Twenty six different species of whales, dolphins & porpoises have been recorded in Ireland, but some are more common than others. Certain species migrate here in search of food, while others are year-round residents. We look at some of the more well-known marine mammals known to swim in Irish waters.
You won’t see these giants in coastal waters, but they have been detected by acoustic monitoring equipment at the edge of the continental shelf as they migrate south in the autumn. The largest animal to have ever lived, the blue whale (pictured above) can grow to 100ft and weigh just under 200 tonnes. Named for its mottled blue skin colour (which can appear light grey), it rarely breaches but tail flukes regularly. When it surfaces to breathe, it can produce blows of up to 12 metres from its blowhole. In 1891, when a blue whale became stranded in Wexford harbour and later died, a newspaper reported that crowds of curious onlookers came to see the “strange visitor from strange seas.”
These active swimmers like to show off! They regularly breach acrobatically, bow ride boats and tail slap the water. They are very inquisitive and often approach boats. Genetic studies and photo identification have enabled researchers to confirm three separate groups in Irish waters. One group resides all year round in the Shannon Estuary, where they have been observed throwing fish into the air. A coastal population move along the coast, sometimes even venturing to Scotland. A third group reside offshore, although little is known about them. Bottlenose dolphins are large, dark grey with a pale underside and the familiar short, stubby beak.
The most regularly sighted dolphins in Irish waters, common dolphins are often seen off the coast of Cork and Kerry. Unfortunately, they are also the most regularly stranded Irish dolphin. Since 2011, reported strandings have increased six-fold, with a record number of 118 reported in 2018. The cause of the increase in deaths is not known. At 1.5 to 2 metres long, common dolphins are smaller than their bottlenose cousins and have a longer, narrower beak. They are dark grey on top with a pale underside and an hourglass pattern on their sides that is yellow near the head and grey at the tail.
Since 1999, at least 92 individual humpback whales have been spotted in Irish waters using photo-identification. Many of these return to the same areas of the southwest every year – some have even been recorded over three decades. They are frequently seen from the shore and during whale watch trips. Humpbacks grow to lengths of 14 to 17 metres and are mostly black in colour with long white flippers. They regularly breach and slap their flippers at the surface, but they’re most famous for tail-fluking just before a deep dive. In April 2019, IWDG researchers captured incredible footage of four humpbacks interacting with a pod of common dolphins off the West Cork coast.
Also known as Orcas, these are actually dolphins. Instantly recognisable with striking black and white colouring, they’re the largest of the species at 8 to 9 metres long. Typically seen cruising slowly, they have been known to approach boats and sometimes engage in spyhopping (sticking their heads out of the water to have a look around). Behaviour also includes breaching and tail or flipper slapping. In 2011, a group of 100 orcas were seen feeding on mackerel to the west of Tory Island – the largest concentration ever recorded in
Irish waters. They are thought to have followed shoals of mackerel from the Hebrides. They sometimes interact with fishing trawlers off the northwest coast.
These huge whales are the second largest creatures on the planet, reaching lengths of 70 feet. Nicknamed “the greyhound of the sea” for their speed, they are the fastest of the great whales and can travel at a top speed of 23mph. They are regular visitors here – if you’re lucky you might even spot one from the coast, although you’ll need to keep a sharp lookout as they almost never breach or tail fluke. Dark grey to brownish-black in colour with white undersides and flippers, they have a tall, curved dorsal fin. Over sixty individuals have been identified in Irish waters, mostly along the south coast.
The harbour porpoise is quite shy, generally avoiding boats and other species. It surfaces very briefly, only breaches occasionally and is most active when feeding. A small, compact animal, it’s about four feet long with short flippers and a small, triangular dorsal fin midway along its back. They can be spotted fairly easily in coastal waters, and are particularly abundant between Howth Head and Dalkey in Co. Dublin where IWDG surveys produce the highest counts anywhere in Ireland.
Many thanks to the Irish Whale and Dolphin Group (IWDG) for the images used here. Discover more about the whales and dolphins in Ireland, and the work of the IWDG.
If you would like to go whale watching, Old Moore’s highly recommends Cork Whale Watch. We recently enjoyed an afternoon aboard Colin Barnes’ boat and saw a humpback, some minke whales and lots of dolphins. Amazing!