otter, it is more vulnerable to predation and a lack of conspicuousness is to its advantage. The Neoptropical Otter is also active during twilight and darkness, reducing the likelihood of conflict with the diurnal Giant Otter,[9] while its smaller prey, different denning habits, and different preferred water types ought to also reduce interaction.[10]

Distribution and conservation status

The Giant Otter once ranged across the entire South American continent. While still present in a number of north-central countries, Giant Otter populations are under considerable stress. Considered "vulnerable" for years, the IUCN listed the species as "endangered" in 1999. It lists Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Paraguay, Peru, Suriname, and Venezuela as current range countries.[2] Although not listed in Argentina, investigation there has shown thinly distributed population remnants.[29] The species is regulated internationally under Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES): all trade in specimens and parts is illegal.[30]

The animal faces a variety of critical threats. Poaching has long been a problem: in the 1980s, pelt prices were as high as $250 on the European market. The threat has been excerbated by the otters' relative fearlessness and tendency to approach human beings.[31] More recently, habitat destruction and degradation has become the principal danger and a further reduction of 50% is expected in Giant Otter numbers within twenty years of 2004, about three generation lengths.[2] Other threats to the Giant Otter include conflict with fishermen, unsustainable mahogany logging,[31] and the concentrations of mercury in its diet of fish; mercury is a by-product of gold mining in parts of the Giant Otter range.[32][33]

Total population numbers are difficult to estimate with an endangered species. Research in 1988 suggested 1000 to 3000 individuals remain, although this may have been an underestimate.[10] One conservation group suggests 2000 to 5000 otters.[13] Populations in Bolivia were once widespread but became a "black spot" after poaching between the 1940s and 1970s; a relatively healthy but still small population of 350 was estimated in the country in 2002.[17] The species has likely been extirpated in southern Brazil, although decreased hunting pressure in the critical Pantanal may have led to recolonization; a rough estimate suggests 1000 animals in the region.[10][31]

As of 1997, only Suriname, French Guiana, and Guyana showed strong population numbers, according to Carter and Rosas.[10] In the last of these, interviews and surveys in 2000 showed relatively widespread populations.[25] Seven years earlier, the IUCN's Otter Specialist Group reported that Columbia was still a stronghold for the species.[7] Tiny Suriname, still has significant forest cover and an extensive system of protected areas, much of which protect the Giant Otter.[34] Duplaix returned to the country in 2000 and found the Giant Otter still present on the Kaburi Creek, a "jewel" of biodiversity; increased human presence and land use suggests that, sooner or later, the species may not be able to find suitable habitat for campsites.[35]

A number of restrictions over land use and human intrusion are required to properly maintain wild populations. Schenk et al., who undertook extensive fieldwork in Peru in the 1990s, suggest specific "no-go" zones where the species is most frequently observed, offset by observation towers and platforms to allowing viewing. Limits on the number of tourists at any one time, fishing prohibitions, and a minimum safe distance of 50 meters offer further protection.[36]

Notes and references

  1. ^ a b Wozencraft, W. C. (2005). "Order Carnivora". In Wilson, D. E.; Reeder, D. M. (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. p. 605. ISBN 978-0-8018-8221-0. OCLC 62265494.
  2. ^ a b c d Template:IUCN2006 Database entry includes justification for why this species is endangered
  3. ^ Spanish: Lobo del Río.
  4. ^ a b c d Londono, G. Corredor (2006). "Reproduction, behaviour and biology of the Giant river otter (Pteronura brasiliensis) at Cali Zoo". International Zoo Yearbook. 40: 360–371. {{cite journal}}: |access-date= requires |url= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help); line feed character in |title= at position 55 (help)
  5. ^ Liddell, Henry George and Robert Scott (1980). A Greek-English Lexicon (Abridged Edition). United Kingdom: Oxford University Press. ISBN 0-19-910207-4.
  6. ^ a b c d Koepfli, K.-P (1998). "Phylogenetic relationships of otters (Carnivora: Mustelidae) based on mitochondrial cytochrome b sequences". Journal of Zoology. 246 (4): 401–416. Retrieved 2007-12-29. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)
  7. ^ a b c Foster-Turley, Pat; Macdonald, Sheila; Mason, Chris (eds.) (1990). "Otters: An Action Plan for their Conservation". IUCN/SSC Otter Specialist Group. International Conservation Union: Sections 2 and 12. doi:10.2305/IUCN.CH.1990.SSC-AP.3.en. Retrieved 2007-11-21. {{cite journal}}: |author= has generic name (help)CS1 maint: multiple names: authors list (link)
  8. ^ Marmi, Josep (2004). "Phylogeny, evolutionary history and taxonomy of the Mustelidae based on sequences of the cytochrome b gene and a complex repetitive flanking region". Zoologica Scripta. 33 (6): 481–499. {{cite journal}}: |access-date= requires |url= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)
  9. ^ a b c d e f g h i j Duplaix, Nicole (1980). "Observations on the ecology and behavior of the giant river otter Pteronura brasiliensis in Suriname". Revue d'Ecologie (Terre Vie). 34: 495–620. {{cite journal}}: |access-date= requires |url= (help)
  10. ^ a b c d e f g h i j k l m n o p Carter, S.K. (1997). "Biology and conservation of Giant Otter (Pteronura brasiliensis)" (PDF). Mammal review. 27 (1): 1–26. Retrieved 2007-11-06. {{cite journal}}: Cite has empty unknown parameter: |month= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  11. ^ a b "Giant Otter". Meet Our Animals. Philadelphia Zoo. Retrieved 2007-11-06.
  12. ^ "Otters: Physical characteristics". Anheuser-Busch Adventure Parks. Retrieved 2007-11-06.
  13. ^ a b "Giant Otter Facts". Meet Our Animals. Earth's Endangered Creatures. Retrieved 2007-11-07.
  14. ^ "Giant Otter". World Wildlife Fund. Retrieved 2008-01-19.
  15. ^ "Giant Otter, the "Water Dog"". Iwokrama International Centre for Rainforest Conservation and Development. Retrieved 2007-11-07.
  16. ^ "Pteronura brasiliensis (giant otter)". Carnivores. Food and agricultural organization of the United Nations. Retrieved 2007-11-07.
  17. ^ a b van Damme, Paul (2002). "Distribution and Population Status of the Giant Otter Pteronura brasiliensis in Bolivia". IUCN Otter Specialist Group. 19 (2): 87–96. Retrieved 2007-11-05. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)
  18. ^ a b c Ribas, Carolina (2005). "Intraspecific Agonism between Giant Otter Groups". IUCN Otter Specialist Group Bulletin. 21 (2): 89–93. Retrieved 2007-11-07. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)
  19. ^ a b Evangelista, Emanuela (2004). "Change Of Partners In A Giant Otter Alpha Couple". IUCN Otter Specialist Group Bulletin. 21 (1): 47–51. Retrieved 2007-11-07. {{cite journal}}: Unknown parameter |month= ignored (help)
  20. ^ a b Johnson, Dominic D.P. (2000). "An analysis and review of the sociobiology of the Mustelidae" (PDF). Mammal review. 30 (3&4): 171–196. Retrieved 2007-11-07. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help) See figure three for home range size estimate.
  21. ^ Rosas, F.C.W. (2003). "Natural Deaths Of Giant Otters (Pteronura Brasiliensis) In Balbina Hydroelectric Lake, Amazonas, Brazil". IUCN Otter Specialist Group Bulletin. 20 (2): 62–64. Retrieved 2007-11-07. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)
  22. ^ a b c Hagenbeck, Carl (1992). "Breeding the Giant otter (Pteronura brasiliensis) at Carl Hagenbecks Tierpark". International Zoo Yearbook. 32: 240–245. {{cite journal}}: |access-date= requires |url= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  23. ^ Grzimek's Animal Life Encyclopedia, vol.XIV, pg.324a (2004).
  24. ^ a b c d Sykes-Gatz, Sheila (2005). International Giant Otter Studbook Husbandry and Management Information and Guidelines (Second ed.). Germany: Zoologischer Garten Dortmund. p. 13.
  25. ^ a b Barnett, Adrian (2000). "Records of the Giant Otter, Pteronura brasiliensis, from Guyana". IUCN Otter Specialist Group. 17 (2): 65–74. {{cite journal}}: |access-date= requires |url= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)
  26. ^ "Giant Otter (Pteronura brasiliensis)". International Otter Survival Fund. Retrieved 2007-11-21.
  27. ^ a b Utreras, V. (2005). "Dry and Rainy Season Estimations of Giant Otter, Pteronura brasiliensis, Home-Range in the Yasuní National Park, Ecuador" (PDF). The Latin American Journal of Aquatic Mammals. 4 (2): 1–4. Retrieved 2007-11-07. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)
  28. ^ Lontra longicaudis. In Duplaix (1980) it was listed as the Guiana Otter under the older binomial Lutra enudris.
  29. ^ Chehebar, C. (1991). "Searching for the Giant Otter in Northeastern Argentina". IUCN Otter Specialist Group. 6 (1): 17–18. Retrieved 2007-11-06. {{cite journal}}: Unknown parameter |month= ignored (help)
  30. ^ "Appendices I, II and III". Convention on International Trade in Endangered Species of Wild Fauna and Flora. Retrieved 2008-01-22.
  31. ^ a b c Ridgley, Heidi (Winter 2007). "The Wolf of the River" (PDF). Defenders Magazine. Defenders of Wildlife. Retrieved 2007-11-09.
  32. ^ Fonseca, Fabrizio R.D. (2005). "Mercurylevels in tissues of Giant otters (Pteronura brasiliensis) from the Rio Negro, Pantanal, Brazil" (PDF). Environmental Research. 98: 368–371. Retrieved 2007-11-09. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  33. ^ Gutleb, A.C. (1997). "Giant otter (Pteronura brasiliensis) at risk? Total mercury and methylmercury levels in fish and otter scats, Peru". Ambio. 26 (8): 511–514. Retrieved 2007-11-09. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)
  34. ^ "Natural Heritage in Suriname". Suriname Natcom. UNESCO. Retrieved 2007-01-21.
  35. ^ Duplaix, Nicole (2001). "A Survey of Kaburi Creek, West Suriname, and its Conservation Implications". 2DocStock Photography. Retrieved 2008-01-22. {{cite web}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  36. ^ Schenck, Christof (1999). "Giant Otter Project In Peru: Field Trip And Activity Report, 1998". IUCN Otter Specialist Group. 16 (1): 1–57. Retrieved 2008-01-22. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)
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