An estuary spa day
Each summer, the cold waters of western Hudson Bay host one of the world's great wildlife gatherings. Approximately 55,000 beluga whales, Delphinapterus leucas, migrate to the region as the sea ice melts. Of these, about 3,000 to 5,000 enter the Churchill River estuary daily during their peak. This specific location has a combination of features that attracts the whales. The river water is warmer and less saline than the bay, creating a comfortable nursery for newborn calves.
The estuary also is a kind of spa. Belugas undergo an annual molt, shedding their outer layer of skin. During the winter, their epidermis thickens and can take on a yellowish hue. To speed up the removal of this old skin, the whales rub their bodies against the coarse gravel and rocks of the shallow riverbed. This exfoliation is an important part of their yearly cycle. The warmer estuary water may also help, possibly increasing metabolic activity that helps in the growth and turnover of skin cells. Beyond skin care, the estuaries are important areas for feeding and giving birth away from their main predators like orcas.