Effects of riparian border size and land use change on tropical amphibians

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Freshwater Biology

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Research Grant


The greatest threat to amphibians today is habitat loss. Currently, Southeast Asia has the highest rate of deforestation in the world, and one of the highest rates of new anuran species description. Thus, SE Asian amphibians are at risk of going extinct before they are even described or their ecology and behavior understood. Much of the deforestation in the region is due to conversion to oil palm, and little is known about how this conversion affects ecologically sensitive species such as amphibians. As part of the SAFE project, I aim to examine changes in anuran ecology associated with conversion of forest to oil palm. There are three main goals of this research.1. Quantify the relationship between riparian border size and change in abundance and diversity. Nocturnal stream surveys will identify abundance and diversity of adult anurans on each stream. I will use these data to determine 1) the rate of change in abundance and diversity due to forest conversion, 2) the effects of riparian border size on abundance and diversity changes, and, utilizing hydrology and net primary productivity data collected by other SAFE researchers, 3) the strongest predictors (dissolved oxygen, sedimentation, net primary productivity) of changes in abundance and diversity of frogs.2. Determine the persistence of source populations by examining presence/absence of tadpoles. Surveys of tadpoles will determine which species seen on the streams as adults are actually breeding in those streams (source populations) and which species are not likely utilizing the streams to breed (sink populations). After forest conversion, I will continue to monitor tadpole abundance and diversity to determine the relationship between persistence time as a source population and a) forest conversion and b) riparian border size. Additionally, utilizing hydrology data such as dissolved oxygen and sedimentation, I can determine the ultimate factors responsible for any observed losses of tadpole populations.
3. Examine changes in advertisement calls as related to riparian border size, and how that in turn affects mate choice and reproductive success. Studies from other areas have shown that frogs alter calls in response to habitat alteration, and this can affect mate choice and reproductive success. Recording calls before and after the clearing, I can determine how habitat alteration affects call parameters such as dominant frequency and call rate. Changes in these parameters normally convey information on the fitness of the male, but few studies have shown how these factors may shift with change in the acoustic environment, and what the consequences of such shifts might be for reproductive success.


I will establish 400 m transects along the six experimental watersheds, and along two control streams, one in the virgin jungle reserve, and one in previously logged forest that will not be cleared for oil palm. Transects will be surveyed 6-7 times each over a two-month period prior to clearing. I will collect voucher specimens of each species on each stream (up to 5 individuals per species per stream) along with tissue samples for future DNA work to examine changes in population genetics.Each stream will also be surveyed for tadpoles prior to clearing. I will use electroshocking methods to survey tadpoles at the bottom, middle, and top of each transect. To insure that these methods do not affect our observations of frogs on night surveys, I will survey tadpoles in each stream the morning after its night survey, giving us the maximum amount of time between diurnal tadpole surveys and the subsequent nocturnal adult surveys. Tadpole surveys will identify species that are breeding on the stream, and species which are observed as adults but are not likely breeding. Effectively, this allows us to identify source and sink populations so that I can quantify the rate of shift from source to sink after conversion to oil palm. I can also correlate changes in tadpole abundance and diversity with changes in abiotic factors such as dissolved oxygen and sedimentation.I will also record advertisement calls of anurans in order to determine how anthropogenic noise and shifts in habitat (from dense primary or secondary forest to oil palm) affect frog calls. Up to ten individuals per species on each stream will be recorded prior to clearing in order to establish baseline call parameters. During and following clearing, I will record calls to determine how the calls shift in response to anthropogenic noise and altered habitat structure.
After the clearing, I will continue to monitor abundance and diversity of adults and tadpoles, and record advertisement calls. My aim is to continue the project for multiple years in order to look at changes in anuran ecology in response to habitat alteration. I am currently pursuing funding that would allow me to pay several research assistants to help with the long-term monitoring, and I plan to spend several months of each year on site, as time and funding permits.
Project members
ResearcherProject roleProject contact
Jennifer SheridanLead Researcher