EPOW - Ecology Picture of the Week

Skink Puzzle

Indo-Pacific Mole Skink (Eugongylus rufescens), Family Scincidae
Ikat Village, Bali, Indonesia

Explanation:  I was exploring a steep, deep stream gorge, in a small village well outside Candidasa, southeast Bali, Indonesia, and happened upon this beautiful lizard.  I knew right away it was a member of the skink family, Scincidae.  But ... what species?

That led me on quite a subsequent bit of research and reading.  My go-to resource was the book A Field Guide to the Reptiles of South-east Asia.  But there was nothing clear therein, to identify what I had discovered and photographed.  The images, descriptions, and site locations of the many skinks listed in that field guide, as wonderful as they were represented and explained, did not align well with what I saw.

I entertained the possibility that it was an introduced species on Bali, or in Indonesia as a whole, but still I could not find a description and image that matched what I found and photographed.  

Eventually, my search led me to the Bar-lipped Sheen Skink, also called the Indo-Pacific Mole Skink in my field guide (Eugongylus rufescens) although a key web resource did not mention Bali as part of its range, only "parts of eastern Indonesia."  Bali is on the far west of the Lesser Sunda Islands of Indonesia, which might pertain.   

Still, the descriptions and photos of its coloration and characteristics did not quite match, showing upper and lower lips with vertical dark bands, and the back with faint transverse banding, and other key markings, but none of which appeared in this individual.  Nothing mentioned the bright orange-yellow sideband (see main photo, above).  But the individual I found did have the oval oricular (ear) openings, the thick tail and body, and even the 3 "keels" (ridges) on each of the scales on its back, as described in some of the resources.  

And it was the general body form and thick tail, along with the oval ear opening, and then especially the (weak) scale keels on the back, that led me to specifically conclude that it is indeed Eugongylus rufescens, in a late juvenile age class.  

Whew!

But still ... a key resource (Koch et al. 2009) on a checklist of reptiles and amphibians of Sulawesi, Indonesia, had only scant information on this species, with no material examined, and no findings of a specimen during their field search there, and with no mention of its occurrence on Bali or elsewhere in the country.  Another key resource (Slavenko et al. 2023) mentioned that Eugongylus rufescens was one of the earliest described skinks from the southeast Asian region because it was large and geographically widespread, so more apt to have been readily discovered, but nothing about modern findings and distributions.  

So unless there has been some reptile surveys and studies in Bali, especially southeast Bali, that have already described this species there, my observation might provide a nice addition to the known distribution of the species in Indonesia.

Information:
     Das, I. 2010. A field guide to the reptiles of south-east Asia. New Holland, London. 376 pp.
     Koch, A. J., E. Arida, A. Riyanto, and W. Böhme. 2009. Islands between the realms: a revised checkilst of the herpetofauna of the Talaud Archipelao, Indonesia, with a discussion about its biogeographic affinities. Bonner zoologische Beiträge 56:107–129.
     Slavenko, A., A. Allison, C. D. Austin, and 16_others. 2023. Skinks of Oceania, New Guinea, and Eastern Wallacea: an underexplored biodiversity hotspot. Pacific Conservation Biology 29(6):526-543. https://doi.org/10.1071/PC22034.