Humpback Whale (Megaptera novaeangliae)

NATURAL HISTORY
Humpback whales are a cosmopolitan species, found in most of the world’s oceans. In the north Pacific, the population has made an impressive comeback in the past 40 years.Humpback whales were heavily targeted by commercial whaling in the north Pacific until 1966; by the end of this harvest, there may have been as few as 1400 humpbacks left. However, a recent study ‘SPLASH’ (Structure of Populations, Levels of Abundance and Status of Humpbacks) now estimates this population has rebounded to 18,000-20,000.

The north Pacific population of humpback whales makes long distance migrations. They range from winter breeding grounds in southern latitudes (Hawaii, Mexico, and Southern Asia) to northern feeding areas from California to Alaska and Russia where they spend the summer months. Humpbacks show great fidelity to their feeding areas and British Columbia is split into two separate regions. The southeast Alaska/northern British Columbia region is estimated to have a population of 3,000-5,000 whales, while the southern BC/Washington population is approximately 200-400 whales. There also appears to be a correlation between feeding and breeding grounds. The majority of humpback whales feeding in northern BC appear to be wintering in Hawaii. The southern BC whales have animals that have been re-sighted off mainland Mexico, as well as Hawaii.

The colder, coastal waters that humpbacks frequent in the summer months are rich in prey, including small schooling fish such as herring, capelin, sandlance and pilchard, as well as krill. Humpback whales are known as a ‘rorqual whale’, which means they have long pleats from their lower jaw to their abdomen that allows the throat to expand, allowing in huge amounts of food-filled water while feeding. Humpbacks then use baleen as a sieve to trap food while removing the salt water. Humpback whales employ several feeding techniques to obtain these mouthfuls; most spectacularly: bubble-netting, where one to several animals may create a circular wall of bubbles to concentrate food before lunging through it.

Breeding in humpbacks whales is very seasonal, occurring in the winter in tropical/sub-tropical areas. In these areas, males sing long, complex songs. The songs are specific to breeding areas and seem to evolve from year to year. These songs are likely used to attract females, though they may also be used in social ordering and competition among males. The gestation is approximately 11 months, calves being born between December and April in the north Pacific. A calf will spent about one year with its mother before becoming independent. Females typically have a calf every 2-3 years, though annual breeding is not unheard of. Besides the mother-calf pairs, humpback whales are not known to have long-term social bonds. In the North Atlantic, both sexes reach sexual maturity around 5 years, but it is unclear whether this is true for the north Pacific population. The lifespan of the humpback whale is still unknown, though it is believed to be at least 48 years.

Humpback whales are identified by the underside and trailing edge of their tail flukes; each one is different just like a fingerprint. In British Columbia humpbacks are given a letter as part of their identification to categorize their fluke based on color. X animals have mostly black tails with less than 20% white on their fluke, Y animals have a fluke that is 20-60% white, while Z animals have more than 60% of their fluke white. Humpback whales often show these tails, or ‘fluke’ while diving, making them ideal candidates for photo-identification projects. Of all the baleen whales, humpbacks are most likely to engage in surface activities such as breaching and slapping their tail flukes and pectoral fins. These behaviours most likely have many different meanings under different contexts.

The primary predator of the humpback whale is the transient (mammal-eating) killer whales that may prey on young animals. Many humpback flukes bear the scars of unsuccessful attacks. It has been proposed that humpback whales may migrate to the tropical areas to avoid killer whale attacks; breeding areas like Hawaii have very few mammal-eating killer whales. One of the hotspots for killer whale predation events on humpbacks appears to be off the coast of California, an area also known to be dangerous for other baleen whale calves.

In many parts of their range, humpbacks are greatly impacted by human activity.  Entanglement and ship strikes are of concern for this species. 

STATUS IN CANADA

The humpback whale is designated as Threatened by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC).

COSEWIC’s assessment of the North Pacific population of humpback whales is as follows:

Heavily reduced by whaling, the North Pacific population appears to be increasing. The number of animals that use British Columbia waters is probably in the low hundreds. The high-level of feeding ground fidelity suggests that if animals are exterminated from a particular area, it is unlikely that the area will be rapidly repopulated from other areas. Two extirpated British Columbia populations have shown no sign of rescue. Humpbacks are occasionally entangled in fishing gear, though the number entangled is not thought to threaten or limit the population. In summary, humpback whales that use British Columbia waters appear to be well below historical numbers and have not returned to some portions of their former range.