At just 8.7 hectares the small island of Middleholm (or Midland) sits between the Marloes peninsula and Skomer, separated by Jack and Little Sounds. A small, un-grazed, rocky islet, it is surprisingly difficult to land on! Myself and the National Trust Area ranger James Roden, tried last winter but in January the conditions made a jump and scramble ashore impossible.

However, the hot and settled conditions in July made landing an option and so we climbed ashore from a small tender and scaled the steep north east corner to reach the plateau. Every move is made with care; the luxuriant red fescue and Yorkshire fog hiding countless Puffin and Shearwater burrows.

The reason for our visit was to install rodent surveillance stations. With Middleholm a stepping stone to Skomer and with the island home to 16,000 pairs of Manx Shearwaters in its own right, it is essential that rats in particular don’t make it ashore. 9 plastic boxes were installed and fitted with wax chew blocks inside. These are made in muffin cases from melted wax and cocoa powder.

The idea being that if a rat were to come ashore, it would find a tasty treat and shelter. Rodents leave their distinctive incisor marks in the wax and we can then identify any species present from the size and shape of the teeth marks left behind on the wax.

We’ll attempt to make another visit in September to check the blocks and secure the stations for the winter. The long-term plan is to check the stations 4 times each year, replacing the wax blocks and checking for other signs of invasive species.

Standing on top of Middleholm is a huge privilege but is also a rather sobering experience. When you see just how close it sits to both Skomer and the mainland, the importance of our continued vigilance as custodians of these fantastic islands is crucial.

Hear more from Lisa Morgan on biosecurity below.