Beneath the surface

The Saimaa ringed seal, endemic to the largest lake in Finland, gives birth during winter in den that's built inside an ice-borne snowdrift. In a previous article, I took you to the ice for a den survey, but now we're going to see the placenta dives.

 Note that this article contains images of a dead animal.

​Yes, I learnt how to say placenta in Finnish. Istukka. Important vocabulary, right?

It's early May, we're a little later in the season, all snow and ice have melted. As a result, the seal placentas that detached during birth have fallen to the bottom of the lake. That's why there are two divers on the boat I embark on in Savonlinna, Minna and Mikko. We also have a driver, Leo. They all work at Metsähallitus, the wildlife and parks government agency that coordinates the Saimaa ringed seal conservation program.

​A long day on the water awaits us, zooming between islands from den site to den site. Every time, we beach the boat, tying it to a rock or a tree, and the divers get into the water. Minna uses a dry suit. Mikko, on the other hand, has a wet suit: it's a bit more challenging, weather-wise (it was cold enough for a snow shower in the morning), but it allows him to dive deeper to recover placentas that would be out of Minna's reach.

​So they get into the water and look around, until they find a placenta or decide it won't be found. When they have it, they transfer it to Leo, who briefly stores it into a colander and then into a sealed plastic bag will all the location details.

​Collecting seal placentas has two main uses: DNA analysis (used to study genetic diversity, family links...) and toxicity analysis (heavy metal poisoning from the industry has been a problem, though I understand it's withdrawing).

In one spot, the divers made a gruesome discovery: the body of a baby seal. They found a second placenta there, which means there were twins. Saimaa ringed seal mostly give birth to a single pup, so that was a significant discovery. Sadly, one didn't make it, but hopeful the other is freely swimming in the lake today.

It was a great day out. I particularly enjoyed landing on little-visited skerries in the middle of the water. The thick carpets of lichen there showed they don't often have visitors!

Note: maps and other location data were obscured to prevent revealing protected information.