DOUGLAS III, H.D.*; CO, J.E.; JONES, T.H.; CONNER, W.E.: Chemistry, Production and Potential Functions of Aldehyde Odorants in the Crested Auklet (Aethia cristatella)

Crested auklets are small planktivorous seabirds of the North Pacific and Bering Sea. This species and the whiskered auklet produce a similar citrus odor. We have identified the odor constituents as octanal, decanal, hexanal, Z-4-dodecenal, Z-6-dodecenal, Z-4-decenal, hexanoic acid, and octanoic acid. A complex and novel organ associated with the integument has been implicated in synthesis, storage and release of the aldehydes. This is consistent with chemical defense in other taxa, where such compartmentalization protects organisms from autotoxicity. Octanal and hexanal are potent invertebrate repellents and are likely deterrents against ectoparasites. Unlike other avian chemical defense systems, these chemical agents are volatile, unstable and transitory in the plumage. The auklet’s odor is potent and persistent during the breeding season, but declines rapidly and disappears after cessation of social activity. Odor production may be a costly trait. The even-chained odorants are likely byproducts of fatty acid metabolism; utilization of these fuels is tightly regulated. Like expensive perfumes then the auklet odorants may have a role in mate selection as honest signals of mate quality and ectoparasite repellency. Preliminary data support this hypothesis. In behavioral tests captive auklets preferred a model with aldehyde odorants. Preliminary results also support orientation as a potential function of the aldehyde odorants.