General facts on humpback whales (Megaptera novaeangliae)
Humpback whales are baleen (filter feeder) whales and belong to the Balaenoptera family. They are probably the most easily recognisable and familiar of all the large whale species in the world. Their scientific name Megaptera novaeangliae is derived from the Greek words “mega” meaning large and “pteron” meaning wing (referring to their long pectoral flippers which are one third of their total body length) and “novaeanglia” meaning New Englander because they were described from New England, USA in 1781. They were given their common name, Humpback whale, due to the small hump under the dorsal fin and also the characteristic hunched shape that is clear when they are about to dive.
Humpback whales are robust whales that grow to a maximum length of 18m and can weigh up to 40 tons. Females are on average 1-1.5m longer than males but the sex is difficult to determine from a boat. They are dark grey to black dorsally and white on their undersides. They belong to a group of whales known as ‘rorquals’; this term refers to the throat grooves that run from the underside of the lower jaw to the naval. These grooves allow the throat to expand when feeding, enabling the whales to engulf large quantities of prey at once. The throat grooves are then contracted, pushing the surplus water out of the mouth through the baleen plates which trap the food items inside the mouth. They have between 200-400 baleen plates hanging from the top jaw that are about 1m in length. Baleen is made of keratin, the same substance as our hair and nails. Their dorsal fin is relatively small and situated two-thirds of the way down the body on top of a raised hump. The dorsal fin shape varies between individuals and researchers frequently use this variation to aid in the identification of individual whales. However, a more reliable feature for research is the unique black and white pattern on the underside of the tail flukes which can be seen and photographed as the whale dives. Humpback whales have unusual knob-like lumps on their head and chin known as tubercles. Each tubercle carries a single hair up to 2.5cm long. They have similar lumps on the leading edge of the pectoral flippers that are thought to help improve their hydrodynamics and manoeuvrability. These tubercles have inspired scientists and engineers to design wind turbines and aeroplane wings based on the shape of the humpback whale flipper, and have significantly improved the efficiency of both by doing so.
Humpback whales were commercially whaled in all major oceans and most stocks were seriously depleted. In the southern hemisphere over 200,000 whales were killed in the 20th century alone. Humpback whales have been protected since 1955 in the northern hemisphere and in 1965 in the southern hemisphere. They were classified by the International Union for the Conservation of Nature (IUCN) in 1986 as endangered. The global population of humpback whales has increased since 1986 and in 2008 they were classified as least concern, but more information is needed to assess the different populations separately. Current threats to the species are traditional hunting, entanglement, vessel collision, human-made noise, habitat destruction and climate change. Humpback whales also have natural predators, mainly orcas, but occasionally some large shark species will attack young or sick individuals.
Please see next week post about humpback whales distribution, breeding and behaviour.
– Whales dolphins and other marine mammals of the world (2006) by Hadoram Shirihai and Brett Jarrett. Prinston field guides 2006
– Smithers’ Mammals of Southern Africa a field Guide by Peter Apps Struik Nature edition 2012
– Jefferson T. Webber M. Pitman R. 2007 Marine mammals of the world: A comprehensive guide to their identification 1st edition
– Best, Peter 2007. Whales and dolphins of the southern African subregion. Cambridge University Press.