English: Blue whale
Spanish: Ballena azul
Length: 24 - 33.6 m
Weight: 80 - 160 tons
Habitat and distribution:
The blue whale is a cosmopolitan species, found in (almost?) all oceans. They are considered highly migratory animals as their distribution varies with season. In the southern hemisphere, these ocean giants feed on krill during the austral summer in cold waters (higher latitudes), and in winter migrate to warmer waters (lower latitudes), where they are thought to mate and give birth to their calves. Blue whales feding off Chiloé and in southern Chile seem to be part of the larger Eastern Tropical Pacific population, and some seem to be migrating to Ecuador (Galapagos) during the austral winter.
Blue whales were abundant in nearly all oceans until the early twentieth century. For more than forty years they were hunted to near extinction until finally becoming a fully protected species (International Whaling Commission) in 1966. Blue whales can be injured, sometimes fatally, because of collisions with large ships at sea and also get entangled or trapped in fishing nets. The continuous increase in ambient noise produced by humans in the ocean, including shipping and some sonar, may interfere with their vocalisations hindering communication. Further threats to the recovery of their populations also include accumulation of persistent organic pollutants (PCBs, DDTs, etc) and other chemicals ingested with their food. Pollutants may cause reproductive disorders and decrease immune responses.
- Branch, T. A., and 40 others (2007). "Past and present distribution, densities and movements of blue whales Balaenoptera musculus in the Southern Hemisphere and northern Indian Ocean." Mammal Review 37(2): 116-175.
- Hucke-Gaete, R., L. P. Osman, C. Moreno, K. P. Findlay and D. K. Ljungblad (2004). "Discovery of a blue whale feeding and nursing ground in southern Chile." Proc. R. Soc. Lond. B (Suppl), biological letters 271: 170-173.
- Reilly, S.B., Bannister, J.L., Best, P.B., Brown, M., Brownell Jr., R.L., Butterworth, D.S., Clapham, P.J., Cooke, J., Donovan, G.P., Urbán, J. & Zerbini, A.N. (2008). Balaenoptera musculus. The IUCN Red List of Threatened Species. Version 2014.3. <>.
- Torres-Florez, J. P., P. A. Olson, L. Bedriñana-Romano, H. Rosenbaum, J. Ruiz, R. LeDuc, R. Hucke-Gaete (2015). First documented migratory destination for eastern South Pacific blue whales. Marine Mammal Science.