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The Asian Common Toad:
A serious threat to Madagascar's amphibians
The threat invasive species pose to the world's biodiversity is second only to habitat loss. In March 2014 the conservation community was alerted to the discovery of the Asian common toad, Duttaphrynus melanostictus, in Toamasina. It is likely that the toad was inadvertently introduced via cargo containers or other packaging on ships arriving at the Port of Toamasina.
The Asian common toad represents a significant threat to Madagascar's endemic frog species in multiple ways. A single female can produce thousands of eggs (up to 10,000!) thus the toad's population can increase and spread quite dramatically and can be accelerated if potential predators are susceptible to the poisonous substance, bufotoxin, covering the toad's skin. Preying on small vertebrates and a wide range of invertebrates, Asian common toads have the capacity to out-compete many of Madagascar's endemic amphibians while the harm they pose as vectors of infectious diseases is currently unknown but of significant concern.
The IUCN Amphibian Specialist Group - Madagascar and their partners worked quickly to initiate a rapid response to this new threat. Immediate actions included villager surveys to ask if they had seen Asian toads and if so, when was the first time they remembered seeing the toad. Posters developed by ASG and MFG to inform local people about the threats posed by the toad and requests to report any sightings to MFG Office were distributed at this time. A series of radio announcements about the toad were also made. Visual encounter surveys, coordinated by the MFG, were carried out in May with the assistance of students from the University of Toamasina, Association Mitsinjo, DREEF (Regional Direction of Environment, Ecology & Forests) and MFG staff with the goal of mapping the toad’s distribution. Additional surveys were done in July and October; some toads were captured for the collection of biological samples to screen for infectious diseases. In November a team of invasive species eradication experts came to Madagascar to assess the feasibility and potential cost of a toad eradication program. Their report should be completed by the end of January 2015.
A New Frog Species
In their 2012 publication on Betampona’s amphibians, Rosa et al identified 76 frog taxa of which 36 were candidate species. A December 2014 publication by Rosa et al. presents the results of mitochondrial, nuclear, bioacoustic and morphological analysis for one of the candidate species that confirms it is indeed a new species, Platypelis karenae. An adult is only 16-18 mm in length and, like other Platypelis, it has an arboreal lifestyle, inhabiting one of two plant species, Crinum firmifolium and a small Pandanus species. Not yet found in other locations, this species may well be restricted to Betampona. The greatest conservation threat to this species is guava because its highly invasive nature can create a monoculture by outcompeting and eliminating native plants. The frog is named in honor of the MFG’s Research Director, Dr. Karen Freeman, who has long recognized the need to control guava and is working with PhD candidate, Lala Randriatavy, to identify an effective and environmentally safe method of control (read about this project).