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The Bottlenose Dolphin

Dolphin underwater at Fanore, Co ClareThe Bottlenose dolphin is one of the most familiar and abundant dolphin species in Ireland, both the Dingle dolphin and those in the Shannon estuary are bottlenose dolphins. The bottlenose dolphin is one of 24 species of cetacean (whales, dolphins and porpoise) recorded in Irish waters.

Description

Bottlenose dolphins are large, robust dolphins and can be recognised by their short, stubby beak (or nose) large sickle-shaped dorsal fin and uniform grey colour. They are an inquisitive and boisterous species, which readily approach boats and often leap clear of the water. If you see dolphins leaping clear of the water look for a short beak and large dorsal fin and you can be fairly sure they are bottlenose dolphins.

Bottlenose dolphins are observed around the entire Irish coast but the west coast holds some of the greatest concentrations in Europe. The only known resident group of dolphins in Ireland occurs in the Shannon estuary and they are regularly seen from the cliff walk at Ballybunion, Co Kerry.

Life history

Bottlenose dolphins are long-lived animals, males are thought to live up to 25-30 years while females may live to over 40 years of age. Female bottlenose dolphins do not breed until they are about 10-12 years of age. The gestation period is 11 months and the new-born calf is totally dependent on the mother for food for the first year of life and remains with the maternal group for a few years afterwards. Even a fully mature female will only breed every 2–4 years, thus the reproductive rate of bottlenose dolphins is low. However, as they live a long time there is a good chance they will rear at least one calf to breeding age in their lifetime and thus the population will remain stable.

Male dolphins have no role in rearing the calf. Mature males often form small groups and will compete to mate with receptive females. Maybe this is the source of the numerous tooth rakes and scars dolphins carry on many parts of their body.

Bottlenose dolphins like all cetacean species are very vocal. Sound travels much better under water than light, therefore dolphins can hear a lot more than they can see. Bottlenose dolphins produce a wide range of clicks, whistle, creaks, groans and other noises. Clicks are used for echolocation, to navigate and find food, while whistles are used to communicate between dolphins. Each dolphin has its own distinct signiture whistle and soon after birth, a mother and calf will learn each others whistle so they can keep in close contact.

Wild, friendly dolphins

Since the reign of the Roman Emperor Augustus when a young boy was saved from drowning by a dolphin there have been incidents of wild, sociable dolphins befriending people. Most were bottlenose dolphins but friendly Risso’s and spinner dolphins and even orca have also been documented. Sometimes, these encounters may last only a few months, sometimes many years. Some dolphins may only follow boats in and out of the harbours or swim near people and not let them touch them, while others allow very close contact.

There have been at least 65 reported cases of wild, sociable dolphins and every incident is different. Males would appear to exhibit more aggressive and exhibit overtly sexual behaviour, but aggressive acts seem to appear more frequently as the dolphins’ residency increases. However, what we may consider an aggressive act may not seem that to the dolphin but may be play to it. They are marine mammals, we are land mammals ! Recognising that dolphins are wild, unpredictable animals, which should be respected in their environment, is important if these encounters are to remain trouble free for dolphin and human.

Dolphin Conservation in Ireland

Bottlenose dolphins are protected under the Wildlife Act (1976). They are also on Annex II of the EU Habitats Directive, which requires that member states designate Special Areas of Conservation (SAC) which correspond to the ecological requirements of bottlenose dolphins. To date only the Shannon estuary has been nominated as a SAC for bottlenose dolphins. A Code of Conduct has been produced for all vessels (including commercial and recreational craft) operating in the Shannon estuary SAC. These include limiting the number of boats around dolphins and the distance and time vessels should be with them. Implicit in the Code of Conduct is that the dolphins initiate any encounters and not the vessels by approaching the dolphins.

Studying bottlenose dolphins in Ireland

Sightings of bottlenose dolphins and cetacean species should be sent to the Irish Whale and Dolphin Group who co-ordinate stranding and sighting schemes throughout the island of Ireland. Sightings can be emailed ( sightings@iwdg.ieSend an e-mail to sightings@iwdg.ie) or submitted on-line ( www.iwdg.ieLink to external site: www.iwdg.ie/sightings). For those interested in doing regular watches, information and recording packs can be obtained from the IWDG, Merchants Quay, Kilrush, Co Clare.

 


The Bottlenose Dolphin
Wild, Sociable Bottlenose Dolphins
Further Reading
Frequently Asked Questions
Whale & Dolphin Roadshow
Events
Wildlife in the Region
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