Habituation allows an observer to closely approach and follow free-ranging animals, as they no longer respond to the observer presence (e.g., through flight, avoidance, display, curiosity). While habituation is implicitly acknowledged as a necessary step before any direct observational studies of primates, there is very little published data on the subject. The aim of this study is to analyse the habituation process over time (17 months) in a wild-feeding troop of northern pigtailed macaques (Macaca leonina) inhabiting a degraded forest fragment of the Sakaerat Biosphere Reserve, Thailand. Based on the number of encounters, contact duration with the studied troop, and behavioural responses to the observer recorded ad libitum and via scan sampling, we found statistical evidence of habituation progress over five stages: early, minimal, partial, advanced, and full. The complete habituation process took nearly 13 months. Factors such as the macaques’ limited experience of human contact, semi-terrestriality, large ranging patterns, fission-fusion dynamics, unpredictable resource use, as well as reduced native fruit availability in this degraded forest fragment may explain the length of the process. It was only possible to collect ranging and behavioural data from the partial habituation stage, although these data were biased toward adult males and sub-adults, while overestimating movement behaviour over inactivity and social behaviours. Our results highlight the importance of analysing behavioural data of fully habituated groups of primates to limit biases of observer presence, and also of not underestimating the habituation process length. This study provides novel information on the habituation process in macaques and proposes an effective methodology to analyse the habituation process across a wide range of primate species.

The forests within and around Singapore’s last substantial tract of intact freshwater swampNee Soon Swamp Forestare extremely diverse floristically and so present challenges in the recognition of plant species. Here we provide two keys and species descriptions, based on characters easily observed in the field, to the 22 species of Lauraceae found there. Two of these are new additions to Singapore’s flora: Cryptocarya nitens (Blume) Koord. & Valeton and Litsea resinosa Blume. This is the first in a series of articles that aim to assist in the identification of the trees of the Nee Soon Swamp Forest

The forests within and around Singapore’s last substantial tract of intact freshwater swamp forest—Nee Soon Swamp Forest—are extremely diverse floristically, and so present challenges in the recognition of plant species. Here we provide a key and species descriptions, based on characters easily observed in the field and on dried specimens, to the Hypericacae of the Nee Soon Swamp Forest. Only the genus Cratoxylum is native to Singapore, with four species, all trees, found in the Nee Soon Swamp Forest. A fifth species, Cratoxylum glaucum, seems to have been erroneously recorded as native to Singapore, but we could find no evidence that it has been collected from here. Cratoxylum glaucum has only been recorded from Peninsular Malaysia, Borneo, and other parts of Indonesia, according to taxonomic accounts for the region, and its natural distribution is not known to include Singapore.

This paper is the third instalment of a continuing series on the tree species of the floristically diverse Nee Soon Swamp Forest, Singapore’s last substantial tract of intact freshwater swamp forest. Here, for the Myristicaceae, we provide a key and descriptions, based on characters easily observed in the field and when dried of Gymnacranthera (three species), Horsfieldia (seven species, with two varieties for Horsfieldia polyspherula), Knema (10 species, with two varieties for Knema curtisii), and Myristica (five species). Horsfieldia tomentosa is unlikely to occur in Singapore based on recent accounts. Horsfieldia grandis and Horsfieldia superba are new records for the Nee Soon Swamp Forest.

This paper is the fourth part of a continuing series on the tree species of the floristically diverse Nee Soon Swamp Forest, Singapore’s last substantial tract of intact freshwater swamp forest. We provide a key and descriptions for six species of Xanthophyllum from the family Polygalaceae, based on characters easily observed in the field and of dried specimens.