Movement of Frogs and Turtles Relevant to Bioinvasions on Borneo

Indraneil, Das (2017) Movement of Frogs and Turtles Relevant to Bioinvasions on Borneo. In: Aquatic Invasive Alien Species in Southeast Asia Symposium, 29 & 27 July 2017, National University of Singapore.

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Abstract

Invasive herpetofaunas on Borneo may be classified as non-native to the island or non-native to specific habitats. Frogs that have benefited from human activities have expanded their ranges. One example is Kaloula pulchra, known till the turn of the century from two isolated localities, and having then spread across the northern coast by the first decade of 2000, and is now widespread in Sarawak State. Other exotic frogs have been less successful: established populations, for one, exist in the immediate vicinity of farms (Hoplobatrachus rugulosus) or have failed to establish as escapees (e.g., Lithobates catesbeianus). Less well known is the invasion of local species into primary forests. Field observations show that creation of roads and disturbance along rivers eventually permit access to forested areas. Specifically, high temperatures associated with standing bodies of water provide suitable breeding areas for such species. Invasive reptiles include Calotes versicolor (introduced at the turn of the century) and Trachemys scripta (earliest introduction at least by the late 1990s); the first, probably introduced with imported plants, the second from the pet trade. Field observations on Megophrys nasuta and Heosemys spinosa were made to gain insights on these surrogates of their respective groups. Frogs were marked with passive integrated transponders; turtles were radio-tracked. Adult frogs show sitefidelity, while juveniles ranged up to 335m over a three-day period. Adult turtles showed restricted movement, changing resting sites by under 44m, and occupying the same shelter for much of the 60 days ofobservation. These studies indicate relatively low mortality in the rainforest herpetofaunas, except for juvenile frogs. Less well understood are movements of invasive species, and emphasise the need for more studies on the introduced herpetofaunas.

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