Singapore's urban transformation over the past two centuries has profoundly impacted its native wildlife, with a recent study from the National University of Singapore (NUS) shedding light on the local extinctions of terrestrial lizards and snakes, collectively known as squamates. Researchers estimated that 17% of these species have been lost from the island, a figure lower than for birds or butterflies but still signaling significant biodiversity challenges. The work highlights opportunities for reintroduction, positioning NUS at the forefront of urban conservation science in Southeast Asia.
This research underscores NUS's commitment to addressing environmental crises through rigorous data-driven approaches, offering actionable insights for policymakers and conservationists in densely populated city-states like Singapore.
Singapore's Biodiversity Journey: From Forest to Metropolis
Singapore, once covered in lowland dipterocarp rainforest, underwent rapid deforestation starting in the 19th century for rubber plantations, tin mining, and later urbanization. By the mid-20th century, primary forest cover plummeted to less than 0.5%, leading to widespread species losses. Today, despite covering just 728 square kilometers, Singapore boasts over 47% green cover, including nature reserves like Bukit Timah and Central Catchment, managed by the National Parks Board (NParks). Restoration efforts have seen secondary forests mature, fostering some natural recoveries in birds, mammals, and butterflies.
However, terrestrial squamates—lizards (Lacertilia) and snakes (Serpentes), totaling over 10,000 species globally—face unique hurdles. Unlike volant species, most cannot cross the Johor Strait from Peninsular Malaysia, making human intervention essential for revival. NUS biologists have tracked these patterns, revealing how habitat degradation thinned populations gradually rather than causing abrupt collapses.
What Are Squamates? Defining the Group Under Study
Squamates, or order Squamata, encompass lizards, snakes, and worm lizards (amphisbaenians), characterized by keratin scales, movable quadrate bones for jaw flexibility, and hemipenes in males. In Singapore, historical records document around 149 native species: 24 frogs (though not squamates), 34 lizards, and 75 snakes, with focus on terrestrial forms excluding marine species. These reptiles play crucial ecological roles as predators of insects, rodents, and smaller vertebrates, and as prey for birds and mammals, maintaining food web balance.
Local examples include the house gecko (Hemidactylus frenatus, introduced) thriving in urban areas, while native forest dwellers like the jade vine snake (Ahaetulla prasina) persist in remnants. The NUS study emphasizes terrestrial squamates' vulnerability due to microhabitat dependence on leaf litter, bark, and understory vegetation.
The NUS Methodology: Harnessing the MODGEE Model
Lead author Ananthanarayanan Sankar, from NUS's Department of Biological Sciences and the Herpetological Society of Singapore, alongside supervisor Ryan A. Chisholm, applied the Matrix of Detections Gives Extinction Estimates (MODGEE) model. This statistical tool, previously used on Singapore's birds, butterflies, and plants, reconstructs extirpation timelines from historical sighting records spanning 1819 to present, drawn from sources like Figueroa et al. (2023) herpetofauna checklist.
MODGEE accounts for 'dark extinctions'—undetected losses—by modeling detection probabilities and habitat correlations. It distinguishes primary forest specialists from secondary forest or parkland tolerant species, estimating extirpation rates with 95% confidence intervals. Published in Biological Conservation (March 2026), the open-access paper (DOI: 10.1016/j.biocon.2026.111721) provides a blueprint for prioritizing reintroductions.
Key Findings: 17% Loss and Patterns of Decline
The model pegs cumulative extirpation at 17% (95% CI: 1-31%) for terrestrial squamates since 1819—resilient compared to 40% for birds and 46% for butterflies. Two peaks emerged: early 1900s amid plantation expansion, and 2000s from urbanization. Primary forest species suffered most, while adaptable ones endured in degraded habitats.
- Overall resilience attributed to thermoregulation via sun-basking and lower population densities than insects.
- Recent rediscoveries, like the Selangor mud snake after 106 years, show potential in maturing forests.
- Fragmentation risks persist, isolating populations vulnerable to stochastic events.
Chisholm notes, 'Squamates may be more resilient to habitat degradation,' highlighting opportunities in recovering landscapes.
Spotlight on Lost Species: Examples from Singapore's Herpetofauna
Among extirpated squamates, forest specialists like the white-spotted cat snake (Boiga draperi) and various geckos vanished early. The study flags three recently lost species as prime reintroduction targets, minimizing 'ecological memory loss'—the mismatch between past and current habitats. Hulk forest gecko (Gekko hulk), last sighted in 1997, tops the list: a mid-sized insectivore thriving in Peninsular Malaysia's similar forests.
Other candidates include species with broad diets and low dispersal needs. Extant natives like the paradise tree snake (Chrysopelea paradisi) demonstrate adaptability, gliding between trees in urban fringes.
Reintroduction Prospects: Reviving Squamates in Urban Singapore
Sankar advocates 'scientific reintroduction' for species like Gekko hulk, sourcing from nearby stocks. Steps include:
- Habitat suitability assessment in reserves like Bukit Timah Nature Reserve.
- Captive breeding or direct translocation, monitoring via camera traps and eDNA.
- Integration with NParks' City in Nature initiative for multi-species rewilding.
- Risk mitigation: disease screening, genetic diversity evaluation.
Mongabay reports experts optimistic, as low hunting pressure and restoration success (e.g., smooth-coated otter reintroduction) pave the way. Challenges: sea barrier, altered predator-prey dynamics, climate change impacts on thermoregulation.
NUS's Pivotal Role in Singapore's Conservation Research
NUS, Asia's top university per QS 2026 rankings, leads biodiversity studies via its Department of Biological Sciences and Yale-NUS College legacy. Prior work estimated 37% overall species loss since 1819, lower than 2003's 60% due to dark extinctions accounting. Collaborations with Herpetological Society and NParks amplify impact, training students in field ecology and modeling.
This squamate study exemplifies NUS's interdisciplinary approach, blending ecology, statistics, and policy for urban sustainability.
Challenges Facing Urban Reptile Conservation
Fragmented reserves limit gene flow; invasive species like the Asian flat-headed gecko compete. Climate projections warn of hotter, wetter conditions disrupting squamate activity cycles. Yet, Singapore's green masterplan—aiming 50% green by 2030—offers buffers. Community engagement via Herpetological Society citizen science aids monitoring.
Stakeholders: NParks prioritizes natives; developers fund offsets; academics provide data.
Global Lessons from Singapore's Squamate Story
As a model 'garden city,' Singapore's efforts inform other tropical urban areas like Hong Kong or Jakarta. Rewilding terrestrial taxa tests resilience in novel ecosystems. NUS research advocates prioritizing recent losses for cost-effective gains, influencing IUCN reintroduction guidelines.
Photo by Maik Winnecke on Unsplash
Future Outlook: Hope for Singapore's Squamates
With maturing forests and tools like MODGEE, reintroductions could restore 5-10% lost functions. Ongoing NUS monitoring via eDNA and AI cameras promises data for adaptive management. Policymakers urged to integrate herpetofauna into biodiversity targets, securing squamates' role in urban ecology. Sankar concludes: 'Targeted translocation can reintegrate species into recovering landscapes.'
For aspiring researchers, NUS exemplifies how higher education drives conservation, from PhD fieldwork to policy briefs.