An investigation of the vulnerability of the Maltese painted frog, 'Discoglossus pictus pictus' populations

Abstract

The Maltese painted frog Discoglossus pictus pictus is the only indigenous amphibian present on the Maltese Islands, research on which is sparse and limited. The current work was intended to study selected populations of the Maltese painted frog, including its distribution, suitable habitats and analyses a series of orthophotos and old cartography with a view to identify pressures such as land-use change. Population density carried greatly between the three researched areas. The highest numbers occur at Chadwick Lakes, followed by the ‘Tal-Wej’ area and lastly ‘Wied il-Luq’ valley. Chadwick Lakes also provided the highest number of adjacent suitable habitats and a higher possibility for ‘migration’ of the species to other location. The most vulnerable location is that of ‘Tal-Wej’ since the area and its catchment is almost totally surrounded by urbanisation, eliminating any possibility for the species to ‘migrate’ to other adjacent areas. This makes it a very important area to protect and manage for the survivability of the present population and to maintain a positive conservation status. Buskett and Chadwick Lakes offer several alternative habitats that act to reduce their vulnerability from pressures such as scarcity of water. However, their vulnerability lies with the fact that connectivity is mainly of a linear nature, jeopardizing the entire population should there be a big enough negative impact which might affect the area. Biggest noted pressure in all the locations investigated was the lack of precipitation experienced during the 2015-2016 wet season, when only approximately 237mm of rainfall was recorded, compared to the annual average of 530mm. Desiccation resulted in a high mortality of larvae. It was concluded that ‘Tal-Wej’ had the highest change in land-use, highest vulnerability and high anthropogenic interference. Hence, appropriate management of the area for its protection is of utmost importance, whilst also ensuring that areas such as Chadwick Lakes and Buskett are afforded sufficient safeguard to avoid further biotope and habitat deterioration.