Humpback Whale Calves

Humpback whales become reproductively mature when they are between five and eight years of age. They mate during their winter migration to Hawaii, and eleven to twelve months later, upon their return to winter breeding grounds, the mother gives birth to a single calf. A fifty foot mother will give birth to a calf approximately fifteen feet long and weighing around two tons. The newborn instinctively swims to the surface within 10 seconds for its first breath. The mother begins feeding her newborn about 100 pounds of milk each day for a period of around six months, then the calf is sustained through a mixture of nursing and independent feeding for six months more. The mother’s milk is pink in color and exceptionally high in fat content (50%) which allows the calves to gain weight quickly. It is imperative for them to develop a thick layer of blubber prior to their 3,000-mile migration back to the cold Alaskan waters. After weaning, the calf has doubled its length and has increased its weight five times, attaining a size of about thirty feet and ten tons.

In Hawaii, humpback whales typically belong to groups consisting of two to three individuals for relatively short periods of time. The longest association between individual whales is when the mother cow, remains with her calf for a year during nursing. The mother generally never lets her calf stray more than a body length away for very long. They spend the first year or so of the calf’s life together, and the calf learns valuable survival lessons in this short amount of time, and is then weaned and separated. In many instances, cow and calf are accompanied by another adult known as an escort. Escorts can be of either sex, but are most often reported to be males, and remain with them for only a short time. Usually, a female humpback will bear one calf every two or three years, with an average life span between 40 and 50 years.