Scottish bottlenose dolphins are large, robust animals measuring up to 3.8 metres long and weighing around 400 kg when fully grown, which is somewhat larger than their counterparts worldwide. Their colour pattern is typically a dark grey back with light grey sides and a near-white belly. Older animals often have scars inflicted by other animals, including rake marks caused by other dolphins’ teeth. Lifespan is about 20 to 30 years.
Habitat and DistributionEdit
Hebridean bottlenose dolphins are at the northern-most extreme of the species' global range, and are seen throughout the entire Hebridean area. They are most frequently seen in inshore waters, close to the coastline around headlands and bays. Hebridean sightings hotspots are the Isles of Mull (in particular the Sound of Mull), Iona, Coll, Tiree, and Barra. Photo-identification work has found that there is a population of 30 to 40 animals inhabiting the Inner Hebrides (Kintyre to Skye) and a separate group of about 12 animals recorded in and around the Sound of Barra.
Bottlenose dolphins are usually seen in social groups of three to ten animals, although larger group sizes are not uncommon. These dolphins are usually fairly slow swimmers, travelling at about 2 mph, but can reach speeds of over 30 mph for brief periods. Famously inquisitive, active and playful, they are often seen bow-riding, and leaping clear of the water.
Food and ForagingEditCo-operative feeding has been observed in bottlenose dolphins in addition to individual foraging; several dolphins will work together to herd fish to the surface to feed. They have 18 to 26 pairs of conical teeth in each jaw, which are used to catch a wide variety of fish, squid, cuttlefish and crustaceans. Bottlenose dolphins are known to use their powerful tails to strike fish in order to stun and catch their prey, a behaviour known as ‘fish-whacking’.
Status and ConservationEdit
Our research has identified around 50 bottlenose dolphins that inhabit the waters off the west coast of Scotland. Other notable populations include those in the Moray Firth on the east coast of Scotland and in Cardigan Bay, west Wales. The total UK inshore population of bottlenose dolphins is thought to be fewer than 300 individuals. As a coastal species, they are affected by human activities including the bioaccumulation of chemical contaminants, accidental capture and drowning in fishing nets, and the general damage and degradation of their marine habitat. Boat activities in coastal waters, including those for shipping, seismic, military and recreational uses, pose threats to all cetacean species by injury from collisions and by loud noises introduced into the marine environment, which may interfere with navigation, food-finding, and communication, as well as possibly causing damage to their ears. Our long-term research project continues to collect baseline data on distribution and abundance, which will help us to understand and protect bottlenose dolphins off western Scotland. Bottlenose dolphins are protected under UK and EU law, principally under Schedule 5 of the Wildlife and Countryside Act 1981, the Nature Conservation (Scotland) Act 2004 and by the 1992 EU Habitats and Species Directive.
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