One of the Inktober prompts from last week was gigantic, so I thought I’d draw a nice big animal for today’s post. Then I realized I haven’t written about blue whales yet, and nothing fits the description of gigantic like the largest animal on Earth.
The biggest blue whales can reach massive proportions. In fact, blue whales are not only the biggest extant animals in the world, they are the largest animals that have ever lived. That includes the dinosaurs, if you can believe it. Blue whales can reach lengths of around 30 m, and weights range from 45 to 136 tonnes.
There are other impressive statistics regarding size in blue whales. Their hearts weigh a massive 180 kg on average, which is the biggest of any known animal. They also hold the record for largest penis of any living animal, and that’s all I’m going to say about that! Their tongues can weigh 2.7 tonnes, and a blue whale’s mouth can hold up to 90 tonnes of water.
Despite the incredible size of a blue whale’s mouth, these terrifyingly large creatures can’t swallow anything larger than a beach ball. So though I’d be utterly terrified if I stumbled across one while swimming in the ocean, blue whales can’t actually swallow people. They subsist primarily on krill, gulping down large quantities of water and then filtering out the krill using baleen plates as filters. A single blue whale can eat up to 40 million krill in a single day.
Such big animals need lots of space to roam in, so it’s not particularly surprising that they are found all over the world’s oceans. Blue whales are generally found in nutrient-rich, high-latitude waters during the summer, and migrate to warmer waters near the equator in the winter to breed.
Blue whales only breed every two to three years, as it takes quite a while to carry a calf to term and then raise it. Gestation in blue whales ranges from ten to twelve months, and the calves weigh 2.5 tonnes at birth — about the size of an adult hippopotamus. They grow very quickly, sometimes gaining almost 100 kg every 24 hours. Calves are weaned at six months but do not reach sexual maturity until five to ten years of age.
Adult blue whales have virtually no natural predators, thanks to their incredible bulk. There are reports of orca pods attacking blue whales, though they don’t have much of a chance of killing one. The only other predator of blue whales is humans. Early whalers weren’t fast or powerful enough to hunt blue whales, but by 1925 blue whales were regularly being hunted. Populations rapidly decreased, until hunting blue whales was banned in 1966. Since then, the population has increased, though the global population is still a fraction of its pre-whaling levels. They are currently listed as an endangered species, but hopefully their population keeps growing.
Cover image “Mike” Michael L. Baird, CC BY 2.0, via Wikimedia Commons
Our Wild World 
