Thermal imagery used for first time to help count seal pups on Farne Islands
Thermal imagery from a drone is being used for the first time by rangers on the Farne Islands to help verify seal pup numbers.
Cared for by the National Trust, the Farnes are home to one of the largest grey seal pup colonies in England.
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 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.
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.
The very first pup was seen on the Wamses, one of the rockier outcrops at the start of October, and this week the first seal pups have been born on the largest island, Inner Farne.
Ranger Thomas Hendry said: “The sighting of the first pup of the year triggers the start of the seal pup count, and we’re excited this year to see if the upward trend continues.
“The increase in numbers in recent years is thought to be down to the lack of predators or disturbance and the fact that the grey seals are generalist rather than specialist feeders.
“This year we are still counting the seals every four days in some locations, weather permitting.
“We are using a drone again this year which as well as filming the pups is fitted with thermal imaging technology to help make the count more accurate and less stressful for the seals.
“Having the extra thermal imaging technology is particularly useful now that the islands are supporting more and more pups and the population is denser. It will hopefully also allow us to detect any seal pups that sadly don’t survive, so that they aren’t accidentally included in our numbers.”
The rangers have also observed that the seals now no longer pup on some of the very small islands. This may be because they are no longer suitable, being more susceptible to storms and sea level rise.
The seals are born with bright white fluffy coats. Although the pups can swim at an early age they don’t normally leave the breeding colony until they have been weaned and after they have moulted their soft white coats. This happens when they are about two or three weeks old and their dense grey waterproof fur grows through. The pups stay with their mother on the islands for around three weeks before they leave to feed, typically returning to breed once they have matured.