Ecological and Biochemical Constraints on Pheromonal Signaling Systems in Asian Elephants and Their Evolutionary Implications

Abstract

The Asian elephant is an unusual example of how intraspecies chemical communication helps maintain societal cohesiveness within familial and herd units. The amount of multi- directional chemical communication is surprising, because long-lived elephants have a highly organized society, are capable of trans-generational passage of information, possess a sophisticated vocalization system, and are capable of complex learning and tool use. This paper discusses the ecological, behavioral, and biochemical aspects of chemical sig- nals in elephants from an evolutionary perspective. Diverse bodily emissions are utilized as intraspecies chemical signals (including pheromones), often with imposed biochemical constraints. In this chapter, chemosignals released from temporal gland secretions and breath of male Asian elephants in musth and a urinary female-to-male preovulatory phero- mone are utilized as examples of these concepts. Furthermore, specific behavioral and bio- chemical studies with (Z)-7-dodecenyl acetate (a female-to-male urinary sex pheromone) demonstrate that social context significantly influences responsivity (demonstrated by field studies in Myanmar) and that additional biochemical requirements, perhaps lipo- cal in-like proteins, may be required for full bioactivity. The remarkable convergent evolu- tion of (Z)-7-dodecenyl acetate, both structurally and functionally, in elephants and Lepidoptera, allows the use in elephant studies of effective biochemical tools developed for insect investigations. This convergence of chemical signaling systems of elephants and insects has several interesting implications.