Dr. Lance Barrett-Lennard and Kathy Heise
Region: Pacific Ocean
Minstrels of the sea
Humpbacks are the noisiest and most-imaginative of whales when it comes to song. The whales sing complex, eerie and beautiful ballads that last for between 10 and 20 minutes and can be heard more than 20 miles away. Today, we know more than ever about the song of the humpback. We know, for instance, that while both male and female humpbacks can produce sounds, only males appear to sing songs with distinct themes and melodies. Males almost always sing on breeding grounds, often while suspended deep below the surface with their long front flippers jutting rigidly from their sides. Male humpbacks frequently repeat the same song dozens of times over a period of several hours, and whales in the same geographic area sing in very similar ‘dialects.’ Song patterns change gradually over time, with new songs emerging every few years.
These giants of the deep are slow swimmers—making them easy targets for whalers in the first half of the 20th century. They were killed by the thousands for their blubber. Now protected, humpback populations have grown to nearly 20,000 worldwide—about 20 percent of their original numbers. Roughly 2,000 live in the northern Pacific today. But the protections must be maintained to ensure the long-term survival of this majestic species.
Often the first sight of a humpback is its broad tail—called a fluke—arcing elegantly out of the water. Then the whale will break the surface and exhale a stream of misty spray that often rises to 10 feet above the two blow holes on the top of its head.
Humpbacks travel in groups—called pods—and form distinct populations. Humpback whales reach sexual maturity at nine years of age, and an adult female will bear a calf typically every two to three years. Female whales develop strong and lasting bonds with their calves. The calf nurses frequently on its mother’s milk until it’s about 11 months old, and remains with its mother for a year or longer.
Humpback whales can live to between 45 and 50 years of age.
With its black back and white belly, deeply grooved throat, and huge fluke, the humpback whale is easy to identify. Small bumps are found on the whale’s head and neck, and a small dorsal fin near the centre of its back. Adults are between 14 and 19 metres long and weigh between 34,000 and 45,000 kilograms. The fluke of a male humpback can measure up to 80 centimetres across. The underside of each whale’s fluke is colored black and white in a pattern that is as unique as a fingerprint.
Humpback whales feed on krill, small shrimp-like crustaceans and a variety of small fish. The whale has no teeth; instead it has a series of fringed plates—called baleen plates—hanging from each side of its upper jaw. During feeding, pleated grooves in the whale’s throat expand enabling it to gulp large mouthfuls of water and prey. When the whale closes its mouth, the water is forced out. The baleen plates act as filters, trapping food on the inside ready to be swallowed.
Humpbacks have developed an ingenious method of hunting known as bubble-net feeding. They circle beneath a large school of fish, blowing a wall of bubbles as they spiral slowly upward. The bubbles force the trapped prey to move to the surface in a concentrated mass, making it easy for the whales to consume large quantities of food in a single gulp.
Majestic and athletic, humpback whales can throw themselves completely out of the water, a feat that’s known as breaching. Sometimes whales twirl around while breaching and slap the water hard as they come back down. Other acrobatic feats include lifting their huge flukes out of the water and slapping them down on the surface—known as tail lobbing—and slapping the water with their flippers, which is called as flipper slapping.
Traveling from the frigid waters of Alaska to the tropical seas off Hawaii, humpback whales migrate through Canadian waters twice a year. The whales generally follow the coastline and take advantage of seasonal currents during their migrations. In the fall, the whales head south to winter and breed in tropical waters; in spring they return to their northern feeding grounds for the summer.
During the breeding season, humpback whales prefer water temperatures between 24° and 28°C. The whales favour areas that offer protection against prevailing winds and which have flat ocean beds at a depth of 15 to 60 metres.
Over-fishing of the whale’s prey—including tiny crustaceans and small fish—has led to a reduced food supply. Depletion in numbers of a small fish called capelin is of particular concern.
Humpback whales sometimes become entangled in the fishing nets of commercial trawlers and drown. Additionally, the whales face potential risks from exposure to significantly higher numbers of oil spills due to increased tanker traffic in coastal areas.
Humpback whales have been protected by the International Whaling Commission since 1955 in the North Atlantic and 1965 in the North Pacific. Canadian whaling regulations prohibit whaling in Canadian waters.
The North Pacific humpback whale is listed as threatened and protected under the Species at Risk Act (SARA). It is also protected under the Marine Mammals Regulations, which fall under the Fisheries Act. A recovery strategy is currently being developed for humpback whales.
In co-operation with the Vancouver Aquarium Marine Sciences Centre (VAMSC), Fisheries and Oceans Canada is working with universities and the eco-tourism industry on a range of projects related to the humpback whale. Programs include public education through displays at the Vancouver Aquarium Marine Science Centre, a web site and other media.
VAMSC is also using standard field methodologies to collect reliable data on the humpback’s population numbers, seasonal distribution, habitat and diet. This survey will result in a CD-ROM catalogue of photo images of individual humpback whales, which will be used by researchers across Canada.
Humpback whales will get the protection they need only if all Canadians work together to reduce threats. Find out more about humpback whales and be aware of man-made threats such as entanglement in fishing gear and oil pollution. Do your best to reduce these threats wherever possible to better protect the whales’ critical habitat. Get involved with the Habitat Stewardship Program for Species at Risk (HSP) or another conservation organization.
Join a stewardship program such as the B.C. Cetacean Sightings Network. The Network’s main goals are to identify key habitats and help reduce threats. The Network also solicits cetacean sighting reports from mariners along British Columbia’s coast. Find out more >>.
Background information provided by Environment Canada in March 2004.