Satellite Images Help Seal Count

A new and novel way has been used to count seals in Antarctica. Researchers have come up with what they believe is the most accurate way to count Antarctica’s Weddell seal population. Using images taken by satellites from space, and with the help of 300,000 volunteers, the Weddell seals have been counted.

Indicator for health of Antartica

Critically, Weddell seals are considered an indicator species. That means they are monitored closely because their numbers help to show the environmental conditions in the area. Weddell seals make the Southern Ocean their habitat, and their presence or absence helps scientists understand how sea ice and feeding habits are changing.

Weddell seals can live up to 30 years in the sea ice around Antarctica. They live further south than any other seal. Due to the harsh environment and the remoteness, up until now counting them has been problematic.

Satellite images used

Previously both ships and planes were used to gauge the seal numbers. However, ships and planes have limited range and can’t cover the whole of Antarctica at the same time. That led the research team to start using satellite images.

The satellite images were broken up in to smaller sections. Each section was given to a volunteer and they were asked to say if they could see any seals within the image. Each image was checked by multiple volunteers to increase the chances of accuracy.

New levels of accuracy

The images used were taken in 2011. At that point in time the Weddell seal population was 40% lower than earlier studies had estimated. That doesn’t mean that there had been a drop in numbers, just that previously estimates had been inaccurate.

The research team discovered that Weddell seals live on about 1% of the ice in Antarctica, that they avoid Adelie penguins, but are happy to tolerate Emperor penguins in small numbers.

This same method of working out population numbers is now being used for counting walruses in the Arctic.