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The Shannon Dolphins

The waters of the Shannon estuary are the residence of the Shannon Dolphins, Ireland’s only resident group of Bottlenose Dolphins. These animals have most likely been living in the estuary for hundreds if not thousands of years. One of the earliest possible accounts of the Shannon Dolphins is the legend of the Cataigh (or Catach). This sea monster that claimed Scattery Island, a small piece of land in the middle of the estuary, was described as an enormous eel with a line of sharp barbs along its back, dagger-like teeth and long enough to curl around the island. As the monster devoured everything that came close, nobody dared to go even near Scattery. As in all good stories the monster met its match eventually, in this tale in the shape of the local saint named Senan. The saint defeated the Cataigh equipped with only a golden cross and the monster subsequently retired to Doolough Lake, a short trip north of the Shannon Estuary, where it has been leading a quiet life ever since. Because there is some truth in every legend it is likely that there really was a sea monster or in this case probably many of them. Witnessing a group of dolphins travelling, their fins cutting through the water, one could indeed imagine an eel like creature swimming along and up close the teeth of a dolphin appear very much dagger-like.

Today over 100 animals are present at the estuary at any given time. Of those around 40 are permanent residents, the others are coming and going throughout the year. The reason the estuary is so popular among dolphins is the same why birds like to come here: The rich food supply that is being brought in by the strong tidal currents. Bottlenose dolphins in general live on a diet of fish, squid and sometimes small crustaceans. The Shannon Dolphins are most likely mainly fish eaters and feed on resident fish like bass and various species of flatfish as well as pelagic species like herring or sprat that venture into the estuary. In late summer and autumn salmon becomes a major part of their diet and the animals can be seen tossing salmon in the air, a behaviour that is either associated with playing or learning or probably both. Dolphins are known for their very clever hunting techniques and in the Shannon they can be observed circling a school of fish to keep them together while individuals repeatedly dash into the tightly packed group to feed.

Bottlenose dolphins travel and hunt in small groups and find their way as well as their prey through echo location. While a dolphin’s eyesight is similar to our own it is only of very little use in the often murky waters of the estuary so echo location is a much more reliable method to get around. The dolphins emit a series of pulses and clicks from an area near their blowhole known as melon. When these sounds hit a solid object like a fish or a boat, they bounce back and the dolphin picks up those echoes through its lower jaw from where they are transmitted to the animal’s inner ear. Because sound travels five time faster in water than in air this way of experiencing the world is very effective. It is also though that certain variations of those clicks and pulses along with whistles are a form of communication between the animals. Tailslapping can also be a kind of communication. Depending on the strength of the slap this behaviour could be a warning to other animals or an attempt to make contact. Tailslapping has also been observed as part of hunting techniques. Other behaviours that can be observed are Spyhopping – the animal pokes its head out of the water to see what is going on above the surface –, Breaching – the animal jumps fully out of the water which could be another way to have a look around or just to have fun and Bowriding – possibly a way to save energy when swimming or yet another way to have fun. Dolphin groups can consist of up to 20 individuals but are on average considerably smaller. While these groups are very fluid, known as fission-fusion society, it is generally individuals of the same sex and age that travel together. Groups of mothers with calves for example can regular be seen in the Shannon Estuary.

 

Dolphins are not the only marine mammals in the Shannon estuary. Other cetaceans, especially Minke Whales and Harbour Porpoises, regularly find their way into the area and bigger whales like Humpbacks and Orcas can be seen passing the headland of Loop Head. Common Seals are regular visitors while Grey Seals are known to rear their young in the small storm beaches at the Mouth of the Shannon and the lower estuary. Unlike Common Seal pups, which are able to swim within hours after birth, the offspring of the Grey Seal is born with a white fluffy coat that needs to be shed before the youngsters can enter the water. This takes up to six weeks and during this time both mother and pup are stationary, the pup hauled up on the beach while the mother can often be seen patrolling the waters around the cove. Otters are also common, but their secretive lifestyle makes them a most elusive animal.

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Birds are also a common sight. In addition to the breeding visitors and year-round residents, Gannets that breed further south on Little Skellig are regular visitors to the estuary.

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