Oral Presentation- Symposium 12th International Mammalogical Congress

Social influences and sex differences in the development of sponge tool use among wild bottlenose dolphins of Shark Bay, Australia (#17)

Janet Mann 1 , Vivienne Foroughirad 2 , Eric M Patterson 1 , Margaret A Stanton 3
  1. Georgetown University, Washington, DC, United States
  2. Biology, Duke University, Raleigh-Durham, North Carolina, United States
  3. Anthropology, George Washington University, Washington, DC, United States

Demonstration of social learning among marine mammals is challenging given the inherent difficulty of conducting detailed behavioral observations and experimental designs. Here, we examine social influences on the ontogeny of sponge tool use among Shark Bay bottlenose dolphins. Although sponge tool use shows strong patterns of vertical transmission and occurs at several sites in Shark Bay, only about 5% of the population uses sponge tools in the eastern gulf. Sighting records (N = 30 calves, 750 surveys) and focal follows (N = 22 calves, 250h) of female spongers and their dependent offspring enabled us to investigate maternal and non-maternal social influences on the development of sponging. Of 41 calves born to female spongers, 5% (1 of 19) of daughters and 45% (10 of 22) of sons did not become spongers post-weaning (> 4 years of age). Mothers of future spongers, compared with those that did not become spongers, tended to spend more time sponging when their dependent offspring were nearby (GLMM, P = 0.07). However, calves that became spongers also spent more time separated (> 10m) from their mothers than those that did not become spongers (GLMM, P < 0.001), likely because they both sponged independently. Of offspring that became spongers, daughters, more than sons, sponged at the same time as their mothers (permutation test, P = 0.002), even though they were rarely together when sponging. In sum, these results demonstrate that maternal foraging behaviour, sociability, and calf sex influence the likelihood of becoming a sponger.