Interactions between the Sumatran tiger Panthera tigris sumatrae and people (e.g. injury or loss of lives of people and tigers, evacuation of injured tigers, loss of livestock and sightings of tigers) can negatively affect the conservation of the subspecies. Land-use change in Sumatra has reduced habitat for tigers, forcing them into human-dominated landscapes and increasing the probability of interactions with people. Although the number of such interactions is high in South-east Asia, few studies have been published since 2000 and for Sumatra there is a lack of information regarding where these events occur. We collated data on human–tiger interactions in the province of Riau using web scraping of news sources published during 2010–2020, and mapped these data to village boundaries. We recorded 101 interaction events, with a total of 107 interactions, which we categorized into seven types (people injured or killed, livestock killed, sightings of tigers, tigers killed, injured or evacuated), in 78 villages. Most interactions with reported locations occurred close to settlements (35%), followed by in plantations (26%) and smallholdings (25%), with forests and forest edges comprising 14% of such events. Interactions were dominated by sightings of tigers, but severe interaction types (human death or injury and attacks on livestock) were also reported. The mean annual number of human–tiger interactions was 4.6 during 2011–2017 and 21.3 during 2017–2020. We highlight the need for mitigation and prevention, such as establishing conflict mitigation teams, improving animal husbandry practices, and providing training and education on human–tiger interactions focused in plantations and settlements.

The flat-headed cat Prionailurus planiceps is one of the rarest small felids, with little known about its distribution, population status or habitat requirements, largely because of the few records of the species. We report here 11 detections of this Endangered species, recorded during 4 years of camera-trap surveys in a peat-swamp forest on the Kampar Peninsula, Riau province, Sumatra. These are the first records of this species on the Kampar Peninsula, in an area of c. 1,300 km2 of peat-swamp forest comprising four adjacent Ecosystem Restoration Concession licences. All records were near water bodies (mean distance 351 m) in lowland peat-swamp forest. These findings add to the existing knowledge of the species' distribution in Sumatra and confirm its presence in these peat-swamp forests. To inform species conservation management planning for the Kampar Peninsula, further research on this species is required.

Encounter rates of carnivores with prey are dependent on spatial and temporal overlap, and are often highest with their preferred prey. The Critically Endangered Sumatran tiger Panthera tigris sumatrae is dependent on prey populations, but little is known about its prey preferences. We collected camera-trap data for 7 years (2010–2016) in Bukit Barisan Selatan National Park, Sumatra, to investigate spatial and temporal overlap of tigers with potential prey species. We also developed a novel method to predict predator–prey encounter rates and potential prey preferences from camera-trap data. We documented at least 10 individual tigers, with an overall detection rate of 0.24 detections/100 trap nights. Tigers exhibited a diurnal activity pattern and had highest temporal overlap with wild boar Sus scrofa and pig-tailed macaques Macaca nemestrina, but highest spatial overlap with wild boar and sambar deer Rusa unicolor. We created a spatial and temporal composite score and three additional composite scores with adjustments for the spatial overlap and preferred prey mass. Wild boars ranked highest for all composite scores, followed by sambar deer, and both are known as preferred tiger prey in other areas. Spatial and temporal overlaps are often considered as separate indices, but a composite score may facilitate better predictions of encounter rates and potential prey preferences. Our findings suggest that prey management efforts in this area should focus on wild boar and sambar deer, to ensure a robust prey base for this Critically Endangered tiger population.

Electron microprobe analyses of prehnites from the Way Linggo low-sulphidation epithermal Au-Ag deposit of southern Sumatra, show that the mole fraction of octahedral Fe3+, expressed as Fe3+/(Fe3++AlVI), ranges from 0.0 to ~0.6, the higher values being among the most iron-rich reported for prehnite in a hydrothermal environment. Prehnites from a diabase sill in the Heber geothermal field of California have mole fractions of octahedral Fe3+ ranging from 0.03 to 0.3. The Way Linggo prehnites formed below 220°C, some 20–30°C lower than those at the Heber field; the lower crystallization temperatures perhaps enhanced the opportunity for Fe3+ to substitute in octahedral sites. In both occurrences, prehnite predates late-stage calcite, consistent with the need for waters depositing prehnite to have aCO2 <0.01 moles. At higher CO2 activities the stability field of calcite would swamp the range of aCa2+/aH+ values appropriate for crystallizing prehnite. Consequently, the presence of prehnite in a hydrothermal environment primarily indicates that degassing of the hydrothermal fluid in CO2 occurred prior to deposition.

The Hatapang granite was discovered during geological mapping and mineral exploration in northern Sumatra by the British Geological Survey in conjunction with the Indonesian Directorate of Mineral Resources. The pluton comprises a two-mica granite which shows significant greisenization and veining around its margins associated with Sn and W mineralization. An Rb-Sr isochron derived for the pluton indicates an age of 80 Ma and an initial 87Sr/86Sr ratio of 0.7151. This together with major and trace element data show the Hatapang to be of clear S-type affinity.

The greisens are quartz-mica-topaz rocks and are almost totally deficient in Na. Trioctahedral mica compositions progress from biotite through siderophyllite to zinnwaldite during final differentiation and greisenization of the granite. Accompanying dioctahedral micas are phengitic. Associated with late-stage differentiation of the granite is the precipitation of tourmaline and various Nb-Ta oxides. Sn and W mineralization is manifested as cassiterite in the greisens, while wolframite tends to be related to quartz veining. A later and lower temperature sulphide event produced a suite of base metal sulphides and Ag-Bi-Pb sulphosalts. The identification of a Sn-W granite of Cretaceous age in northern Sumatra provides a link with occurrences of economically important Late Cretaceous Sn-W granites in Thailand and Burma and increases the potential of an area which until recently was thought to lie outside the SE Asian tin belt.

Two new species of Begonia sect. Bracteibegonia, B. curvifolia Ardi and B. ocellata Ardi, are described from West Sumatra, Indonesia. The species are endemic to Sumatra and belong to the IUCN category Data Deficient. A modified identification key to all 11 species of Begonia sect. Bracteibegonia in Sumatra is provided.

This article examines the geographies and politics of the global trade in orangutans in the name of science and entertainment in the first half of the twentieth century, along the background of the growing international nature protection movement. In doing so, it draws attention to historical processes that led to environmental conservation in northern Sumatra. It looks at some of the causes of the wildlife trade, linking animal-human engagement in northern Sumatra in the early twentieth century to large-scale agricultural development. During this period, wildlife traders brought shipments of orangutans from northern Sumatra to Europe and elsewhere around the world. The orangutan trade and the arrival of large numbers of apes in Europe broadly influenced material practices and decisions central to the colonial project. This included the tightening of borders and surveillance in the ports and on land, as well as the creation of wildlife protection laws and policies that regulated human relationships with the environment in colonial Indonesia.

The Greater Sunda region of South-east Asia supports a rich diversity of economically and ecologically important species. However, human pressures are reshaping contemporary biogeography across the region. Megafaunal distributional patterns have been particularly affected because of deforestation, poaching and human–wildlife conflict. Crocodilians are at the centre of these conflicts in Indonesia and yet remain poorly studied across much of the archipelago. We conducted population surveys of salt-water crocodiles Crocodylus porosus and false gharials Tomistoma schlegelii in Sumatra, and examined whether crocodile abundance and distribution are correlated with variations in human disturbance, fishing pressure, and habitat type. We then used these data to model remaining suitable habitat for T. schlegelii across South-east Asia. We found that abundance of T. schlegelii and C. porosus was correlated with distance from human settlements, and fish-trapping pressure. We recorded the presence of T. schlegelii in a river system in which it was previously unknown, thus expanding the known range of the species. We also found that the predicted remaining suitable habitat for T. schlegelii in Indonesia is largely limited to areas of low human activity. From these empirical and modelling approaches we propose several key conservation priorities: (1) eliminate the use of fish traps in remaining patches of T. schlegelii habitat, (2) prioritize crocodile population surveys in remaining suitable habitat, particularly in remote areas, (3) consider T. schlegelii to be potentially Endangered locally in Sumatra, and (4) expand existing reserves around the Lower Kampar River and Berbak National Park/Sembilang National Park areas of Sumatra.

Monitoring species ranges and suitable and occupied habitat are core components of biogeography, ecology and conservation biology, but it is difficult to do for rare, cryptic, wide-ranging, migratory or nomadic species. We present a transparent and objective process to combine multiple types of locality data (peer-reviewed and grey literature, museum collections, camera-trap inventories, and citizen science reports). We illustrate the advantages of this pooled approach by assessing change in range and patch occupancy for a data-poor and threatened nomadic keystone species, the bearded pig Sus barbatus, in Borneo, Sumatra and Peninsular Malaysia. We used a collated set of all occurrence observations (n = 240) to create minimum convex polygons for forested habitats for two time periods. We evaluated confidence that a patch was truly occupied by the overlap among data types. We found that 62% of the forest habitat of the Sumatran bearded pig S. barbatus oi was lost during 1990–2010 and that its range contracted by 76%; the Bornean bearded pig S. barbatus barbatus lost 23 and 24% of its forest habitat and range, respectively, and in Peninsular Malaysia the 93% range collapse of this subspecies during 1985–2010 is more severe than the 33% habitat loss alone would suggest. We conclude that integrating data types can improve mapping of the ranges of many data-poor species.

Two new species of Paphiopedilum from Sumatra, Indonesia, are described and illustrated. These two species belong in Paphiopedilum section Barbata and are so far known only from Aceh Province in the north of Sumatra.

Determination of the area density of spontaneous fission tracks (ρs) in glass shards of Toba tephra is a reliable way to distinguish between the Youngest Toba Tuff (YTT) and the Oldest Toba Tuff (OTT). The ρs values for YTT, uncorrected for partial track fading, range from 70 to 181 tracks/cm2 with a weighted mean of 108 ± 5 tracks/cm2, based on 15 samples. Corrected ρs values for YTT are in the range of 77–140 tracks/cm2 with a weighted mean of 113 ± 8 tracks/cm2, within the range of uncorrected ρs values. No significant difference in ρs exists between YTT samples collected from marine and continental depositional settings. The uncorrected ρs for OTT is 1567 ± 114 tracks/cm2 so that confusion with YTT is unlikely.

The ρs values of the Toba tephra at Bori, Morgaon, and Gandhigram in northwestern India indicate a YTT identity, in agreement with geochemical data on their glass shards, the presence of multiple glass populations, and a glass fission-track age determination. Therefore, the view of others that OTT is present at these sites – and thereby indicates an early Pleistocene age for the associated Acheulean artifacts – is incorrect.

Six new species of Syzygium Gaertn. from Sumatra are described and illustrated. Three are newly described, namely Syzygium abatakum Widodo, S. bengkulense Widodo and S. ketambense Widodo. The descriptions of the other three species, namely Syzygium angustovatum Widodo & Chikmawati, S. comosum Widodo and S. longipetiolatum Widodo are republished to validate their names. The conservation status of each species is proposed, following IUCN guidelines.

Amomum Roxb. (Zingiberaceae) in Sumatra, Indonesia is revised. Twenty-four species are recognised, most names are typified, detailed descriptions of species are provided and a key to these species is given. Provisional IUCN conservation assessments are supplied for all species. Two new species are described: Amomum mentawaiense A.J.Droop and Amomum oligophyllum A.J.Droop.

In 1994 Alan Rabinowitz decried what he regarded as lackadaisical attempts by governments, NGOs and international funding agencies to conserve the Sumatran rhinoceros Dicerorhinus sumatrensis. Sixteen years on it is timely to evaluate whether his warnings were heeded. We review the current conservation status of D. sumatrensis throughout its range and the latest threats and challenges complicating efforts to conserve this species. Recent data from governments, NGOs and researchers indicate that the global population could be as low as 216, a decline from c. 320 estimated in 1995. Based on lessons learnt and expert opinions we call on decision makers to focus on two core strategies for conservation of D. sumatrensis: (1) the translocation of wild individuals from existing small, isolated or threatened forest patches into semi-in situ captive breeding programmes, and (2) a concomitant enhancement of protection and monitoring capacities in priority areas that have established these breeding facilities or have recorded relatively high population estimates and track encounter rates. At least USD 1.2 million is required to implement these strategies annually in four priority areas: Bukit Barisan Selatan and Way Kambas National Parks on Sumatra, and Danum Valley Conservation Area and Tabin Wildlife Reserve on Sabah. Given that conservation funds are rarely secure and D. sumatrensis is still in decline we call on potential donors to help secure and augment existing capacities of organizations in these four priority areas before committing resources to elucidate the status of the species in other areas such as Gunung Leuser and Taman Negara National Parks.

The size distribution of a tree species gives important information about its regeneration strategy. For example, a tree species that regenerates primarily by sprouting will, in theory, have fewer seedlings than species that regenerate from seedlings, which generally form an L-shaped population size structure because of trade-offs in resource allocation between vegetative sprouting and sexual reproduction (Bellingham & Sparrow 2000, Loehle 2000). The results of some field studies suggest that the number of seedlings decreases with increasing dominance of multi-stemmed sprouters (Kruger et al. 1997, Zimmerman et al. 1994). In their study of four co-occurring species of Castanopsis (Fagaceae), Nanami et al. (2004) showed that species with a high frequency of sprouting adults had fewer juveniles and vice versa. This suggested that these species were able to co-exist as a result of trade-offs between investment in seedlings and sprouting. In this study, we investigated the sprouting trait of 17 co-occurring Fagaceae species in a Sumatran hill forest. The forest stand at this site shows a varied population structure across species, and hence, should have a varied life history. We tested the correlation between population skewness and proportion of sprouting trees, following the methods of Nanami et al. (2004). We hypothesized that the species that frequently form multi-stemmed sprouts will show a lower turnover of individuals because multi-stemmed architecture favours persistence (Bellingham & Sparrow 2009).

Four new species of Boehmeria (Urticaceae) are described and named: Boehmeria listeri Friis & Wilmot-Dear and B. manipurensis Friis & Wilmot-Dear from the eastern part of the Himalayas, B. leptostachya Friis & Wilmot-Dear from southern China (Yunnan), Thailand and northern Sumatra, and B. subintegra Friis & Wilmot-Dear from Papua New Guinea. The species are illustrated and mapped and their habitat ranges are described, and conservation assessments have been produced for all.

The taxonomic history of Porterandia (Rubiaceae) is reviewed. Its plant architecture and other morphological characteristics are compared with those of the related Atractocarpus and Bungarimba. Porterandia species are typically gynodioecious (and sometimes gynomonoecious), with sexual dimorphism in inflorescence form and flowers. Secondary pollen presentation in bisexual flowers is present. In a cladistic analysis using 34 morphological characters, Porterandia, Atractocarpus heterophyllus (type species of Atractocarpus) and Bungarimba were neatly polarised from Aidia, the outgroup. The 20 species of Porterandia in the analysis formed a well-supported monophyletic group, clearly delimited by primary and lower-order branches with terminal cymes in forks, stipules fused into a tube and with hairy inner surfaces, anisophyllous leaf pairs, corollas with stiff bristle-like hairs over the tube outer surface and adaxially hairy lobes. A revision enumerated 22 species of Porterandia, including a new species, P. dinghoui Zahid & K.M.Wong. Borneo, with 19 species, is the centre of diversity; outlying taxa appear to diverge from Bornean taxa in some characters; for example, Porterandia anisophylla and P. scortechinii (Sumatra, Malaya) are the only species with downward-pointing hairs on the corolla tubes (the rest have upward-pointing hairs), and P. celebica (Sulawesi) has atypical hood-like, fused (instead of free) inflorescence bracts. The northwest Borneo region has a significant species diversity and congregation. Extinction of Porterandia populations from heavily disturbed or open sites indicates that habitat conservation and the integrity of large forest patches and tree stands are critical.

Crop raiding by elephants is the most prevalent form of human–elephant conflict and can result in devastating economic losses for farmers, loss of human lives and the killing or capture of elephants. Chilli (capsaicin)-based elephant deterrents have been promoted as tools for reducing such conflict but have been little tested. From October 2005 to April 2006 we tested crop-guarding systems around Way Kambas National Park in Indonesia. We evaluated the effectiveness of community-based guarding using traditional tools (e.g. noise-makers) at one site and community-based guarding plus chilli-grease-covered fences and tripwire-triggered sirens at another site. We monitored human–elephant conflict rates around the Park to assess the effectiveness of our mitigation trials. Over the trial period there were 34 attempts by elephants to enter crop fields at the chilli and sirens site and 57 attempts to enter fields at the conventional site but 91.2% of attempts were repelled successfully at both sites. Over the same period there were 401 crop-raiding incidents elsewhere around the Park. In 2007 farmers at both our former sites voluntarily adopted the methods that had been used at the conventional site, but not at the chilli and sirens site, and were able to repel 156 of 178 (87.6%) attempted elephant raids. We conclude that community-based guarding using conventional tools is the key to keeping elephants out of crops and that chilli-grease fences (and sirens) do not add any significant deterrent effect but do add expense and create additional work. However, other chilli-based deterrents may be effective and chillies have value as elephant-resistant cash crops.