Bottlenose dolphin (Tursiops truncatus) presence and site fidelity in the Ionian sea (Greece)

The Mediterranean population of Tursiops truncatus is classified as Vulnerable by IUCN experts (2006). Nevertheless few information are available for most of the sub-populations inhabiting the basin. Data on bottlenose dolphin presence abundance and site fidelity were collected during each summer from 2008 to 2010, in the Ionian Sea (Greece). The aim of this study was to assess the residency and the evolution in time of bottlenose dolphin population in an area involved in intensive anthropogenic exploitation, especially during the summer season. About 540 survey hours were carried out, and 6500 km were covered surveying an area of about 600 km2. 99 individuals were encountered during monitoring activity, and 39 individuals were identified based on presence of natural markers. 69% of them (27 individuals) were sighted only once, 20% (8 individuals) were sighted twice, 5% (2 individuals) three times, 3% (1 individual) four times and another 3% (1 individual) five times. Individuals sighted several times have been recorded all the three years, suggesting a seasonal site fidelity for the area. Eight of them were found to be strictly associated. The cumulative curve of photo-identified individuals, shows that each year new animals added to the community, suggesting the presence of an open population. Extending surveys area and compare catalogues with adjacent areas will improve knowledge about spatial movements and residency of the investigated population.