Having a big nose: structure, ontogeny, and function of the elephant seal proboscis

• Published in: Canadian Journal of Zoology
• Main Authors: Sanvito, Simona, Galimberti, Filippo, Miller, Edward H.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2007
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; Elephant Seal; Elephant Seals; Mirounga leonina; Southern Elephant Seals
• Online Access: http://dx.doi.org/10.1139/z06-193; http://www.nrcresearchpress.com/doi/full-xml/10.1139/z06-193; http://www.nrcresearchpress.com/doi/pdf/10.1139/z06-193

The proboscis of male elephant seals ( Mirounga Gray, 1827) has been suggested as an example of a secondary sexual trait since Darwin. There has been much speculation about its social function (e.g., optical signal of breeding status, amplification of vocalizations, cue for female choice). However, it has never been studied in detail, probably because its fleshy nature makes measurement difficult. In this paper, we employ photogrammetry to measure the proboscis and facial morphology of a large sample of wild, unrestrained, displaying male southern elephant seals ( Mirounga leonina (L., 1758)). We describe ontogeny and allometry of the proboscis and analyze current phenotypic selection pressures on proboscis traits. We discuss the potential role of the proboscis in optical and acoustic signaling of male resource-holding potential and status. We demonstrate that proboscis size is positively correlated with age and body size independently, and that it is currently under a positive sexual selection pressure when the effect of selection on body size is removed. We suggest that selection on proboscis size is functionally related to the emission of agonistic vocalizations.