The blue whale (Balaenoptera musculus) is a marine mammal and a baleen whale. Reaching a maximum confirmed length of 29.9 meters (98 ft) and weighing up to 199 metric tons (196 long tons; 219 short tons), it is the largest animal known to have ever existed. The blue whale’s long and slender body can be of various shades of greyish-blue dorsally and somewhat lighter underneath.
In general, blue whale populations migrate between their summer feeding areas near the polar and their winter breeding ground near the tropics. There is also evidence of year-round residencies, and partial or age/sex-based migration. Blue whales are filter feeders; their diet consists almost exclusively of krill.
They are generally solitary or gather in small groups and have no well-defined social structure other than mother-calf bonds. The fundamental frequency for blue whale vocalizations ranges from 8 to 25 Hz and the production of vocalizations may vary by region, season, behavior, and time of day. Orcas are their only natural predators.
In this blog, Pritish Kumar discusses the world’s biggest Greyish-blue Mammal, which is found across the world’s oceans.
Blue whales have long, slender mottled greyish-blue bodies, although they appear blue underwater. The mottling pattern is highly variable. Individuals have a unique pigmentation pattern along the back in the region of the dorsal fin which can be used for the purpose of identification.
The blue whale is the largest known animal to have ever existed. The International Whaling Commission (IWC) whaling database reports 88 individuals longer than 30 meters (98 ft), including one of 33 meters (108 ft), but problems with how the measurements were taken suggest that any longer than 30.5 meters (100 ft) are suspect.
The Discovery Committee reported lengths up to 31 meters (102 ft); however, the longest scientifically measured individual blue whale was 30 meters (98 ft) from rostrum tip to tail notch. Female blue whales are larger than males. Hydrodynamic models suggest a blue whale could not exceed 108 ft (33 m) because of metabolic and energy constraints. The highest recorded weight for the species is 199 metric tons (196 long tons; 219 short tons).
The average length of sexually mature female blue whales is 22.0 meters (72.1 ft) for Eastern North Pacific blue whales, 24 meters (79 ft) for central and western North Pacific blue whales, 21–24 meters (68–78 ft) for North Atlantic blue whales, 25.4–26.3 meters (83.4–86.3 ft) for Antarctic blue whales, 23.5 meters (77.1 ft) for Chilean blue whales, and 21.3 meters (69.9 ft) for pygmy blue whales.
In the Northern Hemisphere, males weigh an average 100 metric tons (220,000 lb) and females 112 metric tons (247,000 lb.). Eastern North Pacific blue whale males average 88.5 metric tons (195,000 lb) and females 100 metric tons (220,000 lb). Antarctic males average 112 metric tons (247,000 lb) and females 130 metric tons (290,000 lb). Pygmy blue whale males average 83.5 metric tons (184,000 lb) to 99 metric tons (218,000 lb). The weight measured of the heart from a stranded Northland.
A blue whale’s age is most reliably measured using ear plugs. Blue whales secrete earwax throughout their lives, forming long, multi-layered plugs. Each deposited light and dark layer indicate a switch between fasting during migration and feeding. As one set is laid down per year, the number of layers is an indicator of age. The maximum age of a pygmy blue whale determined this way is 73 years.
Before the ear plug aging method, layers in baleen plates were used; however, these wear down and are not as reliable. The blue whale’s ovaries form a permanent record of the number of ovulations (or perhaps pregnancies), in the form of corpora Albania—fibrous masses that are permanent scars and were once used as an indication of age. In a female pygmy blue whale, one corpus albicans is formed on average every 2.6 year sic blue whale was 0.18 metric tons (400 lb), the largest known in any animal.
Diet and feed
The blue whale’s diet consists almost exclusively of krill. They have also been observed near Magdalena Bay (along the western coast of Baja California, Mexico) feeding on pelagic red crabs. They may accidentally eat small fish that are in the swarms of krill (although this is rare). Blue whales capture krill through lunge feeding, they swim towards them at high speeds with the mouth wide open. They may engulf 220 metric tons (220 long tons; 240 short tons) of water at one time.
They squeeze the water out through their baleen plates with pressure from the throat pouch and tongue, and swallow the remaining krill. Blue whales have been recorded making 180° rolls during lunge-feeding, allowing them to engulf krill patches while inverted. They rolled while searching for prey between lunges, which has been hypothesized as allowing them to survey the prey field and find the densest patches.
Blue whales maximize the intake of energy by increasing the number of lunges they make during a dive while targeting dense krill patches. This allows them to acquire the energy necessary for everyday activities while storing additional energy necessary for migration and reproduction.
Reproduction and birth
Blue whales generally reach sexual maturity at 8–10 years. In the Northern Hemisphere, the length of which they reach maturity is 21–23 meters (69–75 ft) for females and 20–21 meters (66–69 ft) for males. In the Southern Hemisphere, the length of maturity is 23–24 meters (75–79 ft) and 22 meters (72 ft) for females and males respectively.
Male pygmy blue whales average 18.7 meters (61.4 ft) at sexual maturity. Female pygmy blue whales are 21.0–21.7 meters (68.9–71.2 ft) in length and roughly 10 years old at the age of sexual maturity.
Female blue whales give birth every two to three years. Pygmy blue whales are estimated to give birth every 2.6 years. Pregnant females gain roughly four percent of their body weight daily, amounting to 60% of their overall body weight throughout summer foraging periods. Gestation may last 10–12 months with calves being 6–7 meters (20–23 ft) long and weighing 2–3 metric tons (2.0–3.0 long tons; 2.2–3.3 short tons) at birth.
Estimates suggest that because calves require 2–4 kilograms (4.4–8.8 lb.) milk per kg of mass gain, blue whales likely produce 220 kilograms (490 lb) of milk per day (ranging from 110 to 320 kilograms (240 to 710 lb.) of milk per day). The first video of a calf thought to be nursing was filmed in New Zealand in 2016. Calves may be weaned at 6–8 months old at a length of 16 meters (53 ft). They gain roughly 37,500 pounds (17,000 kg) during the weaning period.