Fishing gear and an engine cover are just some of the startling contents found inside the stomachs of sperm whales that recently beached themselves on Germany’s North Sea coast.

The 13 sperm whales washed up near the German state of Schleswig-Holstein earlier this year, the latest in a series of whale strandings around the North Sea. So far, more than 30 sperm whales have been found beached since the start of the year in the U.K., the Netherlands, France, Denmark, and Germany.

After a necropsy of the whales in Germany, researchers found that four of the giant marine animals had large amounts of plastic waste in their stomachs. The garbage included a nearly 43-foot-long (13-meter-long) shrimp fishing net, a plastic car