Volume 19 Issue 2
Pages 62 - 110 (October 2002)
Citation: van Damme, P., Wallace, R., Swaenepoel, K.,
Painter, L., Ten, S., Taber, A., Gonzalez Jimenes, R. Saravia, I., Fraser, A.
and Vargas, J. (2002) Distribution and Population Status of the Giant Otter Pteronura
brasiliensis in Bolivia. IUCN Otter Spec. Group Bull. 19(2): 87- 96
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Distribution and Population Status of the Giant Otter Pteronura
brasiliensis in Bolivia
Paul van Damme1, Rob Wallace2,
Karen Swaenepoel3, Lillian Painter2,
Silvia Ten4, Andrew Taber5,
Rocio Gonzalez Jimenes6, Isabel Saravia1,
Anna Fraser7 and Julieta Vargas8
1 Programa de
Conservación y Manejo de Recursos Hidrobiológicos (COMARH), Centro de
Limnologia y Recursos Acuáticos, Universidad Mayor de San Simón, Cochabamba,
Bolivia. e-mail: Paul.email@example.com
2 Living Landscapes Program, Wildlife Conservation
Society, WCS Bolivia, La Paz, Bolivia.
3Laboratory for Aquatic Ecology, University of
4 Asociación Hombre y Naturaleza: Bolivia.
5J Wildlife Conservation Society, USA.
6 Confauna, Wildlife Conservation Society y Museo de
Historia Natural Noel Kempff Mercado, Santa Cruz, Bolivia .
7 University of Nottingham, Great Britain.
8Colección Boliviano de Fauna, La Paz, Bolivia.
(received 15th December 2002, accepted 12th
Abstract: The giant otter (Pteronura
brasiliensis) is one of the most endangered mammal species in the
Neotropical region. In Bolivia, it has been reduced to very low population
numbers as a result of poaching in the 40s and 70s. Recently, 14
researchers on the giant otter, who together estimated that around 350
individuals exist in Bolivia, published a preliminary distribution map. In
this report, we briefly present the most recent information on the
distribution and population status of this species in the Bolivian Del
Plata and Amazon river basins. Moreover, we comment on the superposition
of giant otter family groups, hydro-ecoregions, and National Parks.
Finally, we present a short discussion on the possibilities of interchange
between Bolivian giant otter subpopulations.
|Française | Español
The giant otter (Pteronura brasiliensis) used to be a common sight in
the Bolivian river floodplains. As in all neighbouring countries, the species
was decimated to the border of extinction by poaching between the 1940s and 70s.
Between 1975 and 1995, the species was only known from very isolated locations
in the Mamoré, Iténez and Madre de Díos basins (DUNSTONE
and STRACHAN, 1988; CAMERON et al., 1989; BARRA
et al. 1992). On a continental scale, Bolivia represented one of the black
spots on the distribution map of the giant otter (EISENBERG
and REDFORD, 1999). This pessimistic view changed with the discovery of
relatively healthy populations in the Iténez-Guaporé river basin by PAINTER
et al. (1994), GONZÁLES JIMÉNEZ (1997), FRASER
et al. (1993), van DAMME et al. (2002) and PALMER
(pers. comm.). These authors reported a minimum total population of 350
individuals, organized into more than 40 family groups. The present report
summarizes the distribution and population status of this species. We also
discuss the protection status of the respective giant otter populations and the
possibilities of interchange between neighbouring populations. This report is a
brief summary of a recently published review (van DAMME et al.,
The present report is based on field observations from the period 1993-2002.
Some of the observations have been published in scientific articles (TEN
et al., 2001), but most were only available in relatively inaccessible
reports (FRASER et al., 1993), Management Plans of
National Parks (FAN-WCS, 1994; PAINTER et
al., 1994), RAP expedition reports (EMMONS, 1998) and
student theses (GONZÁLES JIMÉNEZ, 1997; SARAVIA,
unpubl.). None of the previously mentioned authors used a standardized
methodology, though there are some constant patterns in their approach. For
example, most observed otters from a boat, which in most cases was equipped with
an outboard motor. Some observations were made in the framework of other studies
on neotropical mammals.
FRASER et al. (1993) conducted a study on giant otters
in the River Iténez. GONZÁLES JIMENEZ (1997) and van
DAMME et al. (2002) focused their attention on the River Paraguá, on the
western border of the Noel Kempff Mercado National Park. PAINTER
et al. (1994) conducted field surveys in the Blanco, Negro, Negro de
Caimanes and San Martin rivers, whereas TEN et al. (2001)
focused on more downstream segments of the latter river and other rivers in the
Iténez National Park. In addition, isolated observations were made by REBOLLEDO
and QUIROGA (unpublished data) in the Bolivian Pantanal, VARGAS (unpublished
data) in the Etanahua river (Madidi River basin), TORRES (unpublished data) in
the Ipurupuru River (Iténez-Guaporé basin), and WALLACE, PAINTER, TABER and
RUMIZ (unpublished data) in the Iténez-Guaporé, Negro and San Martin rivers
(for a summary see van DAMME et al. 2002).
Distribution and population status
Distribution data are presented in Fig. 1. More detailed
results can be obtained in van DAMME et al. (2002).
In Bolivia the largest populations of giant otter occur in the Iténez-Guaporé
river basin. In this basin, four important populations were reported:
- a rather large population in the Parque Nacional Noel Kempff Mercado and
its surroundings, in the upper Iténez-basin (EMMONS, 1998;
FRASER et al., 1993; GONZÁLES
JIMÉNEZ, 1997, WALLACE and PAINTER, unpublished data; van
DAMME et al., 2002; PALMER, pers. comm.). Most of the giant otters were
found in the rivers (Iténez, Paraguá, Tarvo) and dead river arms that
border the National Park.
This population probably consists of more than 100 individuals.
- a subpopulation in the middle Iténez basin and in the lower parts of some
tributaries, e.g. San Martin, in the Iténez Reserva and its surroundings (TEN
et al., 2001; TEN, unpublished data). This population consists of more
than 120 individuals.
- a smaller population in the upper parts of the same tributaries, i.e. the
Ríos Blanco y Negro Wildlife Reserve and surroundings (PAINTER
et al., 1994;GONZÁLES JIMÉNEZ, 1997; RUMIZ,
unpublished data). This population consists of around 44 individuals.
- a very small isolated population was recorded in the Upurupuru and Negro
Caimanes rivers, in the lower Iténez river basin. In contrast with the
above-mentioned rivers, these do not drain the Precambrian Shield, but the
Beni alluvial lowlands.
|Figure 1: National Parks and
Giant otter populations in Bolivia
(Click to see larger version)
1. Surveys for Pteronura brasiliensis in Bolivia (1992-2002)
||National Park Noel Kempff Mercado
||Iténez, Paraguá, Paucerna, Verde
||River channels and old river arms that are
permanently connected with rivers
|van DAMME et al
||National Park Noel Kempff
Mercado / Indigenous Territory Bajo Paraguá
||Paraguá river channel,
river arms permanently connected with river, lakes of fluvial origina
21 groups / 76 ind.
|TEN et al (2001)
||National Park Iténez
||Iténez, Negro de
Iténez, San Martin, San Simón, San Antonio
||Rivers and lakes
6 groups / 40 ind.
||National Park Noel Kempff
Mercado / Indigenous Territory Bajo Paraguá
||Río Paraguá, San MArtin
||River channels and old
river arms that are permanently connected with rivers
12 groups / 27 ind.
|PAINTER et al
||Wildlife Reserve Ríos Blanco y Negro
||Blanco, Negro, Negro de Caimanes
||Rivers and streams
12 groups / 44 ind.
|FRASER et al
||National Park Noel Kempff
||Iténez, Paucerna, Verde
||River channels and old
river arms that are permanently connected with rivers
1 group / 2 ind.
2 groups / 9 ind.
6 groups / 26 ind.
In the Mamoré river basin, very few giant otters have been recently
observed. In the upper Mamoré basin, some historical records exist. The last
known group in the Ichilo river basin (in an oxbow lake of the Sajta river) was
extinguished a few years ago. The last giant otters in this river basin may
occur in the Isiboro-Sécure National Park, where indigenous people have
Finally, in the most western parts of the Amazon basin, in the Madre de
Díos and Beni river basins, individual otters or isolated family
groups were recently recorded in the Heath, Madidi, Etanahua, Tuichi, Hondo,
Quiquibey, Emero and Tequeje rivers (WALLACE et al., unpublished data; MONTAMBAULT,
2002; VARGAS, unpublished data). CARBAJAL (pers.comm.) recently observed a
group of 8 giant otters in the Manuripi-Heath National Park (not indicated in
Fig. 1). A systematic survey of these rivers has not been carried out so far.
In the basin of the Paraguay river, the giant otter has not been
studied very well, though it may be expected to occur given its proximity to the
Brazilian pantanal, where a relatively large population of giant otters occurs (SCHWEIZER,
1992). Recently, a family group was observed in the Cáceres lake, within
the Otuquis National Park (REBOLLEDO Y QUIROGA, pers. comm.).
Recently, NAVARRO and MALDONADO (2002) proposed a
classification of Bolivia in hydro-ecoregions. Within the distribution range of
the giant otter in the Amazon and De Plata basins, they distinguished three
hydro-regions: the alluvial lowlands, the Precambrian Shield and the Oriental
Mountain Ridge (Table 2).
|Table 2: Number and percentage
of individual Pteronura brasiliensis reported in different
hydro-ecoregions (division in hydro-ecoregions based on NAVARRO and
||PAST OR PRESENT
||TOTAL NUMBER OF
||% OF INDIVIDUALS2
||Fluvial seasonal alluvial lowlands
||Fluvial alluvial lowlands
||Dry alluvial lowlands
||Hills, Ridges and Mesetas
||Alluvial lowlands of the Precambrian Shield
||Chiquitano mountain ridge and mesetas
||Mesetas from the Precambrian Shield
||Fluvial seasonal mountain ridge and hills
||Fluvial mountain ridge and hills
||Fluvial seasonal sub-Andean valleys
||Fluvial seasonal Piedemonte
||(based on anecdotal / historical reports)
||Anecdotal and historical reports were not included
Among the sectors that can be distinguished in these hydro-regions, the giant
otter was most often reported in the alluvial lowlands of the Precambrian Shield
(88.5% of all individuals), overlapping with the floodplain of the Iténez-river
and some of its tributaries (Paraguá and San Martin rivers). Fewer individuals
were recorded in the Fluvial alluvial lowlands of the white-water floodplains of
the Mamoré and Madre de Díos rivers, whereas in other sectors only anecdotal
and historical reports were available. Overall, more than 85% of the
observations so far were made in small rivers, most of them draining the
Precambrian Shield. So far, very few giant otters have been reported in
white-water oxbow lakes, though they are expected to occur.
Protection status of the giant otter
Current data (Table 3) suggest that only 7% of giant
otters can be found in protected areas with a management plan. Twenty four
percent were observed in rivers that are borders between National Parks and
indigenous territories. Eight percent were found in international rivers that
represent the border of Bolivian National Parks and 61% were found in areas
without adequate official protection status.
|Table 3: Number and Percentage of Pteronura
brasiliensis reported from National Parks, Indigenous Territories, areas
in the process of titulation, areas without protection, in rivers that
represent limits between different types of areas and in international
||% OF INDIVIDUALS
|Within protected areas
|Immovilized parks (with management plan)
partly superposed with indigenous territories
|Within National Parks
with uncertain conservation status
Territories (TCO) 1
|In rivers that are
borders of National Parks and Indigenous Territories
|In international rivers
(Brazil, Peru) that are at the same time borders of National Parks
|Areas without official
1 The giant otters observed in the TCO Tacana
were not included
The giant otter is a rare species in Bolivia and is found only in National
Parks and in remote areas. According to preliminary estimates, the minimum
population size is 350 individuals. However, the effective population size is
much smaller, considering that each family group consists of only two adults.
The population status is particularly alarming in the white-water floodplains of
the Amazon (Mamoré, Beni and Madre de Díos river basins), though low estimates
may partly reflect low research effort in this area. In the Iténez-Guaporé
river basin, however, relatively healthy populations can be found in the
black-water floodplains of the rivers San Martin, Paraguá, Paucerna, Iténez
One of the central issues in conservation science is the degree of isolation
of animal populations. EISENBERG (1989) and EISENBERG
and REDFORD (1999) indicated that the actual giant otter populations have a
patchy distribution in the Amazon, with little possibilities of gene
interchange. Connection of Peruvian and Bolivian populations in Peru is highly
probable considering the conservation status of the border area (Bahuaja-Sonene
and Madidi National Parks in Peru and Bolivia, respectively). The nearby
populations in Brazil (> 500 ind.) can be found in the Bolivian Pantanal (SCHWEIZER,
1992; CARTER and ROSAS, 1997), but connection between
the Amazon and Pantanal populations is less probable given the fact that the
Pantanal belongs to the La Plata river basin and that interchange can only be
realized over land, which is heavily affected by deforestation. In the Brazilian
states of Rondonia and Mato Grosso, some conservation units neighbouring the
Noel Kempff Mercado and Iténez National Parks might also harbour giant otters,
though so far there are no otter reports from these areas.
Within Bolivia, connection between the upper Iténez and middle Iténez
populations is highly probable (subpopulations A and E in Fig.
1). The major human impact on this river is commercial navigation and
commercial fisheries, but it is thought that these activities do not disrupt the
function of the River Iténez as a corridor for giant otters. The population in
the upper San Martin and Negro rivers (subpopulations C and D in Fig.
1) may be relatively more isolated as they are separated from the lower
river populations by a colonized area, characterized by increased deforestation
and habitat destruction. Interconnections of the populations of the Blanco y
Negro protected area (subpopulations C and D in Fig. 1)
and the Noel Kempff Mercado National Park (subpopulation B) might be realized by
individuals that cross terra firma forest. According to some authors (WALLACE,
pers. obs.) giant otters may cross high forest stretches, but the relative
importance of this terrestrial route is not known.
In Surinam and Guyana, the giant otter seems to prefer slow-moving rivers
with transparent water (DUPLAIX, 1980; LAIDLER,
1984). This also seems to be the case in Bolivia, where giant otters are
predominantly found in the so-called black- or clear-water rivers that drain the
Precambrian Shield. These rivers are characterized by a high water transparency,
abundance of submerged and emergent macrophytes (KILLEEN and
SCHULENBERG, 1998) and the occurrence of steep riverbanks. The giant otters
prefer the downstream segments of these rivers, upstream parts probably not
providing enough food to sustain viable populations.
In the past, giant otters probably inhabited white-water oxbow lakes, an
otter habitat similar to the one described for this species in the Manú and
Bahuaja-Sonene National Parks in Peru (SCHENK and STAIB, 1998;
GROENENDIJK et al., 2001), and in lakes of tectonic
origin. This is indicated by their relict presence in these habitats in the
white water floodplains of the rivers Mamoré, Beni and Madre de Díos. There
are also indications that they occurred historically in the clear water
tributaries of these white water rivers. The white water river channels
themselves were possibly used as corridors for colonization of new river
stretches or lakes.
There are strong indications that general habitat characteristics determined
the original distribution patterns of giant otters in Bolivia. Other factors,
such as food availability, and carrying capacity may become important in smaller
river basins where the carrying capacity for giant otters is reached, such as on
the rivers Paraguá, San Pedro and San Martin in the Iténez river basin. In
some of these rivers, competition for fish with fishermen may already occur (van
DAMME et al., in prep.). The spatial distribution and the abundance of the fish
resource may also determine giant otter group size. For example, in the lower
San Martin river, large groups of up to 20 individuals (possibly 2 or 3 family
groups that temporally feed together) are sometimes formed around fish-rich
river stretches that dry up in summer (TEN, pers. obs.).
Nevertheless, current distribution pattern of giant otters in Bolivia may
reflect the ease of human access to areas where giant otters originally
occurred. The giant otter is extremely susceptible to hunting pressure. Its
large size, diurnal activity and social behaviour make it an easy prey for
fishermen who assert that giant otters compete with them for fish, and to
occasional hunters in search of a trophy (OJASTI, 1996; GROENENDIJK
et al., 2001). The negative correlation between human population density and
otter occurrence suggests that human presence represents a major threat to the
species and is probably related to the booming skin trade of the last century,
In Bolivia, occasional kills, habitat loss and disturbance caused by river
traffic seem to be important causes of current population stagnation or decrease
(van DAMME et al., 2002). Mercury contamination (MAURICE-BOURGOIN
et al., 1999) and demographic isolation of populations may represent
additional threats that will need to be seriously considered in the future. This
situation makes the development of national research and conservation strategies
for the species a pressing priority, particularly given the flagship nature of
the species, the globally threatened situation for giant otters, the probable
ecological importance of the species, and the potential economic importance in
terms of ecotourism opportunities.
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van Damme, P.A., Ten, S., Wallace, R., Painter, L.,
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Distribución y estado de las poblaciones de londra Pteronura brasiliensis
en Bolivia. Revista Boliviana de Ecología y Conservation Ambiental.
Résumé : Répartition et Statut des Populations de
Loutres Géantes Pteronura brasiliensis en Bolivie
La loutre géante (Pteronura brasiliensis) est l'une des espèces de
mammifere les plus menacées de la ceinture néotropicale. En Bolivie, les
effectifs des populations se sont effondrés du fait du braconnage durant les
années 50 et 60. Récemment, 14 lutrologues ont produit une première carte de
répartition, estimant à environ 350 l'effectif total de loutres géantes
subsistant dans le pays. Le présent article rapporte brièvement les
connaissances les plus récentes concernant la répartition et le statut des
populations de l'espèce sur les bassins boliviens de 1'Amazone et du Rio del
Plata. Est ensuite étudiée la correspondance entre groupes familiaux de
loutres, hydro-ecorégions et Parcs Nationaux. Les possibilités de brassage
entre differéntes sous-populations boliviennes de loutres sont enfin
Revenez au dessus
Resumen: Distribución y Estado Poblacional de la
Nutria Gigante Pteronura brasiliensis en Bolivia
La nutria gigante (Pteronura brasiliensis) es uno de los mamiferos más
amenazados de la región Neotropical. En Bolivia ha sido reducida a muy poco
números como resultado de la caza durante los 50s y 60s. Recientemente 14
especialistas en nutrias han publicado un mapa preliminar de distribución en el
que se estima que aproximadamente unos 350 individuos existen en Bolivia. En
esta nota presentamos brevemente información mas reciente sobre la
distribución y el estado poblacional de esta especie en la cuenca boliviana de
los ríos Amazona y del Plata. Además comentamos la superposición de grupos
familiares de nutria gigante con hidroregiones y parques nacionales. Por ultimo,
presentamos una breve discusión sobre las posibilidades de intercambio entre
las subpoblaciones bolivianas de la especie.
Vuelva a la tapa
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