Evolution of chemical signals in the Asian elephant, Elephas maximus: behavioural and ecological influences

In antiquity, the Asian elephant, Elephas maximus, gradually spread southwa rd and eastward to become a successfully surviving, ecologically dominant m egaherbivore in the tropical environment of south-east Asia. The changing p hysical environment forced dynamic fluxes in its social structure and alter ed its metabolism. Such events shaped the production and ultimately the sta bility of certain chemicals released by body effluvia. Some of these chemic als took on significance as chemical signals and/or pheromones. This articl e demonstrates by experimental and observational evidence, and hypothesizes based on speculative reasoning, how and why specific chemical signals evol ved in the modern Asian elephant. Evidence, including the functional criter ia required by elephant social structure and ecology, is presented for the hypothesis that the recently identified female-emitted, male-received sex p heromone, (Z)-7-dodecenyl acetate evolved first as a chemical signal. Subse quently, the cohesiveness and harmony of small, matriarchally-led female gr oups were strengthened by a female-to-female chemical signal, recently defi ned behaviourally. The looser societal structure of freer, roaming males al so became bounded by chemical signals; for the males, breath and temporal g land emissions, as well as urinary ones function in chemical signalling. Ba sic knowledge about elephant chemical signals is now linking chemical infor mation to behaviour and beginning to demonstrate how these signals affect e lephant social structure and enable the species to cope with environmental changes.