Distressing images of young, red deer stags in Killarney National Park, some with deformed antlers and clearly unbalanced, have begun circulating on social media.

The Irish Deer Commission suspects the animals are suffering from a condition called “staggers”, which affects deer and other animals that have come into contact with toxins from fungus on ryegrass.

The disease is incurable and the deer should be taken out on animal welfare grounds, its spokesman Damien Hannigan said.

However, the Department of Arts, Heritage and the Gaeltacht, which is in charge of the National Park and Wildlife Service (NPWS), said it will not comment on the condition of some of the deer in Killarney until it has the full results of tests.

The Irish Deer Commission is calling on the National Wildlife Service to carry out culls of the affected animals and to identify exactly the cause of the condition. It is also calling for the location of the ryegrass to be identified so the grass can be destroyed.

'Staggers' is caused by a fungus spread from one generation of ryegrass plant to the next when consumed by deer or livestock and the symptoms include head tremors, or trembling of the muscles of the neck, shoulder or back, he said.

Severally affected animals can fall over and thrash or have convulsions. The condition can result in deformed antler growth and even death.

Hundreds of people have begun arriving in Killarney for the annual deer rut season. A number of deer have been observed falling over and having difficulty walking.

The Department of Arts, Heritage and the Gaeltacht said in a statement: “The National Park and Wildlife Service, in observing behaviours recently in a very limited number of deer at Killarney National Park, is following the appropriate veterinary protocols and until tests are completed will neither comment nor speculate further on any matters related to the wild deer population there.”