Friday, July 12, 2013

[Herpetology • 2012] Novel behaviors of Southeast Asian rhacophorid frogs (Anura, Rhacophoridae) with an updated anuran species list for Danum Valley, Sabah, Malaysian Borneo

FIGURE 2. A. Rhacophorus pardalis constructing leaf nest around foam egg mass.

Land-use change and the predicted impacts of climate change are major threats to the biodiversity of Southeast Asia. Judging their impacts requires baseline biodiversity data and an understanding of the behavior of resident species in order to effectively manage that diversity. Here, we present an updated anuran species list for Danum Valley Field Center from the results of a nine-week survey expedition. We employed nocturnal stream searches as the basis of sampling and include data gathered from opportunistic encounters. We documented 47 anuran species, including one new locality record. In addition, we recorded a single species of caecilian (Gymnophiona). During this survey period we also documented aggressive territoriality in Rhacophorus appendiculatus, the manipulation of leaves to surround eggs by Rhacophorus pardalis, and predation of an adult Rhacophorus dulitensis by Polypedates otilophus. These observations and their implications are discussed.

Key words: Amphibians, Rhacophorus, Polypedates, reproduction, predation, diet, call recording

Rhacophorus pardalis nest construction.
– On three occasions, we observed female Rhacophorus pardalis laying eggs, and subsequently manipulating leaves to cover the foam nest. In each case, the female laid her eggs on a single leaf and after the male departed, used her front and hind limbs to pull an adjacent leaf towards the egg mass or folded over the leaf on which her eggs were placed, to form a cover for the foam nest. The female then positioned herself in a way that allowed her to press the two leaves together around the eggs (Fig. 2A), which appeared to 'glue' the leaves or leaf blades to the egg mass. Each time, the female sat near the bottom or top of the clutch with her front and hind feet splayed to press the leaves, or halves of the single leaf, together for approximately 30 minutes, then shifted her position to the top or bottom end, again pressing the leaves together for an additional 30 minutes. 

FIGURE 2.  B. Polypedates otilophus consuming Rhacophorus dulitensis

Frog predation by Polypedates otilophus.
– On a single occasion, we observed an adult Polypedates otilophus in the process of consuming an adult male Rhacophorus dulitensis (Fig. 2B). Upon collection of the P. otilophus, the meal was disgorged. To our knowledge, this is the first documented case of frog predation by a rhacophorid.

The novel behaviors and new locality records reported here for Danum Valley highlight the importance of preserving lowland Bornean forests. Currently, much of Southeast Asia is being logged or converted to oil palm plantations (Sodhi et al., 2004; Sodhi et al., 2010), with devastating consequences for ecosystem services and biodiversity in general. Studies are currently under way to determine the effects of conversion of forest to oil palm on biodiversity of amphibians. Continued monitoring of lowland biodiversity is essential as a baseline to judge the impacts of forest fragmentation and potential latitudinal and elevation range shifts, through lowland biotic attrition, predicted under climate change scenarios. It may be possible for many species to behaviorally adapt to land use and climate change, and it is important to document baseline behavioral patterns where possible. We encourage further research on Bornean amphibian ecology, evolution, and behavior in order to more fully understand the region‘s biodiversity before it is lost.

Sheridan, J.A., S.D. Howard, P. Yambun, J.L. Rice, R. Cadwallader-Staub, A. Karolus, and D. Bickford. 2012. Novel behaviors of Southeast Asian rhacophorid frogs (Anura, Rhacophoridae) with an updated anuran species list for Danum Valley, Sabah, Malaysian Borneo. Tropical Natural History. 12 (1): 1-8.