Beaked Whale Beaching’s along the Irish coastline August- September 2018.

**UPDATE** Over a period of six weeks from the 3rd of August to the 12th of September, 21 Cuvier's beaked whales ( Ziphius cavirostris ) were reported stranded along the Irish coastline from Co. Mayo to Co. Donegal and Co. Antrim. The most recent report came from Cansore Point, Co. Wexford.

It was reported that 38 beaked whales stranded off the Scottish coasts and 2 more were reported stranded in Iceland. That is a total o 61 beaked whales stranded over a short period of time. These are minimum estimates of mortality as they do not account for animals which may have sunk to the seabed or animals stranded in remote places and remain unreported. Previous studies on cetacean carcass drift have suggested that strandings represent a minimum of at sea mortality; depending on drift conditions carcasses may not always wash ashore, thus, the actual number of dead animals may be much higher (Peltier et al., 2014).

Cuvier’s beaked whales are rarely seen alive in Irish waters, although strandings of them are also infrequent through-out the year. Beaked whales are distributed in deep offshore waters beyond the continental shelf and are rarely sighted in coastal waters.

Between 1990 and 2015 there was a total of 85 strandings of beaked whales on Irish shores. In 2015, over a 45 day period, there was a mass stranding fifteen beaked whales along Irish and U.K. shores. This stranding event brings the total number of strandings of beaked whales to date to 94 individuals. Interestingly most strandings of Cuvier's beaked whale occur during the spring seasons. It is unusual to have more then a few strandings of this species during the year, and some years there are no reports of Cuvier's stranding.

In 2013 there were also very notable strandings of True’s beaked whale ( Mesoplodon mirus )with three separate records of single animals from Five Fingers Strand, Malin, Co. Donegal on 12th May 2013 Trawbreaga, Malin, Co. Donegal on 14th May 2013 and Ballyconneely, Co. Galway on 27th May 2013.

The first beaked whale of this unusual mortality event (UME) was reported to the Irish Whale and Dolphin Group from Omey Island, Co. Galway on 3rd of August. On August 4th 2018, it was reported to ORCireland that a Cuvier’s beaked whale was found dead at Duncap Head, Co. Donegal. According to the Irish Whale and Dolphin Group (IWDG) that included one of three whales that stranded dead in Donegal and Mayo. One beaked whale found beached on Gola Isle was reported on August 5th, in addition to one adrift in Sheephaven Bay, Co Donegal and one at Tirraun on the Mullet Peninsula. On the 7th of August another beaked whale was reported to the IWDG from Cliffony, Co. Sligo. On August 8th 2018, another Cuvier’s beaked whale was reportedstrandedto "ORCireland"by "Inishowen Whale and Dolphins" at the “Castles”, Isle of Doagh.

Cuvier’s beaked whale can be distinguished from other beaked whales by the single pair of short (up to 6cm long) conical teeth at the tip of the lower jaw. Usually these teeth erupt from the jaw only in adult males, while they not be visible in immature and adult females. Their main identifying features for this species are cigar shaped body, a small triangular dorsal fin, set two thirds of the way down their back, and a well-defined beak, even though less pronounced than other beaked whale species.

They are brown to light grey in colour, depending on the age. Calves and immature are usually brown, while adult appear paler, also due to the presence of scarring caused by intra-specific competition, parasites and other injuries. Dark patches around the eyes are common in adult animals.

They are usually sighted alone or in small groups (composed by 2 to 12 individuals). Cuvier’s beaked whale is perhaps the most common beaked whale with more reported sightings and strandings than any other beaked whale. There are currently no worldwide abundance stimates for this species, but it is likely to be over 100,000 animals.

Cuvier’s beaked whales are excellent divers, with maximum dive depth and duration having been reliably recorded to depths of over 1, 800m and for up to 85 minutes. Spending up to 80% of their life underwater at depth, operating close to their physiological limits. Feeding mainly on deep water squid species, Cuvier’s beaked whales use echolocation to locate their prey, like other toothed whales or odontocetes. They produce on average ~ 2 usual clicks per second and when they close in on prey they produce ~ 250 echolocation clicks per second. This sequence is also called a “buzz”. The buzz coupled with the dive profile indicates that foraging occurs during the deep dives. It has been estimated that they attempt to catch on average 30 prey items per dive.

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