The discovery is outlined in a paper to be published in The Anatomical Record. Bowhead whales are large baleen whales. Baleen is a hair like growth used to filter small organisms such as krill out of sea water. The scientists believe the organ serves a two-fold purpose: to regulate body temperature and as a sensory organ.
The newly discovered organ, dubbed the Corpus Cavernosum Maxillaris, is about twelve feet long. It is composed of the same sponge-like tissue that gives mammalian penises the ability to enlarge and harden when engorged with blood. The organ's blood vessels link in with blood vessels in the base of the bowhead's brain. The scientists believe that when the whale takes in water to feed, it sends blood to the organ in order to cool it off. While it may seem strange that an Arctic species needs to worry about overheating, whales have thick layers of blubber insulation to keep in body heat. That is a double edged sword, as it puts the whales at risk of overheating when they exert themselves.
The organ is also rich with nerves, which lead the scientists to believe it may be used to sense how much krill is in water it will filter through baleen. Such a function would be useful since it would be a waste of energy to attempt to feed in waters with low food content.