The Blue World Institute undertakes research activities into several large marine vertebrates. Our main research is on the coastal communities of bottlenose dolphins in the region. Other project activities also focus on other cetacean species including the Fin whale, Cuvier’s beaked whale, Risso’s dolphin, striped dolphin and common dolphin as well as the Mediterranean monk seal. In cooperation with the Croatian Natural History Museum, we conduct research into sharks, giant devil rays, and sea turtles. All marine mammals – Cetaceans, Pinnipeds, Sirenians, the sea otter (Enhydra lutris) and polar bear (Ursus maritimus) – are considered to have evolved at various times from land dwelling ancestors. Although cetaceans look more like fish than their closest living relatives, the Hippopotamus (Hippopotamus amphibius), their anatomy, physiology and embryology are certainly mammalian. Like all true mammals, Cetaceans give birth to live young and females possess mammary glands. As a member of the Odontoceti suborder, dolphins have teeth, whereas baleen whales have baleen plates. The Delphinidae constitute the largest and most diverse family of cetaceans, including the Killer whale (Orcinus orca). Currently there are three sub-orders of cetaceans: Archaeocetes – now completely extinct, Odontocetes – the toothed whales and Mysticetes – the baleen whales. It is commonly believed that both Odontocetes and Mysticetes share a common ancestor from among the Archaeocetes. New genetic and morphological analyses uncover links between species previously considered distinct and differences between commonly associated species. Similarly, many recent discoveries of new species made through genetic research indicate that the number of living cetaceans is significantly higher than about 80 currently recognised. Factors like individual variability in vocalisation, feeding preferences and behaviour, colour, skeletal characteristics, the presence of isolated sub-populations and inter-fecundity between species all add to this uncertainty.
Cetacean species in the Adriatic Sea
Eleven Cetacean species are present with regular populations in the Mediterranean Sea and contiguous area. Three of these species have limited ranges; the killer whale (Orcinus orca) is present in the Strait of Gibraltar, the rough-toothed dolphin (Steno bredanensis) in the Levantine basin and the harbour porpoises (Phocoena phocoena relicta) in the Aegean Sea. The other eight species are present throughout the Mediterranean and are recorded in the Adriatic Sea with different densities. These include the common bottlenose dolphin (Tursiops truncatus) the short-beaked common dolphin (Delphinus delphis), the striped dolphin (Stenella coeruleoalba), the fin whale (Balaenoptera physalus), the sperm whale (Physeter macrocephalus), the long-finned pilot whale (Globicephala melas), the Risso’s dolphin (Grampus griseus) and the Cuvier’s beaked whale (Ziphius cavirostris). Additionally, two more species (considered visitors to the Mediterranean Sea), the false killer whale (Pseudorca crassidens) and the humpback whale (Megaptera novaeangliae), have been recorded with solitary individuals in the Adriatic Sea. Current knowledge of the status of Cetacean species in the Adriatic Sea indicate that only the common bottlenose dolphin is regularly present in the entire Adriatic Sea. The striped dolphin, the Risso’s dolphin and the Cuvier’s beaked whale are present in different densities only in the southern Adriatic, while sperm whales occasionally visit the area. Fin whales are present seasonally in the central and southern Adriatic. The long-finned pilot whale, false killer whale and humpback whale present rare visitors to the Adriatic Sea. Finally, the short-beaked common dolphin, once present in the entire Adriatic Sea should be considered regionally extinct, as it is present only through either remnant or stray animals.