Herpetological Review 45(2), 2014
Herpetological Review, 2014, 45(2), 209–212.
© 2014 by Society for the Study of Amphibians and Reptiles
Amphibian Diversity on Floating Meadows in Flooded
Forests of the Peruvian Amazon
Floating meadows are often associated with Amazonian
white-water flooded forests (varzea), where they grow between
the tree line and open-water. Seasonal flooding in varzea results
in an unstable forest floor for terrestrial species. However,
floating meadows may offer a refuge for some species that would
otherwise be displaced by rising water. Floating meadows consist
of herbaceous water plants that begin growing at the end of the
low water period, taking root in the waterlogged soils of river,
channel and lake banks. As the water rises, some plant species
grow rapidly upwards, others become free-floating and grow
horizontally, expanding the surface area they occupy (Junk 1970,
1997). As water levels begin to recede, currents and rainfall can
dislodge sections of floating meadows to create rafts that are then
transported via the river current.
The importance and diversity of floating meadows has
been highlighted for several taxa (Goulding et al. 1996; Junk
1997; Schiesari et al. 2003; Dias et al. 2011; Ferreira et al. 2011),
yet studies focusing on amphibian use of floating meadows are
relatively scarce. Junk (1973) found that amphibians were rarely
encountered on floating meadows. However, methodology was
not provided by Junk (1973), and if nocturnal surveys were not
undertaken, amphibians were unlikely to have been adequately
sampled. Carrying out specific amphibian surveys, Hödl (1977)
found 15 anuran species on floating meadows and concluded
that this habitat was a potential breeding site. Hoogmoed (1993)
published a list of the herpetofauna known to occur on or near
to floating meadows in Suriname, Bolivia, and Brazil, adding to
Hödl’s (1977) list. This research brought the total number of am-
phibian species recorded on floating meadows to 26 (Hoogmoed
1993). On the Solimoes River, Schiesari et al. (2003) observed 42
individuals comprising eight anuran and one caecilian species,
all on floating meadow rafts. They highlighted the importance of
rafts of floating meadow vegetation as dispersal vectors for fish
and potentially also for amphibians (Schiesari et al. 2003). In a
preliminary study of only 18 days, Upton et al. (2011) found 16
anuran species on floating meadows. The amphibians recorded
on floating meadow habitats to date are listed in Table 1.
This paper aims to: 1) Update the current list of amphibians
found on floating meadows in Peruvian varzea flooded forest,
and 2) update the information on reproductive habitat use
provided by Hödl (1977), which showed evidence of reproductive
behavior on the floating meadow habitat (see Hödl 1977; Fig. 3,
Materials and Methods
Study site.—Our study was conducted in the Samiria River
basin of the Pacaya-Samiria National Reserve, Loreto, Peru
Durrell Institute of Conservation and Ecology,
School of Anthropology and Conservation, University of Kent,
Marlowe Building, Canterbury, Kent, CT2 7NR, UK
Fundamazonia, Malecon Tarapaca N° 332, Iquitos, Loreto, Peru
*Corresponding author; e-mail: email@example.com;
taBle 1. List of amphibian species that have been recorded on, or
near, floating meadows (x = on, [x] = near). Numbers for localities:
1. Brazil, Solimões (Hödl 1977); 2. Suriname, Para River (Hoogmoed
1993); 3. Bolivia, Perserverancia (Hoogmoed 1993); 4. Brazil, Caxi-
uanã (Hoogmoed 1993); 5. Brazil, Solimões (Schiesari et al. 2003).
Species 1 2 3 4 5
Rhinella marina x [x] x
Dendropsophus haraldschultzi x
Dendropsophus leucophyllatus x x x
Dendropsophus minusculus x
Dendropsophus nanus x [x]
Dendropsophus rossalleni x
Dendropsophus triangulum x
Dendropsophus walfordi x
Hypsiboas boans x [x]
Hypsiboas geographicus [x] x
Hypsiboas lanciformis x
Hypsiboas punctatus x x x x
Hypsiboas raniceps x [x] x
Hypsiboas wavrini x
Dryaderces pearsoni x
Lysapsus boliviana x
Lysapsus caraya x
Lysapsus laevis x x
Scinax boesemani x
Scinax nebulosus x x x x
Scinax ruber x
Sphaenorhynchus carneus x x
Sphaenorhynchus dosisae x
Sphaenorhynchus lacteus x x
Leptodactylus leptodactyloides x
Leptodactylus wagneri x [x] x
Pipa pipa x
Typhlonectes compressicauda x
Total species on floating meadows 15(15) 7(10) 8(10) 3(4) 9(9)
Herpetological Review 45(2), 2014
(4.893256°S, 74.355526°W). The Pacaya-Samiria National Reserve
is one of the largest varzea forests in western Amazonia spanning
over 20000 km2 between the confluence of the Ucayali and
Data collection.—Preliminary data for this study were
collected in May and June 2009, with more extensive surveys
conducted from March to October 2012. Most surveys were
carried out at night from 1800–2400 h, with some daytime searches
between 1400–1700 h.
The floating meadows surveyed were located in the Samiria
River basin at PV1 Shiringal, PV2 Tacshacocha, Huishto Cocha,
and PV3 Hungurahui. These sites cover a small proportion of the
Samiria River Basin, which spans a wide area; however, they were
chosen as they have varying levels of disturbance by local fishermen
and tourism. At each site, surveys were conducted across all river
systems, in both the main Samiria River and in adjacent channels
and lakes. In total, 221 surveys were conducted, 52 in 2009 and 169
in 2012. The surveys in 2012 were split as follows: 71 in lakes, 60 in
channels, and 38 on the main Samiria River. Around the lake edges,
floating meadow surveys were conducted at 100-m intervals. Within
the channel and main river, less floating vegetation was available
to survey, so all sections were surveyed at least once. A 10-m boat
with outboard motor was slowly driven into the floating meadow
vegetation, causing it to part on either side of the boat with the aim
of reducing disturbance. On each sampling occasion, an area of 2
m on either side of the boat (50 m2 in total) was searched for fifteen
minutes. During this time, all frogs encountered were captured
and placed in individually marked pots. Time
of capture, species, behavior (e.g., calling male)
and location (including plant species and
height above water), were recorded. All surveys
were completed with one local field guide, one
biologist, and three or four student volunteers.
To locate frogs at night, one main flashlight was
used by either a guide or the biologist (CB2-L1
Clubman Deluxe, LI-ION 9.2AH half-million
candle power); all students used smaller
flashlights such as the Petzl Tikka to search.
Species identification was undertaken using
several field guides (Ouboter and Jairam 2012;
Duellman 2005; Bartlett and Bartlett 2003;
Rodriquez and Duellman 1994). Although
identification of Amazonian amphibians can
be very difficult, many of the species observed
on floating meadows are distinctive and
can be quickly identified in the hand using
identification guides. Voucher specimens were
not taken as the collection of specimens from
within this protected reserve was prohibited
under the permit and authorization being used
(Resolucion Jefatural No 005-2013-SENANP-
Data analysis.—To analyze microhabitat
use, the data were separated into the four main
genera: Dendropsophus, Hypsiboas, Scinax, and
Sphaenorhycnhus. Kruskal-Wallis tests were
then used to determine if there were significant
differences in the median calling heights among
species in the same genus.
Nineteen amphibian species and 1090 individuals were
recorded on the floating meadow habitat representing four families
(Table 2). Six species have not been previously recorded on floating
meadows: Dendropsophus leali, Osteocephalus taurinus, Scarthyla
goinorum, Scinax garbei, Scinax pedromedinae, and Leptodactylus
petersii. Most of the species recorded on floating meadows were
hylids (15) compared with only two leptodactylids, one bufonid,
and one pipid. The most abundant species were Dendropsophus
triangulum and Hypsiboas punctatus with 371 and 314 individuals,
respectively. No other species was represented by more than 100
individuals. Scarthyla goinorum and Scinax pedromedinae were
both represented by only two individuals while Pipa pipa and
Hypsiboas boans were represented by just one individual each
The median height in which amphibians were found and the
most commonly used (over 50% of encounters) plant species are
presented for all species observed (Fig. 1, modelled after Hödl
1977, figure 3). One species, Pipa pipa, was found swimming at the
water surface; all others were on the floating meadow or adjacent
emergent vegetation. All leptodactylid and bufonid species were
most often found on Water Lettuce (Pistia stratiotes), a species
that floats on the water surface. Paspalum repens was the most
commonly used plant species on the floating meadows and also
the most abundant in the survey area. Only in Sphaenorhychus
were there significant differences in perch height between
species (Kruskal-Wallis chi squared = 16.62, P< 0.05, df = 2), with
S. carneus occupying lower heights than S. lacteus. Calling males,
taBle 2. Species list including number of individuals captured and life stages on the float-
ing meadows of the Samiria River in Pacaya-Samiria National Reserve, during May–June
2009 and March–October 2012. F = gravid female; M = calling male; A = adult (sex un-
known); J = juvenile; *above the floating meadow either on a branch or tree trunk; ° not
previously recorded on floating meadows.
Species F M A J Total 2009 Total 2012
Rhinella marina 9 1 8
Dendropsophus haraldschultzi 1 29 10 2 38
Dendropsophus leali 1 1 3 5°
Dendropsophus rossalleni 3 23 16 10
Dendropsophus triangulum 12 106 232 21 33 338
Hypsiboas boans 1 1*
Hypsiboas lanciformis 14 8 3 25
Hypsiboas punctatus 30 38 184 62 14 300
Osteocephalus taurinus 1 1°
Scarthyla goinorum 2 2°
Scinax garbei 2 8 4 1° 13
Scinax pedromedinae 2 2°
Scinax ruber 3 1 2
Sphaenorhynchus carneus 2 28 44 6 5 75
Sphaenorhynchus dorisae 2 6 50 2 38 22
Sphaenorhynchus lacteus 1 16 50 3 22 48
Leptodactylus leptodactyloides 23 7 16
Leptodactylus petersii 20 12° 8
Pipa pipa 1 1
Total number of species 6 11 17 10 12 19
Herpetological Review 45(2), 2014
gravid females, and juveniles were all found on floating meadows,
although only for hylids (Table 2, modelled after Hödl 1977).
Calling males were observed for 11 of the 15 hylid species while
ten species were represented by juveniles and six represented by
gravid females. Leptopdactylids were only represented by adults,
as were Rhinella marina and Pipa pipa.
Hylids were the most frequently encountered family on the
floating meadows. The two most common species, Dendropso-
phus triangulum and Hypsiboas punctatus, are either rare or ab-
sent from the adjacent terrestrial habitat (pers. obs.), highlight-
ing the importance of floating meadows for some hylid species.
Other species were only represented by one or two individuals.
One example is Pipa pipa, a fully aquatic species that is rarely en-
countered on land; this individual was caught swimming at the
surface of the water. The floating meadow root system potentially
offers refuge and cover to aquatic species such as Pipa pipa.
Few leptodactylids and bufonids were observed on the
floating meadows, as these species are usually terrestrial and
are regularly encountered on the forest floor within the leaf litter
(Allmon 1991) or on river banks (Bartlett and Bartlett 2003), and
it is therefore possible that frogs in these families are only using
floating meadows as a refuge during high water periods. In both
2009 and 2012 the water level in Pacaya-Samiria exceeded all
records from the last 100 years (Bodmer et al. 2012). During these
high water periods up to 95% of the reserve can be inundated, with
water levels reaching a depth of several meters within the forest.
This reduced availability of terrestrial habitat may have displaced
some individuals onto floating meadows.
Hödl (1977) noted frogs showing call site segregation, with
most species associated with specific plant species. Calling males
were regularly observed on the floating meadows in this study,
with most species calling from a certain plant species at similar
heights. For example the three Sphaenorhynchus species called
from significantly different heights on Paspalum repens. Anuran
morphology may influence plant choice, for example, the small S.
carneus was sometimes observed calling from Oxycoryum cubense,
a small grass species. Male S. carneus are usually between 15–18
mm and females 22–23 mm SVL, compared to S. lacteus males
which are 26–29 mm and females 36–40 mm SVL (Rodríguez
and Duellman 1994). The latter, larger species may be unable to
physically climb up on this smaller grass species. Other species
that showed preference for certain plants includes D. triangulum,
which was most commonly found on Paspalum repens, and
Fig. 1. Anuran species found on floating meadows, the most common plant species on which they were found, and the median
height at which they were found. 1) Rhinella marina 2) Dendropsophus haraldschultzi, 3) Dendropsophus leali, 4) Dendropsophus
rossalleni, 5) Dendropsophus triangulum, 6) Hypsiboas boans, 7) Hypsiboas lanciformis, 8) Hypsiboas punctatus, 9) Osteocephalus
taurinus, 10) Scarthyla goinorum, 11) Scinax garbei, 12) Scinax pedromedinae, 13) Scinax ruber, 14) Sphaenorhynchus carneus, 15)
Sphaenorhynchus dorisae, 16) Sphaenorhynchus lacteus, 17) Leptodactylus leptodactyloides, 18) Leptodactylus petersii, 19) Pipa pipa.
Herpetological Review 45(2), 2014
H. punctatus, which was found on either Paspalum repens or
Eichhornia crassipes. This is consistent with Hödl’s (1977) findings
in which D. triangulum and H. punctatus were both observed on
plants in the genus Paspalum.
Hylids may potentially be using floating meadows for
breeding, as calling males, gravid females, egg masses, and newly
metamorphosed juveniles of twelve species were observed. These
findings are consistent with Hödl’s (1977) observations of calling
males and pairs in amplexus on floating meadows. Many hylids
are arboreal and are documented to move from higher strata to
breed in temporary or permanent pools of water in the terrestrial
habitat (Rodríguez and Duellman 1994; Bartlett and Bartlett 2003;
Dodd 2010). However the flooded forest in the Pacaya-Samiria
Reserve can be inundated for up to 6–9 months a year, resulting
in an unstable terrestrial habitat. Additionally, the draining of
floodwaters occurs rapidly, with fluctuations of up to 30 cm a day.
Thus, temporary pools are only available for short periods, if at all.
Floating meadows may be a more stable habitat, available for
the 6–9 months that the terrestrial habitat is flooded, and also offers
an opportunity to study species that are not often encountered
within the terrestrial habitat. In addition, floating meadows may
offer an important refuge for other anuran families during extreme
flooding. Marked oscillations in annual water levels are becoming
more common due to climate change (Bodmer et al. 2012). The
availability of floating meadows is dependent on the water level.
Therefore it will be important to further elucidate the role of
floating meadows in maintaining amphibian diversity in flooded
forests as seasonal flooding becomes more extreme.
Acknowledgments.—This research is supported by the University
of Kent alumni scholarship, which is fully funded by alumni of the
university. Thanks to Richard Bodmer and Richard Griffiths for sup-
port and guidance. Thanks to the Pacaya-Samiria National Reserve
Authority (SERNANP) (Resolucion Jefatural No 005-2013-SENANP-
JEF) for authorization and permission to conduct this research, and
to the following for helping to fund this project and for logistical
support: Durrell Institute of Conservation and Ecology, FundAma-
zonia, Wildlife Conservation Society, Earthwatch Institute, Opera-
tion Wallacea and Operation Earth. Finally we thank all the Earth-
watch, DICE, Operation Wallacea, and Operation Earth volunteers
as well as Sophie Rost, Hannah Conduit, Lizz Willott, Abbie Parke,
Elizabeth Wells, and Eric Woebbe.
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