WHALES aquatic mammals
Whales and dolphins are cetaceansfrom the Greek word ‘ketos’ or whale • They originated as land mammals, but evolved from the land to the sea about 50-60 million years ago. • The bones in a whale’s pectoral fin are very similar to the bones in a human arm showing their common ancestry.
Whales of Australasia • There are 35 species of cetacean in New Zealand waters: • 8 are baleen whales • 27 are toothed whales • New Zealand has 3 species not occurring in Australia • Australia has another 10 species which are not found in New Zealand.
Toothed Whales & Baleen Whales • Whales are divided into 2 groups according to the way they obtain their food. • Toothed whales have teeth. This group of cetaceans are called Odontoceti. • Baleen whales do not have teeth but instead have a mesh of bristles called baleen that is attached to the upper jaw and acts as a filter. Baleen, like human hair, is made of keratin. This group of cetaceans are called Mysticeti.
BALEEN WHALES • Baleen means ‘with moustaches’. • They have evolved to eat huge quantities of small organisms called planktonwhich are available in some areas e.g. krill in Antarctic waters. • They generally live longer than toothed whales, up to 70 – 80 years has been known. • They have two blowholes.
Baleen Whales The humpback whale above represents a typical baleen whale.
Howthey feed - • Some of them gulp in the water including the food and squeeze the water out the side of their mouth. These whales are rorquals and have pleats under their throats which expand to allow them to gulp huge quantities of water. A Blue Whale can gulp up to 5 tons of water. • Others such as the Right Whale swim with their mouths open and swing their head from side to side using the baleen to filter out the plankton. • Now try the investigation to show how baleen filters food.
TOOTHED WHALES • They have one blowhole. • Most female toothed whales are smaller than males while in baleen whales females are generally larger than the males. • In the next diagram, a bottlenose dolphin is used to represent toothed whales.
Howthey feed - • Toothed whales eat fish and squid by grasping them in their teeth. • They do not chew their food, but use their tongue to turn the fish so that it goes down head first. • The Killer Whale is the only true eater of warm-blooded prey. They have been known to eat seals and other cetaceans. • Watch the video of Orca hunting.
Whales are not fish! They are mammals • They are warm-blooded & give birth to live babies (tail first) and feed them with milk rich in nutrients. • The gestation period varies according to the species but may be between 9 to 18 months. • Baby whales don’t suck, instead the milk is squirted out of the teats down the baby’s throat. • Whale tail flukes are horizontal structures; their tails move up and down, instead of side to side as fish tails do.
Mammal breathing …. not fish breathing • Whales must surface in order to breathe, unlike fish. This can be spotted by an observer by the ‘blow’ or ‘spout’ from the whale’s blowhole. Click here to watch a sperm whale ‘blowing’. • Blowholes are like nostrils on top of their heads and the ‘blow’ is actually condensing water vapour. • Whales are able to stay under water because their lungs fill to their capacity and they change up to 90% of this each time they breathe.
How do whales keep warm? • They store some of their food as an insulating layer of blubberjust under the skin’s surface. • The blubber reduces heat loss to the surrounding water and also acts as an energy reserve for long migrations. • Now try the experiment to demonstrate how blubber is effective in reducing heat loss.
Sleeping and Swimming • Whales have very streamlined bodies to help them move easily through the water. • Cetaceans are among the fastest swimmers in the sea. They are powered by their tail flukes moving up and down. • Their flippers are for balance and steering. • Whales sleep with their blowhole just at the water surface. They control their breathing even when asleep. • If they lose consciousness the blowhole closes to avoid drowning. • Whales tend to take short naps.
Being Social • Cetaceans generally live in groups called pods which vary greatly in size according to the species. • Some group into nursery groups at breeding times with the males remaining apart at other times. • Another whale is often involved during the birth of a calf and helps nudge the calf to the surface to take its first breaths. • It may be that some social behaviour is responsible for whales not leaving other stranded whales after they themselves have been rescued.
Sensing • The sense of sight is not the predominant one for whales given the murkiness of their environment. • The sense of touch is present & demonstrated by whales rubbing against each other. • Toothed whales do not have a sense of smell, and it is limited in baleen whales. • Toothed whales use echolocation to sense things around them. Baleen whales may use it but less is known about this.
Echolocation • The whales make a clicking sound which produces vibrations that travel through the water. • The sound waves are bounced off any solid objects, and the whale is able to work out the direction and distance of the object, and even its shape, e.g. whether it is another animal or the sea floor. • Watch the video of echolocation helping to hunt a giant squid.
Communicating • Toothed whales communicate by making whistling sounds which appear to transmit complex and intentional messages. • Baleen whales produce a variety of sounds including whistles, clicks, thumps and moans. • Humpbacks are known for their ‘singing’ –some songs can last up to 30 minutes and are thought to be the longest and most complex of any animal. These are really ‘love songs’ and occur during the breeding season. • A Blue Whale’s whistle is the loudest sound known to be produced by anything living. • Watch the video about research that was carried out on how and what whales hear.
Migration • Many whales migrate between feeding and breeding grounds, e.g. • Humpbacks migrate north to around Samoa, Tonga and New Caledonia to breed in autumn and south to the Antarctic to feed in spring. • The whales migrate in 3 phases: • The pregnant females leave first in order to get to the new feeding grounds first and so get the most food. • The males migrate next. • Finally, the non-pregnant females and those with calves.
Tracking & the effects of humans on whales • Marine scientists have been tracking the migratory patterns of whales in order to study how whales are affected by changes in the environment. • For example, scientists have found that toxic pollutants in the water suppress whales’ immune systems, causing many to grow sick and die.