A seal wearing a helmet with an antenna might look unusual, but eight Weddell seals, each with a 580g monitoring device on their heads, have been helping Japanese researchers survey the waters under the thick ice sheet in Antarctica.

Tapped for a research project between March and November 2017 — winter in Antarctica — the seals were equipped with the head-mounted conductivity, temperature and depth sensor, which allows scientists to collect observation data, such as water temperatures and salt levels, in areas with extremely harsh environmental conditions.

Project leader Nobuo Kokubun said such research helps scientists trace the animals’ behavioural patterns and ecology...