Indigo Expeditions identified the need for further surveys in Laguna del Tigre National Park to assess the full impact of the 2015 El Niño phase on reptile and amphibian biodiversity. Funding for the El Niño Biodiversity Survey was secured through a 30 day crowdfunding campaign.


 

9 March 2016. Laguna del Tigre National Park, Guatemala.
Authors: Rowland Griffin and Adela Mei. Translation: Sheriyar Bokhari.
DOWNLOAD REPORT: El Niño Biodiversity Report 2016

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.


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.

Oxyrhopus petola, Banded calico snake, Indigo Expeditions

Oxyrhopus petola (Photo: Rowland Griffin)

Mexican mussarana, Clelia scytalina, Indigo Expeditions

Clelia scytalina (Photo: Rowland Griffin)

Triprion petasatus, Yucatán casquehead treefrog, Indigo Expeditions

Triprion petasatus (Photo: Rowland Griffin)


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.

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.


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


 

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).

Rhynophrynus dorsalis , Indigo Expeditions

Rhynophrynus dorsalis (Photo: Rowland Griffin)

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.

Oxybelis aeneus, Indigo Expeditions

Oxybelis aeneus (Photo: Rowland Griffin)

 

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.

Spilotes pullatus, Tiger ratsnake, Indigo Expeditions

Spilotes pullatus (Photo: Rowland Griffin)

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.

Drymarchon corais, Indigo snake, Indigo Expeditions

Drymarchon corais (Photo: Rowland Griffin)

 


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.


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.

DOWNLOAD REPORT: El Niño Biodiversity Report 2016


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.

 

Indigo News!

Receive the latest Expedition and Research news.

Your sign up was a success!

Indigo News!

Receive the latest Expedition and Research news.

Your sign up was a success!