Balaenoptera acutorostrata – Common Minke Whale

Common Name: Common Minke Whale
Scientific Name: Balaenoptera acutorostrata
Classification: Kingdom Animalia → Phylum Chordata → Class Mammalia → Order Cetacea → Family Balaenopteridae → Genus Balaenoptera → Species Balaenoptera acutorostrata
IUCN Conservation Status: Least Concern (LC)

Subspecies of Common Minke Whale:

Balaenoptera acutorostrata, commonly known as the Common Minke Whale, is the smallest member of the rorqual family (Balaenopteridae). Two primary subspecies are recognized globally:

1. B. a. acutorostrata – Northern Hemisphere (Common Minke Whale)
2. B. a. scammoni – North Pacific population
   A third form, B. bonaerensis (Antarctic Minke Whale), was formerly considered a subspecies but is now recognized as a separate species. The individuals occasionally sighted around Sri Lanka are thought to belong to the B. a. acutorostrata complex of the Indo-Pacific population.

Geographic Range (where the species is found):

The Common Minke Whale is a cosmopolitan marine species found in all major oceans, from the Arctic to the Antarctic. In the Indian Ocean, including Sri Lankan waters, it occurs offshore along the southern and eastern coasts — particularly near Trincomalee, Mirissa, and the continental slope regions, where nutrient-rich waters attract prey species.

Description:

A small and streamlined baleen whale, reaching 7–10 meters in length and up to 10 tonnes in weight. It has a dark gray to bluish-black back, pale gray flanks, and a white underside. The pointed snout, tall curved dorsal fin, and white band on each pectoral fin are key identifiers. The body is sleek, adapted for fast swimming and deep diving.

Habitat:

Marine, mainly pelagic (open ocean) waters. Occasionally observed near continental shelves and coastal zones where prey is abundant. Around Sri Lanka, sightings occur in deep offshore waters influenced by monsoonal upwellings.

Diet :

Carnivore (filter feeder).
Feeds primarily on small schooling fish (e.g., anchovies, sardines) and krill. Uses baleen plates to filter large volumes of water, trapping prey while expelling seawater.

Ecological Role of the Common Minke Whale:

Acts as a mid-level predator in marine ecosystems. Helps regulate populations of small fish and krill, indirectly supporting balance in oceanic food webs. Its fecal matter contributes to the biological pump, recycling nutrients like iron and nitrogen that sustain plankton growth.

Life Cycle (brief overview of developmental stages):

Calves are born after a 10–11 month gestation, measuring around 2.5–3 meters at birth. They nurse for 5–6 months and grow rapidly. Juveniles mature sexually between 5–8 years, and adults may live for 40–50 years in the wild.

Reproduction (mating season, number of offspring):

Breeding occurs in tropical and subtropical waters during the winter months. Females give birth to a single calf every 2–3 years. There is no fixed mating site; pairs form temporarily during the breeding season.

Behaviour:

Typically solitary or found in small groups. Known for its curiosity toward boats and swift, agile swimming. Feeds by lunging through dense schools of fish. Surfaces frequently but produces a small, inconspicuous blow. Occasionally performs short breaches or rolls near the surface.

Key Adaptations:

• Streamlined body for high-speed swimming and reduced drag.
• White pectoral fin bands possibly used for visual coordination during feeding.
• Thick blubber layer for insulation and energy storage.
• Flexible baleen plates for efficient filtration feeding.
• Deep-diving ability (up to 200 m) to access prey layers.

Threats:

• Ship collisions in high-traffic maritime zones.
• Bycatch in fishing gear, though relatively rare in Sri Lanka.
• Noise pollution disrupting communication and navigation.
• Plastic pollution and microplastics ingestion.
• Climate change, altering prey distribution and migration routes.
  Historically affected by commercial whaling, but populations have recovered since the moratorium.

Interesting Fact:

The Common Minke Whale is the smallest baleen whale, yet it can consume up to 500 kg of fish or krill per day. It often approaches whale-watching boats, earning it the nickname “friendly whale” among marine naturalists.

REFERENCES

Animal Diversity Web – Balaenoptera acutorostrata – Detailed species account covering morphology, habitat, and ecology.

NOAA Fisheries – Minke Whale – Official species profile including conservation status, threats, and biology.

NAMMCO – Common Minke Whale – North Atlantic Marine Mammal Commission facts on identification, range, and life history.

IWC Handbook – Minke Whale – International Whaling Commission species overview with global conservation data.

OBIS-SEAMAP – Balaenoptera acutorostrata – Distribution records, sightings data, and mapping resources for the species.

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