The majority of baleen whales feed by either opening their mouths after targeting a specific prey and taking in a large amount of fish plus sea water, then forcing the excess water out through their baleen, or by actively swimming with their mouths open while straining the water. The latter is the method of feeding used by the North Atlantic Right Whale.
While entanglement is not limited to this species, they do tend to pick up a great deal of vertical line from the water column. With eyes placed on the sides of their heads, these whales have limited vision directly in front of them, similar to horses. Lastly, North Atlantic Right Whales have an unusual downward angled curve to the back of their lips, creating the perfect anchor space for any rope they may accidentally sweep up in their search for food.
Other causes of entanglement:
Seine nets, monofilament nets and lines, and mooring lines are just a few of the underwater threats faced by dolphins, porpoises, sea turtles, sharks, and pinnipeds (seals, sea lions) as well as a whole host of whales, both large and small.
-Kim Sawicki December 2018