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Across broad taxonomic groups, life history models predict that increased ecological predictability will lead to conservative investment in reproductive effort. Within species, however, organisms are predicted to have increased reproductive rates under improved environmental conditions. It is not clear how these models apply to closely-related species. In(More)
Geographic variation in some aspects of chimpanzee behavior has been interpreted as evidence for culture. Here we document similar geographic variation in orangutan behaviors. Moreover, as expected under a cultural interpretation, we find a correlation between geographic distance and cultural difference, a correlation between the abundance of opportunities(More)
Assessment of energetic condition is a critical tool for behavioral and reproductive ecologists. However, accurate quantification of energy intake and expenditure is labor-intensive, and it can be problematic for field scientists to obtain regular data on individual animals. C-peptide, a polypeptide segment of the proinsulin molecule that is secreted along(More)
Male orangutans (Pongo spp.) display an unusual characteristic for mammals in that some adult males advance quickly to full secondary sexual development while others can remain in an adolescent-like form for a decade or more past the age of sexual maturity. Remarkably little is understood about how and why differences in developmental timing occur. While(More)
Arbitrariness is an elementary feature of human language, yet seldom an object of comparative inquiry. While arbitrary signals for the same function are relatively frequent between animal populations across taxa, the same signal with arbitrary functions is rare and it remains unknown whether, in parallel with human speech, it may involve call production in(More)
The vital role of body protein as an energy reserve has received little focus in studies of wild primates. Owing to the relatively low protein content of fruit, some frugivorous primates could face a protein deficit if body protein is catabolized for energy during periods of low fruit availability. Such an imbalance can be detected if fatty acids, amino(More)
Arbitrariness is an elementary feature of human language, yet seldom an object of comparative inquiry. While arbitrary signals for the same function are relatively frequent between animal populations across taxa, the same signal with arbitrary functions is rare and it remains unknown whether, in parallel with human speech, it may involve call production in(More)
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