On the west coast of Sweden, we are taking advantage of new technologies, like drones and artificial intelligence, to observe seals in their natural environment without the risk of disruption. In the first year of a new individual identification programme, we have already made an unlikely discovery.

We have identified a young grey seal hidden among a harbour seal colony in the Skaggerak area of Western Sweden. Grey seals are extremely rare in this area and, when observed, are usually large males thought to be exploring far from their breeding sites. This sighting could be the first indication that the area is being recolonised by breeding grey seals after more than 100 years of absence. Although not enough on its own to draw firm conclusions, this sighting highlights the complexity of the marine ecosystem, where close observation is needed to unravel population trends and interactions between species.

Seals are members of the Pinneped clade, which translates as ‘fin footed.’ Although all seals share adaptations to their aquatic home, like streamlined bodies, individual species have vastly different lifestyles. Three seal species make a permeant home in Sweden, each with a unique method of survival and role to play in the ecosystem. In the Northern Baltic, the smallest of the three residents; the ringed seal, is perfectly adapted to living on ice. This species is considered vulnerable to extinction as climate change puts sea ice at risk.

The west coast of Sweden is dominated by the harbour seal. Slightly larger than the ringed seal, this opportunistic predator returns year on year to the same skerries to give birth during the summer months. The harbour seal population has shown an incredible ability to bounce back from natural and human made disasters. Over the previous century they have been hunted to the point of population collapse and experienced two outbreaks of the deadly Phocine distemper virus, also known as ‘seal plague.’ For two decades however, the population has been steadily recovering. Now, a new threat is on the horizon for this charismatic species as our surveys have shown lower than expected birth rates two years in a row, possibly as the result of limited access to food in the heavily fished North Sea.

The third and largest resident seal species in Sweden is the grey seal. A unique and isolated population of this species lives in the Baltic Sea. Unlike the ringed seal, who are completely reliant on ice to breed, and harbour seals, who are intolerant to the cold, grey seals in the Baltic can give birth on either land or ice. Grey seal pups have a better chance at surviving on ice where they can spread out, reducing the spread of parasites and infections.