Volume 17 Issue 2 Pages 59 - 99 (October 2000)

Citation: Barnett, A., Shapley, R., Lehman, S., Henry, E. & Benjamin, P. (2000) Records of the Giant Otter, Pteronura brasiliensis, from Guyana IUCN Otter Spec. Group Bull. 17(2): 65 - 74

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Records of the Giant Otter, Pteronura brasiliensis, from Guyana

Adrian Barnett¹, Rebecca Shapley², Shawn Lehman³, Everton Henry⁴, Paul Benjamin⁵

¹School of Life Sciences, University of Surrey Roehampton, West Hill, London, SW15 3SN, UK, e-mail: infovore@wombat.net
²Akodon Ecological Consulting, Concord, CA 94518, USA
³Department of Anthropology, University of Calgary, 2500 University Drive, NW, Calgary, Alberta T2N 1C3, Canada.
⁴ Everton's Ecological Expeditions Georgetown, Guyana
⁵Chenapou Primary School, Chenapou, Potaro, District 8, Guyana.

INTRODUCTION

As one of the Neotropics largest piscivores, the giant otter Pteronura brasiliensis is an apex predator and a good indicator of the health of the riverine ecosystems it inhabits. The 1996 IUCN Red List categorizes P. brasiliensis as vulnerable: VU A2cd (BAILLIE and GROOMBRIDGE, 1996). In a recent review of the biology of the species, CARTER and ROSAS (1997) called for the species to be placed in the 'endangered' category. The IUCN-SSC Otter Action Plan (FOSTER-TURLEY et al., 1990) considers the species to be severely threatened (p. 64) and call for more field surveys and refined distributional data (p. 82). Within Guyana, they consider distribution and status surveys to be conservation priorities for the species (p. 70).

[*: Vulnerable. Declining population. Population decline projected or suspected based on, decline in area of occupancy/quality of habitat, actual or potential levels of exploitation.]

In their review of the status of P. brasiliensis CARTER and ROSAS (1997) note that Guyana is one of the species' last major strongholds (see also FOSTER-TURLEY et al., 1990). In Guyana, P. brasiliensis has been recorded from several river systems including the upper Mazaruni, upper Essequibo, Abary, Rupanuni and upper Potaro (CARTER and ROSAS, 1997). However, many of these records are more than a decade old. Here we report recent sightings of P. brasiliensis on the Potaro Plateau, western Guyana, and other localities within the country (Fig. 1).

Figure 1. Sightings of P. brasiliensis Click on image for larger version

MATERIALS AND METHODS

Interviews:

1. As part of a country-wide primate survey conducted between November 1994 and August 1997 (LEHMAN, 1999), interviews were conducted with forty local people during surveys along rivers. Interviews consisted of:
   1. having people identify local aquatic mammals from pictures,
   2. asking for local names of aquatic mammals,
   3. asking people to distinguish between aquatic mammals that occur in the immediate area versus those that occur elsewhere in Guyana,
   4. asking for physical descriptions of each species,
   5. asking about the relative abundance of aquatic mammals in the area [i.e., not found, sometimes seen, abundant, very abundant], and
   6. requesting information on hunting techniques. The main occupation of the interviewees was ascertained whenever possible (e.g. hunter, logger, pork knocker [miner], farmer).
   Pictures were laminated plates from EMMONS and FEER (1990) and laminated photographs of non-neotropical mammals.
    
2. Between June 20 and August 4 1998, zoological surveys were conducted on the southwestern portion of the Potaro Plateau as part of the Potaro Plateau Zoological Expedition (PPZE). Questions relating to otters were also included as part of a broader interview about the region's mammals (BARNETT and SHAPLEY, 1999; BARNETT et al., 2001; BARNETT et al., in press; SHAPLEY, et al., submitted; SHAPLEY et al., in prep.).

Questioning was oral, informal, did not follow a rigid questionnaire and centered on laminated colour photocopies of the plates in EISENBERG (1989) and REID (1998). These included those of canids, procyonids and felids as well as Neotropical Mustelidae. The PPZE conducted twenty-seven such interviews in the Patamona indigenous villages of Chenapou and Tiger Bay and at Kaieteur Falls with the staff of the Kaieteur National Park. Question protocol followed that used by CUNHA and BARNETT (1989) and, following BELLAMY (1993), was designed to avoid leading questions. Most interviewees were older men, each considered within the community to be of good character and well-informed about the region's animals. All were long-term residents of the Plateau. Interviews consisted of:

1. having interviewees identify local mammal species from the laminates;
2. asking for physical descriptions of various species;
3. asking about the relative abundance of selected mammal species (primates, giant otters etc.) in the area (i.e., not found, rare, sometimes seen, abundant, very abundant); and
4. requesting information on hunting techniques (if any).

Surveys:

1. One of the authors of this article (S. LEHMAN [SL]) recorded encounters with P. brasiliensis that occurred opportunistically during the countrywide primate survey mentioned above. During this, a total of 596 km of river was surveyed by canoe. Surveys were conducted along the following rivers: Abary, Berbice, Mahaicony, Madewini, Wikki, Wairuni, Canje, Pomeroon, Arunamai, and Sebai. Rivers were surveyed by paddling slowly (1.5-2.0 km/h) along riverbanks, either alone or with the assistance of local guides. During surveys, data were recorded on:
   1. species of aquatic mammal,
   2. time of day,
   3. weather,
   4. riverbank habitat,
   5. number of animals in group,
   6. cue by which animals detected,
   7. activity, and
   8. location using a Magellan NAV 5000D global positioning system.
   Ad libitum notes on behaviour, vocalizations, and group composition were made whenever a group of P. brasiliensis was encountered.
    
2. Between July 28 and 1 August 1998 (wet season), paddling canoes, the other authors actively searched for P. brasiliensis at two locations, Muri-muri Creek and Anamuri Creek in the eastern part of the Potaro Plateau. Both creeks are left bank tributaries of the Potaro River. Choice of these locations followed the advice of local fishermen. Both are small creeks (no more than 4m wide), less than 3m deep, and fallen trees frequently block passage on them. The creek banks are of mud and white sand and, at the time of the survey, were between 0.5 and 1.5m above water level. Because of the black-water nature of the river, aquatic plant biomass is low (GOULDING et al., 1988; JUNK and FURCH, 1985). Searching began shortly after dawn and continued until mid-afternoon each day. An estimated total of 18 km of creek was paddled during the survey period.

RESULTS

Guyana-wide, surveys:

A group of four adult-sized P. brasiliensis were observed on April 20, 1995, near the headwaters of the Mahaicony River (6°9' 54" N, 57°, 56', 13"W). The animals were extremely shy. The first individual to see the approaching boat gave an alarm call that sent the entire group diving and swimming for cover under trees overhanging the riverbanks. Attempts to approach the group failed and the animals swam quickly away. P. brasiliensis (N=3) were seen on December 31, 1995, near the headwaters of the Canje River in NE Guyana (5° 12' 54" N, 57°30' 04"W). The group appeared to be composed of two adults and a juvenile or sub-adult. All animals were extremely shy and swam away from the boat quickly and quietly.

That giant otter on the upper Berbice have little experience (or fear of) humans is illustrated by an encounter on June 6, 1996, with a group of P. brasiliensis near a natural dam known as The Gate (5° 6' 54"N, 58° 13' 4"W). During the evening whilst camped alongside the river, SL heard a noise coming from the boat. Investigating with a flashlight, SL startled an adult P. brasiliensis that had climbed into the boat! The animal jumped into the water and, with seven other P. brasiliensis, spent the next twenty minutes vocalizing and barking, apparently chastising him for disturbing them. There are no permanent human settlements in the region of The Gate, although there are small groups of gold miners who work in the area.

Terry HENKEL (pers. comm.) reports that giant otters were recently seen along the Sipu River and they are very abundant along the Kuyuwini River (south-east of Aishalton). WARREN (1971) reported giant otters to be abundant on the Kato and lower Waruma rivers (though not recent, this record is mentioned since it is not included in CARTER and ROSAS [1997]).

Guyana-wide, interviews:

Whether or not P. brasiliensis was reported as being hunted varied locally and seemed strongly influenced by the people's cultural precepts. Overall, most informants reported that P. brasiliensis was hunted neither for its skin nor for food. There were two exceptions: one apparently well-travelled informant, interviewed at Kaieteur Falls, said that otters were hunted near some of the bauxite mines in eastern Guyana, and interviews conducted with Bush Negroes (N=5) along the Canje River revealed that giant otters- as well as manatees and river otters- were hunted (no otters were seen along this river). In addition, there were persistent, but unsubstantiated, reports from the Rupanuni District of pelt collecting and subsequent shipment to Brazil. On the Mahaicony River, most people along the river's northern half are Hindus whereas the southern half of the river is used almost exclusively by Amerindians. Hindus interviewed during surveys (N=8) informed SL that giant otters are not hunted for food due to Hindu religious taboos. (Amerindians along the Mahaicony River were not interviewed due to lack of permits).

Potaro Plateau, surveys:

On July 28 two giant otters were seen entering the water as we approached an otter campsite on Muri-muri Creek. The site had a holt entrance (approximately 60cm high and 40cm wide), amongst the roots of a large tree (DBH > 60cm). This lay within 3m of a very gently sloping muddy bank that led to a small shallow embayment. The site, estimated at 10m long and 3m wide, contained a fresh spraint and several identifiable piles of fish scales and bones. Samples were collected, washed and dried. Based on scales and teeth these have been identified by William SAUL (Philadelphia Academy of Natural Sciences) as (probably) Aequidens, Guianacara or Geophagus (all Cichlidae). On the Potaro Plateau fish of these species are rarely longer than 15 cm (EIGENMANN, 1912; BENJAMIN, pers. obs.; HENRY, pers. obs.). Fish reported in the otter diet are generally much larger than this (DUPLAIX, 1980; LAIDLER, 1984; CARTER and ROSAS, 1997).

Subsequently four giant otters were seen some 200m upstream beneath dense overhanging vegetation. They showed little fear of us, supporting the statements of local people that they did not hunt them. The otters stayed low in the water much of the time. When they did elevate their bodies, intervening vegetation meant that we were unable to record any of the individually characteristic throat patterns. Three individuals appeared to be approximately the same size, the fourth animal appearing a little larger and with a bigger head. This may indicate a pair, accompanied by last year's young. Eleven more campsites were seen in a 5 km stretch of the creek. None were in use, all being overgrown to some extent with vegetation or sprouting seedlings, indicating that the creek had been a favoured otter habitat for several, possibly many, years.

On July 30, two adult-sized giant otters were seen on Anamuri Creek 9.5 km upstream from Muri-muri. The two creeks are more than 1 hour apart by motor boat and, from available maps (and BENJAMIN, pers. obs.) do not appear connected. As the sighting here and on Muri-muri Creek were only two days apart it is difficult to believe that the animals on these two creeks are from the same group, even though the distance lies within the reported group home range size for P. brasiliensis (3 km by DUPLAIX, 1980; 32 km by LAIDLER, 1984).

Again, the creek showed evidence of prolonged usage by the otters, with 8 former campsites being counted in the 4 km stretch surveyed. An old, disused, holt with an entrance some 50x30cm, was found. It was dug beneath the roots of a large tree, on a steep muddy bank, less than 1m from the river. The surveyed portion of the creek is probably the only part that is habitable by otters. After this, the banks become very steep and rocky as the creek flows over a ridge system and the scant soil is very sandy.

Prior to the sightings by the PPZE, SL had visited Muri-muri Creek on foot in March 1995 (dry season) from Kaieteur Falls. Two P. brasiliensis were seen and a number of bank-side resting spots were found.

Potaro Plateau, interviews:

All interviewees knew the giant otter well. In each case, individuals clearly distinguished between Pteronura brasiliensis and Lutra longicaudis and between these and the region's other carnivores (plus a number of spurious alternatives). In all cases, P. brasiliensis was considered common in small creeks, but rare on the main river. It was reported to be present in the creeks in the dry season, while in the rainy season the species was considered to range more widely through the wet and flooded forest. Though local knowledge of the region's waterways was extensive and detailed, all seven interviewees who expressed an opinion on the matter gave the same four creeks as supporting otters (of which those surveyed are two). This indicates some degree of habitat specificity. In interviews at Kaieteur Falls, informants reported that Pteronura was common nearby, particularly along some of the more remote streams. The Patamona name for the giant otter is turáclá.

Patamona interviewees at Chenapou, and miners at Kaieteur Falls, all reported that giant otter steal fish from nets. However, all were adamant that they took no punitive action and that the giant otter was hunted on the Plateau neither for food nor for its pelt.

At several locations on the Plateau's rivers, dredging operations occur, seeking to extract diamonds and gold from the riverine sands. These activities cause considerable sedimentation to the waters (Carol KELLOFF, pers. comm.; authors, pers. obs.). Interviewees reported that such operations cause the giant otters to shift their range. One river, the Ireng, where P. brasiliensis were formerly considered common, was now said to be too polluted by mining activities to be habitable by them. But other rivers were said to have been recolonized by giant otters after mining operations had ceased.

Though the species was not sighted, we had frequent reports of Neotropical river otter Lutra longicaudis in the region. In contrast to the giant otters, these were considered to live almost exclusively in the main river and rarely, if ever, enter the creeks. By contrast, SL, working mostly with miners in the Kaieteur Falls region of the park, did not receive any reports of L. longicaudis in the region. The Patamona name for this species is saró.

DISCUSSION

Though subject to some detailed botanical work (MAGUIRE et al., 1948; HENKEL, 1994; KELLOFF and FUNK, 1998), the Potaro Plateau has been little studied by zoologists (BARNETT and SHAPLEY, 1999; LIM and ENGSTROM, in press). Only one previous published record of giant otter exists for the Plateau, a sighting of a family of six on the Kwitaro River by Elizabeth and Keith LAIDLER in 1981. This brief visit, an adjunct to the former's PhD fieldwork, was reported only in the popular book The River Wolf (LAIDLER and LAIDLER, 1983, p. 162) and did not appear in her thesis (LAIDLER, 1984). CARTER and ROSAS (1997) cite the record, but they do not give the locality. The Kwitaro is some 7.5 land km/ 17.75 river km upstream from the current localities. The LAIDLERS considered the Plateau's P. brasiliensis population to be "healthy". Though both surveyed creeks showed evidence of long use by giant otters, our survey was too brief and too restricted confirm or deny the LAIDLERS' subjective optimism.

The apparent lack of hunting, the absence of commercial (as opposed to subsistence) fisheries in the region and the proximity of the observed sites to the airstrip near Kaieteur Falls, would make the site a promising one for future fieldwork. This might also be important for the conservation of the Plateau's giant otters. The two creeks are less than 15 km from the commercial community of Menzies' Landing, which is itself close to the airstrip at Kaieteur Falls. The proximity of an airstrip at Kaieteur Falls would facilitate the logistics of any future detailed studies of the giant otters of the Potaro Plateau. Such studies could address a number of conservation-related issues:

• Clarifying the conservation status of Pteronura on the Potaro Plateau:
  This could include studies of the effects of sedimentation from dredging on the giant otters distribution and a study the levels of mercury in both the food fish and in the otters themselves (see, e.g. EVANS et al., 1998; HARDING et al., 1998). Up to 45% of mercury used in small-scale gold mining can enter adjacent rivers as metallic mercury (GROENENDIJK et al., 2000), and is a potential threat to giant otter populations far from the contamination source (GUTLEB et al., 1997).
   
• The potential impact of ecotourism:
  Several thousand tourists visit the Falls every year (ANDERSEN, 1996; WORLD BANK, 1998) and it must be considered a strong possibility that ecotourism, offering visits to see the giant otters, could develop without regulation. Ecotourism, especially when unregulated, has been shown to be a potent source of stress for P. brasiliensis in Peru (STAIB and SCHENCK, 1994a), causing loss of litters (STAIB and SCHENK, 1994b) and abandonment of traditional localities (SCHENK et al., 1999; GROENENDIJK et al., 2000). Base-line ecological studies of the Plateau's otters could establish the feasibility of ecotourism operations and study, and perhaps recommend, acceptable limits for the frequency of such visits.
   
• Comparative ecological studies:
  
  1. Few P. brasiliensis have been recorded at higher altitudes: OCHOA et al. (1993), working in Venezuela's Canaima National Park, over the border from the Potaro study site, records giant otter only from its lower altitudes. EMMONS (1993) records P. brasiliensis from Guyana's Kanuku Mts., but does not give an altitude. Given the social and behavioural plasticity of this species (CARTER and ROSAS , 1997), the great rarity of fish longer than 20 cm on the upper Potaro and its affluents (EIGENMANN, 1912; BENJAMIN, pers. obs.; HENRY, pers. obs.) could have effects on the otters social ecology. It would be interesting and instructive to compare the ecology of Plateau's otters with those of The Gate, on the upper Berbice River.
  2. the Plateau has three aquatic carnivores: the two otters and the yapok (Chironectes minumus). Synecological studies could focus on the interactions between them.

ACKNOWLEDGEMENTS - AB and RS would like to thank the Guyanese Environmental Protection Agency, Minister for Amerindian Affairs for permission to work in the region, and the people of Chenapou village for their help and cooperation, Silvia Sykes and Reg Hoyt (Philadelphia Zoo), Bill Saul (Philadelphia Academy of Natural Sciences), Mark Engstrom (Royal Ontario Museum) and the librarians at the Zoological Society of London and the Philadelphia Academy of Natural Sciences. SL thanks Dean Indirjit Ramdas, Dean Catherine Cox, Mr. Phillip daSilva, Mr. John Caesar, Dr. Karen Pilgrim, Office of the President, University of Guyana, Department of Biology at the University of Guyana, Ministry of Amerindian Affairs, Ministry of Health, National Parks Commission, Tropenbos Guyana, Demarara Timbers Ltd., Iwokrama Rain Forest Reserve, and Wildlife Division of the Department of Health for permission to conduct his studies. Funds for this study were provided in part by grants from the International Otter Survival Fund, the Royal Geographical Society, the Percy Sladen Memorial Fund, University of Surrey Roehampton (to Adrian Barnett & Rebecca Shapley), from Esso-Guyana (to Paul Benjamin), and from Lincoln Park Zoo Scott Neotropic Fund, the Biological Diversity of the Guianas Program of the Smithsonian Institution, USAID, the Ministry of Finance of the Government of Guyana, the Global Environmental Fund of the World Bank, the L.S.B. Leakey Foundation, a Sigma Xi Grant-in-Aid of Research, and Washington University (to Shawn Lehman).

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