Through the eyes of children: perceptions of environmental change in tropical forests.

This study seeks to understand children's perceptions of their present and future environments in the highly biodiverse and rapidly changing landscapes of Kalimantan, Indonesian Borneo. We analyzed drawings by children (target age 10-15 years) from 22 villages, which show how children perceive the present conditions of forests and wildlife surrounding their villages and how they expect conditions to change over the next 15 years. Analyses of picture elements and their relationships to current landscape variables indicate that children have a sophisticated understanding of their environment and how different environmental factors interact, either positively or negatively. Children appear to have landscape-dependent environmental perceptions, showing awareness of past environmental conditions and many aspects of recent trends, and translating these into predictions for future environmental conditions. The further removed their present landscape is from the originally forested one, the more environmental change they expect in the future, particularly declines in forest cover, rivers, animal diversity and increases in temperature and natural disasters. This suggests that loss of past perceptions and associated "shifting environmental baselines" do not feature strongly among children on Borneo, at least not for the perceptions we investigated here. Our findings that children have negative expectations of their future environmental conditions have important political implications. More than other generations, children have a stake in ensuring that future environmental conditions support their long-term well-being. Understanding what drives environmental views among children, and how they consider trade-offs between economic development and social and environmental change, should inform optimal policies on land use. Our study illuminates part of the complex interplay between perceptions of land cover and land use change. Capturing the views of children through artistic expressions provides a potentially powerful tool to influence public and political opinions, as well as a valuable approach for developing localized education and nature conservation programs.

People's perceptions about the importance of forests on Borneo.

We ascertained villagers' perceptions about the importance of forests for their livelihoods and health through 1,837 reliably answered interviews of mostly male respondents from 185 villages in Indonesian and Malaysian Borneo. Variation in these perceptions related to several environmental and social variables, as shown in classification and regression analyses. Overall patterns indicated that forest use and cultural values are highest among people on Borneo who live close to remaining forest, and especially among older Christian residents. Support for forest clearing depended strongly on the scale at which deforestation occurs. Deforestation for small-scale agriculture was generally considered to be positive because it directly benefits people's welfare. Large-scale deforestation (e.g., for industrial oil palm or acacia plantations), on the other hand, appeared to be more context-dependent, with most respondents considering it to have overall negative impacts on them, but with people in some areas considering the benefits to outweigh the costs. The interviews indicated high awareness of negative environmental impacts of deforestation, with high levels of concern over higher temperatures, air pollution and loss of clean water sources. Our study is unique in its geographic and trans-national scale. Our findings enable the development of maps of forest use and perceptions that could inform land use planning at a range of scales. Incorporating perspectives such as these could significantly reduce conflict over forest resources and ultimately result in more equitable development processes.

Acoustic variability and individual distinctiveness in the vocal repertoire of red-capped mangabeys (Cercocebus torquatus).

Acoustic variability and individual distinctiveness of vocal signals are expected to vary with both their communicative function and the need for individual recognition during social interactions. So far, few attempts have been made to comparatively study these features across the different call types within a species' vocal repertoire. We collected recordings of the six most common call types from 14 red-capped mangabeys (Cercocebus torquatus) to assess intra- and interindividual acoustic variability, using a range of temporal and frequency parameters. Acoustic variability was highest in contact and threat calls, intermediate in food calls, and lowest in loud and alarm calls. Individual distinctiveness was high in contact, threat, loud and alarm calls, and low in food calls. In sum, calls mediating intragroup social interactions were structurally most variable and individually most distinctive, highlighting the key role that social factors must have played in the evolution of the vocal repertoire in this species. We discuss these findings in light of existing hypotheses of acoustic variability in primate vocal behavior.

Sex differences in the vocal repertoire of adult red-capped mangabeys (Cercocebus torquatus): A multi-level acoustic analysis.

Sex differences in the vocal behavior of nonhuman primates can take various forms: sex-specific call types, differential production of shared call types, or sex discrepancy in phonation. Also, a growing literature is evidencing that systematically analyzing the vocal repertoires of primates at the call level might lead to underestimating their communicative abilities. Here, we present an extensive multi-level analysis of the still unknown vocal repertoire of adult red-capped mangabeys (Cercocebus torquatus), with a special emphasis on sex differences. We collected recordings from seven adult males and seven adult females housed in captivity. We present a structurally-based classification of mangabey calls that we cross-validated by an analysis of the associated contexts of emission. We found 12 sound units (including six sex-specific) that were concatenated to form eight call types (including four sex-specific), which were produced either singularly or in sequences composed of one ("repetition") or several ("combination") call types. We extracted organizational principles that ruled call composition and calling patterns. This revealed a high degree of potentially meaningful variability in terms of semantics and syntax. Male-female discrepancy in terms of phonation could be related to morphological dimorphism and would enable listeners to behave appropriately according to the sex of the caller. Sex differences in repertoire size, structural gradation, and call usage could reflect specificities of male-female social roles. We discuss the pertinence of these sex differences according to social system and habitat quality.