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Science  08 Jul 2005:
Vol. 309, Issue 5732, pp. 222b
DOI: 10.1126/science.309.5732.222b

Wild bottlenose dolphins in Shark Bay, Western Australia, have been shown to break off pieces of marine sponge, which they then wear over their closed snouts while probing for fish concealed in the seabed. It has been uncertain whether this “sponging” behavior, which is apparently confined almost entirely to a subset of females, is transmitted genetically or culturally, or whether it reflects ecological preferences of individuals for foraging in particular locations. It is difficult to make direct observations of social learning in wild animals (especially underwater); instead, attempts may be made to rule out alternative explanations. Krützen et al. show that ecological explanations for sponging are unlikely, as spongers and nonspongers (both male and female) forage in the same deep channels. Genetic data gathered from almost 200 individual dolphins, coupled with mating behavioral observations of the animals over a 14-year period, indicate that none of the plausible modes of single-locus inheritance could account for transmission of the behavior. Nevertheless, mitochondrial DNA data indicate that sponging is passed on through a single matriline and that all spongers are closely related. It seems possible that all spongers are descended from a recent, innovative “sponging Eve,” whose daughters and granddaughters have learned the behavior from their mothers. — AMS

Proc. Natl. Acad. Sci. U.S.A. 102, 8939 (2005).

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