Species: Tursiops truncatus (Montagu 1821)
The bottlenose dolphin reaches an average length of 3.8 meters and a weight of 350 kg. The female is slightly smaller than the male.
The shape of the body is quite robust more than the one of other delphinids. The coloration is quite blanded and highly variable between specimens. Usually, the back is gray, the sides of a lighter gray fading without a dividing line in the whitish belly.
The species is found in all tropical and temperate waters in the coastal areas (including lagoons, estuaries, and bays) and pelagic areas. In the Italian seas, the species is widespread.
They feed primarily on bluefish, mullet, squid, and sometimes benthic invertebrates.
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Serious conservation problems affect the Mediterranean and Black Seas, where past hunting (bottlenose dolphins were intentionally killed until the 1960s because they were considered harmful to fisheries), bycatch in fishing gear and degradation of the marine environment have caused population declines.
The Mediterranean population is fragmented and subject to the continuous decline of mature individuals.
Other factors, such as overfishing of dolphin prey, vessel traffic disturbance, and noise pollution, also influence habitat loss and degradation. An additional source of concern is the high levels of pollutant contamination detected in dolphin tissues.
The local Population
The data collected during our study show that, for this local population of bottlenose dolphins, the waters around the island of Ischia represent a feeding and breeding area, as well as an important place in which to raise their young.
The groups are numerous, reaching over 60 individuals. Young and newborns are often present in the groups. In the study area, bottlenose dolphins seem to prefer the summer period for reproduction, in fact, the maximum number of newborns observed was recorded in July and August; lower numbers, but equally significant, were recorded in June and September.
Photo-identification analysis allowed us to catalog 204 individuals, including 44 females. Many animals, return over the years, demonstrating site fidelity.
With few exceptions, bottlenose dolphins are primarily distributed in coastal waters, concentrating northwest of Ischia.
The bottlenose dolphin is a highly social species that uses sound emission for feeding and socialization. The data analyzed so far, cover the spring-summer period over two years (2015-2016). A total of 24 hours of recording and 1800 whistles were selected for analysis. Multiple comparisons were made to test how the combination of different factors (group size, group composition, behavior, boat presence, depth, and distance from the coast) could affect whistle parameters. Preliminary results show that group composition is a factor that could influence frequency parameters, as well as behavior.