The Structure and Function of Male Thomas Langur Loud Calls

This study has addressed the acoustical structure of male loud calls and their function in Thomas langur social organisation. Thomas langurs are medium sized primate that lives in Sumatra, Indonesia. Ome of the characteristics of this species is the loud call of males. Several functions for loud calls have been suggested such as mate-defence, resource-defence and mate-attraction. In this study playback studies were applied to determine that loud calls function in between-group spacing and resource-defence. The function of loud calls in mate-attraction was not demonstrated directly, but an analysis of long-term data showed that females often choose newly adult males when the transfer between groups. These newly adult males have loud calls of shorter duration than adult males that already have associated with females and have offspring. This indicates that females may use loud calls as a cue to choose newly adult males. Since newly adult males are better in protecting offspring against infanticidal extra-group males and predators, it is functional for females to choose these males. In addition, it was shown that males show individual variation in loud call characteristics and that calls also differ between behavioural context, such as dawn chorus or alarm

Birds of Gunung Leuser National Park, Northern Sumatra – Part 2

Gunung Leuser National Park (GLNP) in northern Sumatra has over 85% of Sumatra5 resident breeding bird species and important populations of globally threatened mammals such as Sumatran orangutan Pongo abelii and Sumatran rhinoceros Dicerorhinus sumatrensis. Information is here presented on a number of important bird records from GLNP from March 1995 to December 2000. These records include: 23 new species for the park, seven globally threatened species, and several species for which there are few previous records for Sumatra. An appendix lists the 413 species recorded in GLNP comprising records from previous publications (van Marle &: Voous 1988; Holmes 1996; Wind 1996a) and the new records included here

A simple alternative to line transects of nests for estimating orangutan densities

We conducted a validation of the line transect technique to estimate densities of orangutan (Pongo pygmaeus) nests in a Bornean swamp forest, and compared these results with density estimates based on nest counts in plots and on female home ranges. First, we examined the accuracy of the line transect method. We found that the densities based on a pass in both directions of two experienced pairs of observers was 27% below a combined sample based on transect walks by eight pairs of observers, suggesting that regular line-transect densities may seriously underestimate true densities. Second, we compared these results with those obtained by nest counts in 0.2-ha plots. This method produced an estimated 15.24nests/ha, as compared to 10.0 and 10.9, respectively, by two experienced pairs of observers who walked a line transect in both directions. Third, we estimated orangutan densities based on female home range size and overlap and the proportion of females in the population, which produced a density of 4.25-4.5 individuals/km2 . Converting nest densities into orangutan densities, using locally estimated parameters for nest production rate and proportion of nest builders in the population, we found that density estimates based on the line transect results of the most experienced pairs on a double pass were 2.82 and 3.08 orangutans/km2, based on the combined line transect data are 4.04, and based on plot counts are 4.30. In this swamp forest, plot counts therefore give more accurate estimates than do line transects. We recommend that this new method be evaluated in other forest types as wel

Addressing environmental and atmospheric challenges for capturing high-precision thermal infrared data in the field of astro-ecology

Using thermal infrared detectors mounted on drones, and applying techniques from astrophysics, we hope to support the field of conservation ecology by creating an automated pipeline for the detection and identification of certain endangered species and poachers from thermal infrared data. We test part of our system by attempting to detect simulated poachers in the field. Whilst we find that we can detect humans hiding in the field in some types of terrain, we also find several environmental factors that prevent accurate detection, such as ambient heat from the ground, absorption of infrared emission by the atmosphere, obscuring vegetation and spurious sources from the terrain. We discuss the effect of these issues, and potential solutions which will be required for our future vision for a fully automated drone-based global conservation monitoring system.Comment: Published in Proceedings of SPIE Astronomical Telescopes and Instrumentation 2018. 8 pages, 3 figure

Acoustic models of orangutan hand-assisted alarm calls

B.d.B. was funded by the European research council starting grant ABACUS project and the Innoviris ‘Brains back to Brussels’ programme. S.A.W. was funded by the Netherlands Organisation for Scientific Research NWO. A.R.L. was funded by the Menken Funds (University of Amsterdam).Orangutans produce alarm calls called kiss-squeaks, which they sometimes modify by putting a hand in front of their mouth. Through theoretical models and observational evidence, we show that using the hand when making a kiss-squeak alters the acoustics of the production in such a way that more formants per kilohertz are produced. Our theoretical models suggest that cylindrical wave propagation is created with the use of the hand and face as they act as a cylindrical extension of the lips. The use of cylindrical wave propagation in animal calls appears to be extremely rare, but is an effective way to lengthen the acoustic system; it causes the number of resonances per kilohertz to increase. This increase is associated with larger animals, and thus using the hand in kiss-squeak production may be effective in exaggerating the size of the producer. Using the hand appears to be a culturally learned behavior, and therefore orangutans may be able to associate the acoustic effect of using the hand with potentially more effective deterrence of predators.Publisher PDFPeer reviewe

Ape Population Abundance Estimates

This annex presents ape abundance estimates at the site level. The term “site” refers to a protected area and its buffer zone, a logging concession or group of concessions, or any discrete area where a survey has taken place in the past two decades, although this annex also lists a few sites that were last surveyed in the 1970s and 1980s.Output Type: Online-only anne

Terrestrial Megafauna Response to Drone Noise Levels in Ex Situ Areas

Drone use has significantly grown in recent years, and there is a knowledge gap on how the noise produced by these systems may affect animals. We investigated how 18 species of megafauna reacted to drone sound pressure levels at different frequencies. The sound pressure level on the low frequency generated by the drone did not change the studied species’ behavior, except for the Asian elephant. All other studied species showed higher noise sensitivity at medium and high frequencies. The Asian elephant was the most sensitive species to drone noise, mainly at low frequencies. Felines supported the highest sound pressure level before showing behavioral reactions. Our results suggest that drone sound pressure levels in different frequencies cause behavioral changes that differ among species, which is relevant to assessing drone disturbances in ex situ environments. The findings presented here can help to reduce drone impact for target species and serve as an experimental study for future drone use guidelines.M.M.P. contract is funded by the European Union “NextGenerationEU” Programa María Zambrano, Ministerio de Universidades, Spain. Fundación Barcelona Zoo, 310557 Project (Ayuntamiento de Barcelona)

Small room for compromise between oil palm cultivation and primate conservation in Africa

Despite growing awareness about its detrimental effects on tropical biodiversity, land conversion to oil palm continues to increase rapidly as a consequence of global demand, profitability, and the income opportunity it offers to producing countries. Although most industrial oil palm plantations are located in Southeast Asia, it is argued that much of their future expansion will occur in Africa. We assessed how this could affect the continent's primates by combining information on oil palm suitability and current land use with primate distribution, diversity, and vulnerability. We also quantified the potential impact of large-scale oil palm cultivation on primates in terms of range loss under different expansion scenarios taking into account future demand, oil palm suitability, human accessibility, carbon stock, and primate vulnerability. We found a high overlap between areas of high oil palm suitability and areas of high conservation priority for primates. Overall, we found only a few small areas where oil palm could be cultivated in Africa with a low impact on primates (3.3 Mha, including all areas suitable for oil palm). These results warn that, consistent with the dramatic effects of palm oil cultivation on biodiversity in Southeast Asia, reconciling a large-scale development of oil palm in Africa with primate conservation will be a great challenge

Envisioning a future for Bornean orangutans: Conservation impacts of action plan implementation and recommendations for improved population outcomes

Populations of the Critically Endangered Bornean orangutan (Pongo pygmaeus) are declining despite more than 10 years of conservation action plan implementation. Here we analyzed the impacts on species' population and habitat from orangutan conservation strategies implemented between 2007 and 2017. We also assessed data on investments into orangutan conservation, orangutan population trends and landcover change in orangutan range between 2007 and 2017. Diverse strategies addressed the range of threats to orangutans but were not implemented at scales that impacted species’ level populations and habitats. Since 2007 orangutan populations and forests across orangutan range have declined, with orangutan killing and deforestation as the major drivers of loss. Protected areas have increased since 2007, notably in Malaysian range states and in Central Kalimantan, Indonesia. However, 80% or tens of thousands of orangutans live outside protected areas in Kalimantan alone. Our results underscore scientific findings that have demonstrated this species’ resiliency and modified previous understanding of their habitat use. Orangutans are regularly found using agriculture landscapes (acacia, oil palm, and timber plantations), and exploited forests. This plasticity must be considered to design more effective orangutan conservation strategies. We need to revise the notion of “orangutan habitat” to extend beyond forests alone, incorporating all landscapes where P. pygmaeus can be found. Orangutans cannot survive in exclusively monoculture production areas; they need some natural forest to fulfill their ecological requirements. However, individuals surviving in isolated forest patches or mosaic landscapes play an important role in sustaining the long-term viability of the local metapopulation through provision of crucial genetic, reproductive and socioecological connectivity. Our findings suggest removing these individuals through translocations weakens overall metapopulation health. All necessary efforts must be made to maintain individuals in isolated forest patches or mosaic landscapes in order to support healthy metapopulations. Improved orangutan population outcomes will require addressing habitat connectivity at the landscape level, incorporating both non-forested and anthropogenically modified areas, and developing efficient management strategies for human and orangutan co-existence within these multiple-use landscapes