Thermal imagery used for first time to help count seal pups on the National Trust’s Farne Islands

Thermal imagery used for first time to help count seal pups on the National Trust’s Farne Islands - National Trust

Example shot of the thermal imaging technology the team will start using on the Farne Islands in the coming weeks. Credit TerraDrone, Oxford University and Sea Mammal Research Unit — Example shot of the thermal imaging technology the team will start using on the Farne Islands in the coming weeks. Credit: TerraDrone, Oxford University and Sea Mammal Research Unit

Thermal imagery from a drone will be used for the first time by rangers on the Farne Islands off the coast of Northumberland to help verify seal pup numbers at one of the largest grey seal pup colonies in England.

Cared for by the National Trust, the Farnes are one of the UK’s most important wildlife habitats, home to thousands of seabirds and destination for hundreds of adult grey seals in late autumn and early winter.

Globally, the Atlantic grey seal is one of the rarest seal species and is a protected sea mammal. Global numbers are estimated to be around 300,000 with half living in British and Irish waters.

The rangers who work on the islands have traditionally counted the seals every four days using dye, and in 2018 used a drone for the first time to help verify numbers. This year, the rangers are working with researchers at Newcastle University, Oxford University, the Sea Mammal Research Unit (SMRU) and TerraDrone to continue trials counting the seals with a drone that uses two separate cameras, one to film the seals from above as visible with the naked eye, and the second using a thermal imaging camera.

Using drones to monitor and count wildlife is a relatively new practice. It allows conservationists to look at large areas easily and quickly, count whole populations rather than just a sample, and is far less intrusive and stressful for the animals than the close interaction of human led surveys. It also allows the team to count pups on outlying islands in difficult conditions.

Using drone photography also allows the rangers to quickly and accurately count the seal pups on the images using computer based machine learning – making the surveys quicker, more cost effective and more accurate than was previously possible.

Thousands of adult seals return to the Farne Islands each year to pup – typically giving birth to one pup. The survival rate varies from year to year but in spite of this, the last recorded seal pup numbers in 2019 reached a record high of 2,823 - an increase of 62 per cent over the last five years. The team were unable to carry out the count last year due to the covid pandemic but believe that the numbers would have continued their upward trend.