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159
Movement and habits of Eunectes notaeus
Open access at hp://www.salamandra-journal.com
© 2020 Deutsche Gesellscha für Herpetologie und Terrarienkunde e.V. (DGHT), Mannheim, Germany
15 May 2020 ISSN 0036–3375
SALAMANDRA 56(2): 159–167 SALAMANDRA
German Journal of Herpetology
Home range size, movement, and habitat use of yellow anacondas
(Eunectes notaeus)
N P. S, L F. B. M, J A. R C S,
1) Programa de Pós Graduação em Ecologia e Conservação da Biodiversidade, Instituto de Biociências,
Universidade Federal de Mato Grosso – UFMT, Brazil
2) Department of Biology, New Mexico Highlands University, USA
3) Faculdade de Medicina Veterinária, Universidade Federal de Mato Grosso – UFMT, Brazil
Corresponding author: N P. S, e-mail: npsmaniotto@gmail.com
Manuscript received: 24 October 2019
Accepted: 10 April 2020 by A S
Abstract. Movement ecology is an important tool for understanding animal behaviour toward basic needs, as well as to
design conservation and management priorities. Animals usually do not move randomly and may prefer certain types of
habitats over others. e yellow anaconda (Eunectes notaeus) is one of the largest snakes in South America. However, lit-
tle is known about its natural history. Here, we present results from a telemetry study to quantify movement patterns and
habitat use of eight yellow anacondas in a protected, seasonally ooded area in Midwestern Brazil. Yellow anacondas were
associated to small channels with macrophyte stands and bushy vegetation. ey moved relatively little ( m monthly)
and had small home range (mean . ha); they used native pastures and abandoned farmlands with forest patches more
than expected by chance. Our results contribute to the understanding of dispersal patterns, habitat choices, and life his-
tory of this large aquatic snake and to the body of knowledge needed for management and conservation of its populations
and habitats.
Key words. Squamata, Serpentes, Boidae, home range, wetland, landscape ecology, South America.
Introduction
Studies of animal movement have a long history, but recent-
ly they attracted enormous attention, because of advances
in tracking technology and analytical methods (K et al.
). Clearly understanding animal movements is crucial
to establish management priorities in undeveloped areas
with high diversity (V M et al. ). To under-
stand individuals’ movements and how they might con-
nect habitat selection and home range, we need to examine
a wide range of life-history trade-os and environmental
variability (N et al. ). ermoregulation and
weather conditions (i.e. temperature, relative humidity,
and wind speed) (M G , G
et al. ), foraging, local seasonal migrations, and mating
(R ) highly inuence snake movements and habi-
tat choice.
Large snake species can act as top predators in aquat-
ic and terrestrial ecosystems (H G ,
M ), and move in response to prey movements
(K D , S et al. ). ere is evi-
dence that individual movement rates and home range are
positively correlated with body size (P G J
, B-R et al. ). Vagile snakes with
large home ranges oen cross disturbed habitats, which
makes individuals more vulnerable to predation or anthro-
pogenic mortality, such as intentional killing or roadkill
(B et al. , J et al. ). Studies with
relatively large snakes have registered huge home ranges –
for both ambush and active foragers – but they also point-
ed a large individual variation in the home ranges. For ex-
ample, M et al. () registered for king cobra an
average of ha (–), while Burmese python has an
average home range of ha (–; H et al. ).
However, the two anaconda species studied so far seem to
be more sedentary, with a home range varying between .
and ha (R , D L Q et al. ).
Anacondas (Eunectes spp.) comprise a group of large
constricting snakes, widely distributed in tropical and
subtropical areas of South America (D B
). However, information on the natural history of the
four species of anacondas, particularly on home range and
movement patterns, remains limited and biased towards
green anacondas (E. murinus; R et al. , , D
L Q et al. ), and Beni anacondas (E. benien-
sis; D L Q et al. ). Studies on yellow ana-
conda (Eunectes notaeus) show that it is a generalist preda-
tor closely associated with freshwater wetlands of the La
160
N P. S et al.
Plata basin (MC-M et al. , S
et al. , M et al. ). Evidence about popula-
tion structure and gene ow from Argentine Humid Chaco
yellow anacondas showed a sex-biased dispersion. More-
over, they showed that the conguration of rivers and sur-
rounding habitats, like oodplains and small creeks, was
important to explain the spatial structure of populations
(M C -M et al. ). Furthermore, close
association with aquatic-terrestrial transition zones or per-
manently ooded areas seems important because of ther-
moregulatory constraints, such as preventing exposure to
extreme critical thermal temperatures (S
S , MC et al. ).
Some populations have been exploited for multiple uses,
such as food, leather industry, ornamentation, and medici-
nal practices (M W , A et al. ),
and gene ow among populations may be impaired for nat-
ural or anthropogenic reasons (MC-M et
al. ). In the Brazilian portion of the Pantanal – the larg-
est tropical wetland – yellow anacondas are intentionally
killed to protect livestock, and alterations in ood dynam-
ics associated to land use change in upland habitats of Pan-
tanal may also be a threat to this large and poorly-known
predator (M et al. , R et al. ).
Using radio telemetry, we evaluated home range, habi-
tat preferences, and movements of the yellow anaconda in
the northern part of the Pantanal ecoregion. We focused
on the following questions: i) how large is the home range
and how far does an anaconda move? ii) what kind of habi-
tats yellow anacondas use? We expected that individuals
select the locations close to permanent wetlands, because
they largely depend on resources from aquatic environ-
ments. In addition, we discuss issues on tracking a large
semi-aquatic snake.
Methods
Study area
We conducted our eldwork at the Serviço Social do
Comércio Pantanal Natural Heritage Private Reserve (here-
aer SESC Pantanal; °’”S, °’”W), a particular
protected area located in the oodplain of the Cuia bá River
(state of Mato Grosso, Brazil) that also is recognized by the
Ramsar Convention. e reserve has an area of , km²
and includes a mosaic of freshwater environments (ephem-
eral and permanent ponds, channels, and ooded areas),
grasslands, savannas, and dry forests. Annual ood events
are common in the rainy season (December to March) due
to river overow and rainfall runo. As in most areas of
the Pantanal ecoregion, SESC Pantanal has a homogene-
ous topography with low lying relief (– m a.s.l.), and
micro topography is an important factor for local ood-
ing patterns (G ). Flood beginning is character-
ized by appearance of distinct aquatic environments (rain
puddles, shallow ooded areas, temporary ponds) that are
not necessarily connected with rivers or permanent ponds.
During the steady ood period, the oodplain is almost
completely covered by surface water (varying from cm
to cm), except for paleo-levees with higher elevation
(– m above ood level). In the drawdown period, natural
drainage channels and oodplain ponds are largely discon-
nected from the river channel/permanent ponds. So, hy-
droperiod is quite variable, depending on ood intensity.
During the dry season, many ponds dry out completely,
except for scattered permanent ponds and small drainage
channels, and are subject to sporadic res.
Small-scale variation in vegetation types is closely relat-
ed to soil properties and hydrological conditions (J
N C ). So, local vegetation types do not
show a clear distinction between woody and grassy forma-
tions, although grasslands are more common in areas with
higher ood duration and dierent types of forests occur at
intermediate ood levels. Grasslands comprise a mosaic of
native and exotic grasses, such as Imperata brasiliensis, Ax-
onopus purpusii, Elyonorus muticus, Paspalum carina tum,
and Urochloa humidicola. Monodominant stands com-
posed by Vochysia divergens, locally known as cambarazal,
are common in riverine forests and areas with high ood
duration (– mo). However, cambarazal has spread vigor-
ously in abandoned pastures of the Pantanal. Dense arbo-
real savannas (a mix of dry forests and closed woodlands)
occur in rarely or permanently non-ooded areas and are
composed mainly of Anadenanthera colubrina, Tabebuia
ochracea, and Curatella americana (B et al. ).
An extensive cattle ranching was the major land use until
the creation of the SESC Pantanal reserve in . Cattle
access is not allowed since then, although sporadic cattle
grazing may occur at reserve borders. In addition to ex-
tensive grazing, ecological integrity of the wetlands in the
reserve has been aected over time by re, as well as by
regulation of the Cuiabá River for hydropower generation
(Z M , B et al. ).
Snake captures and transmitter implantation
We captured anacondas at the end of dry season in
(October and November). Most individuals displayed a
number of injuries and scars (bite marks, burns, and tail
loss; Supplementary Fig. S). Anacondas are inconspicuous
snakes and dicult to nd in the aquatic environments of
the Pantanal during the oods; however, this becomes eas-
ier as the water in the oodplain recedes and these snakes
move to the remaining ponds or channels. e area sam-
pled at the SESC Pantanal included permanent wet-
lands, such as ponds and small channels (Fig. ). Yellow
anacondas were located by active search mainly during
the day, but night searches using ashlights were also per-
formed. Teams of three to ve people waded through shal-
low water probing aquatic vegetation and water with feet
or sticks (R et al. ). Aer detection, snakes were
captured by hand and restrained by putting a cotton sock
over the head before further processing (R et al. ).
We recorded capture locations using a handheld GPS unit.
All individuals were measured (snout–vent length – SVL,
161
Movement and habits of Eunectes notaeus
and total length – TotL) using a string to follow the middle
line of the body (R et al. ), weighed, sexed, and
marked with passive integrated transponder tags. Suitable
individuals (TotL > . m and body mass > . kg) were
kept in captivity for surgical implantation of transmitters.
We captured E. notaeus during person-hours of
searching. All snakes were found during daytime in aquat-
ic environments (mean depth of cm and mean water
temperature of .°C), entirely submerged or with part of
the body out of the water among oating vegetation. Eight
snakes (six females and two males, hereaer treated as
ID–) were implanted subcutaneously with a VHF trans-
mitter and GPS receiver coupled in a single device < .
of snake body weight (dimensions × × mm, whip
antenna mm, weight g; Tigrinus Equipamentos para
Pesquisa Ltda., Santa Catarina, Brazil). Surgeries were made
at the Veterinary Hospital of the Universidade Federal de
Mato Grosso (UFMT, Cuiabá, Mato Grosso, Brazil), under
isourane inhalational anaesthesia. e telemetry device
was positioned laterally in the posterior third of the snake’s
body. Sutures with nylon threads were used to close the inci-
sion. During the recovery period, they were kept in captiv-
ity in individual enclosures and received local and systemic
antimicrobial therapy to prevent infection. Anacondas were
released at the place of capture – days aer surgery.
Telemetry survey and habitat categories
Anacondas shelter in dense vegetation or underground in
burrows, therefore the x (i.e. GPS location) success rate
of receiver may be compromised and more battery will be
used. In this sense, GPS receivers were programmed to
record locations every four hours with a time-out period
of ve minutes for x acquisition, and battery life span was
estimated to last – months. Data points were down-
loaded aer each transmitter was recovered. In a dry run,
we used GPS in dierent simulated conditions (underwa-
ter, inside a sh, buried, etc.) and found that the GPS gath-
ered about of expected data in environmental condi-
tions similar to the study site. It failed to gather informa-
tion only when buried.
When satellite and VHF radio telemetry are used joint-
ly, VHF component is not used only for data acquisition,
being critical for the retrieval of data stored on GPS tags.
So, our tracking protocol was designed to minimize inter-
ference on snake’s behaviour and also to avoid signal loss of
individuals that could move out of range of the radio. We
radio tracked anacondas from November to October
in monthly expeditions of seven days each. Each in-
dividual was located approximately every h (. ± .)
by expedition. We limited radio tracking intervals between
Figure 1. Map indicating the location of Pantanal ecoregion (inset map, dark grey area) and wetlands sampled (white circles) where
eight yellow anacondas were radiotracked in the SESC Pantanal reserve (polygon, naturally limited by the Cuiabá River – le – and
São Lourenço River – right), Brazil.
162
N P. S et al.
:–:. Tracking was performed mainly on foot with
locations recorded using the handheld GPS unit, although
a boat was necessary during the ood peak. When direct
observation was not possible, the position of the snakes
was determined using a small unidirectional antenna sur-
rounding the source of the maximum signal. Even if an an-
aconda could not be seen, its location could be determined
within an area of m².Once located we recorded whether
the snake was visible or not, water depth, type of wetland
(pond, small channel, or ooded area), and microhabitat
(open water, macrophyte stands, grasses, and bushes; see
Table ). Locations taken from an airplane were occasion-
ally used when the animals had gone too far or the habi-
tat prevented us from following the animal. In this case,
we typically searched for individuals from altitudes around
m and as soon as a signal was received we approached
this spot from several directions to pinpoint a location.
To visualize movement patterns, we assumed line-
ar movement and created tracks by connecting succes-
sive points using the adehabitatLT package (C et
al. ). Estimates of home range (HR) were based on
Minimum Convex Polygon (MCP) using the ade-
habitatHR package (C ) in R (version ..;
RFoundation for Statistical Computing, Vienna, Austria,
see www.R-project.org). To assess macrohabitat use, we
overlaid the individual home range maps onto the SESC
Pantanal land-use maps using QGIS .. (QGIS Devel-
opment Team ). e study area was classied into four
broad macrohabitat types: native grasslands, abandoned
farmlands with forest patches (mixed exotic pasture occu-
pation associated with monodominant stands), mosaic of
dense arboreal savannas, and mosaic of native grasslands
and exotic pastures. We based our category allocation on
Google Earth imagery, using a land-cover classication for
developed by Brazilian Institute of Geography and
Statistics (IBGE ).
We estimated macrohabitat availability as the propor-
tion of each land use type within the study area (a circular
buer with a m radius) from LANDSAT imagery, us-
ing QGIS. We used a Fisher’s two-tailed exact test (S
C ) to compare the observed use of macro-
habitat with the available macrohabitat under the null hy-
pothesis that there was no preference for the macrohabitat
type the snakes used. Home range of one anaconda (ID )
was not included in the macrohabitat availability analysis
because it was far from the remaining anacondas (~ km)
and the habitats available for it were very dierent.
Results
We monitored the yellow anacondas for days, gath-
ering a total of locations from all eight snakes in the
eld. Animals , , and were lost and their signal could
not be heard even aer two monitoring ights (September
and October ). In the other ve cases, attempts to lo-
cate snakes revealed only the transmitters on the ground
without any signs of a snake carcass nearby (ID , , , ,
and ) during the nal part of the monitoring. Only one
GPS data logger contained stored locations (ID ) with
points. Because these GPS points did not add new periph-
eral points for home range estimates, we used only VHF
data for estimates of home range and movement patterns
for all individuals.
During the monitoring period, the average air tempera-
ture was °C (.–) and water temperature was .°C
(.–). Anacondas were found mostly in the water
(.), among macrophyte stands (.) or ooded ar-
eas with bushy vegetation (.) at a mean depth of .m.
Anacondas were in ponds . of the time, . in
small channels, and . in ooded areas (Table ). Dur-
ing the study, only two of the radio-tracked snakes were
sighted basking or swimming in small channels (Fig. ). Of
the locations, in only three there was a direct observa-
tion of the individual, with the visual detection probability
of a snake at < .
Yellow anacondas have a mean monthly movement of
around m (Tab. ). Of the eight tracked anacondas, the
Table 1. Type of wetland and microhabitat used by Eunectes notaeus radio-tracked in the private reserve SESC Pantanal, Brazil, between
November 2015 and October 2016. Values correspond to number of locations by individual (% locations). Depth corresponds to the
mean of water depth from all individual localizations.
Wetland Microhabitat Water depth
(m)
ID Ponds Small channel Flooded areas Open water Macrophyte stands Grasses Bushes
1 0 7(100) 0 4(57.1) 1(14.3) 2(28.6) 0 1.7
2 0 2(25) 6(75) 2(25) 0 0 6 (75) 1.6
3 1(6.2) 15(93.8) 0 13(81.3) 3(18.7) 0 0 2.0
4 7(100) 0 0 0 7(100) 0 0 0.4
5 0 12(100) 0 1(8.3) 11(91.7) 0 0 2.1
6 0 3(23) 10(77) 0 2(15.4) 1(7.6) 10(77) 1.5
7 5(45.5) 0 6(54.5) 0 5(45.5) 0 6(54.5) 0.9
8 3(60) 0 2(40) 0 3(60) 1(20) 1(20) 0.4
Total used 16(20.2) 39(49.4) 24(30.4) 20(25.3) 32(40.5) 4(5.1) 23(29.1) –
163
Movement and habits of Eunectes notaeus
Figure 2. Some of the individuals of yellow anacondas (Eunectes
notaeus) radiotracked during the study: A) male coiled on a
macro phyte ra; B) female being inspected for signs of infec-
tion and inadequate healing; C) female found swimming among
aquatic vegetation.
maximum monthly distance travelled was m for fe-
males (December) and m for males (March). However,
three “nomadic” females moved three to four times more
than other anacondas followed during this study (ID , , ;
Table ). e majority of the tracked anacondas remained
inside the permanent wetlands where they had been cap-
tured, but one female (ID ) moved into an oxbow lake
of the Cuiabá River (Supplementary Fig. S). Individual
home ranges overlapped in three cases, between a female
and a male (ID and , ID and ) and between two fe-
males (ID and ).
Home ranges calculated from MCP varied between
. and . ha (Table ). e three “nomadic” females
had home ranges greater than ha, while home ranges
of the remaining ve anacondas varied between . and
.ha. Although most anacondas were radio-tracked for
less than eight months, small home ranges did not seem
to be related to short monitoring period (Table ). With-
in individual home ranges, anacondas used areas of native
grasslands and abandoned farmlands with forest patches
(Fig.). Only one individual was tracked in a mosaic of na-
tive grasslands/exotic pastures (Table ). Native grasslands
were used substantially more than expected (observed: ;
expected: .; two-tailed Fisher’s exact test; p = .; Ta-
ble ).
Discussion
Our results show that yellow anacondas are strongly de-
pendent on aquatic habitats, using small channels and rel-
atively shallow waters with macrophyte stands and bushy
vegetation. Yellow anacondas were sedentary, even during
the ood season, suggesting some delity to permanent
wetland boundaries. Small to moderate home range sizes
for large species are oen associated to high food availa-
bility. is is particularly common in generalist predators,
including reptiles living in oodplains (B et al. ,
F et al. , W et al. ). Other factors
that may inuence movement are thermoregulation needs,
avoidance of predators, mating and other social interac-
tions (B et al. , G et al. , Z
et al. ). However, the sampling period was just aer the
mating season – which occurs at the end of the dry season
(W et al. ) – so mating was not likely an impor-
tant driver at this time.
Whilst our ndings provide evidence that yellow ana-
condas have small home ranges, we are limited in the scope
of our conclusions given the short sampling period (prima-
rily – months), and the few (–) relocations by track-
ing with VHF due to the failure of the GPS tags. So, di-
rect comparisons of movement rates should be made with
caution. e use of burrows, underwater habitats, or shel-
ters amidst thick vegetation hamper GPS performance and
may resulted in the failure of the GPS transmitters (F
et al. ). Moreover, from the eight transmitters implant-
ed, three were not recovered. e other ve were found le
in the eld. While it is possible that the ve associated ana-
164
N P. S et al.
Table 3. Macrohabitat used by Eunectes notaeus radiotracked in the private reserve SESC Pantanal, Brazil, between November 2015
and October 2016. Values correspond to number of locations (% locations).
ID Native
grasslands
Mosaic native grasslands/
exotic pastures
Abandoned farmlands
with forest patches
Dense arboreal
savannas
1 7 (100) 0 0 0
2 8 (100) 0 0 0
3 15 (93.7) 0 1 (6.3) 0
4 0 7 (100) 0
5 12 (100) 0 0 0
6 13 (100) 0 0 0
7 0 0 11 (100) 0
8 1 (20) 0 4 (80) 0
Total used 56 (70.9) 7(8.9) 16(20.2) 0
Figure 3. Aerial views with minimum convex polygon (100%) areas of two radio-tracked anacondas, showing home ranges at dierent
land uses in the SESC Pantanal, Brazil. A) Individual (ID) 3 using natural grassland and forest patches. B) ID 4 using mosaic of native
grasslands/ exotic pastures. Numbers correspond to the ID in Tables 1 and 2.
Table 2. Individual characteristics, days and numbers of locations (VHF data only), and movement data for eight yellow anacondas
(Eunectes notaeus) radiotracked in SESC Pantanal, Brazil, between November 2015 and October 2016. TotL: Total length, SVL:Snout–
vent length.
ID TotL
(m)
SVL
(m)
Mass
(kg)
Sex Monitored
days
Number of
locations
Mean monthly
distance (m)
Total distance
travelled (m)
Home
range (ha)
1 1.97 1.76 4.5 Male 179 7 30.1 182.1 0.3
2 2.85 2.62 12.8 Female 181 8 106.2 641.1 2.3
3 2.68 2.45 11.5 Female 217 16 296.5 2078.3 17.7
4 2.63 2.43 11.1 Female 88 7 105.25 207.4 0.6
5 2.10 1.87 5.0 Female 295 12 30.4 122 0.1
6 1.92 1.77 3.6 Male 206 13 160 767.2 0.7
7 3.57 - 21.2 Female 288 11 301.7 1699.5 16.4
8 3.36 - 11.1 Female 292 5 474.8 4281 11.2
Average 2.6 2.15 10.1 218 10 188.1 1247.3 6.2
165
Movement and habits of Eunectes notaeus
condas have died and were subsequently scavenged, leav-
ing only the transmitter in the eld, no traces of carcass-
es were found nearby. Furthermore, former studies have
documented that internal transmitters can be expelled in
faeces or through the body wall (P S ,
S et al. ). us, we have no way to discern what
happened to these snakes.
Our results are consistent with previous ndings of
E.murinus habitat preference in Venezuela, and E. benien-
sis in Bolivia. Both species preferred shallow water with
abundant aquatic vegetation (R , D L Q-
et al. ). Home ranges here reported for E.notaeus
are also similar to those for E. beniensis, which have a home
range between .–. ha (D L Q et al. ),
and E. murinus, with a home range of . to ha (R-
). A study in northern Argentina with E. notaeus
also found a comparable home range (– ha; N
et al. ). e somewhat smaller home range found in
this study can be explained by the short time of the study,
which was limited to only one rainy season and one dry
season. However, long periods of inactivity and reduction
of home range sizes (home range < . ha) were reported
under suboptimal conditions or during pregnancy (R
, D L Q et al. ). In fact, most of the fe-
males in our study, with the exception of ID , presum-
ably had enough fat reserves to have been breeding (R
), so the low mobility could be a result of the females
likely being pregnant (R ).
Eunectes notaeus is an ambushing or foraging preda-
tor and feeds most commonly on wading birds and shore-
birds (S , M et al. , C
et al. ), which are reduced during ooding periods
(F et al. , D et al. ). Subsequent-
ly, aquatic predators, such as the giant otter (Pteronura bra-
siliensis, Mustelidae) and caimans (Caiman yacare, Alliga-
toridae) take advantage of ooded grasslands and forests in
the areas adjacent to rivers (L et al. ,
C et al. ). e great number of scars observed
in the anacondas captured for the study could be caused
either by defensive eorts of prey or from predator attacks
(R, ).
e benets of using shallow aquatic habitats may be
also responsible for the small home ranges registered here.
By spending long periods partially submerged and coiled
in shallow waters, yellow anacondas can reduce ther-
moregulatory costs because the average water temperature
is usually high (MC et al. ). is may re-
duce the odds of predation. In addition, oating and root-
ed vegetation may provide both microhabitat for foraging
aquatic birds and camouage for anacondas (see Fig. ).
With regard to the overall macrohabitat choice, the appar-
ent preference for open land cover may be attributed to
variation in water availability. In Pantanal, dense arboreal
savannas are established in patches of drier terrains that
become ooded only for a few days or weeks, or that does
not ood at all. In Bolivia, E. beniensis seems to have a sim-
ilar tendency, avoiding forested areas with little availability
of permanent wetlands (D L Q et al. ).
Although GPS telemetry has advantages in studies with
large constrictors (S et al. ), we unfortunately ex-
perienced issues of equipment failures and loss of trans-
mitters. In light of these issues, we highlight that the choice
of transmitters should be done with caution. For aquatic
and semi-aquatic snakes, we suggest the use of VHF com-
ponent of GPS transmitters for joint data acquisition.
In conclusion, we showed that individuals of E. notae-
us select native grasslands; their home ranges are relative-
ly small, and closely associated with permanent wetlands,
both in dry and in rainy seasons. Our results add valuable
information about life history and ecology of E. notaeus,
and are a key step to help to ll knowledge gaps on this
poorly understood large snake.
Acknowledgements
We are grateful for the nancial support of “Conselho Nacional
de Desenvolvimento Cientíco e Tecnológico” (Edital Univer-
sal, /-; CNPq/PELD – /-) and “Funda-
ção de Amparo a Pesquisa do Estado de Mato Grosso” (process
number /). NPS and LFBM thank “Coordenação de
Aperfeiçoamento de Pessoal de Nível Superior” (CAPES) for a
Master’s and a postdoctoral (PNPD; process ) fellow-
ship, respectively. CS thanks Conselho Nacional de Desen-
volvimento Cientíco e Tecnológico for a research fellowship
(CNPq /-). We thank the SESC Pantanal for lo-
gistical support during eld activities. We thank the eld work
researchers’ team from the Universidade Federal de Mato Gros-
so (UFMT). We thank E. G for editorial comments on
the manuscript. We are grateful to V. A. C for help in
the project conception and E. B. P. M for help captur-
ing the snakes for the study. We especially thank S. H. R. C-
for providing invaluable support at the Veterinary Hospi-
tal of UFMT, the surgeons P. R. S and M. B. Stocco, the
anaesthesiologists J. V. A. G and T. A, and R. H.
S. F and W. F. S for help during the surgeries and
quarantine. We declare that the data collection complied with
current Brazilian laws (SISBIO-permit -; CEUA/ UFMT-
process ./-).
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Supplementary data
e following data are available online:
Supplementary document S1. Some injuries found in the radio-
tracked anacondas in the SESC Pantanal.
Supplementary document 2. Map showing the home ranges for
eight yellow anacondas tracked in the SESC Pantanal.
