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Tursiops truncatus 

Scope: Europe
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Mammalia Cetartiodactyla Delphinidae

Scientific Name: Tursiops truncatus (Montagu, 1821)
Regional Assessments:
Common Name(s):
English Common Bottlenose Dolphin, Bottle-nosed Dolphin, Bottlenosed Dolphin, Bottlenose Dolphin
French Dauphin souffleur, Grand dauphin, Souffleur, Tursiops
Spanish Delfín Mular, Pez Mular, Tursión
Synonym(s):
Tursiops gephyreus Lahille, 1908
Tursiops gilli Dall, 1873
Tursiops nuuanu Andrews, 1911
Taxonomic Notes: All bottlenose dolphins around the world were previously recognized as T. truncatus, but recently the genus has been split into two species: T. truncatus and T. aduncus (the smaller Indo-Pacific bottlenose dolphin: Wang et al. 1999, 2000a,b). However, the taxonomy of bottlenose dolphins is confused, due to geographical variation, and it is very possible that additional species will be recognized in the future. For example, two forms in the North Atlantic, an offshore and a coastal form, are distinguishable on the basis of morphology and ecological markers (e.g. Mead and Potter 1995), have fixed genetic differences and, therefore, eventually may be assigned to different species (Leduc and Curry 1997, Hoelzel et al. 1998, Reeves et al. 2003).

Bottlenose dolphins in the Black Sea are recognized as a subspecies possessing morphological differences from Atlantic and Pacific dolphins (Barabasch-Nikiforov 1960, Geptner et al. 1976). The Black Sea subpopulation is also differentiated genetically from other bottlenose dolphins in the eastern and western Mediterranean and the northeastern Atlantic (Natoli et al. 2005), and the available evidence (Birkun 2006) supports recognition of the subspecies T. t. ponticus.

Assessment Information [top]

Red List Category & Criteria: Data Deficient (Regional assessment) ver 3.1
Year Published: 2007
Date Assessed: 2007-01-26
Assessor(s): Species account by IUCN SSC Cetacean Specialist Group; regional assessment by European Mammal Assessment team
Reviewer(s): Philip Hammond
Justification:
This species has a varying status in different parts of its European range. In the Mediterranean and Black seas there have been substantial population declines; the Mediterranean population was recently assessed as Vulnerable (A2cde), and the Black Sea subspecies T. t. ponticus was classed as Endangered (A2cde)(Reeves and Notarbartolo di Sciara 2006). However, although there are no estimates of population size or trend from offshore waters of the North Atlantic, the population there is likely to be large and shows no evidence of significant decline. Overall in the European Mammal Assessment region, it is not possible to quantify the population trend because the relative size of the different subpopulations is not known. Consequently the species is assessed as Data Deficient at the European regional level.

Geographic Range [top]

Range Description:Common bottlenose dolphins are distributed worldwide through tropical and temperate inshore, coastal, shelf, and oceanic waters (Leatherwood and Reeves 1990, Wells and Scott 1999, Reynolds et al. 2000). Bottlenose dolphins generally do not range pole-ward of 45° except in northern Europe (as far as the Faroe Islands 62°N 7°W: Bloch and Mikkelsen 2000). The species is rare in the Baltic Sea (it may best be considered extralimital there), and is vagrant to Norway (Wells and Scott 1999).
Countries occurrence:
Native:
Bulgaria; Croatia; Cyprus; Denmark; France; Germany; Gibraltar; Greece; Ireland; Italy; Malta; Montenegro; Netherlands; Norway; Portugal; Romania; Russian Federation; Serbia; Slovenia; Spain; Sweden; Turkey; Ukraine; United Kingdom
FAO Marine Fishing Areas:
Native:
Atlantic – western central; Atlantic – northeast; Atlantic – eastern central; Atlantic – southwest; Atlantic – southeast; Atlantic – northwest; Indian Ocean – western; Indian Ocean – eastern; Mediterranean and Black Sea; Pacific – southeast; Pacific – northeast; Pacific – northwest; Pacific – eastern central; Pacific – western central; Pacific – southwest
Additional data:
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:Abundance has been estimated for several parts of the species' range. Summing available estimates, a minimum world-wide estimate of common bottlenose dolphins is 600,000.

Total abundance in the Mediterranean is unknown but thought to be in the low 10,000s based on observed densities in areas that have been surveyed (Reeves and Notarbartolo di Sciara 2006). Surveys in the northwestern Mediterranean estimated 7,654 (CV=45%) dolphins (Forcada et al. 2004). An estimated 584 (CV=28%) animals occur in the Alboran Sea (Cañadas and Hammond 2006). Mediterranean bottlenose dolphins exhibit population structure based on toxicology and diet (Borrell et al. 2005) and genetics (Natoli et al. 2005).

The total population size in the Black Sea is unknown. However, there are recent abundance estimates for parts of the range suggesting that population size is at least several thousands (Reeves and Notarbartolo di Sciara 2006).

Preliminary estimates from the late 1980s indicate about 1,000 dolphins occur around the Faroe Islands (Sigurjónsson et al. 1989, Bloch and Mikkelsen 2000). A wide scale survey in 2005 of western European continental shelf waters including the western Baltic, North Sea and Atlantic margin as far as southern Spain estimated that there were 12,600 bottlenose dolphins in this area (CV=27%, P. Hammond pers. comm.).

Reeves and Notarbartolo di Sciara (2006) estimate generation time in the common bottlenose dolphin to be c.20 years.
Current Population Trend:Decreasing
Additional data:
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:Common bottlenose dolphins tend to be primarily coastal, but they can also be found in pelagic waters (Wells and Scott 1999). Where distinct ecotypes are known, the inshore form frequents estuaries, bays, lagoons and other shallow coastal regions, occasionally ranging far up into rivers. The offshore form is apparently less restricted in range and movement. Some offshore dolphins are residents around oceanic islands. In many inshore areas bottlenose dolphins maintain definable, long-term multi-generational home ranges, but in some locations near the extremes of the species range, coastal bottlenose dolphins are migratory. Black Sea bottlenose dolphins are common over the continental shelf; they sometimes occur far offshore (Reeves and Notarbartolo di Sciara 2006).

Bottlenose dolphins are commonly associated with many other cetaceans, including both large whales and other dolphin species (Wells and Scott 1999). Mixed schools with Indo-Pacific bottlenose dolphins have been found, for instance off China and Taiwan (J. Wang, pers. comm.). Spring and summer, spring and fall, or single summer calving peaks are known for most areas where this has been studied (Wilson 1995, Wells and Scott 1999). In general, bottlenose dolphins consume a wide variety of prey species, mostly fish and squid (Barros and Odell 1990, Barros and Wells 1998, Santos et al. 2001). They sometimes eat shrimps and other crustaceans.
Systems:Marine
Generation Length (years):20

Threats [top]

Major Threat(s): Coastal and island-centered populations are especially vulnerable to hunting, incidental catch, and habitat degradation (see Curry and Smith 1997 for a review). Acute conservation problems are known in the Mediterranean and Black seas (IWC 1992, Reeves and Notarbartolo di Sciara 2006) as well as a number of other areas in the global range (outside Europe). Dolphin catches for bait, human consumption, or to remove competition with fisheries have been reported worldwide (see reviews in Wells and Scott 1999, 2002).

The only Mediterranean area with quantitative historical information is the northern Adriatic Sea, where bottlenose dolphins likely have declined by at least 50% over the past 50 years, largely as a consequence of historical killing in extermination campaigns to reduce competition for fish, followed by habitat degradation and overfishing. The extermination campaigns were conducted until the early 1960s (Bearzi et al. 2004, Reeves and Notarbartolo di Sciara 2006). For the north-western Mediterranean, the available information suggests similar trends (Reeves and Notarbartolo di Sciara 2006).

Drive fisheries have been reported from the Faroe Islands and Japan. Up to 308 are taken annually in the Faroe Islands drive fishery (dating back to 1803), often with long finned pilot whales (Reyes 1991). The Black Sea subspecies has had extensive directed takes for commercial products (Kleinenberg 1956, Tomilin 1957, Buckland et al. 1992), including takes of at least 24,000-28,000 during 1946-1983 in the Black Sea off Turkey. However, the total number of dolphins killed was certainly much greater (probably by tens of thousands) as figures do not include, or only partially include, catch statistics from other Black Sea countries (Reeves and Notarbartolo di Sciara 2006).

Live-capture removal of Black Sea bottlenose dolphins, including mortality during capture operations, is estimated at 1,000-2,000 since the early 1960s. Live-captures continue in the Russian Federation, with 10-20 animals taken annually from a small area in the Kerch Strait, Russia (Reeves and Notarbartolo di Sciara 2006). According to CITES statistics, at least 92 individuals were removed from the Black Sea region during 1990-1999 (Reeves et al. 2003) and Russia reportedly has exported at least 66 for travelling shows since 1997 (Fisher and Reeves 2005).

Incidental catches of common bottlenose dolphins are known from throughout the species’ range, in gillnets, driftnets, purse seines, trawls, long-lines, and on hook-and-line gear used in commercial and recreational fisheries, but numbers of mortalities are often poorly documented (Wells and Scott 1999). Annual Black Sea bottlenose dolphin incidental mortality in bottom-set gillnets from 1946 through the 1980s is roughly estimated in the hundreds. The scale of this mortality almost certainly increased in the 1990s-2000s owing to the rapid expansion of illegal, unreported and unregulated fishing (Reeves and Notarbartolo di Sciara 2006). According to Öztürk (1999) at least 200-300 bottlenose dolphins per year may be taken incidentally in Turkish fisheries in a variety of fishing nets, especially bottom-set gill nets.

Common bottlenose dolphins in coastal areas are exposed to a wide variety of threats in addition to direct and indirect takes. Threats that are cause for concern include: 1) the toxic effects of xenobiotic chemicals; 2) reduced prey availability caused by environmental degradation and overfishing (Pauly et al. 1998, Jackson et al. 2001); 3) direct and indirect disturbance and harassment (e.g. boat traffic and commercial dolphin watching and interactive programs); 4) marine construction and demolition and 5) other forms of habitat destruction and degradation (including anthropogenic noise). Although these and other threats are technically challenging to quantify by comparison with takes, their cumulative impact is likely to result in longitudinal population declines. Lack of historical data in many cases hampers understanding of long term trends, possibly resulting in shifting baselines. The contribution of anthropogenic factors to an increasing number of Unusual Mortality Events involving bottlenose dolphins remains to be determined (Spradlin et al. 2005).

Conservation Actions [top]

Conservation Actions: The bottlenose dolphin has been afforded special protected status under Annex II of the EU Habitats Directive. Commercial hunting of Black Sea cetaceans including bottlenose dolphins was banned in 1966 in the former USSR, Bulgaria and Romania, and in 1983 in Turkey. Research on population structure, abundance and removals of common bottlenose dolphins is needed so that risks to regional populations can be assessed.

Citation: Species account by IUCN SSC Cetacean Specialist Group; regional assessment by European Mammal Assessment team. 2007. Tursiops truncatus. The IUCN Red List of Threatened Species 2007: e.T22563A9374943. . Downloaded on 24 October 2017.
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