Amphibian conservation in an urban park: A spatial approach to qualifying threats to Anura in Table Mountain National Park
Seven amphibian species which are endemic (or near-endemic) and threatened to the Cape peninsula are the focus of my MSc study. Past assessments have highlighted general threats to these species e.g.: the threat of alien invasive plants. However, the spatial extent of multiple and cumulative threats has not been assessed or analysed. To do this I am taking a spatial analytic and modelling approach, using a Geographical Information Systems. This analysis will be used to create a cumulative proximity-to-threat layer for each species. Additionally, threats observed in field (fine-scale mapping, near breeding habitats) will also be spatially analysed. SANParks’ Table Mountain National Park places Heleophryne rosei as its top ranked animal species of special concern (SSC), and listed as Critically Endangered by the IUCN. The threats to this species are generalizations and assumptions based on the precautionary principle; while in reality, threats are different within different sub-populations. I am to explain the observed variation in habitat (tadpole) productivity by examining the water chemistry at each sub-population. In-so-doing define an ‘optimal’ ecological envelope for H. rosei tadpoles.
With this MSc, I aim to evaluate how populations of a frog species endemic to the Cape Peninsula, Arthroleptella lightfooti, are affected by invasions of exotic woody vegetation. The Fynbos Biome contains more invasions of alien plants compared to any other vegetation type in South Africa. The presence of invasive woody species such as Pinus pinaster and Acacia saligna in the mossy seepage habitat of these frogs may have an effect on the population densities of the frog. Higher degrees of invasion by the plants may result in lower population densities of A. lightfooti. This hypothesis will be explored using an acoustic Spatially Explicit Capture Recapture method (aSECR). An array of microphones arranged around a recording device can capture the chirp-like calls emitted by male A. lightfooti. These calls can be analysed using aSECR (noting which microphones did and did not capture a particular call). Together with information such as the differences between the time of arrival (TOA) and signal strength (SS) of each call across the different microphones, the density of calling frogs can be estimated. With the current global decline of amphibian populations, mastering effective means to evaluate or monitor amphibian populations is quintessential for conservation efforts.