pteronura brasiliensis monitoring study

Transcription

PTERONURA BRASILIENSIS MONITORING
STUDY
© Nicole Duplaix: http://animals.nationalgeographic.com
Author: Mónica Gallego Peñalva
July 2014
Pteronura brasiliensis Monitoring Study: July 2014
Contents
Introduction .......................................................................................................................................... 3
i. The Importance of Giant Otters in the Ecosystem ......................................................................... 3
ii. Meeting the Requirements of the Natural Forest Standard .......................................................... 3
1. Description of Giant Otters (Carter and Rosas 1997) ........................................................................ 4
1.1 Morphology ................................................................................................................................ 4
1.2 Diet ............................................................................................................................................. 4
2. Habitat and ecology (Carter and Rosas 1997) ................................................................................... 5
3. Distribution in Brazil and Abundance (Carter and Rosas 1997) ......................................................... 6
4. Threats (Carter and Rosas 1997) ....................................................................................................... 8
4.1 Hunting ....................................................................................................................................... 8
4.2 Colonisation and Deforestation .................................................................................................. 8
4.3 Hydroelectric Dams ..................................................................................................................... 8
4.4 Mining ......................................................................................................................................... 9
4.5 Fossil fuels ................................................................................................................................... 9
4.6 Industrial pollution...................................................................................................................... 9
5. Monitoring Giant Otters (Habitat, 2005)......................................................................................... 10
5.1 Distribution survey .................................................................................................................... 10
5.2 Characteristic Signs of Giant Otter Presence – Campsites, Dens and Tracks ............................. 11
5.2.1 Campsites ........................................................................................................................... 11
5.2.2 Latrines .............................................................................................................................. 11
5.2.3 Dens ................................................................................................................................... 11
5.2.4 Tracks ................................................................................................................................. 12
5.2.5 Cylindrical scats .................................................................................................................. 12
5.2.6 Scratch walls ...................................................................................................................... 12
5.3 Population census ..................................................................................................................... 13
5.3.1 Ageing a Giant Otter Campsite or Den ............................................................................... 13
5.3.2 Recording Tracks ................................................................................................................ 13
5.4 Observing, Counting and Recording Giant Otters ..................................................................... 14
5.4.1 Throat markings ................................................................................................................. 14
5.4.2 Surveying in a paddle boat ................................................................................................. 14
5.4.3 Counting individuals ........................................................................................................... 14
5.4.4 Determining age classes of individuals ............................................................................... 15
Trocano Araretama Conservation Project - Pteronura brasiliensis Monitoring Study 2014
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5.4.5 Sexing individuals ............................................................................................................... 15
6. Survey Protocol ............................................................................................................................... 15
6.1 Essential Survey Equipment ...................................................................................................... 15
6.2 Seasonal timing ......................................................................................................................... 16
6.3 Periodicity of surveys ................................................................................................................ 16
7. Monitoring Otters in the Project Area ............................................................................................ 16
8. Conclusion....................................................................................................................................... 18
9. References ...................................................................................................................................... 19
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Introduction
i. The Importance of Giant Otters in the Ecosystem
The giant otter is a predator at the top of the aquatic food chain. This means that they play an
important role in the nutrient cycle by transferring nutrients from one ecosystem to another. They
take nutrients from the aquatic ecosystem by feeding upon fish and other aquatic organisms and
then transfer those nutrients to the terrestrial ecosystem by depositing their waste on land, feeding
the plants that are in the forest (KentuckyAwake.org 2011).
Furthermore, as otters consume many animals (predominantly fish), an absence of otters would
result in a lack of regulation of prey populations, and an overabundance of smaller animals (and
possibly non-native species that could further threaten the ecosystem) can deplete the other
animals and plants in the food web, disrupting the balance and resilience of the whole system.
Without otters, the ecosystem can become unstable (Paws.org 2014).
Otters are good “indicator species,” allowing us to learn how well our clean water efforts are
working by monitoring otter populations, since they can only live in a river completely void of
pollution. As charismatic and cute animals, they also serve as great ambassadors for connecting
people with the importance of protecting their local watersheds (AquariumOfTheBay.org 2014).
ii. Meeting the Requirements of the Natural Forest Standard
The Natural Forest Standard (NFS) is designed to be applied to large areas of natural forest. It is a
uniquely designed voluntary carbon standard that integrates social, biodiversity and carbon values
for REDD forest projects. As these forests are likely to have high ecological significance, the
biodiversity management element of the project is vital in ensuring the project has a positive impact
and it should be ensured that there is ‘no net loss of biodiversity’ arising from the project’s existence
in comparison to a baseline situation without the project.
To achieve this, the standard requires projects to take appropriate measures for protecting the
existing biodiversity within the project area, and requires an understanding of the ecosystems and
species present within and around the project area. Knowledge of the threats and likely causes of
biodiversity loss and mitigation actions to avoid biodiversity loss in the project area should be
considered as part of project implementation.
In order to determine which species reside in the project area, several studies such as the one
carried out by INPA in the book, “Biodiversity in the Madeira River: set the ground for the
conservation” were researched. Through this we discovered that many species, such as the
Pteronura brasiliensis (commonly known as giant otters), are endangered.
Taking this information into account, we will carry out a comprehensive study of Pteronura
brasiliensis with the intention of maintaining the current population and ultimately conserving their
presence in the project area. The methods we will employ are in compliance with the NFS, and will
subsequently conserve not only the endangered species, but also the forest itself through the
consequential positive impacts of biodiversity monitoring.
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1. Description of Giant Otters (Carter and Rosas 1997)
1.1 Morphology
The giant otter is the largest of the four Latin American otters. Their total body length typically
ranges from 1.5 to 1.8 m in males and 1.5 to 1.7 m in females (Hershkovitz 1969; Mondolfi 1970;
Duplaix 1980). Historically, considerably larger measurements were reported: Cabrera & Yepes
(1940) state that old males with a total body length of 2.20 m have been hunted. The giant otter is
the only species of otter in which the rhinarium (moist surface surrounding the nostrils) is
completely covered in hair (Foster-Turley et al 1990) and each individual can be identified from birth
by the irregular pattern of whitish or cream-coloured hairs on their chin and throat. The thick coat is
composed mainly of short, soft guard hairs, 8 mm long; there is very little underfur (Foster- Turley et
al 1990). Fur colour varies from fawn to reddish brown or darker, appearing almost black when wet
(Harris 1968; Husson 1978). Two anal scent glands are used in territorial marking and may be
involuntarily contracted if the animal is startled (Duplaix 1980; Laidler 1984; D.K. Carter personal
observation).
Figure 1: Giant otter resting on branch. Source: Arkive.org
1.2 Diet
Direct observation and faecal analysis in various regions have revealed that fish constitute the
majority of the giant otter’s diet. They generally fish in the shallow margins of lakes and rivers
(Duplaix 1980; Defler 1983; Brecht-Munn& Munn 1998; Schweizer 1992) where fish density is high
(Lowe-McConnell 1975). Giant otters may catch up to 3.2 fish/h/otter in shallow water (<0.60 m),
while hunting in deeper water (3-10 m) is much less rewarding (1.8 fish/h/otter) (Laidler 1984). Wild
adults consume an estimated 3 kg of fish daily (Duplaix 1980; Schweuzer 1992).
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Most fish consumed by giant otters belong to the suborders Characoidei (characins), Percoidei
(perch) and Siluroidei (catfish). Species are consumed in varying amounts according to their relative
abundance and vulnerability to giant otter predation. Although some authors have observed giant
otters eating enormous catfish (probably Pseudoplatystioma fasciatum, which easily attain lengths
of over 1 m) in the Amazon and Orinoco basins (Mondolfi 1970; Santos 1984), Characoids appear to
be the most widely consumed prey of giant otters.
In only one study did an invertebrate species occur in a significant portion of spraints (otter faeces):
Duplaix (1980) found crab remains in 40% of analysed samples with most of them being single
spraints that appeared to be deposited outside the core areas of home ranges, tentatively
suggesting that crab may have been a prey item consumed on seasonal visits to outer limits of the
home range. In all other studies, mammal, amphibian, reptile, bird, crustacean and mollusc remains
were rare (Laidler 1984; Benetton et al 1990; F.C.W. Rosas et al unpublished data). Other
vertebrates consumed in other locations include anacondas under 3 m, other snakes under 2 m,
black caimans under 1.5 m and turtles (Laidler 1984; Brecht-Munn & Munn 1998; Schenck & Staib
1992; Martuscelli in press).
Graph 1: Seasonal analyses of the frequency of fish families. Source: Marcia et al 2010
2. Habitat and ecology (Carter and Rosas 1997)
Giant otters inhabit many types of rivers, creeks and lakes in the tropical forests, llanos and wetlands
of South America. Slow moving rivers and streams and oxbow lakes are preferred (Duplaix 1980;
Schenck and Staib 1992). Some authors report that giant otters prefer larger rivers (Mondolofi 1970;
Donadio 1978), although they also frequently inhabit smaller forest creeks (Duplaix 1980; S.K Carter
&F.C.W. Rosas personal observation) and occasionally reservoirs of large dams (Laidler 1984; Colares
1988) and agricultural canals (Chehebar 1990). A decided preference is shown for black or clear
waters (Mondolfi and Trebbau, 1978; Duplaix 1980; Scheweizer 1992).
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In seasonally flooding areas, territories are defended continuously throughout the dry season in
order to exploit the influx of fish (Duplaix 1980; Schweizer 1992). In more stable environments, giant
otters may display cyclic foraging patterns; visiting and defending specific territories for a 2-3 day
period every 2-3 weeks (Fugger 1981; Laider 1984). They are most often constructed on shaded level
ground that has little ground cover and easy access to small forest creeks, swampy areas, or
shallower waters of larger rivers (Duplaix 1980; Laidler 1984; S.K. Carter & F. C. W. Rosas personal
observation). High banks, which seldom or never flood, are preferred over lower areas and low
human disturbance, which is also important in site selection (Duplaix 1980; Laidler 1984).
Giant otters generally live in groups of three to nine individuals, consisting of a mated pair and one
or two litters. Group size varies with region, habitat and season. Occasionally ‘super-groups’ of 12-20
individuals are observed that may be a result of grouping around plentiful food sources or groups
temporally travelling together (Mondolfi 1970; Duplaix 1980; Laidler 1984).
Individuals not living in family groups are referred to as transients. Transients may be sub-adults
recently split from their family group or adults which have lost a mate. They lack established
territories and are usually shy and difficult to sight. Associations observed between transients and
family groups with sub-adults nearing dispersal age may indicate a preliminary form of mate
selection (Laidler 1984; Schweizer 1992).
Giant otters are exclusively diurnal. Family groups may travel over 17 km daily, alternately fishing
and patrolling their territories (Laidler 1984). In their natural habitat, these otters spend
approximately half of their time hunting, travelling, and patrolling their territories and half resting
and marking ashore (Duplaix 1980; Schweizer 1992). Recent observations by the authors of captive
adult female at the National Institute of Amazonian Research (INPA), showed that 42.9% of daylight
hours were spent in aquatic activities, 26.2% in terrestrial activities, 5.5% eating and 26.3 % resting.
3. Distribution in Brazil and Abundance (Carter and Rosas 1997)
The giant otter originally inhabited most of South America, ranging from the Guyanas across
Venezuela and Colombia, southern to northern Argentina and west to the Andes (Harris, 1968;
thornback and Jenkins 1982). Although the latitudinal range of the giant otter remains large, intense
pelt hunting greatly reduced their numbers and completely eliminated populations in many localised
areas. The current population of giant otters may be as low as 1000 - 3000 individuals (Brecgt-Munn
1988). However, this is probably an underestimate as 500 inhabit the southern portion of the upper
Paraguai river basin of Brazil alone (Schweizer 1992). The presence of giant otters has been
confirmed in each location within the last 25 years unless otherwise noted.
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Map 1: Distribution of Pteronura brasiliensis in South America. The project area and the boundaries of the
Legal Amazon of Brazil are also shown.
In Brazil, the Amazon encompasses 5 million km2 of sparsely populated land and most likely supports
a significant population of giant otters in remote areas, although this is unconfirmed due to the
logistical problems of surveying an area this large. In the Madeira river basin, giant otters were
present in 1979 on the Canuma, the Aripuana and its Branco tributary (C.R. Bueno personal
communication; K. Yuyama personal communication) and groups were sighted on the Roosevelt
river in 1992 (J. Ferraz personal communication; G.M Santos personal communication). Sizable
populations are reported from the upper Jamari (C. Colares, personal communication) and a group
was shifted in Paraiso Creek of the Ji-Parana in 1987 (P. Martuscelli personal communication). In the
Uatuma river basin, giant otters are present in the area of balbina hydroelectric dam (F.N. Armond
personal communication; Colares 1988) and groups were observed on the Pitinga River in 1994 (A. A.
Sourza personal communication; Colares 1988). Sizable populations are reported from the upper
Jatapu River (C. Colares personal communication).
Further east in the Amazon, the IUCN (1982) reports giant otters in Tapajos national park and Ique
ecological station, and George et al (1988) state that they are most likely present on remote
tributaries of the Tapajos. Giant otters were reported in the Trombetas river federal biological
reserve by the IUCN (1982), and groups were observed on a tributary of the upper Trombetas and on
the Curuana River in 1985 and 1982, respectively, (C, Py-Daniel personal communication; Salvo
Souza 1982). The IUCN (1982) reports that the species inhabits the Piratuba Lake in the federal
biological reserve and Araguaia national park, whose groups still inhabit the Paraim River of the
upper Tocantins basin (C. L. Magalhanes personal communication, Lima and Lima 1984). Almeida,
Pimentel and Pimentel (1992) indicate that the otters are present in Maranhao state but give no
specific distribution information.
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4. Threats (Carter and Rosas 1997)
4.1 Hunting
Giant otters can be easily located on account of their noisy diurnal habits and conspicuous
campsites. These characteristics, combined with the high value of their pelts (Doughty and Myers
1971; Donadio 1978; Ayres and Best 1979), led to extensive uncontrolled hunting in the 1950s and
1960s. Official statistics indicate that over 40,663 pelts were exported from Brazil alone from 1960
to 1967 (Best 1984). This is probably a gross underestimation of the actual number of otters killed
because 60% of animals sink before they can be recovered by hunters (Combra- Filho 1972); any
dependent cubs are effectively killed with the death of a parent; and the sale of many skins never
appear on official records because of smuggling or under-invoicing by exporters (Donadio 1978).
Small numbers of giant otters are also hunted for meat by Amerindians in Colombia and Guyana
(Laidler and Laidler 1983; Defler 1986), captured for the zoo trade (Schweizer 1992) and robbed by
locals from their dens as cubs to be sold or kept as pets (Duplaix 1980; S.K. Carter and F. C. W. Rosas
personal observation). However, the current effect on the overall population from direct capture or
killing of animals is minor compared with the increasing threat to existing populations from habitat
loss and degradation.
4.2 Colonisation and Deforestation
The increasing development and subsequent human invasion of vast tracts of tropical forest is
rapidly making many areas incapable of supporting giant otter populations. Colonisation of the
Amazon basin has historically been limited to the areas along navigable waterways, but recently
many roads have been built by logging and mining companies and for government projects. This
opens up large areas to invasion by hunters and settlers and consequently more people must
depend on the river for food, as fish is their principal source of animal protein (Santos, Ferreira and
Zuanon 1991). Also, the nutrient-poor soil in the amazon basin will support agricultural crops and
cattle pasture for only 3-4 and 100 years, respectively, which leads to further clearing and burning of
the forest.
4.3 Hydroelectric Dams
Hydroelectric dams have been constructed on rivers throughout the Amazon, Orinoco and La Plata
Basins. The majority of rivers selected for damming are black or clear water (Junk and Nunes de
Mello 1987), the favoured habitat of the giant otter. Thus, the fate of aquatic fauna in these
reservoirs and their future suitability as the otter’s habitat is of great importance to them.
Dams make formerly inaccessible areas accessible, leading to the indiscriminate exploitation of
natural resources in the area and potential invasion by hunters (Junk and Nunes de Mello 1987).
Three years after damming the Tocantins River at Tucurui (Brazil), the fish population remained
unstable, and biomass and species diversity were significantly decreased (Leite and Bittencourt
1991). In Suriname, the Brokopondo reservoir was still relatively poor in aquatic fauna and flora after
20 years (Junk and Nunes de Mello 1987).
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4.4 Mining
Gold mining is common in areas of the Orinoco and upper Paraguai river basins, and on rivers
throughout the Amazon basin including the Madre de Dios, Madeira, Negro, Branco and Tapajos.
This produces large amounts of suspended particulate matter in the water, which interferes with
light penetration, buries bottom-dwelling algae species and asphyxiates fish (Alho, Lacher and
Goncalves 1988). Once sludge is removed, mercury is used to separate and amalgamate the gold
particles. Approximately 1.3 - 4.0 kg of mercury is released into the surrounding environment for
each 1.0 kg of gold produced (Mallas and Benedicto 1986; Pfeiffer and Larceda 1988). Recent
research by Forsberg et al (in press) has shown that mercury contamination is especially critical in
black-water-rivers, which promote naturally high mercury concentrations because of their low pH
and conductivity, and high content of dissolved organic material.
Once in the aquatic ecosystem, metallic mercury may be changed to its more dangerous organic
form (methylmercury) and transferred through the food chain, magnifying at successive trophic
levels. Predatory fish accumulate significantly higher concentrations of mercury in their fat tissue
than herbivorous and omnivorous species from the same area of the Amazon (Martinelli et al 1988;
Forsberg et al in press, C. R. Padovani B. R. Forsberg & T. Pn. Pimientel, unpublished data). Kucera
(1983) found that North American river otters accumulate 10 times more mercury than predatory
fish. Bioaccumulation has been demonstrated in giant otters as well, which is accumulated in the
hair, liver, kidney, muscle and brain tissues, causing progressive central nervous system
deterioration and death (O, Conner and Nielsen 1980; Kucera 1983; Wren 1986).
The most dangerous consequence of mining other mineral resources such as bauxite, iron and coal
in the Amazon may be the accompanying development, resulting in large areas of forest being
disturbed, cleared or settled as the mining companies develop the surrounding area to further aid
their mining objectives.
4.5 Fossil fuels
Oil is currently exploited in the Orinoco and far western Amazon basins and recently large deposits
of oil and natural gas have been discovered in the Urucu and Jurua River basins in the western
Brazilian Amazon (Johns 1988). The road building involved in oil exploration often leads to invasion
of these areas by settlers, as happened in the Cuyabeno Wildlife Reserve and will likely happen in
Yasuni National Park, both legally protected areas in Ecuador inhabited by Pteronura brasiliensis
(Collins 1990). During drilling and recovery, there is the risk of a spill or blow-out along with further
contamination of water system from oil, effluents and drilling mud (a mixture of clay, water,
chemicals and sometimes oil) (IUCN 1991). Contamination is extensive in Ecuador where ruptures in
one main pipeline have spilled over 16 million gallons of oil into the water system in the last 20
years. The petroleum industry dumps ten thousand gallons of untreated toxic waste into the
watershed daily (Kane 1994).
4.6 Industrial pollution
Industrial pollution in the more developed Paraguai, Orinoco and La Plata basins have also affected
aquatic fauna. Alcohol distilleries in the Pantanal produce large amounts of stillage, a by-product of
the sugar cane distillation process. The distilleries widespread discharge of stillage into the water
causes eutrophication and oxygenation of water, alters its temperature and pH, and has been linked
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to numerous fish deaths (Alho et al 1988). In the Orinoco, the heavy use of pesticides in the
Portuguesa and Cojedes sub-basins has caused fish mortality (Colonnello 1990), and the new
industrial development project in the basin includes plans for a wood pulp processing plant and a
large crude oil refinery that would likely increase pollution in other areas. Changes have also been
observed in fish species of lower La Plata basin, a system polluted with agricultural and industrial
toxic substances and altered by various hydroelectric dams (Quiros 1990).
5. Monitoring Giant Otters (Habitat, 2005)
The purpose of the monitoring is to figure out where the giant otters are, how many of them we
have in the project area, as well as obtaining an estimation of the absolute or relative population
abundance. In doing so, we will be able to control the information for the future, distinguishing any
change in its population or in its presence. The absence of the otter, or particularly a population
decrease, in a specific area would represent an opportunity to better examine the reasons for
decline (hunting, habitat loss) in that specific place. Later, we would be able to propose accurate
mitigation actions that improve the conditions of the otters in the project area.
A standardised otter monitoring method is recommended by the Pteronura brasiliensis section of
the IUCN/SSC Otter Specialist Group. Therefore, we are going to proceed using this methodology,
covering the following monitoring steps:
-
-
-
Distribution survey
The main objective of a distribution survey is to determine the spatial occurrence of the
species within a given area, expressed in terms of presence or absence.
Population census
A population census aims at counting all giant otter individuals within a defined survey area
in order to determine population size.
Relative abundance survey
Incomplete counts of individuals within the total or sample area, or complete counts within
a sample area, using established sample count techniques, allow us to estimate absolute or
relative population abundance.
5.1 Distribution survey
When conducting a survey, identifying signs of the Pteronura brasiliensis activity such as campsites,
dens, and tracks is sometimes the only means by which presence of the species can be confirmed.
Familiarity with existing giant otter literature, especially descriptions (including photographs and
measurements) of the campsites, dens, and tracks is therefore necessary.
Correctly identifying a giant otter den or campsite is all that is required in a distribution survey;
estimating whether it was used recently or not is unnecessary.
During a distribution survey, all signs are identified by sight and are recorded by a GPS receiver (the
GPS should be given sufficient time to acquire its satellite locations before writing down the
reference point). Surveyors also must record all survey site start point and end point positions in the
decimal geographic degree format and the UTM format, and with the datum of WGS 84.
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5.2 Characteristic Signs of Giant Otter Presence – Campsites, Dens and Tracks
5.2.1 Campsites
Campsites are recognisable as irregularly-shaped patches of land on the banks of water bodies,
which have been cleared of vegetation (if present) and are used for defecating, scent marking,
drying out, grooming and resting (Duplaix 1980, Laidler 1984, Schenck 1999, Staib 2002). A campsite
may be used once only and then never again, or for many years (even decades) by different groups
(Staib 2002, Duplaix 2003), so it is important to specify which kind of campsite we are discussing.
Figure 2: Campsite on a river bend, Xixuau Reserve, Amazonas, Brazil. Source: Habitat, E. Evangelista
Evolution of the physical appearance of a campsite:
-
When very fresh, the campsite’s odour is powerful, fishy and may carry far.
As the days pass (and the campsite is not re-visited), insect activity gradually decreases and
the bees, ants and butterflies may be replaced by termites.
With increasing age, fish scales become separated and are dispersed by insect & bird activity
and rain, the odour becomes mustier and leaf litter starts to accumulate.
It is very important to note that the evolution of the appearance of a given campsite is:
-
Highly weather related,
Dependent on location (e.g. a campsite under dense, overhanging vegetation appears
fresher for longer than one fully exposed on a beach),
Dependent on whether the otters have used the site repeatedly (visits may be spaced
several days apart, or the site may be visited daily for a period of time).
5.2.2 Latrines
Within each campsite there is one or more latrine area of varying freshness, often on the periphery
of the site, characterised by the presence of scales and other hard fish remains such as vertebrae,
otoliths, teeth and large spines (for this reason, people sometimes say campsites are places where
giant otters eat their prey).
5.2.3 Dens
A den consists of one or more tunnels leading to one or more oval chambers excavated into the
bank of a water body. A recently used den is indicated by:
-
Moist, trampled vegetation,
A muddy ‘slide’ or concave path (through repeated use), and/or numerous tracks that lead
from the entrance directly to the water’s edge,
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-
Usually at least one latrine which is often located either directly in front of or to one side of
the den entrance, or in the immediate vicinity.
Figure 3: Den high above water level, Balbina, Amazonas, Brazil. Source: Habitat, E. Evangelista
5.2.4 Tracks
The most distinctive features of giant otter’s tracks are their size and their elongated toes, rather like
the prints made by the tips of human fingers. Tracks are not only associated with dens and
campsites; the otters often walk over shallow beaches or river banks, and their tracks may provide a
useful hint of the direction they were travelling in.
5.2.5 Cylindrical scats
In most regions of the Pteronura brasiliensis’ range, the otters’ spraint does not have a defined
shape, are usually trampled on campsite latrines, and are not deposited singularly.
Duplaix (1980, 2003) hypothesises that giant otters deposit cylindrical scat seasonally and only in
certain types of habitats, namely rocky, flat granite plateaus where rivers in the dry season are
studded by numerous islands, sand bars and outcroppings. In the wet season, these cylindrical scat
sites are submerged and the otters resort to campsites (some of which are the same as during the
dry season) that tend to be spaced further apart.
5.2.6 Scratch walls
A ‘scratch wall’ is a vertical, often clayey patch of bank, usually near a den or campsite, which is
covered in long, deep scratch marks. These may be visible for many weeks or months after the den
or campsite was last used and may therefore be a deliberate visual signpost.
Figure 4: Scratch wall at mouth of small creek, Palma Real River, Peru. Source: F. Hajek
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5.3 Population census
5.3.1 Ageing a Giant Otter Campsite or Den
During a population census, dens and campsites are recorded as being either ‘not recently in use’ or
‘recently in use’, in order to determine zones of recent activity where more time needs to be spent.
The word ‘recently’ may have different meanings for different surveyors; therefore, here ‘recently’ is
broadly defined as meaning up to an estimated two weeks prior to the surveyor’s visit.
The three primary factors (in order of priority) for determining whether a site is ‘recently in use’ are:
- Presence of dispersed fish hard parts,
- Appearance of vegetation trampled by giant otters during marking,
- Clarity of tracks
All are influenced by recent and current weather conditions.
A campsite is only recorded as ‘recently in use’ if:
- Dispersed fish hard parts are present
- Moist trampled vegetation and/or clear giant otter tracks leading up to, or in, the site are
present
A den is only recorded as ‘recently in use’ if:
- Dispersed fish hard parts are present together with either moist trampled vegetation and/or
clear tracks leading up to, or in, the entrance
- Fish hard parts are absent, but moist trampled vegetation and clear tracks leading up to, or
in, the site are present
Figure 5: Giant Otter periscoping1 at the surveyor. Cocha, Balbina Reservoir, Amazonas, Brazil.Source:
Habitat, N. Duplaix
5.3.2 Recording Tracks
Tracks are only recorded if found to not be associated with dens and campsites, or if found on dens
and campsites where the latrines have not been recently used (possibly indicating a visit by a
transient).
1
Periscoping is defined as the emergence of the otters from the water with their heads held straight so they can observe
their surroundings
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5.4 Observing, Counting and Recording Giant Otters
5.4.1 Throat markings
Giant otters have irregular, pale throat patterns, each of which is unique like a person’s fingerprint
(Dupliax 1980). These throat markings greatly facilitate identification of individuals from birth.
When there is any doubt as to otter species, a giant otter sighting should not be recorded. In this
way, for identifying otters through their throats there are two options: filming and photography.
5.4.2 Surveying in a paddle boat
At least two people are necessary to efficiently and simultaneously count and film a group of
Pteronura brasiliensis. It is when the animal ‘periscopes’ or rests on land that throat markings are
obtained most easily; ideally, with the aid of binoculars to scan the river ahead or the shoreline in
order to observe the otters before they see the surveyor. Then there are five options:
-
To approach the group, very slowly and discreetly so that the surveyor remains unobserved,
To approach without the surveyor attempting to conceal him/herself,
For the surveyor to hide amongst vegetation by the shore and wait for the otters to
approach,
To directly head towards the group and actively ‘force’ a periscoping situation, or
To follow the group at a distance, while it is aware of the surveyor’s presence.
5.4.3 Counting individuals
When a large family of giant otters is first encountered, it is easy to gain the impression that there
are at least twenty animals. Giant otters, particularly transient individuals, may travel large distances
(tens of kilometres) within a short space of time. Groups may split up into smaller sub-units for short
periods.
Total number of otters per group is not a criterion for group identification. If less than 60% of throat
markings are obtained per group, two different sightings of groups must be spaced at least 40km
apart, for the groups to be considered different.
While one person is filming, the other concentrates on repeatedly counting the otters,
simultaneously assisting the cameraman by positioning the boat and by pointing out which animals
are hanging back. The number of individuals recorded is the total number of heads that are seen
together above water at any single moment, or the total number of different neck markings filmed
after an encounter. Thus, if four individuals are seen simultaneously at one point, and the surveyor
strongly suspects there is another, but all five heads were not observed out of the water together,
then the census total for the family should be noted as Σ ≥ 4, indicating that a minimum of 4
individuals was encountered.
If the group is large (say, 8 individuals or more), it can take an experienced surveyor several days to
establish with complete certainty the total number of individuals. Counting does not necessitate a
periscoping situation.
14
5.4.4 Determining age classes of individuals
In order to determine population size all we are interested in is otter numbers. However, as
population censuses are, and probably will continue to be, often associated with studies of
demographics or population dynamics, surveyors are also interested in determining age classes of
individuals.
5.4.5 Sexing individuals
Sexing is only possible when individuals are entirely out of the water, usually when basking or
grooming on logs. It is sometimes possible to film the otters as they emerge from the den first thing
in the morning or as they enter at dusk. These are excellent opportunities to film throat markings
and to establish the sex of individuals. However, it carries a high risk of disturbance and should never
be carried out during the beginning of the dry season when cubs are very young and especially
vulnerable.
6. Survey Protocol
6.1 Essential Survey Equipment
-
-
-
-
A motor-powered, wooden or aluminium canoe/boat for transport along rivers is needed.
The length of the boat is determined, amongst other factors (e.g. duration of survey), by the
type of river to be surveyed, with shorter boats or canoes being more manoeuvrable in
narrow, shallow rivers, especially during the dry season. When actually carrying out the
survey, only a low-power motor is necessary. In other areas, two-stroke outboard motors
are used (15 or 25HP). Nowadays, there are also four-stroke boat engines available which
are considerably more silent than the traditional outboard. They are more expensive, but
they consume less gasoline and do not require oil.
Two-person, robust, stable, inflatable boat (not the swimming pool type) for use on lakes or
paddling downriver. An inflatable boat is used to survey slow-flowing streams and lakes
(since it can be easily carried overland in a backpack frame) and can be stored in a spine/tear
resistant canvas bag with lightweight paddles, a pump for inflating the boat plus a spare, and
a suitable kit to repair punctures, with extra adhesive.
A handheld GPS receiver that can be linked to a computer to download the data.
A digital video camcorder or mini-DV with a powerful zoom (20x or 30x) and at least two
long-life batteries (single batteries lasting up to 16 hours are now available at reasonable
prices) with spare cassettes and battery re-charger. Digital gives better image quality and
images can be sent to a computer, frozen and manipulated.
Semi-automatic camera with 300mm+ telephoto zoom lens, fill flash, and 300/400 ASA film.
A pair of good quality binoculars (10 x 40-50), preferably waterproof.
A robust, waterproof storage case and plenty of silica gel for all optical and electrical
equipment.
Maps (laminated and as up-to-date as possible) to the scale of 1:100,000 or lower (e.g.
1:50.000) should be used, if available for the survey area.
A satellite photograph or detailed map of the survey area will help to avoid loss of time
(through attempting to locate non-existent water bodies).
15
-
Notebooks, pens, pencils, felt markers, tape measure.
Throat pattern catalogue.
Laminated Field Tips sheets.
Survey data collection reports (including one laminated copy).
6.2 Seasonal timing
Seasonal timing of the distribution survey is critical. If a river or lake is surveyed only once a year, or
less frequently, then it is important to do so when water levels are low and rain is infrequent so that
dens and campsites are more easily encountered, recent activity is not erased, and the animals
themselves are more restricted to permanent water courses. However, it may prove necessary to
avoid the height of the dry season, since water levels can be so low as to make navigation
problematic.
Generally, it is recommended to conduct the distribution survey in the period of intermediate water
levels (at the end of the wet season / beginning of the dry season when banks are becoming exposed
and little rain is expected). The best period in each locality, however, is to be decided by the
surveyor, taking into account local climatic and hydrological conditions. It is suggested to initiate a
survey day in the early morning after first light and to finish before sunset (to avoid low light
conditions which make it difficult to distinguish giant otter signs from amongst the vegetation and
bank features). Although the otters are active throughout the day, there is a peak in activity
between 7 and 10am and a less marked increase in the late afternoon (Duplaix 1980 & Staib 2002);
these are times when giant otters are encountered most frequently. A break is recommended
around midday, to maximise surveyor ability to identify signs.
6.3 Periodicity of surveys
Ideally, a range-wide distribution survey should be initiated every 7 years, with each range-wide
survey being completed within a maximum time period of 5 years (the first 5 years of each survey
cycle).
During the last two years of each cycle, data can be analysed, interpreted and published. It seems
unrealistic at this stage to establish a tighter schedule. However, the time frame of 7 years should be
evaluated in due course because important Pteronura brasiliensis distribution changes might occur
within shorter time intervals.
These studies are generally limited to dry-season observations of a few animals or groups over a
relatively short period of time. Information on movement patterns, habitat use and diet during the
flooded season is scarce due to the labour-intense nature of observing aquatic mammals in areas of
extensive seasonal flooding.
7. Monitoring Otters in the Project Area
Giant otters were present in the Madeira river basin of the Brazilian Amazon in 1979, in the rivers:
Canuma, Aripuana and its Branco tributary (C.R. Bueno, personal communication; K. Yuyama,
personal communication) and groups were sighted on the Roosevelt river in 1992 (J. Ferraz personal
communication; G.M Santos personal communication). Sizable populations are reported from the
16
upper Jamari (C. Colares personal communication) and a group was shifted in Paraiso Creek of the JiParana in 1987 (P. Martuscelli personal communication).
Map 2: Giant otter’s presence in the project area. Source: CGV
For this reason it is highly likely that the otter species is present throughout the Madeira River,
which is in the Central Area of the project. However since funds and time are limiting factors, it will
be necessary to prioritise areas in order to obtain the best value for money and effort invested, in as
short a time frame as possible, but on the understanding that all other areas will also be surveyed
eventually (Reuther and Roechert 2005).
For that, we will define where the highest possibility of otters being present is. According to C.R.
Bueno, otters were spotted in the Madeira river basin, so we must focus our attention on this river
and its tributaries, combining this with data from people of the region who know and have seen the
otters in the rivers. Furthermore, information about areas where the fish is abundant is also crucial,
as the species feed primarily on fish.
17
It would be also proposed to categorise priority areas as:
-
Border areas that can be realistically surveyed,
Border areas that are currently difficult to survey,
Potential corridors between known populations, and
Imminent/actual threat areas (e.g. gold mining areas)
8. Conclusion
Pteronura brasiliensis is the largest of the four Latin American otters, whose population is decreasing
considerably due to hunting, mining, pollution, mines, dams and loss of habitat.
Their role in the ecosystem is crucial to its continued maintenance, as it regulates prey populations,
transfers nutrients from one ecosystem to another, and acts as a good indicator species for overall
habitat health.
Their distribution is generally centred on Brazil, where the species was observed in the Madeira
basin region. Thus, it is very likely that otters can be found in the project area, so we should monitor
them in order to determine their presence and absence, as well as their population.
However, as the Madeira River is a huge water body, we should prioritise the specific areas that we
are more interested in. Therefore, we should discover where it’s more probable for otters to be
located with the help of former studies, information about the spots with big fish populations (due
to their fish diet), and data from people who have seen them in nature.
Following this, we will monitor them in the chosen spots, and we will endeavour to discover the
causes of their disappearance, so that we can improve their conditions in the project area and help
to facilitate the conservation of the species and its habitat.
18
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