Heat-seeking technology gives better picture of seal pup numbers

Wildlife experts are using heat-seeking drones to count pup numbers at one of England’s largest grey seal colonies.

The Farne Islands, off the Northumberland coast, is an important haven for thousands of seabirds and hundreds of adult seals, and are looked after by the National Trust

The Atlantic grey seal is one of the rarest seal species, is protected and their numbers are carefully counted on the Farnes every autumn.

National Trust rangers have used drones in recent years to do the count on outlying islands, using aerial images which are then analysed later to survey the new population.

Now rangers are working with academics, sea mammal specialists and expert fliers to use drone with two cameras.

One films the seals from above in the normal way and a second uses thermal imaging, with the dual approach giving the analysts more accurate results.

Drones have been used more and more in wildlife counts as an eye in the sky is less intrusive and stressful for animals than having a human up close.

The last survey was completed in 2019 with a record number of 2,823 pups born, an increase of 62% since 2014, and numbers were thought to have continued upwards since then.

Ranger Thomas Hendry said: “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. 

“Once born, they’re sprayed with a harmless vegetable dye to indicate the week they are born.

“Using a rotation of three or four colours allows the rangers to keep track of the numbers.

“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.

“The drone gives us an excellent view of the islands and from the clear images we can count the total numbers of seal pups born on each island. 

“It also allows us to see onto the smaller islands more frequently which can be more challenging to visit at this time of year due to difficult sea conditions.”