International concern is mounting for a pod of killer whales trapped by miles of drift ice near the northern Japanese island of Hokkaido.The mammals spend the majority of their time on the surface of the ocean — usually spending ten minutes or less submerged underwater. Japanese media broadcaster NHK published a video Tuesday of about 12 orca whales bobbing up and down in a tight group surrounded by ice on all sides. The pod clustered about one kilometre from the Rausu coast of the Shiretoko peninsula, which is a UNESCO world heritage site, preserved for its abundance of wildlife. The coast guard is aware of the situation, a Rausu official told NHK, but the ice is so thick, there is no way to clear it to free the orcas. “We have no choice but to wait for the ice to break up and for them to escape that way,” the town official said. Marine expert Seiichiro Tsuchiya captured the drone footage of the whales while collecting data on sea lions. “I saw about 13 killer whales with their heads sticking out of a hole in the ice,” he said. “They seemed to be struggling to breathe, and it looked like they included three or four calves.”In 2005 several orcas died due to the build up of so much ice in the region.