A dead dolphin was found along the banks of a river in Co Carlow on Wednesday.
It was discovered by a resident, washed up along the river Barrow in the St Mullins area.
The common dolphin carcass appeared scratched and was partially submerged in water.
Pádraig Whooley, a sightings officer with the Irish Whale and Dolphin Group (IWDG) said the dolphin was more than likely following a food source up the river, probably species such as herring and sprat “that come into our bays and estuaries to spawn”.
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“Over the period of a couple of days, there’s absolutely no harm to seeing dolphins in river systems. But certainly after a couple of days, you’d see them turning around and heading back out towards open water.”
He explained how difficult it can be for dolphins to find their way out of rivers after extended periods as they become “completely confused” and their “echolocation, which is their primary GPS system, is completely malfunctioning.”
Echolocation, he said, works in an open water environment.
“It’s not designed for a narrow river bank that’s probably only metres across in places and the acoustics are not going to work anything like the way they would in open ocean.”
He believed the dolphin discovered in Carlow died from live stranding.
“The further away you go from the source of the sea, the smaller these rivers get and the narrower they get and the more obstacles there are, obstacles they are unfamiliar with.”
He described live stranding as an “exponential risk” for dolphins when they move out of open waters and noted that in the last week there had been four sightings in the rivers Bandon, Lee, Suir and Barrow.
“It’s something we notice every winter,” he said. “It is a particular phenomenon because it coincides every year with the spawning of fish.”
Carlow County Council said its environment team engaged with the IWDG on the “best course of action given the unique scenario presented”.
On Thursday, it and Waterways Ireland removed the carcass from the water for disposal.
