reptile diversity

Lost, Hidden, and Found: The Herpetofauna of Samar’s Karst Labyrinth

A recent field study to document reptile and amphibian diversity found in Samar Natural Park (SINP) and Samar Island unveils fascinating results.

Guest Blog Post by the Research Team of Samar Island’s Herpetofauna

In the darkness of the Samar rainforest, a flash of color stopped the research team in their tracks. Their headlamps illuminated a small shrub on a worn limestone trail, revealing a tiny pink snake. With a quiet sense of triumph, Yñigo del Prado readied his camera and leaned forward to photograph the coiled serpent within the branches of the shrub.

Although unknown to del Prado’s research team at the time, their rediscovery of the rare blindsnake Ramphotyphlops marxi would become one of the significant findings of the most recent comprehensive field study to document reptile and amphibian diversity found in Samar Natural Park (SINP) and Samar Island. Indeed, first recorded by the eminent zoologist Dioscoro Rabor in 1957 and unseen since, the snake is now a key highlight of the the survey, now published in the open-access journal ZooKeys.

*Ramphotyphlops marxi* – Marx’s worm snake. (Image credit: Yñigo del Prado).

“Samar Island is a biological frontier hiding in plain sight,” remarks Arvin Diesmos, a former curator in herpetology at the National Museum of the Philippines, and present senior director at the ASEAN Centre for Biodiversity. He was part of an expedition team from the Herpetological Research Collection of the University of Santo Tomas to survey the biodiversity of Samar Island Natural Park.

The primary goal of the expedition was to generate updated and comprehensive data on the terrestrial vertebrate fauna—from amphibians and reptiles to birds and mammals—that aim to strengthen the scientific foundation for the nomination of SINP to the UNESCO World Heritage List.

The diverse team of biologists was assembled by UST Assistant Professor Mae Diesmos and head of UST–HRC, to spearhead the terrestrial faunal surveys, while project was designed by Professor Eric Zerrudo, also from UST, and the director of the Center for Conservation of Cultural Property and Environment in the Tropics.

Together with biologists from the University of the Philippines in Diliman and Los Banos campus, in close partnership with the Department of Environment and Natural Resources and the Samar provincial government, the project undertook a month-long biodiversity survey of the karst rainforest of SINP – a ~333,339 hectare protected area of intact lowland forest over limestone and a Key Biodiversity Area in the Philippines.

Karst rainforest of SINP. (Image credit: Yñigo del Prado).

At an estimated area of ca 1,310,700 ha, Samar and the nearby island of Leyte count as one of the largest islands of the Philippines. While Samar has gradually experienced progressive decline in forest cover over the last couple of decades, its interior still houses one of the largest intact labyrinths of habitats spanning karst rainforest and cave systems.

“The reptiles and amphibians in limestone karst systems have evolved in remarkable ways. Every major survey [we] conducted reveals something new, something previously undetected just hiding under the woodworks. Which tells us that Samar remains one of the most important—and often understudied, biodiversity strongholds in the eastern region of the Philippines.”
Mae Diesmos

Though, perhaps “understudied” is an overstatement. A number of biological surveys have been conducted in SINP, as referenced in the article, with some of the extensive surveys dating back as early as the 1850s.

With the benefit of hindsight, the team integrated historical records into their paper, updating species names and distributions to match current classifications. This process effectively cleared up past confusion over identification. In addition, the larger taxon-based field biologists from UST and UP, allowed for more targeted sampling of several taxonomic groups. Increasing the sampling effort subsequently led to more extraordinary discoveries.

Case in point, the team found an additional 39 new records of reptiles and amphibians that bolstered the listing in SINP to a total of 79 species, and new distribution records of three species previously unknown from the island. And of course, there was the collection of the two specimens of R. marxi, whose existence had only been known from two historical records.

Dog-toothed cat snake. (Image credit: Yñigo del Prado).
Bornean keeled pit viper. (Image credit: Yñigo del Prado).
Philippine shrub snake. (Image credit: Yñigo del Prado).

Striped leaf gecko. (Image credit: Yñigo del Prado).

Acquiring this valuable data was by no means a simple task. The herpetology team was beset by the onset of the monsoon season, meaning that dry transect walks and even dry clothing were rare. The team also faced the strong currents and high rapids of the adjacent Ulot River as they moved from one site to another, and endured sandfly-infested campsites.

Ulot River Stream. (Image credit: Yñigo del Prado).

Encounters with local herpetofauna were always a joy. In the search for unique and cryptic species of lizards and snakes, the herpetology team relied on some tried and tested methods such as targeted microhabitat sampling of decaying logs, forest litter, and stream banks to look for fossorial species. Some methods were largely improvised; collapsible fishing poles became indispensable to shake down arboreal species or at the very least, encourage them to descend from the canopies.

Some species, however, had to be approached differently, as was the case for Platymantis bayani. The species is part of a larger complex of limestone frogs that could be found in karst formations in the Philippines, and each known species is unique to the location where it is found. On more than one occasion, the herpetology team had to search through overgrown limestone crevices; in others, the group descended into the depths of massive limestone caves in the dark to search for these elusive frogs.

*Platymantis bayani* – Walter’s limestone frog. (Image credit: Yñigo del Prado).

But Filipinos are nothing if resilient, as a local adage goes. Certainly, Mae Diesmos and her team had their work cut out for them. The officials of the Samar provincial government were notably also very thorough in their coordination and movement across study sites, to ensure the safety of the team. This highlights the importance of collaborative work between research institutions and local government units and stakeholders. Research is considerably more difficult without proper funding and local coordination.

This issue is not unique to Samar. Limited and precious funding to support scientific research remains a challenge to sustain biodiversity surveys across many islands and regions of the country. Much work remains to be done because numerous areas and habitats still lack detailed biodiversity surveys. Field biologists and conservationists have, for many decades now, been locked in a dizzying and (at times) disheartening race against habitat destruction and population decline of key species.

Semper’s forest dragon. (Image credit: Yñigo del Prado).

As more field studies continue, Samar and nearby islands will likely continue to reveal even more of its hidden biodiversity. An inspiring reminder to future researchers that even in the 21^st century, the rainforest of the Philippines still holds many scientific discoveries waiting to be made.

Original source:

Diesmos MLL, del Prado YLC, Kim PMM, Caguimbal NALE, Venturina REL, Lorenzo II AN, Diesmos AC (2026) Amphibians and reptiles of Samar Island Natural Park, Philippines, with an updated checklist, a rediscovery, and new records for Samar Island. ZooKeys 1269: 303-328. https://doi.org/10.3897/zookeys.1269.173854

For more articles on zoology, visit the ZooKeys website and follow the journal on BlueSky and Facebook.

Is It a Snake or a Lizard? Understanding the Formosan Legless Lizard

These lizards are among the most secretive and least studied groups in Taiwan.

A research team from the National Taiwan Normal University has clarified the status of a secretive reptile through a new study published in the open-access journal ZooKeys. Led by Si-Min Lin, the team focused on the Formosan legless lizard, scientifically known as Dopasia formosensis. These lizards are among the most secretive and least studied groups in Taiwan, living primarily under leaf litter and humus in moist forests. This elusive behavior makes field observations and ecological studies extremely difficult.

The study resolves a century of taxonomic debate over whether Taiwan’s legless lizards comprise one species or two. For decades, these populations were classified as Dopasia harti, a status complicated by the loss of the original Dopasia formosensis type specimen after World War II. To stabilise the identity of the species and re-establish it as the distinct lineage Dopasia formosensis, the research team has designated a “neotype” – this is a new physical specimen that serves as the official reference for the species name.

*Dopasia* *formosensis* in natural habitat: A fully mature adult male showing its dorsal bluish marking; A relatively younger male; A young individual with pale brown dorsal coloration and sharply contrasting black ventral surface. (Photo credit: Yu-Jhen Liang).

Physical Characteristics

The Formosan legless lizard is a medium-sized reptile that lacks external limbs. Adult males typically have a body length between 175 and 230 millimeters, while females are similar in size. A key feature of this species is its exceptionally long tail, which can be nearly double the length of its body.

People often mistake these lizards for snakes, but they possess several distinct features that set them apart. Unlike snakes, legless lizards have external ear openings, although they are quite small. They also have moveable eyelids, which means they can blink, a trait no snake possesses. Further, these lizards have a prominent lateral fold, which is a longitudinal groove running along each side of the body. This fold allows the skin to expand, which is useful for breathing and when females are carrying eggs.

Head morphology of the neotype of *Dopasia* *formosensis*; an adult male from Mingchi, Yilan County, Taiwan. (Photo credit: Chih-Wei Chen and Chin-Chia Shen).

Etymology and Colouration

The species name formosensis is rooted in the historical name for Taiwan, “Formosa”, derived from the Portuguese phrase Ilha Formosa (“Beautiful Island”). The name combines this geographical reference with the Latin suffix “-ensis”, which indicates the place of origin.

**Top:** Landscape near the type locality of *Dopasia formosensis* in Hinokiyama, currently known as a part of the Fuba Cross-ridge Trail.

**Bottom:** Landscape of the collection site of the neotype near Mingchi, Yilan, Taiwan. (Photo credits: Chung-Wei You and Kai-Xiang Chang).

The study also clarified a major point of ambiguity regarding the species’ color. Previously, lizards with bright blue spots were thought to be a different species than those without them. The research team confirmed that these markings are actually a form of sexual dichromatism – while females and young lizards usually have a plain pale brown or bronze color, fully mature adult males often display these conspicuous blue markings as a form of secondary sexual signalling.

Behavioural Characteristics

Since these legless lizards are so rarely seen, the research team relied on citizen science data from the Taiwan Roadkill Observation Network to gather information. In the wild, these lizards prefer high-humidity environments in mid-elevation forests with dense canopy cover.

Sampling sites of *Dopasia* *formosensis* (Kishida, 1930), D. *harti* (Boulenger, 1899), and D. *hainanensis* (Yang, 1983) available from GenBank.

The researchers also noted parental care as a key behavioural characteristic for the species, suggesting that they may exhibit more complex social behaviors than many other reptiles. In related species within the Dopasia genus, for instance, females are known to exhibit egg-guarding behavior, where they remain with their clutch to protect it from predators and environmental hazards until the offspring hatch.

Egg guarding by a female *Dopasia* *formosensis* in the wild, observed in Pingtung County, southern Taiwan. (Photo credit: Weizun Wang).

A prior study documenting the species now recognised as Dopasia formosensis (previously identified as D. harti) notably also detailed its interesting fighting behavior. The encounter begins with a ritualised display where the lizards circle each other with mouths agape, flattened throats, and elevated forebodies. This posturing eventually escalates into physical combat, characterised by one-sided biting and rotational rolling as the males attempt to subdue one another.

Conclusion

The Formosan legless lizard is currently listed as a protected species under Taiwanese law. The research team emphasises that a stable scientific name and clear understanding of the species is critical for future conservation.

“Through these efforts, we aim to provide a more stable framework for future taxonomic, ecological and conservation studies of this overlooked lizard group.”
The Research Team

By making their data openly available, they hope to encourage further study of these unique animals across East Asia.

Original source:

Lin S-M, Shen C-C, Lin T-E, Liang Y-J, Chang W-H (2026) Redescription and neotype designation of Dopasia formosensis (Kishida, 1930) (Squamata, Anguidae) from Taiwan. ZooKeys 1270: 69-98. https://doi.org/10.3897/zookeys.1270.173752

For more articles on zoology, visit the ZooKeys website and follow the journal on BlueSky and Facebook.

Guest blog post: Unique feeding behaviour of Asian kukri snakes gutting frogs and toads

Guest blog post by Henrik Bringsøe

In September 2020, we reported the first evidence for a newly discovered behaviour in snakes, as we provided extensive photographic documentation, demonstrating a macabre feeding strategy of Asian kukri snakes of the species Oligodon fasciolatus, the Small-banded Kukri Snake: a snake cutting open the abdomen of a toad, inserting its head and pulling out the toad’s organs which are then swallowed.

A Small-banded Kukri Snake attacking a Painted Burrowing Frog, which is inflating its lungs. The snake makes rotations about its own longitudinal body axis (“death rolls”), as it is biting and holding the belly of the frog. Video by Navapol Komanasin.

This is done while the toad is alive and it may take several hours before it dies! We have now provided new evidence that two other species of kukri snakes also exhibit this highly unusual behaviour: Oligodon formosanus, the Taiwanese Kukri Snake, and Oligodon ocellatus, the Ocellated Kukri Snake. These three species are closely-related and belong to the same species group in the genus Oligodon.

On two occasions in Hong Kong, a Taiwanese Kukri Snake was observed eviscerating frogs of the species Kaloula pulchra, the Painted Burrowing Frog or Banded Bullfrog. In one case, the snake had cut open the belly of the frog and inserted its head deep into the frog’s abdomen. In this position, the snake performed repeated rotations about its own longitudinal body axis, also called “death rolls”! We believe that the purpose of these death rolls was to tear out organs to be subsequently swallowed. In the other case, the organs of the frog had been forced out of its abdomen.

A Taiwanese Kukri Snake with its head buried deep into the abdomen of a Painted Burrowing Frog. Initially, the frog moves its long fourth toe of the left hind foot up and down 21 times. During the subsequent active struggle, the snake makes three “death rolls”. Video by Jonathan Rotbart.

A Small-banded Kukri Snake was also observed eating a Painted Burrowing Frog in Northeast Thailand, but it swallowed the frog whole. That snake also performed death rolls, although we have never before seen that behaviour in this species of kukri snake (this species was treated in our 2020 paper). This frog is not considered toxic and is also eaten by other snakes. We believe that prey size is crucial in determining whether the gape width allows large prey to be swallowed whole by kukri snakes. If the prey is too large, the snake may eviscerate a frog or toad, in order to swallow the organs. Afterwards, the snake will perhaps be able to swallow the rest of the frog or toad.

In another new paper, we describe and illustrate the Ocellated Kukri Snake eating the toxic toad Asian Black-spotted Toad (Duttaphrynus melanostictus) in Vietnam. Initially, the large snake’s head was buried past its eyes into the abdomen of the toad, but eventually the snake swallowed the toad whole despite its toxicity. We interpret this behaviour that kukri snakes are in fact resistant to the toads’ cardiac glycoside toxins. Furthermore, toads are only eviscerated if they prove too large to be swallowed whole.

An Ocellated Kukri Snake first pierced this poisonous Asian common toad and buried its head deeply into the abdomen of the amphibian, as it was probably eating the organs. However, as seen in the photo, the kukri snake proceeded to swallow the toad whole.
Photo by James Holden.

We suggest that the unique behaviour of eviscerating frogs and toads and eating their organs may have evolved specifically in a group of kukri snakes named the Oligodon cyclurus group or clade because it has now been recorded in three of its species, namely Oligodon fasciolatus, Oligodon formosanus and Oligodon ocellatus. We hope that future observations may uncover additional aspects of the fascinating feeding habits of kukri snakes though we may indeed call them gruesome.

See more video recordings of the snakes’ unique, even if quite gruesome, behaviours provided as supplementary files to one of the discussed research papers.

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Research papers:

Bringsøe H, Suthanthangjai M, Suthanthangjai W, Lodder J, Komanasin N (2021) Gruesome twosome kukri rippers: Oligodon formosanus (Günther, 1872) and O. fasciolatus (Günther, 1864) eat Kaloula pulchra Gray, 1831 either by eviscerating or swallowing whole. Herpetozoa 34: 49-55. https://doi.org/10.3897/herpetozoa.34.e62688

Bringsøe H, Holden J (2021) Yet another kukri snake piercing an anuran abdomen: Oligodon ocellatus (Morice, 1875) eats Duttaphrynus melanostictus (Schneider, 1799) in Vietnam. Herpetozoa 34: 57-59. https://doi.org/10.3897/herpetozoa.34.e62689