Evolution of chemical signals in the Asian elephant, Elephas maximus: behavioural and ecological influences
L E L Rasmussen
Department of Biochemistry and Molecular Biology, Oregon Graduate
Institute of Science and Technology,
PO Box 91000, Portland, OR 97291-1000, USA
(Fax, 503-748-1464; Email, firstname.lastname@example.org)In antiquity, the Asian elephant, Elephas maximus, gradually spread southward and eastward to become a successfully surviving, ecologically dominant megaherbivore in the tropical environment of south-east Asia. The changing physical environment forced dynamic fluxes in its social structure and altered its metabolism. Such events shaped the production and ultimately the stability of certain chemicals released by body effluvia. Some of these chemicals took on significance as chemical signals and/or pheromones. This article demonstrates by experimental and observational evidence, and hypothesizes based on speculative reasoning, how and why specific chemical signals evolved in the modern Asian elephant. Evidence, including the functional criteria required by elephant social structure and ecology, is presented for the hypothesis that the recently identified female-emitted, male-received sex pheromone, (Z)-7-dodecenyl acetate evolved first as a chemical signal. Subsequently, the cohesiveness and harmony of small, matriarchally-led female groups were strengthened by a female-to-female chemical signal, recently defined behaviourally. The looser societal structure of freer, roaming males also became bounded by chemical signals; for the males, breath and temporal gland emissions, as well as urinary ones function in chemical signalling. Basic knowledge about elephant chemical signals is now linking chemical information to behaviour and beginning to demonstrate how these signals affect elephant social structure and enable the species to cope with environmental changes.
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