Herpetofauna topics

Country codes: HO (Honduras), IN (Indonesia), MA (Madagascar), ME (Mexico), PE (Peru), SA (South Africa)

HO06 Abundance and distribution of threatened amphibian populations in Cusuco cloud forest

Amphibians are the most threatened vertebrate group globally and this is exacerbated for the amphibians of Cusuco National Park due to rapid, recent expansion of coffee farms and pastures for cattle ranching within the buffer zone and core zone of the park. If the amphibian populations continue to decline, decisions must be made regarding the value of ex-situ conservation of key species for subsequent release once the threats to the population have been resolved. In order to make such decisions, it is imperative that we have reliable estimates of amphibian population dynamics. Thus, data are urgently required on the population sizes and distributions of each of the cloud forest amphibian species and the catchments in which each occur. Data collection for this project involves sampling amphibians from both the forests and rivers at multiple locations in the park. These data may then be used to calculate reliable estimates of species abundance and may also be added to existing GIS maps of the park to investigate species distribution patterns.

Extended Project Summary

HO07 Evolution of aposematic colouration and mimicry in coral snakes

Brightly coloured and deadly coral snakes and their harmless mimics are some of the most striking denizens of Cusuco National Park. The primary driver of this type of bright coloration is convergent evolution, where natural selection impels distantly-related organisms towards a shared phenotype. Biologists have long been fascinated by how selection can cause organisms to converge on a single phenotype despite different developmental and genetic backgrounds and being separated by millions of years of evolution. Mimicry is one of the most dramatic examples of convergent evolution and in particular, coral snake mimicry is a powerful example of Batesian mimicry, which occurs when a harmless species resembles a harmful species for a protective purpose. Coral snakes are dangerously venomous elapid snakes that are usually brightly coloured and banded. Across the geographic range of coral snakes, and sometimes outside of their geographic range, harmless snakes mimic the coral snakes with the same coloured crossbands. For this project, we will study the ecological and evolutionary dynamics of coral snake mimicry in Cusuco National Forest, which is home to at least two coral snake species and nine coral snake mimicking species. Dissertation students will participate in all aspects of this project (except that venomous snakes will only be handled by a trained herpetologist), which will include 1) using spectrophotometry or full-spectrum photography to quantify colour of coral snakes, mimics, and non-mimicking snakes, 2) characterising the ecological and habitat distributions of coral snakes and mimics and 3) using plasticine models to test for predation rates on different coral snake and coral snake mimic banding patterns.

HO08 Prevalence of chytrid in amphibian populations within Cusuco

The effective conservation of Cusuco National Park is imperative for many endemic species, none more so than cloud forest amphibians. The spread of chytrid fungus has caused severe declines in many amphibian populations and is a major concern for global amphibian conservation. Chytrid is known to have been present within the amphibian populations of Cusuco for at least 15 years, but its prevalence within specific areas of the forest and the extent to which different species are affected are not well known. Amphibian species will be encountered during diurnal and nocturnal transects and swabbed for chytrid. Swabs will be taken back to the lab at base camp and tested for the presence of chytrid using polymerase chain reaction (PCR) and visualised using agarose gel electrophoresis. Individuals will also be assessed for visual signs of infection. Prevalence of chytrid will be mapped in the park using multiple years’ data to assess whether the disease is continuing to spread to previously uninfected areas to contribute to the investigation into the underlying mechanism of infectivity.

Extended Project Summary

MA35 Spatial behavioural ecology of the Malagasy giant hognose snake

The Malagasy giant hognose snake (Leioheterodon madagascariensis), is Madagascar’s largest colubrid snake, attaining sizes greater than 1.5m in length. This species has been documented engaging in ritual combat and active nest defence, and a preliminary investigation suggests that the behavioural ecology of L. madagascariensis is more complex than previously thought. For this project all sightings will be recorded using a GPS receiver and all animals encountered will be captured, measured, weighed and microchipped to allow individual identification. Other novel methods may also be employed to investigate the daily habitat usage patterns of each individual. All data collected will be visualised and analysed utilising GIS software.

Extended Project Summary

MA36 Ecology of amphibians in Mahamavo

Amphibians play a vital role in the ecosystems where they are found. Nine species of amphibians are currently known from Mahamavo, some of which occur in relatively high abundances, even during the long dry season. Data for this project will be obtained by surveying rice paddies, ephemeral and permanent ponds and lakes; recording all encounters; noting the species, the number of individuals and the specific details of the immediate habitat where the animals are found. All data collected will be used to create a monitoring system for future studies whereby the species composition at each water body can be monitored.

Extended Project Summary

MA37 Colour variability and the ecological use of colour in the chameleons and geckos of Mahamavo

There are a wide range of endemic lizards in the dry deciduous forests of northwestern Madagascar. Colour is used in fundamentally distinct ways by the different taxonomic groups of lizards found in Mahamavo. Chameleons are depicted in the media as solely using colour change for crypticity, but in reality the main role of colour change here is in communication with other chameleons. There is some interesting colour variability within Angel’s chameleon and Oustalet’s chameleon as well. There are three species of Uroplatus geckos that really do use colour and colour-change to maintain crypticity. One species is a dead-leaf mimic, a second is a twig mimic and the third is a bark mimic. Colour is variable within species and some change colour quite effectively. Phelsuma are a third group of lizards in which there is substantial colour variability within individuals. They respond to changes in lighting and temperature as well as potential threats from predators. Questions regarding variation in colour and how colour change is being used can be addressed in all three groups of lizards. Colour can be quantified through using standardized photographs or by using a specialised reflectance spectrometer depending on the specific research question being addressed. Analyses of colour can use general linear models to examine variation in hue, saturation and value and look for statistically significant differences or by using principal components analysis to examine and compare entire reflectance spectrums.

Extended Project Summary

MA38 Microhabitats and niche partitioning in chameleons, skinks, geckos or snakes in Madagascar

The dry forests in Mahamavo support a very diverse reptile assemblage which share the same habitat. Competitive exclusion theory suggests that sympatric species must partition their niches for them to persist and the reptiles in this forest provide a great system to investigate how this occurs. In Mahamavo there are two abundant chameleon species, Furcifer oustaleti and Furcifer angeli. It is thought that Oustalet’s chameleon prefers more degraded forest to Angel’s chameleon, but additionally these species may be selecting different microhabitat niches in terms of height above the ground selected for feeding, branch thickness, ambient temperatures or structural complexity of vegetation. A similar situation exists with a pair of closely related skink species Trachylepis elegans and Trachylepis gravenhorstii which are both very abundant in the forest. It appears that T. elegans is more abundant in drier habitats than T. gravenhorstii, but the picture is probably more complicated at the microhabitat scale. There are also three species of leaf-tailed Uroplatus geckos: U. ebenaui, U. henekli and U. guntheri which share the same cryptic adaptations and feeding strategies yet differ markedly in size. With field data collected from a large number of individuals, it would be possible to compare niches and identify factors which separate species’ niches using principal component analysis, linear discriminant models or regression trees.

Extended Project Summary

ME47 Herpetofaunal species distribution and niche partitioning in the Calakmul Biosphere Reserve, Mexico

The herpetofauna of the Yucatan Peninsula is diverse and contains a high percentage of endemic species that have evolved to adapt to the unique forest habitat. Despite this, the herpetofauna of the Calakmul Biosphere Reserve is poorly studied. There is a notable rainfall gradient from the north to the south of the reserve, which significantly affects tree diversity and forest structure. The only source of water in the reserve comes from lakes known as aguadas. Some are permanent, but the majority are temporary that form on low lying ground during the rainy season. This variation in habitat is likely to have a notable effect on the abundance and distribution of herpetofauna within Calakmul. Herpetofauna surveys will be conducted at five different research locations within the reserve that have notable differences in habitat type. Within each location, herpetofauna will be surveyed using pitfall traps and diurnal and nocturnal active searching along transects. Students will also assist with habitat surveys in which tree diversity, tree DBH, understorey vegetation, leaf litter and sapling density are recorded in a selection of 20m x 20m forest plots at each survey location. Research projects could therefore investigate differences in herpetofaunal species assemblages between different sites and in relation to distance from aguadas. These projects could incorporate a wide range of species or could focus on specific groups (e.g. anurans, lizards, snakes). Alternatively, projects could focus on herpetofauna community structure in aguadas of varying sizes. These projects would involve timed searches of the aguadas for amphibian species combined with trapping surveys for lizards, snakes, turtles and crocodiles.

Extended Project Summary

ME52 Abundance of immature green turtles in relation to seagrass biomass in Akumal Bay

There are seven species of sea turtle in the world, all of which are either threatened or endangered. Akumal (meaning “home of the turtles”) contains one of the few remaining healthy seagrass habitats in the Mexican Caribbean coastline and is home to a large resident population of green turtles, Chelonia mydas. Immature green turtles (roughly 5-20 years of age) feed exclusively on seagrasses before reaching sexual maturity and travelling out to sea. Due to an influx of sargassum macroalgae in the Yucatan Peninsula in 2015, many of the seagrass habitats in the region died, meaning that Akumal is one of only a small handful of suitable feeding grounds for immature turtles. Over 80 individuals have been recorded in the seagrasses of Akumal Bay, but several years of unregulated snorkel tours with these turtles resulted in a decline in the turtle population and considerable damage to the seagrasses. As Akumal Bay is now a marine protected area, the hope is that the turtle population will recover. Snorkel tours with turtles have been restricted to a set route around the bay and the use of snorkel fins is prohibited in order to allow seagrasses chance to recover. As the turtles preferentially graze in different areas each year, the distribution of seagrasses in the bay change over time and the location of the designated snorkel route needs to change in line with this to ensure the continued recovery of the ecosystem. Research into green turtle feeding preferences will involve snorkelling with the turtles throughout the day to record their foraging patterns. Seagrass quadrats surveys will be used to determine the availability of the various species of seagrasses, which can then be compared to turtle feeding preferences obtained from behavioural observations. Belt transects throughout the bay will be used to estimate population density of the turtles and photographs of turtles along transects will be used to identify individuals in order to monitor departure of turtles as they reach sexual maturity and new arrivals into the bay. Photographs will also be used to monitor the recovery of turtles suffering from tumours that resulted from the combination of water contamination and chronic stress from unregulated snorkel tours prior to the formation of the new protected area.

ME53 Effect of tourism on immature green turtle behaviour in Akumal Bay

Year-round you can find immature green turtles (Chelonia mydas) feeding on the seagrasses in Akumal Bay. These turtles have become a popular tourist attraction and there is concern that both the number of tourists and the behaviour of tourists is affecting the behaviour and welfare of the turtles. Multiple studies of “swim with wild dolphin” based tourism has indicated that when the number of tourists gets too high, or the tourists attempt to touch them, the dolphins issue evasive responses to attempt to escape from the tourist and, if the tourism continues to maintain high numbers, the dolphins simply move their home range to areas inaccessible by tour boats. As the availability of healthy seagrasses in the Mexican Caribbean coastline is limited, the turtles in Akumal Bay may not have the option of leaving the area to avoid large numbers of tourists so the snorkel with turtle tours need to be strictly regulated. As Akumal Bay has just been declared a protected area, data is urgently required to determine the carrying capacity of snorkel based tourism. Research into green turtle behaviour will involve snorkelling with the turtles throughout the day to record their activity budgets and rates of evasive responses to tourists using focal animal sampling with continuous recording. Each turtle can be recognized individually and at the start of each focal sample the turtle will be photographed from various angles for subsequent identification from the turtle photo ID database. The number of tourists within a 5m radius of each turtle and the behaviour of these tourists (whether they abide by the rules and maintain a safe distance from the turtles or attempt to interact with them) will be recorded throughout each focal sample to determine the effect of tourism on turtle behaviour.

Extended Project Summary

PE59 Species assemblages and niche separation of amphibians within the Pacaya-Samiria Reserve

Amphibians are a highly diverse class, with species specialising across all habitats (terrestrial, aquatic, arboreal and fossorial). The Pacaya-Samiria Reserve is primarily composed of seasonally flooded forests which create a number of unique habitats for amphibians resulting in very interesting species assemblages and high abundances of specialist species within the area. Climate change has been having a huge impact on the Pacaya-Samiria Reserve in recent years, resulting in extreme periods of flooding and drought. This in turn is affecting habitat availability for certain specialist species of amphibians present. Data is collected across the two main macrohabitats (terrestrial and floating meadows) using visual encounter surveys via transects on the terrestrial habitat and quadrats from a boat on the floating meadows. One project could look into how species assemblages differ across the macrohabitats and try to determine specialist and generalist species. Another project could examine niche separation within each macrohabitat. Climate change could also be linked into a project to determine whether changing habitat availabilities are having an effect on species presence or habitat choices.

Extended Project Summary

PE60 Niche separation in caiman species

There are three caiman species (common, black and smooth-fronted) found in the Pacaya-Samiria National Reserve. This topic could examine the habitat usage and feeding ecology of the three species to identify how they separate their niches. Spotlight surveys are completed along the edges of the main river and in a series of oxbow lakes within the forest, some of which are still connected to the main river while others are totally separated during the dry season. The species, estimated size and habitat usage of each of the caimans observed during these surveys are recorded. Animals smaller than 2m would be captured by noose wherever possible and more detailed measurements (e.g. length, weight, sex) recorded from these captured animals. Diet of the captured caimans can be examined by flushing out the contents of the stomach, filtering the regurgitated food and classifying the main constituents. The high abundance of these species and the length of the survey season should ensure a good number of data points for this study, with the average number of stomach samples around 15. In addition there are long datasets available from previous annual surveys of the caiman against which changes in abundance of the various species could be assessed.

Extended Project Summary