EL NINO
EXPEDITION 2016
El Niño Biodiversity Assessment Report
9 March 2016
Laguna del Tigre National Park, Guatemala
Authors: Rowland Griffin and Adela Mei. Translation: Sheriyar Bokhari.
2016
El Niño Biodiversity
Assessment Report
Laguna del Tigre National Park
Authors: Rowland Griffin and Adela Mei
Translation: Sheriyar Bokhari
9 March 2016
Indigo Expeditions
[email protected]
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Introduction
The El Niño Southern Oscillation (ENSO) cycle is a term used to describe fluctuations
of oceanic and atmospheric temperature in the Equatorial Pacific. The ENSO cycle
oscillates between two opposite phases often referred to as La Niña (the cold phase)
and the better known El Niño (the warm phase). The two phases are known to have
wide-reaching effects on local and global weather systems (Ropelewski & Halpert
1987).
The El Niño phase has a 5-7 year cycle and early effects are a rise in ocean surface
pressure and a fall in air pressure in the Eastern Pacific region. This causes trade winds
over the south Pacific to weaken and warm air to rise near Peru, leading to
precipitation in the northern Peruvian deserts (Ropelewski & Halpert 1987). The most
recent El Niño phase was observed in 2015.
The shift in rain patterns to the south cause the summers in Central and North America
to be drier than average. In Guatemala this means that the onset of the rainy season is
delayed by several months. In Laguna del Tigre National Park, an area that receives
relatively low rainfall and is subject to high drainage, the effects can be striking
(Ropelewski & Halpert 1987).
In June 2015, Indigo Expeditions conducted 6 weeks of fieldwork at Estación Biológica
las Guacamayas in the south east region of Laguna del Tigre. The surveys were part of
ongoing inventory work that we carry out and were timed with the start of the
traditional rainy season to coincide with peaks in amphibian breeding activity.
During those surveys we observed lower than usual rainfall, with consistent heavy rain
occurring on approximately six days in the 6 week period, and consequently low
amphibian observations. No evidence of amphibian breeding was noted due to lack of
suitable water bodies.
Indigo Expeditions identified the need for further surveys later in the year in order to
assess the full impact of the 2015 El Niño phase. Funding for the El Niño Biodiversity
Assessment was secured through a 30 day crowdfunding campaign.
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Target Species
WE FOCUSED ON THREE TARGET SPECIES:
1 - OXYRHOPUS PETOLARIUS - FALSE CORAL CALICO SNAKE
Our previous records of O.petolarius have all been gathered between October and
December. We have never found them during our surveys in June and July. With the
delayed rainy season in 2015 we hypothesised that snake activity would be higher
following the advent of rains. We hoped we would be able to increase our knowledge
of this species in Laguna del Tigre National Park.
2 - CLELIA SCYTALINA - MEXICAN MUSSARANA
Clelia scytalina is considered a rare snake and very little information has been published
on its natural history and ecology. We have previously found seven individuals during
our fieldwork over the last few years. Only one of these, encountered in June 2015,
was an adult. Again, we hoped that encounters of this snake would be increased by the
late rains and that we would be able to increase our knowledge of the ecology of this
little known species.
3 - TRIPRION PETASATUS - YUCATÁN CASQUE-HEADED TREEFROG
Treefrogs of the genus Triprion are known to show highly seasonal activity patterns.
They spend most of the year resting in tree holes. At the beginning of the rainy season
they emerge to breed and feed before returning to their resting places (Lee 1996).
Only one individual has ever been seen during our fieldwork in May 2013. We hoped
that with the delayed rains we would locate the species again and use this as a proxy
for timing of overall amphibian breeding activity in 2015.
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Methodology
We selected an area thought to be representative of the typical habitat in each of four
habitat types,
• Agricultural Edge (AE),
• High Forest (BA),
• Low Forest (BB) and
• Natural Edge (NE).
Two parallel 100m transects approximately 50m apart were cut in each habitat. The
direction of the transects was chosen to follow typographic gradients rather than
traverse them. Transects were marked every 25m with flagging tape and GPS (Garmin
GPSMap 62s) and waypoints were taken at the start and finish points.
Surveys were undertaken between 8th and 15th December 2015.
Visual Encounter Surveys (VES)
Due to the density of the vegetation “Distance” surveying was deemed inappropriate as
most species would not be detectable after one metre distance from the transect. We
opted for using a fixed-width method and thoroughly searched the vegetation for
reptiles and amphibians up to one metre each side of the transect line and up to two
metres high (Heyer et al. 1994; McDiarmid et al. 2012).
To maximise our chances of encountering species each transect was surveyed three
times during our study, twice at night and once in the morning.
For each transect the following environmental data was recorded at the start and
finish: time (24hr), air temperature (ºC) and relative humidity (%). Additionally, cloud
cover (%) was estimated at the beginning of each transect and daily rainfall (mm) was
recorded.
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Methodology
When safe to do so, each individual encountered was captured and the following data
recorded: time encountered (24hr), location (recorded using a Garmin GPSmap 62s),
activity (rest, basking, foraging), position (leaf litter, shrub layer and branch including
diameter of the perch) each individual was first observed, species, age (adult, juvenile,
neonate), sex (if possible), length (mm) and weight (g).
Biometric data for amphibians and most lizards was taken in the field. All snakes
captured were brought back to Estación Biológica las Guacamays for collection of
biometric data for ease.
All individuals were released at the point of capture within 48 hours.
Quadrat Survey
A single 8x8m leaf-litter quadrat survey was completed in each forest habitat.
Quadrats were positioned randomly between the two transects in each forest habitat.
GPS waypoints were taken at the centre of each quadrat. Leaf-litter within each
quadrat was surveyed thoroughly for the presence of reptiles and amphibians as per
Jaeger and Inger (1994). The data collected was the same as for VES, however,
environmental data was only recorded at the start of the survey. Data for individuals
encountered was the same as for VES. Quadrats were only conducted during the day
due to safety reasons and the likelihood of encountering the highly venomous barba
amarilla (Bothrops asper).
Casual Observations
If deemed appropriate (rarely seen or previously unrecorded species) individuals were
encountered outside of the VES or Quadrat surveys they were recorded as Casual
Observations (CasObs). Data for individuals encountered in this manner was collected
following the protocol for VES.
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Results
Including casual observations a total of 34 species of reptiles and amphibians were
recorded during the study. Of these 24 were reptiles (including10 lizards, 10 snakes, 3
turtles and 1 crocodylian) and 10 were anuran amphibians.
We did not encounter any of our three target species (Oxyrhopus petolarius, Clelia
scytalina and Triprion petasatus) during this study. However, four species encountered
were new records for Laguna del Tigre National Park.
Eight species were recorded during VES or Quadrat surveys (table 1).
Species
Number of Individuals
Found in VES Surveys
Number of Individuals
found in Quadrat
Surveys
Gastrophryne elegans
1
0
Hypopachus variolosus
2
0
Tropidodipsas sartorii
1
0
Corytophanes cristatus
1
0
Oxybelis aeneus
1
0
Anolis (Norops) capito
1
1
Anolis (Norops) uniformis
0
2
Spilotes pullatus
1
0
Table 1: number of species encountered during VES and Quadrat surveys in each
forest habitat
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New Records
Rhinophrynus dorsalis
On the 9th December a tourist group staying at Las Guacamayas reported seeing a
large aggregation of some 1000’s of newly metamorphed gulf coast toads on the road
to the Mayan ruins of Wak’a. After looking at their photos we decided to visit the
location they were seen at the following day to confirm species identification. Upon
arrival at the location, a cave next to the road, on the 10th December, we located the
toads but in much smaller numbers (ca 20 individuals). We confirmed their
identification as Mexican burrowing toads (Rhinophrynus dorsalis).
Oxybelis aeneus
On the 13th December we encountered an adult female brown vine snake (Oxybelis
aeneus) during a survey of high forest. She was sleeping in the branches of a young
cordoncillo tree (Piper aduncum L) at approximately two metres in height. She
measured 1257mm in total length and weighed 32g.
Spilotes pullatus
On the morning of the 14th December we conducted a survey of the Natural Edge
transects and encountered a large male tiger ratsnake (Spilotes pullatus) basking on
the forest floor. It weighed 1000g. At a total length of 2191mm it is the longest snake
we have encountered at Las Guacamayas.
Drymarchon corais
In the late afternoon of the 15th December a large male indigo snake (Drymarchon
corais) was found by the staff at Las Guacamayas on the path next to the water pump
near the dock. It measured 1895mm in total length. It weighed 1880g making it the
largest snake we have found so far at Las Guacamayas.
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New Records
RHINOPHRYNUS DORSALIS
SPILOTES PULLATUS
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OXYBELIS AENEUS
DRYMARCHON CORAIS
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Discussion
Target Snake Species: While we did not encounter either of our target snake species,
we did encounter three species that had not been officially recorded in Laguna del
Tigre before (Oxybelis aeneus, Spilotes pullatus, and Drymarchon corais). The coral
snake mimic, Tropidodipsas sartorii, was also found for the first time in the low forest
near one of the low lying lakes, known locally as aguadas, near the Mayan ruins of
Wak’a. Previously it had only been found in high forest, agricultural edge or around the
buildings of Estación Biológica las Guacamayas.
Amphibian Breeding Season
Although we did not locate our target species, the Yucatán casque-headed treefrog
(Triprion petasatus), we did locate another anuran that exhibits an even more
pronounced seasonal activity pattern. The Mexican burrowing toad (Rhinophrynus
dorsalis) is a large anuran that spends most of the year underground using its highly
developed rear feet to burrow in search of ants. These explosive breeders only appear
above ground for a few days each year at the beginning of the rainy season. Breeding
occurs in the first few nights of rain before the adults disappear back underground
until the following season. The tadpoles take approximately three months to
metamorphose into toadlets (Lee 1996).
Our observations of burrowing toads in December is not only significant in that it is the
first confirmed record of this species in Laguna del Tigre, but also that we can track the
onset of the 2015 rainy season to September (ca 3 months before our observation).
We can also hypothesize, given that this species bred successfully in September, that
other amphibian species also bred successfully around the same time.
During the El Niño Biodiversity Assessment we recorded four species that had not
officially been recorded in Laguna del Tigre National Park before. Two of the three
snakes (Oxybelis aeneus, and Spilotes pullatus) had been known from anecdotal
observation. The anuran Rhinophrynus dorsalis and the snake Drymarchon corais are
the first records of those species from Laguna del Tigre.
With these four additions the total number of reptile and amphibians recorded from
Laguna del Tigre National Park is 92 species. Our work continues to highlight the
importance of Laguna del Tigre for reptile and amphibian biodiversity in northern
Guatemala.
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References
• Ropelewski, C.F. and M.S. Halpert. 1987. Global and Regional Scale Precipitation
Patterns Associated with the El Niño/Southern Oscillation. Monthly Weather Review
115.pp1606-1626
• Heyer, W.R., M.A. Donnelly, R.W. McDiarmid, L-A.C. Hayek, & M.S. Foster. 1994.
Measuring and Monitoring Biological Diversity: Standard Methods for Amphibians.
Smithsonian Institution Press. Washington.
• Jaeger, R.G. & R.F. Inger. 1994. Quadrat sampling. Pp 97-102 in Measuring and
Monitoring Biological Diversity: Standard Methods for Amphibians (Heyer, W.R.,
M.A. Donnelly, R.W. McDiarmid, L-A.C. Hayek, & M.S. Foster eds). Smithsonian
Institution Press. Washington.
• Lee, J.C. 1996. The Amphibians and Reptiles of the Yucatán Peninsular. Comstock,
Michigan.
• McDiarmid, R.W., M.S. Foster, C. Guyer, J.W. Gibbons, & N. Chernoff. 2012.
Reptile Biodiversity: Standard Methods for Inventory and Monitoring. University of
California Press. Berkeley.
Acknowledgements
Indigo Expeditions extends huge thanks to all those who supported the El Niño
Biodiversity Campaign and made this study possible. We also thank the staff at
Estación Biológica Las Guacamayas for their logistical support and enthusiasm for our
work, not to mention their neverending willingness to assist with surveys. Additionally
we thank CONAP, Wildlife Conservation Society Petén and Asociación Balam for their
continued support.
This study was carried out under research permit 008/2015 issued by CONAP.
This work is licensed under a Creative Commons Attribution-ShareAlike 4.0
International License.
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Appendix1
Oxyrhopus petola (TOP) Clelia scytalina (BOTTOM)
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Appendix1
Triprion petasatus (TOP)
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Appendix 2
Rhinophrynus dorsalis (TOP) Oxybelis aeneus (BOTTOM)
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Appendix 2
Spilotes pullatus (TOP) Drymarchon corais (BOTTOM)
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This work is licensed under a Creative Commons Attribution-ShareAlike 4.0
International License.