What’s the biggest animal that ever lived?
Yes, blue whales are the largest animal that ever lived – larger than the largest dinosaur!
Biggest blue whale ever recorded was ~110 feet (33m). Our whale is pretty big – she’s 85 feet long, which is about 25 m. That’s as long as two school buses parked end to end!
- A blue whale’s tail is as wide as a soccer net (a professional soccer net, not a school one). That’s about 25 ft (8m).
- A blue whale’s flipper (which is analagous to a human’s hand) is as long as you are tall.
- Blowhole (which is like your nose, it’s just on top of their head so it’s easy for them to breathe in water), is large enough for a baby to crawl through. When they exhale, the blow can reach 30 feet tall (and smells terrible).
- Arteries are big enough for a baby to crawl through, at about 9 inches in diameter (approx the same diameter as a dinner plate).
- Heart is as big as a small car (VW beetle for example).
- Blue whale mouths are huge, too – they can swallow a volume of water larger than themselves. Their throat stretches down to their navel. Tongue is the size of an elephant. You and 400 of your friends could fit in its mouth.
- A baby blue whale is about the size of 2 minivans.
Ecology
What do blue whales eat? Are they vegetarians? Do they eat other whales? Do they eat fish?
The largest animal in the world feeds almost exclusively on one of the smallest – krill (euphasiids).
What are krill?
They are small, shrimplike invertebrates, on average only 1 or 2 centimeters long. This means that blue whales are about 1250 times larger than their food. If humans ate food that much smaller than ourselves, we would eat nothing larger than a grain of sand.
They eat 4 – 6 tonnes of krill a day (about as much as an elephant, the largest land animal, weighs) Imagine eating an elephant every single day! That’s about 40 million krill – that’s more than number of people of Canada. Every day.
How do they do this?
They are filter feeders. They basically eat what’s stuck between their teeth (actually, keratin bristles called BALEEN).
They have a giant mouth – extends all the way to their belly button. They also have these big pleats, so their mouth can expand – sort of like you blowing out your cheeks, but more dramatic. They open their mouth, swallow a volume of water bigger than themselves (imagine swallowing yourself), then push all the water back out through their baleen (what they have instead of teeth). The baleen is like a comb, and the krill get stuck inside their mouths – they end up with a big mouthfull of food.
Swarms of krill can stretch for hundreds of square km of ocean – imagine swimming along for miles and miles, then stumbling on hundreds of square km of food, and swimming through it with your mouth open, eating whatever you catch. The swarms of krill aren’t always right at the surface, and whales will sometimes feed deep beneath the surface. They can dive as deep as 300 m, and can stay down for 30 minutes at a time.
Where do they live?
Whales have huge ranges, and are found in every ocean in the world. There are several distinct populations of blue whales – northern hemisphere, southern hemisphere, Atlantic and Pacific. They travel thousands of km every year. They feed in the northern oceans, and build up their fat reserves – maybe you eat a little more in winter, when it’s dark and there are lots of holidays and nothing else to do, but maybe in summer you’re too busy playing outside, or hanging out with your friends – maybe you just have a salad for dinner. In summer, they head for the equator, and the warmer oceans to have their babies.
Tell me about the babies!
Moms have one baby at a time, and give birth about every 2 or 3 years. Whales start calving between age 6 and 10. Babies are 8m long when born, and weigh about 4 tonnes, about size of 2 minivans. It’s important that the moms have good fat reserves, because these babies are hungry – they drink 50-100 gallons of milk per day, which is 50-100 jugs of milk. They grow really rapidly – gain 8 pounds an hour – 200 pounds a day – that’s about a Dad a day!
Blue whales are thought to live to 100, but we don’t actually know how long they live – there are many things we don’t know about blue whales.
Evolution
What is a blue whale? What are they most closely related to? Who are their evolutionary cousins?
Answer – Hippo
But that’s a land animal! Whales are mammals that have adapted to a life in the ocean, but their ancestors lived on land. When did whales return to the ocean – during the early Eocene, about 53 – 54 million years ago.
What was the world like in the early Eocene?
It was in a period of global warming, the oceans were much warmer than they are today. Temperate forests extended to the poles, and tropical forest was found as far north ats 45 from the equator – that’s about Portland, OR. India was travelling away from Africa, colliding with Asia, and the Himalayas were born. [map of early eocene]. Palm trees grew in Alaska, and subtropical rainforest grew at the edges of Antarctica. Early members of other mammal orders were appearing, including bats, rodents, primates, and marsupials. Plants were already far along, having begun to invade the land over 400 million years ago – flowering plants have been around for ~ 200 mya.
The land ancestors of whales were carnivorous mammals called Mesonychids – the largest, Andrewsarchus, was 3.7m and was the largest carnivorous land mammal EVER!
How can we tell that the ancestors of whales lived on land?
Breathe air (no gills)
Fin bones resemble land mammals’ jointed hands except that whales are missing their middle finger.
Spine is shaped more like a running terrestrial animal than like a fish – moves up and down rather than side to side
They have tiny pelvic bones – much reduced, and a tiny femur, too (which is just a tiny little ball). Lots of individual variation in whales for the number of metacarpals, non-cervical vertebrae. That means that when we were digging up the whale, we didn’t know exactly how many bones we were looking for.
Circulatory and respiratory systems are similar
Their lungs are adapted for diving – trachea extends all the way to the centre of their lungs – our cartilaginous windpipe only extends as far as the branching
All whales have multi-chambered stomachs, inherited from their ungulate ancestors, but of no use in the ocean, including blue whales. Baleen whale stomachs have 3 chambers – forestomach (often contains rocks, to help the muscular walls grind up fish bones and crustacean exoskeletons), main stomach, and pyloric stomach.
Whales need to sleep – but they only put one side of their brain to sleep at a time, like birds do
What are some adaptations of a whale’s body to an aquatic environment?
Streamlined bodies for moving through the water
Forelimbs have become flippers, to move them through the water
Hindlimbs are almost gone – pelvic bone is tiny, their femur is just a little ball!
Broadened tail that moves up and down, not side to side like a fish
No hair, are insulated with blubber instead (except some lip hair, perhaps 4 on their upper lip, and 40 on their lower).
Nose is on top of their head
Senses are adapted to the ocean – they have fantastic hearing (they can hear much lower frequencies than we can).
Population, Conservation, Distribution
Where are blue whales found? How many are there?
They are found in every ocean of the world, and there used to be hundreds of thousands of them. They are fast swimmers (able to reach a top speed of 50 kph when spooked), and for a long time they were too fast and elusive for the whalers to catch.
People have been hunting whales for their oil, blubber, baleen, and meat since prehistory. Blue whales were quick enough to outrun most whalers until about 1868, when the steam engine, explosive harpoons, and air compressors (what were they used for? To inflate dead whales, so they could tow them back to port to be ‘rendered’) were introduced.
What did people use whale products for?
The blubber was rendered for use in lighting, fine soapmaking, and machine lubrication. "Whalebone", the keratin plates baleen whales use to strain food out of the ocean, was prized for corset stays, umbrella ribs, and carriage springs; applications where plastic or steel would now be used.
Blue whales were hunted in great numbers from then on, reducing their numbers from 350,000 to 1 or 2 thousand.
In 1966, the International Whaling Commission banned hunting of blue whales, and today their numbers are estimated at 4,500. Blue whales are on the IUCN Red List of Endangered Species, and are listed as Endangered under the Canadian Species-at-Risk Act.
Today, scientists estimate there are about 4500 blue whales left on the planet, so their numbers are increasing slowly.
They are still under threat. What threatens blue whales?
Pollution – mammals store pollution in their tissues, and they pass it all on to their firstborn, while it’s gestating and breastfeeding.
Oil spills
Changes in ocean that affect food supply (krill)
Ship strikes (our blue was probably killed by a ship strike)
Noise pollution – blue whales are not only the biggest, but also the loudest animal on the planet – their call is 190 decibels, which is louder than a jet engine, more than twice as loud as a person shouting (about 70 dB). If you happened to be swimming next to one (and you wouldn’t be, because you can’t withstand the pressures at that depth, it would do some serious damage. 150 dB will cause permanent hearing damage.
Whales use song to communicate with one another, and to find mates. Blue whales are mostly solitary. They can call to each other across thousands of km. In Newfoundland, you can hear whales singing in Puerto Rico (that’s like being able to hear someone in Toronto singing when you’re standing where you are right now).
A whale’s acoustic bubble used to be about 1000 km, and now it’s just 100km. There’s so much noise pollution in the oceans from propellers, sonar, etc., that if people were working down there, WorkSafe BC would make them wear ear protection.
Imagine being a single blue whale out in the ocean, and you’re looking for a mate – you used to have hundreds of thousands to choose from, and you used to be able to hear songs from thousands of km away – now there are only a few thousand, and you can’t hear most of them because of all the noise – they’re living in a construction site.
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