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.

Freshwater decapod crustaceans serve important ecological functions in tropical stream ecosystems. Stream surveys for decapod crustacean fauna were conducted between February 2015 and April 2016 at nine sites in Bukit Timah Nature Reserve (BTNR). A total of eight species (four freshwater crab, three freshwater shrimp and one crayfish species) out of the nine species known from BTNR were recorded. In general, the species were recorded from sites matching environmental conditions previously known or reported for each species, with some crab species showing minor overlap in their spatial distributions. This highlights the importance of broad-based conservation efforts focusing on the entire stream network in BTNR rather than on specific/selected streams as the various species each appear to have largely unique habitat requirements. The updated information on freshwater decapod crustaceans in BTNR can be used to inform the formulation of conservation and management measures including the establishment of monitoring programs for the protection of our native and threatened aquatic fauna in BTNR.

Re‐establishing extirpated wildlife—or “rewilding”—is touted as a way to restore biodiversity and ecosystem processes, but we lack real‐world examples of this process, particularly in Southeast Asia. Here, we use a decade of aggregated camera trap data, N‐mixture occupancy models, and input from local wildlife experts to describe the unassisted recolonization of two native large herbivores in Singapore. Sambar deer (Rusa unicolor) escaped from captivity (in private or public zoos) in the 1970s and contemporary camera trap data show they have only colonized nearby forest fragments and their abundance remains low. Wild pigs (Sus scrofa), in contrast, naturally recolonized by swimming from Malaysia in the 1990s and have rapidly expanded their range and abundance across Singapore. While wild pigs have not recolonized all viable green spaces yet, their trajectory indicates they soon will. We also note that a third ungulate, the muntjac deer (Muntiacus muntjak), was captured in camera trapping in 2014 and 2015 but was never recorded afterward despite increased sampling effort, and thus we do not focus on their presumably unsuccessful recolonization. The divergent rewilding trajectories between sambar deer and wild pigs suggest different conservation outcomes and management requirements. Sambar deer may restore lost plant–animal interactions such as herbivory and seed dispersal without requiring significant management. Wild pigs, in contrast, have reached high numbers rapidly and may require active management to avoid hyperabundance and negative ecological impacts in regions, such as Singapore that lack both hunting and large predators.

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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.