https://phys.org/news/2018-06-secret-life-enigmatic-antarctic-apex.html

Seal ecologist Dr. Iain Staniland, lead author of the study says:

"Leopard seals are notoriously difficult to study because they live and hunt in inaccessible places: they are relatively scarce, lead solitary lives and live mostly in the water or 'hauled out' on sea ice around Antarctica.