The humpback whale (Megaptera novaeangliae) is a massive marine mammal belonging to the suborder Mysticeti, or baleen whales. These giants are filter-feeding predators and are biologically classified as carnivores. Their entire food intake consists of animal matter, primarily tiny ocean crustaceans and small schooling fish. This specialized diet requires a unique anatomical structure and feeding technique.
Defining the Humpback’s Trophic Role
A carnivore is defined as an organism that derives its energy and nutrient requirements exclusively from animal tissue. The humpback whale fits this description, consuming no plant material and relying entirely on zooplankton and fish for survival. While technically carnivorous, their feeding habits are distinct from the active hunting seen in toothed whales like orcas.
Their position in the food web is quantified by a trophic level, which for North Pacific humpbacks averages around 3.6. This confirms a mixed diet, placing them between strict plankton-eaters (zooplanktivores) and dedicated fish-eaters (piscivores). Their filter-feeding method allows them to efficiently harvest dense aggregations of smaller animals.
Humpbacks are considered rorquals, characterized by throat pleats that expand dramatically to engulf large volumes of water and prey. This gulp-feeding strategy contrasts with the skim-feeding used by right whales, which swim continuously through the water with their mouths open.
Specifics of the Humpback Diet
The humpback whale’s diet is highly seasonal, depending on the location of its feeding grounds in colder, high-latitude waters. Primary prey items are dense swarms of crustaceans, particularly Antarctic krill (Euphausia superba) in the Southern Hemisphere. In the Northern Hemisphere, their diet is more varied, often including various species of copepods.
Small, schooling fish are also a major component of the humpback diet, especially in northern feeding grounds. They target species such as:
- Herring
- Capelin
- Atlantic mackerel
- Sand eels (sand lance)
These fish form tight, concentrated schools, which the whales exploit for maximum caloric intake.
To sustain their body mass and long-distance migrations, an adult humpback must consume vast amounts of food, sometimes up to a tonne of prey each day during the summer feeding season. This heavy feeding period is essential because the whales fast for four to six months during their migration and while on their warmer, low-latitude breeding grounds. During this time, they rely entirely on the thick layer of blubber they accumulate in the summer to fuel their energy needs.
The Baleen Filtration System
Humpback whales are able to consume their tiny, numerous prey using a unique anatomical structure called the baleen filtration system. Instead of teeth, the whale possesses hundreds of overlapping plates made of keratin, the same protein found in human fingernails. These plates hang down from the upper jaw, forming a dense, fringed curtain.
The plates function as a sieve, allowing the whale to take in a massive gulp of water mixed with prey. When the mouth closes, the ventral throat grooves contract to push the water out. The fine, hair-like inner fringe of the baleen traps the small fish and crustaceans inside. The whale’s esophagus is surprisingly small, roughly the size of a grapefruit, meaning the prey must be filtered and swallowed as a concentrated mass.
Humpbacks employ two primary techniques for capturing prey. Lunge feeding involves a rapid, open-mouthed acceleration through a dense school of fish or krill to engulf the maximum amount of food in one gulp. Another element is bubble-net feeding, a cooperative strategy where a group of whales circles beneath a school of prey while releasing air bubbles in a ring. This wall of bubbles corrals the prey into a tight column near the surface, allowing the whales to swim up through the center and engulf the concentrated food mass.