1. Ecological, social and genetic forces shaping behavioural variation in bottlenose dolphins
- Author
-
Kopps, Anna
- Subjects
- Bottlenose dolphin, Social transmission, Tool use, Individual-based model, Fine-scale genetic structure, Cultural hitchhiking, Sponging, Social structure
- Abstract
Genes and culture are two inheritance systems through which information can be passed on between generations. For my PhD, I investigated the interplay between genetic make up and the apparently culturally transmitted behaviour “sponging” in bottlenose dolphins (Tursiops sp.) in the western gulf of Shark Bay, Western Australia, and compared my results to findings from the eastern gulf. Spongers wear conical sponges as tools over their rostra which apparently aids foraging in deep water. Within each gulf, spongers share a maternally inherited mitochondrial DNA haplotype – indicative of vertical social transmission. However, haplotypes differ between gulfs. We conducted boat based surveys and collected biopsy samples of dolphins in the western gulf of Shark Bay and identified 40 spongers. As in the eastern gulf, spongers are predominantly female. In the western gulf, spongers invest more time in foraging and rest less compared to non-spongers. A distinct segregation was found between dolphins with different mitochondrial DNA haplotypes and habitat use, despite different habitats being separated by just tens of meters. Dolphins with the sponger haplotype were in one habitat (deep water) where resting and travelling groups were larger than in shallow habitat. However, foraging groups were smaller in shallow water suggesting that predation pressure is higher and resource abundance lower in deep water. Community analysis revealed that the genetic differences found between habitats are also reflected in the social structure: female dolphins preferentially associate with females from the same habitat and rarely with females from the other habitat. The two matrilines within the deep water habitat interacted. Socially learnt foraging specialisations may have lead to natal habitat preference so that the observed genetic structure arose from cultural hitchhiking of the mitochondrial DNA. An individual-based model showed that a new vertically transmitted trait is often lost by chance but once established it can be maintained. In order to assess the relative influence of potential factors driving sponging, a combined analysis of genetic, ecological and social factors showed that ecological and social but not genetic factors drive sponging. In summary, vertically transmitted, habitat-dependent foraging specialisations influence the social and genetic population structure and thus the evolutionary success of a population.
- Published
- 2012