Let's talk about the largest animal on the face of the planet. When we say the largest animal, we also mean the largest animal known to have ever existed. Which is really incredible if you think about how palaeontologists talk about the fact that, on average, animals are smaller now than they were in previous times in history. The blue whale is so large that it has a heart the size of a small car.
The blue whale is a long, slender, almost torpedo-shaped animal with relatively small pectoral fins. It can grow to a maximum length of 30 m (100 ft). They are found in all the world's oceans and are split up into four distinct subspecies. The most common subspecies is the Pygmy Blue Whale. Pygmy blue whales, as their name suggests, are smaller than other subspecies. They grow to a maximum of 24 m (79 ft). The largest subspecies of the blue whale can weigh up to 200 tonnes, whereas the pygmy blue whale tops out at about 130 tonnes.
Blue whales are krill feeders and are found in most areas of the ocean. They have been known to engulf up to 220 tonnes of water, which they then filter by pushing out through their baleen plates, trapping the krill in their mouths. They have been found to require a little over 1000 kg (2,200 lbs) of krill per day.
Despite being the largest creatures to ever grace this planet, they are not without their threats. The only known natural predator of the blue whale seems to be the orca, also known as the killer whale. There have been numerous reports of orcas chasing and attacking blue whales. The largest orca kill of a blue whale seems to have been off the coast of Western Australia, where they killed an individual about 20 m (66 ft). Orcas more commonly take the calves than the adults. Regardless, they will swim next to the individual and try and get on top or above the hunted whale. The whale will be unable to surface to breath and will eventually drown.
There have been a few instances where blue whales have bred with other species of related whales. The vast majority seems to be between the blue whale and the fin whale. However, there have been a few instances where they have bred with Sei Whales, and there is also a report of a blue whale-humpback whale hybrid.
If you get grossed out easily, reading on might not be the best choice. To age blue whales, the most accurate way we currently know how is to count the layers of earwax. The whales start producing earwax at birth. The earwax has different colours depending on whether the whale is fasting while migrating or feeding. These layers are then counted and the age determined. The current oldest blue whale was a pygmy blue whale that had an age of 72 years.