1349 Bottlenose dolphin Tursiops truncatus
Description and ecological characteristics
Bottlenose dolphin Tursiops truncatus around the UK are considerably larger than individuals of the same species in most parts of the world, reaching up to around 4 m in length, although 2.5-2.7 m is a more usual adult length. It is primarily an inshore species, with most sightings within 10 km of land, but they can also occur offshore, often in association with other cetaceans. Most offshore animals probably represent a separate population, although some inshore dolphins may move offshore during the winter months. Large aggregations of many hundreds of individuals have been recorded off the Atlantic coast of Ireland, but typically single animals or small groups of up to 25 animals are sighted. A small number of semi-resident inshore populations are known.
European status and distribution
Bottlenose dolphin Tursiops truncatus have a near-global distribution (except the polar regions), and are widely distributed in North Atlantic, West African, Mediterranean and UK waters. They are scarce in the southern North Sea.
UK status and distribution
There are two main areas of UK territorial waters where there are semi-resident groups of bottlenose dolphin Tursiops truncatus: Cardigan Bay and the Moray Firth. Away from these two areas, there are smaller groups off south Dorset, around Cornwall and in the Sound of Barra, Outer Hebrides. Dolphins from all of these areas may range some distance from their apparent core range. For example, since the mid-1990s, Moray Firth dolphins have increasingly made extended movements eastwards and southwards, and probably account for regular sightings off east Scotland including the Firth of Forth. Transient groups are not infrequent almost anywhere around the British coast except the southern North Sea and south-east England. Other dolphin groups, presumed to be of transients, are recorded further offshore in deeper water along the continental shelf edge to the west of Scotland. The total population in UK inshore waters is probably less than 300 individuals. The species was formerly more widespread, especially in the southern North Sea and English Channel (although a further semi-resident group is based around the Channel Islands), and has certainly declined in range. There is insufficient evidence to comment on any change in abundance.
Site selection rationale
The only two areas in UK waters that have been identified as having the physical and biological factors essential to the life and reproduction of a population of bottlenose dolphins Tursiops truncatus are Cardigan Bay and the Moray Firth. Both have been selected as SACs. These sites hold the only two substantial semi-resident populations of the species in UK waters. While the individuals using the two sites may range further afield during certain times of the year, dolphins are present throughout the year and individuals have been seen over periods of several years. While the SAC series makes a contribution to securing favourable conservation status for this Annex II species, wider measures are also necessary to support its conservation in the UK. Such measures are detailed in the Species Action Plan for small dolphin species.
Cardigan Bay/ Bae Ceredigion
Extra-Regio, West Wales and The Valleys
The bottlenose dolphin Tursiops truncatus population of Cardigan Bay off the west coast of Wales has been estimated to consist of around 125 individuals. The dolphins appear to use the inshore waters of Cardigan Bay for both feeding and reproduction, and in the summer months calves and juveniles are often observed with adult individuals or groups.
The Moray Firth in north-east Scotland supports the only known resident population of bottlenose dolphin Tursiops truncatus in the North Sea. The population is estimated to be around 130 individuals (Wilson et al. 1999). Dolphins are present all year round, and, while they range widely in the Moray Firth, they appear to favour particular areas.
SACs where this Annex II species is a qualifying feature, but not a primary reason for site selection
- Pen Llŷn a'r Sarnau/ Lleyn Peninsula and the Sarnau East Wales, Extra-Regio, West Wales and The Valleys
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