Slender Scotch Burnet moth is back on island cliffs of Mull

A RARE moth which is found in only five sites in the world has reappeared at a Hebridean habitat for the first time in years.

The Slender Scotch Burnet is only found on Mull and the neighbouring isle of Ulva, and its numbers are under threat by the invasive plant cotoneaster, which is taking over one of its favourite habitats.

The moth had not been seen at Kilninian, on Mull’s west coast, since 2008, but after annual efforts to cut down the plant, it was seen there again this summer.

Over the past six years, Butterfly Conservation Scotland has been doing battle with cotone­aster at the Slender Scotch Burnet site at Kilninian. This work has been undertaken by contractors as well as volunteers, cutting back the cotoneaster and applying herbicide to the cut stumps to prevent them from regrowing.

The plant, which grows almost like a blanket over the cliff face, is threatening the moth’s perfect habitat. The Slender Scotch Burnet was refound at the site this summer after an absence of four years. Good numbers of Transparent Burnets were also seen.

A group of volunteers are now planning to go beyond the call of duty this weekend to do battle with the cotoneaster again.

The team will put on their walking boots and their waterproofs and make their way to the steep slopes below the cliffs of Kilninian to cut the plant down.

Tom Prescott, of Butterfly Conservation Scotland, said they were anxious to keep the plant at bay, as earlier clearance work had paid off with the moth’s return to Kilninian this summer.

He said: “Once cotoneaster gets a grip, nothing else really grows through it and the moth likes the wild flowers that grow, rather like a hay meadow, on the slopes at Kilninian.

“What is happening is that this cotoneaster, probably over 100 years, has taken over large areas of the cliffs and it’s growing rather like a blanket.”

Professional contractors have been tasked with clearance on the high cliff area, and Mr Prescott said: “Obviously we won’t be putting people over the cliffs this weekend, but in the past people have found it quite
difficult to walk out to the site, just getting to the site on that part of Mull is a big adventure.

“It’s a 15-20-minute walk to the steep slopes where they will be working.”

He added: “We were a bit
concerned that, as they [the moths] hadn’t been seen there for a while, we were too late, but I was there in June and we saw six of the adult moths – and that is the first time they have been seen there for about four years.”

The area is a draw for the moth because it is a suntrap, and Mr Prescott said: “What it is after is a really warm micro-climate, and these cliffs are amazing. As soon as the sun comes out, it’s like you have a solar panel there.

“The cliffs point south, and once the sun has been out for a while it’s like having big storage heaters. You can feel the heat radiating over the site; the big rocks act like a radiator.”

He added: “In the Ice Age there would have been a small area off the west of Scotland that would have been ice-free. The moths, in the 10,000 years since, have moved to these locations.”