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.
Canaries of the sea
Beluga whales are famously vocal, earning the nickname "canaries of the sea" from early sailors. They produce many chirps, clicks, whistles, and squeals to communicate, navigate, and hunt. The bulbous organ on their forehead, called a melon, is filled with oil and wax. It is flexible and helps to focus and project the sounds they use for echolocation.
Researchers studying the Churchill belugas use hydrophones to listen in on this complex social environment. Studies have shown that belugas use specific "contact calls" to maintain group cohesion, particularly between mothers and calves. These calls, which can sound like a creaking door, appear to be individually distinct. Like bottlenose dolphins, which have unique signature whistles that function like names, belugas may use these distinct calls as vocal signatures to identify one another in the bustling estuary. This allows scientists to track individuals and better understand the population's social structure without ever touching the animals.