Four separate authorities are investigating the discovery of the decomposing carcasses about 10 horses, four cattle and three calves at the bottom of the spectacular Baltard Cliffs in Doonbeg, Co Clare.
Clare ISPCA officer Frankie Coote described the dumping as "planned and sinister".
Another horse lay within 200 yards of the edge atop the cliffs and had to be put down by a veterinary surgeon who visited the scene this week.
Up to 15 of the animals were located close together at the bottom of the isolated cliffs, while another dead horse lay close by.
"We can confirm that we're carrying out an investigation in conjunction with the ISPCA, the Department of Agriculture and Clare County Council. We can't say any more at the moment for operational reasons," a Kilrush Garda spokesperson confirmed.
Clare ISPCA officer Frankie Coote visited the cliffs this week, where he examined the dead animals.
“I found nine horses, four cattle and three calves together at the bottom of the cliffs. Their ears had been cut off to remove the tags. This was planned. Whoever did it, it took quite a lot of work. Plus removing all identification from the animals made it sinister,” Mr Coote said.
He believes the dead animals were thrown 300ft from the clifftop.
“In my opinion they’ve been there definitely more than two months. They wouldn’t decompose that quickly near the sea and with cold weather - although in summer they would. From down below it looks like they were thrown off from the top. Whether they were dead or alive, you can’t tell. They weren’t shot but their necks and legs are broken,” he said.
Examining the dead animals was one of the most difficult tasks he has had to carry out in his professional career, he added.
“It’s even hard when you’re standing with them identifying them because they’re all entwined in each other, rotting into each other. To look from the top of the cliff it looks like 14 or 15 foals but when I was down there I got a big shock, to be honest with you,” he said, adding that he had contacted the Department of Agriculture with news of the grim discovery.
A walker from the west Clare area who wishes to remain anonymous discovered the bloated carcasses on Monday while walking on the rocky shore. The walker reported the discovery to Kilrush gardaí, who attended soon after.
“I counted about 16 animals on Monday,” the walker said. “There are tyre marks all the way up to the edge of the cliffs,” the individual noted, adding they had also discovered the injured horse atop the cliffs.
“We were walking on Monday and what we thought was a dead horse was lying in the field. The horse actually started moving. The poor thing was dying so we called the gardaí. They came out and called the vet to put the horse down,” the walker said.
Kilkee-based veterinary surgeon Fergal Hennessy attended the scene.
“I haven’t come across anything like that before,” he said, adding he has been working as a vet since 1992.
Mr Hennessy said that, in general terms, animal welfare is an issue in Ireland. "The animal welfare organisations are inundated with horses being abandoned."