Max De Yuan Khoo
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Research Subjects
Max De Yuan Khoo has a total of 70 co-authors. Here are the top co-authors by number of shared publications:
- Benjamin P. Y.-H. Lee
Wildlife and Natural Heritage, Royal Commission for AlUla, AlUla 43544, Saudi Arabia
3 shared publications - Kenneth Boon Hwee Er
National Parks Board Singapore Singapore
3 shared publications - Malcolm C. K. Soh
National Parks Board, Singapore Botanic Gardens, Singapore
3 shared publications Adrian H. B. Loo
National Parks Board Singapore Singapore
2 shared publications- Adrian H. B. Loo
National Parks Board, Singapore Botanic Gardens Singapore
2 shared publications Bryan T. M. Lim
National Parks Board, Singapore, Singapore
2 shared publications
Latest Publications
- Open Access
- 29 June 2026
- Published by Springer Nature in Discover Conservation
- Vol. 3 (1)
Assessing pangolin scale morphology and genetic identifiability following varied processing treatments
Pangolins are among the most heavily trafficked mammals worldwide, with their scales widely traded for traditional medicine. Recent enforcement reports highlight an emerging challenge which involves the trafficking of processed scales, which are more difficult to visually recognise and often with degraded DNA. As processing alters both morphology and DNA integrity, reliable species identification from such material is uncertain, yet remains essential for forensic investigation and enforcement as well as conservation. Here, we experimentally assessed the impacts of four trade-reported processing treatments on Sunda pangolin ( Manis javanica ) scales. We quantified changes in physical traits (length, width, thickness, and hardness) and evaluated how processing affected DNA quantity and consequently, molecular identification success using Bayesian logistic regressions. We found that processing altered scale appearance (causing thickening, yellowing, blistering, and burnt marks) but diagnostic morphological features remained intact, enabling recognition of pangolin origin. To support enforcement practice, we provided a guide for morphological identification of processed scales. DNA quantity was also not a strong predictor of species assignment; while higher concentrations improved identification success, many low-yield samples still produced viable sequences. Despite processing treatments causing DNA degradation, we found that the overall probability of successful species identification across treatments remained at 89.7%, with even the most damaging treatment of frying with sand plus vinegar quenching, still yielding a relatively high probability of identification of 76.3%. These findings emphasise the importance of an integrative approach to processed scale identification, with morphological traits providing a rapid and accessible first line of assessment, while molecular tools providing confirmation and resolution.
- 29 June 2026
- Published by Springer Nature in Discover Conservation
- Vol. 3 (1)
Open AccessAssessing pangolin scale morphology and genetic identifiability following varied processing treatments
Pangolins are among the most heavily trafficked mammals worldwide, with their scales widely traded for traditional medicine. Recent enforcement reports highlight an emerging challenge which involves the trafficking of processed scales, which are more difficult to visually recognise and often with degraded DNA. As processing alters both morphology and DNA integrity, reliable species identification from such material is uncertain, yet remains essential for forensic investigation and enforcement as well as conservation. Here, we experimentally assessed the impacts of four trade-reported processing treatments on Sunda pangolin ( Manis javanica ) scales. We quantified changes in physical traits (length, width, thickness, and hardness) and evaluated how processing affected DNA quantity and consequently, molecular identification success using Bayesian logistic regressions. We found that processing altered scale appearance (causing thickening, yellowing, blistering, and burnt marks) but diagnostic morphological features remained intact, enabling recognition of pangolin origin. To support enforcement practice, we provided a guide for morphological identification of processed scales. DNA quantity was also not a strong predictor of species assignment; while higher concentrations improved identification success, many low-yield samples still produced viable sequences. Despite processing treatments causing DNA degradation, we found that the overall probability of successful species identification across treatments remained at 89.7%, with even the most damaging treatment of frying with sand plus vinegar quenching, still yielding a relatively high probability of identification of 76.3%. These findings emphasise the importance of an integrative approach to processed scale identification, with morphological traits providing a rapid and accessible first line of assessment, while molecular tools providing confirmation and resolution.
- Open Access
- 5 June 2026
- Published by Springer Nature in Urban Ecosystems
- Vol. 29 (4) , 168
Land use legacies shape wild boar (Sus scrofa) diet along a forest-urban gradient in Singapore
- 5 June 2026
- Published by Springer Nature in Urban Ecosystems
- Vol. 29 (4) , 168
Open AccessLand use legacies shape wild boar (Sus scrofa) diet along a forest-urban gradient in Singapore
- Open Access
A suite of wildlife crossing structures facilitates mammal movement across tropical forest fragments in a city
Wildlife crossing structures and road calming measures are frequently implemented to improve habitat connectivity and mitigate the risks of wildlife–vehicle collisions on roads. Although Southeast Asia is a known biodiversity hotspot, majority of studies assessing effectiveness of such structures were conducted outside the region. Existing studies also tended to be non‐comparative and focused on crossing structures in silo. We addressed this gap by simultaneously surveying and comparing the usage frequency of mammals across three crossing types—culverts, roads and rope bridges—along a road surrounded by forests in Singapore. This allowed us to evaluate the preferences of mammals, assess usage patterns and investigate factors influencing the use of different crossing types. Using camera traps and closed‐circuit televisions, we documented 1133 independent crossing events across a 9‐month study period from March to November 2021. Fourteen mammal species were detected across all crossing types, with wild boar (Sus scrofa) being the most prevalent species (68.2%). Locally critically endangered species such as the Malayan porcupine (Hystrix brachyura), Sunda pangolin (Manis javanica), and Raffles' banded langur (Presbytis femoralis femoralis) were also recorded to use culverts, roads, and rope bridges for crossings, respectively. Although many species used multiple crossing types, most species had a preferred crossing method. Between culverts and roads, factors that influenced crossing preferences included group size for wild boars and time of day and presence of fences for other mammals. Even though such culverts were intended for drainage, they were still widely used by mammals. Overall, all three crossing methods were crucial in facilitating the movement of animals between habitats. Thus, a variety of infrastructure and measures to accommodate the diversity of wildlife moving across forest patches in a fragmented landscape is recommended.
Open AccessA suite of wildlife crossing structures facilitates mammal movement across tropical forest fragments in a city
Wildlife crossing structures and road calming measures are frequently implemented to improve habitat connectivity and mitigate the risks of wildlife–vehicle collisions on roads. Although Southeast Asia is a known biodiversity hotspot, majority of studies assessing effectiveness of such structures were conducted outside the region. Existing studies also tended to be non‐comparative and focused on crossing structures in silo. We addressed this gap by simultaneously surveying and comparing the usage frequency of mammals across three crossing types—culverts, roads and rope bridges—along a road surrounded by forests in Singapore. This allowed us to evaluate the preferences of mammals, assess usage patterns and investigate factors influencing the use of different crossing types. Using camera traps and closed‐circuit televisions, we documented 1133 independent crossing events across a 9‐month study period from March to November 2021. Fourteen mammal species were detected across all crossing types, with wild boar (Sus scrofa) being the most prevalent species (68.2%). Locally critically endangered species such as the Malayan porcupine (Hystrix brachyura), Sunda pangolin (Manis javanica), and Raffles' banded langur (Presbytis femoralis femoralis) were also recorded to use culverts, roads, and rope bridges for crossings, respectively. Although many species used multiple crossing types, most species had a preferred crossing method. Between culverts and roads, factors that influenced crossing preferences included group size for wild boars and time of day and presence of fences for other mammals. Even though such culverts were intended for drainage, they were still widely used by mammals. Overall, all three crossing methods were crucial in facilitating the movement of animals between habitats. Thus, a variety of infrastructure and measures to accommodate the diversity of wildlife moving across forest patches in a fragmented landscape is recommended.
- Open Access
- 14 October 2024
- Published by Wiley in Journal of Applied Ecology
- Vol. 61 (11) , 2822-2836
Urban bird commensals maintain coexistence under extreme food shortages
In developed cities, bird communities are typically comprised of a few dominant invasive species that can cause considerable social and economic costs. While various studies advocate restricting anthropogenic food as a suitable management approach, a significant knowledge gap persists regarding how these species interact and respond to such an intervention. Here, we evaluate whether limiting a shared food resource may affect their abundances similarly and assess whether such limitations influence their niche dynamics. In Singapore, open food centres for people, colloquially known as hawker centres, serve as key food sources for three highly adapted urban birds: feral pigeons, Javan mynas and house crows. We counted these three species across 63 hawker centres and analysed their niche dynamics across different phases—before, during COVID‐19 social restrictions when dining‐in was prohibited, and during an enforcement phase mandating the return of crockery. We modelled their counts, diet niche widths and niche overlaps, considering predictors which include the sampling phases, food availability, structural characteristics of hawker centres and spatial attributes such as distance to public housing. During social restrictions, feral pigeon and Javan myna counts showed a significant decline, while the count proportions of the three species compared to each other remained relatively stable. Hawker centres closer to bridges and public housing, and those that structurally more open, attracted more birds. The niche widths of feral pigeons and Javan mynas significantly narrowed during social restrictions due to reduced food availability. However, their niche overlaps remained consistent across sampling phases, indicating resource partitioning strategies to cope with extreme food shortages—feral pigeons adapted by foraging more on grass verges outside, while Javan mynas frequented tray return stations. This resilience in maintaining species proportions and the absence of significant niche overlap suggested the existence of an ecological balance despite substantial reductions in available food. Synthesis and applications. Our study underscores the importance of controlling human‐provided food to collectively manage dominant urban bird commensals. Beyond the two social restriction phases, curbing the availability of anthropogenic food through enforcement also kept nuisance birds away, validating a cost‐effective approach in reducing their counts.
- 14 October 2024
- Published by Wiley in Journal of Applied Ecology
- Vol. 61 (11) , 2822-2836
Open AccessUrban bird commensals maintain coexistence under extreme food shortages
In developed cities, bird communities are typically comprised of a few dominant invasive species that can cause considerable social and economic costs. While various studies advocate restricting anthropogenic food as a suitable management approach, a significant knowledge gap persists regarding how these species interact and respond to such an intervention. Here, we evaluate whether limiting a shared food resource may affect their abundances similarly and assess whether such limitations influence their niche dynamics. In Singapore, open food centres for people, colloquially known as hawker centres, serve as key food sources for three highly adapted urban birds: feral pigeons, Javan mynas and house crows. We counted these three species across 63 hawker centres and analysed their niche dynamics across different phases—before, during COVID‐19 social restrictions when dining‐in was prohibited, and during an enforcement phase mandating the return of crockery. We modelled their counts, diet niche widths and niche overlaps, considering predictors which include the sampling phases, food availability, structural characteristics of hawker centres and spatial attributes such as distance to public housing. During social restrictions, feral pigeon and Javan myna counts showed a significant decline, while the count proportions of the three species compared to each other remained relatively stable. Hawker centres closer to bridges and public housing, and those that structurally more open, attracted more birds. The niche widths of feral pigeons and Javan mynas significantly narrowed during social restrictions due to reduced food availability. However, their niche overlaps remained consistent across sampling phases, indicating resource partitioning strategies to cope with extreme food shortages—feral pigeons adapted by foraging more on grass verges outside, while Javan mynas frequented tray return stations. This resilience in maintaining species proportions and the absence of significant niche overlap suggested the existence of an ecological balance despite substantial reductions in available food. Synthesis and applications. Our study underscores the importance of controlling human‐provided food to collectively manage dominant urban bird commensals. Beyond the two social restriction phases, curbing the availability of anthropogenic food through enforcement also kept nuisance birds away, validating a cost‐effective approach in reducing their counts.
- Open Access
- 13 September 2024
- Published by Wiley in Ecology and Evolution
- Vol. 14 (9) , e70249
Why do understorey Licuala palm fruits turn from red to white and then black when ripe?
Licuala ferruginea Becc., a tropical forest understorey palm, is observed to have fruits that appear red in colour when unripe, turning pink, then white, purple and finally black in colour as they ripen. We monitored 13 fruiting palms in rainforest fragments and recorded the consumption of fruits by animals via camera traps. We also documented the fruiting phenology of two palms in the nursery. In the rainforest fragments, a Cream‐vented Bulbul ( Pycnonotus simplex ) was observed plucking a mature purple fruit from a L. ferruginea palm, before flying away with the fruit in its beak. This was the only bird that was observed feeding on the mature fruit. A range of mammals, dominated by edge species such as the Long‐tailed Macaque and Wild Boar, were observed to consume L. ferruginea fruits indiscriminately across all five colour stages, thereby limiting the dispersal of the fruits. Forest bulbul gape sizes also matched the fruit size, suggesting that forest bulbuls are the likely dispersers of the palm in the original forest where edge species are not in high densities. We further posit that the initial phase of red fruits, with high contrasting red reflectance against a green foliage background, might be a form of early advertisement to birds. The fruit then turns pink and white, which have high green reflectance and is less contrasting, thereby reducing the conspicuity of the fruit. This allows the fruit to ripen with high fructose and glucose content, and turn purple and black, which are known visual cues for birds. This study provides indicative support for the dispersal syndrome hypothesis and highlights the potential effects of forest fragmentation on plant–frugivore interactions.
- 13 September 2024
- Published by Wiley in Ecology and Evolution
- Vol. 14 (9) , e70249
Open AccessWhy do understorey Licuala palm fruits turn from red to white and then black when ripe?
Licuala ferruginea Becc., a tropical forest understorey palm, is observed to have fruits that appear red in colour when unripe, turning pink, then white, purple and finally black in colour as they ripen. We monitored 13 fruiting palms in rainforest fragments and recorded the consumption of fruits by animals via camera traps. We also documented the fruiting phenology of two palms in the nursery. In the rainforest fragments, a Cream‐vented Bulbul ( Pycnonotus simplex ) was observed plucking a mature purple fruit from a L. ferruginea palm, before flying away with the fruit in its beak. This was the only bird that was observed feeding on the mature fruit. A range of mammals, dominated by edge species such as the Long‐tailed Macaque and Wild Boar, were observed to consume L. ferruginea fruits indiscriminately across all five colour stages, thereby limiting the dispersal of the fruits. Forest bulbul gape sizes also matched the fruit size, suggesting that forest bulbuls are the likely dispersers of the palm in the original forest where edge species are not in high densities. We further posit that the initial phase of red fruits, with high contrasting red reflectance against a green foliage background, might be a form of early advertisement to birds. The fruit then turns pink and white, which have high green reflectance and is less contrasting, thereby reducing the conspicuity of the fruit. This allows the fruit to ripen with high fructose and glucose content, and turn purple and black, which are known visual cues for birds. This study provides indicative support for the dispersal syndrome hypothesis and highlights the potential effects of forest fragmentation on plant–frugivore interactions.
- Open Access
- 23 October 2023
- Published by Wiley in Conservation Biology
- Vol. 38 (2)
Uncovering the magnitude of African pangolin poaching with extensive nanopore DNA genotyping of seized scales
Trade in pangolins is illegal, and yet tons of their scales and products are seized at various ports. These large seizures are challenging to process and comprehensively genotype for upstream provenance tracing and species identification for prosecution. We implemented a scalable DNA barcoding pipeline in which rapid DNA extraction and MinION sequencing were used to genotype a substantial proportion of pangolin scales subsampled from 2 record shipments seized in Singapore in 2019 (37.5 t). We used reference sequences to match the scales to phylogeographical regions of origin. In total, we identified 2346 cytochrome b ( cytb ) barcodes of white‐bellied ( Phataginus tricuspis ) (from 1091 scales), black‐bellied ( Phataginus tetradactyla ) (227 scales), and giant ( Smutsia gigantea ) (1028 scales) pangolins. Haplotype diversity was higher for P. tricuspis scales (121 haplotypes, 66 novel) than that for P. tetradactyla (22 haplotypes, 15 novel) and S. gigantea (25 haplotypes, 21 novel) scales. Of the novel haplotypes, 74.2% were likely from western and west‐central Africa, suggesting potential resurgence of poaching and newly exploited populations in these regions. Our results illustrate the utility of extensively subsampling large seizures and outline an efficient molecular approach for rapid genetic screening that should be accessible to most forensic laboratories and enforcement agencies.
- 23 October 2023
- Published by Wiley in Conservation Biology
- Vol. 38 (2)
Open AccessUncovering the magnitude of African pangolin poaching with extensive nanopore DNA genotyping of seized scales
Trade in pangolins is illegal, and yet tons of their scales and products are seized at various ports. These large seizures are challenging to process and comprehensively genotype for upstream provenance tracing and species identification for prosecution. We implemented a scalable DNA barcoding pipeline in which rapid DNA extraction and MinION sequencing were used to genotype a substantial proportion of pangolin scales subsampled from 2 record shipments seized in Singapore in 2019 (37.5 t). We used reference sequences to match the scales to phylogeographical regions of origin. In total, we identified 2346 cytochrome b ( cytb ) barcodes of white‐bellied ( Phataginus tricuspis ) (from 1091 scales), black‐bellied ( Phataginus tetradactyla ) (227 scales), and giant ( Smutsia gigantea ) (1028 scales) pangolins. Haplotype diversity was higher for P. tricuspis scales (121 haplotypes, 66 novel) than that for P. tetradactyla (22 haplotypes, 15 novel) and S. gigantea (25 haplotypes, 21 novel) scales. Of the novel haplotypes, 74.2% were likely from western and west‐central Africa, suggesting potential resurgence of poaching and newly exploited populations in these regions. Our results illustrate the utility of extensively subsampling large seizures and outline an efficient molecular approach for rapid genetic screening that should be accessible to most forensic laboratories and enforcement agencies.
- 6 May 2021
- Published by Magnolia Press in Zootaxa
- Vol. 4966 (5) , 563-570
Description of the larva of Brachygonia oculata (Brauer, 1878) (Odonata: Libellulidae) with notes on rearing technique
The larva of the genus Brachygonia Kirby, 1889 is described and illustrated for the first time based on the larvae of Brachygonia oculata (Brauer, 1878) discovered and successfully reared in Singapore. Compared to known larvae from genera in the rather heterogeneous subfamily Brachydiplacinae, B. oculata is most similar to species from the genus Brachydiplax Brauer, 1868 after comparison is made with the larva of Brachydiplax farinosa Kruger, 1902.
- 6 May 2021
- Published by Magnolia Press in Zootaxa
- Vol. 4966 (5) , 563-570
Description of the larva of Brachygonia oculata (Brauer, 1878) (Odonata: Libellulidae) with notes on rearing technique
The larva of the genus Brachygonia Kirby, 1889 is described and illustrated for the first time based on the larvae of Brachygonia oculata (Brauer, 1878) discovered and successfully reared in Singapore. Compared to known larvae from genera in the rather heterogeneous subfamily Brachydiplacinae, B. oculata is most similar to species from the genus Brachydiplax Brauer, 1868 after comparison is made with the larva of Brachydiplax farinosa Kruger, 1902.
- Open Access
- 23 July 2020
- Published by Wiley in International Zoo Yearbook
- Vol. 54 (1) , 60-71
The urban Smooth‐coated otters Lutrogale perspicillata of Singapore: a review of the reasons for success
Urbanization has a major impact on biodiversity, especially on carnivores. Otters are particularly sensitive to urbanization as it increases their risk of being persecuted and threatens the key requirements essential for their survival. Because of this, many otter species have suffered population declines throughout the world. However, in Singapore, the Smooth‐coated otter Lutrogale perspicillata has made a tremendous rebound after an absence of three decades. The species is now widely distributed across the river systems and reservoirs, and can even be found in the highly urban city centre. This return of the Smooth‐coated otters to Singapore was so successful that it was touted by many as a conservation success and role model for otters in the city. With more populations of otters elsewhere in the world threatened by the effects of urbanization, lessons can be drawn from the successful return of otters to Singapore and applied to these other countries. These lessons include the importance of laws, social factors and public–private partnerships in facilitating the return of a top carnivore to the city.
- 23 July 2020
- Published by Wiley in International Zoo Yearbook
- Vol. 54 (1) , 60-71
Open AccessThe urban Smooth‐coated otters Lutrogale perspicillata of Singapore: a review of the reasons for success
Urbanization has a major impact on biodiversity, especially on carnivores. Otters are particularly sensitive to urbanization as it increases their risk of being persecuted and threatens the key requirements essential for their survival. Because of this, many otter species have suffered population declines throughout the world. However, in Singapore, the Smooth‐coated otter Lutrogale perspicillata has made a tremendous rebound after an absence of three decades. The species is now widely distributed across the river systems and reservoirs, and can even be found in the highly urban city centre. This return of the Smooth‐coated otters to Singapore was so successful that it was touted by many as a conservation success and role model for otters in the city. With more populations of otters elsewhere in the world threatened by the effects of urbanization, lessons can be drawn from the successful return of otters to Singapore and applied to these other countries. These lessons include the importance of laws, social factors and public–private partnerships in facilitating the return of a top carnivore to the city.
- Open Access
- 26 June 2020
- Published by Wildlife Information Liaison Development Society in Journal of Threatened Taxa
- Vol. 12 (9)
Dusky Langurs Trachypithecus obscurus (Reid, 1837) (Primates: Cercopithecidae) in Singapore: potential origin and conflicts with native primate species
The introduction of exotic species can have detrimental effects on local populations via factors such as resource competition and new threats from disease. Singapore has three native species of non-human primates: Sunda Slow Loris Nycticebus coucang, Long-tailed Macaque Macaca fascicularis, and Raffles’ Banded Langur Presbytis femoralis. Over the past few months, several non-native Dusky Langurs Trachypithecus obscurus were observed in Singapore. We document our observations, compile reports from social media, and attempt to assess the potential impacts on local primates. Whenever Dusky Langurs were encountered, we recorded the date, time, GPS coordinates, group demographics, and behaviour, including interactions with native primates. We also monitored sighting reports of Dusky Langurs posted on local major Facebook groups from 30 December 2019 to 31 January 2020, and privately messaged the person(s) for more information. On 31 August 2019, three Dusky Langurs were seen near a residential area in the northern part of Singapore, and two to three individuals were reported on 14 subsequent occasions. During one encounter on 18 January 2020, an adult male Long-tailed Macaque chased a group of Dusky Langurs from a feeding tree. The next day the same group of Dusky Langurs chased a group of 11 Banded Langurs from another feeding tree. The Dusky Langurs appeared to be healthy and wild, indicating that they may have swum across the Johor Strait and/or traveled on the Johor-Singapore Causeway from Malaysia. Further monitoring of these Dusky Langurs will be required to assess their impact on local primates.
- 26 June 2020
- Published by Wildlife Information Liaison Development Society in Journal of Threatened Taxa
- Vol. 12 (9)
Open AccessDusky Langurs Trachypithecus obscurus (Reid, 1837) (Primates: Cercopithecidae) in Singapore: potential origin and conflicts with native primate species
The introduction of exotic species can have detrimental effects on local populations via factors such as resource competition and new threats from disease. Singapore has three native species of non-human primates: Sunda Slow Loris Nycticebus coucang, Long-tailed Macaque Macaca fascicularis, and Raffles’ Banded Langur Presbytis femoralis. Over the past few months, several non-native Dusky Langurs Trachypithecus obscurus were observed in Singapore. We document our observations, compile reports from social media, and attempt to assess the potential impacts on local primates. Whenever Dusky Langurs were encountered, we recorded the date, time, GPS coordinates, group demographics, and behaviour, including interactions with native primates. We also monitored sighting reports of Dusky Langurs posted on local major Facebook groups from 30 December 2019 to 31 January 2020, and privately messaged the person(s) for more information. On 31 August 2019, three Dusky Langurs were seen near a residential area in the northern part of Singapore, and two to three individuals were reported on 14 subsequent occasions. During one encounter on 18 January 2020, an adult male Long-tailed Macaque chased a group of Dusky Langurs from a feeding tree. The next day the same group of Dusky Langurs chased a group of 11 Banded Langurs from another feeding tree. The Dusky Langurs appeared to be healthy and wild, indicating that they may have swum across the Johor Strait and/or traveled on the Johor-Singapore Causeway from Malaysia. Further monitoring of these Dusky Langurs will be required to assess their impact on local primates.