Humpback Whales of Iceland: Behaviour and Biology

The waters surrounding Iceland harbour one of the North Atlantic's most magnificent marine spectacles: vast populations of humpback whales that arrive each summer to feed in the nutrient-rich seas. These 40-tonne giants have transformed Iceland into one of Europe's premier whale-watching destinations, with the dramatic feeding behaviours and acrobatic displays of *Megaptera novaeangliae* drawing over 300,000 visitors annually to witness nature's most compelling maritime theatre.

The Iceland Migration Pattern

Humpback whales follow one of the longest migration routes in the animal kingdom, travelling up to 25,000 kilometres annually between their tropical breeding grounds and Arctic feeding areas. Iceland's waters serve as a crucial summer feeding station, with whales arriving from late April through October, peaking during June through September when sea temperatures reach 8-12°C and plankton blooms are at their most abundant.

The whales approach Iceland's coast following the warm currents of the Irminger Current, which carries nutrient-rich waters from the Denmark Strait. This oceanographic phenomenon creates ideal conditions for krill populations—particularly *Meganyctiphanes norvegica* and *Thysanoessa* species—that form the foundation of the humpback's diet during their Icelandic sojourn.

Recent satellite tagging studies conducted by the Marine and Freshwater Research Institute of Iceland have revealed that humpbacks feeding in Icelandic waters originate from breeding grounds in the Cape Verde Islands and the Caribbean, with some individuals showing remarkable site fidelity, returning to the same feeding areas around Iceland year after year.

Physical Characteristics and Identification

Humpback whales are among the most distinctive of the baleen whales, easily identified by their elongated pectoral fins—the longest appendages in the animal kingdom at up to 5 metres in length. Adults measure 12-16 metres and weigh between 25-40 tonnes, with females typically larger than males. Their distinctive dorsal fin sits atop a pronounced hump, from which the species derives its common name.

Each humpback possesses unique markings on the underside of its tail fluke, creating individual identification patterns as distinctive as human fingerprints. The North Atlantic Humpback Whale Catalogue, maintained by the College of the Atlantic in Maine, contains over 8,000 individual identification photographs, including more than 1,200 whales documented in Icelandic waters.

The species' most remarkable feature may be their tubercles—the distinctive bumps covering their heads and jaws, each containing a single sensory hair follicle. These tubercles enhance hydrodynamic efficiency and may aid in detecting water movement and prey location during feeding manoeuvres.

Feeding Behaviour in Icelandic Waters

Iceland's coastal waters provide humpback whales with an abundance of small schooling fish, particularly herring, capelin, and sand eels, supplemented by vast swarms of euphausiid krill. The whales employ sophisticated cooperative feeding strategies rarely observed elsewhere in their range, most notably the spectacular behaviour known as bubble-net feeding.

This cooperative hunting technique involves groups of 3-12 whales diving beneath a school of fish and swimming in an expanding spiral whilst exhaling to create a cylindrical "net" of bubbles. One whale typically serves as the "caller," producing specific feeding calls that coordinate the group's movements. As the bubble net contracts, the trapped fish are concentrated into a dense ball, allowing the whales to surge upward through the centre with mouths agape, often breaching the surface in a dramatic feeding lunge.

In Skjálfandi Bay, near Húsavík, researchers have documented some of the most sophisticated bubble-net feeding behaviours ever recorded, with groups of up to 15 whales participating in coordinated feeding events. These feeding aggregations often persist for weeks, creating exceptional opportunities for observation and research.

Acoustic Communication

Humpback whales are renowned for their complex vocalisations, and the populations feeding around Iceland contribute to the North Atlantic song repertoire. Unlike the tropical breeding grounds where males produce the elaborate "songs" for mating purposes, vocalisations in Icelandic feeding areas consist primarily of feeding calls and social communication sounds.

These feeding calls range from simple grunts and barks to complex sequences of whoops and thwops that coordinate group feeding behaviour. Hydrophone recordings from Faxaflói Bay have identified over 30 distinct call types, with some vocalisations carrying across distances exceeding 10 kilometres through Iceland's acoustically complex coastal waters.

Breeding and Life Cycle

Whilst humpback whales do not breed in Icelandic waters, understanding their reproductive cycle is crucial for comprehending their behaviour during the feeding season. After departing Iceland in late autumn, the whales undertake their southward migration to tropical breeding grounds where mating and calving occur during the winter months.

Females reach sexual maturity at approximately 5-10 years of age and give birth every 2-3 years following an 11-12 month gestation period. Calves measure 4-5 metres at birth and gain approximately 45 kilograms daily whilst nursing on milk containing 30-35% fat content. This rapid weight gain is essential for survival during their first migration to Arctic feeding grounds.

Remarkably, pregnant females and nursing mothers often forego feeding entirely during their 6-8 month reproductive cycle, relying entirely on blubber stores accumulated during their previous summer in waters such as those around Iceland.

Conservation Status and Threats

The humpback whale population in the North Atlantic has shown remarkable recovery since commercial whaling ceased. Current estimates suggest 10,000-15,000 individuals frequent North Atlantic waters, with approximately 2,000-3,000 utilising Icelandic feeding areas during peak summer months.

However, modern threats persist. Ship strikes pose significant risks in Iceland's busy shipping lanes, particularly the route between Reykjavík and continental Europe. Entanglement in fishing gear, whilst less common than in other regions, occasionally affects whales feeding near Iceland's extensive fishing grounds.

Climate change presents longer-term challenges, as shifting ocean temperatures and changing plankton distributions may affect the distribution and abundance of prey species in Icelandic waters. Recent warm water events have already altered the timing of capelin migrations, potentially affecting humpback feeding success.

Best Viewing Opportunities

Iceland offers exceptional humpback whale watching opportunities from multiple locations. Húsavík, on the Skjálfandi Bay, provides the highest success rates, with humpback sightings on over 95% of tours between June and August. Tour prices range from 5,500-8,900 ISK (€38-62, $42-69) for 3-hour excursions.

Reykjavík's whale watching tours departing from the Old Harbour report humpback encounters on approximately 70-80% of summer trips, with tours priced at 6,900-9,900 ISK (€48-69, $53-77). The 2.5-3 hour excursions traverse Faxaflói Bay, where feeding aggregations are common between July and September.

From Akureyri, operators access the northern feeding grounds where bubble-net feeding behaviour is frequently observed. These tours, costing 7,500-10,500 ISK (€52-73, $58-81), offer perhaps the best opportunities to witness complex feeding behaviours.

The optimal viewing period extends from mid-June through early September, when sea conditions are most favourable and whale populations reach their peak. Early morning tours often provide calmer seas and enhanced photographic opportunities.

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