What are Whales & Dolphins?
Whales, Dolphins & Porpoises are MAMMALS: they breathe air into lungs, have hair (although they have a lot less than land mammals, and have almost none as adults), are warm-blooded (they maintain a high body temperature), have mammary glands with which they nourish their young, and they have a four-chambered heart. As a group of creatures they are known as Cetaceans & belong to the Order Cetacea. There are 87 species currently known to science within the Order Cetacea. The Order Cetacea is divided into 2 Suborders:
1) Baleen Whales (or True Whales or Moustached Whales) – MYSTICETI – 14 species
2) Toothed Whales – ODONTOCETI – 73 species
Here are a couple of distinguishing differences between Baleen & Toothed Whales:
Toothed whales are predators that use their peg-like teeth to catch fish, squid, and marine mammals, swallowing them whole. They have one blowhole (nostril) and use echolocation to hunt. Except for the sperm whale, most toothed whales are smaller than the baleen whales.
Baleen whales are large filter-feeders with baleen (comb-like structure that filters the whales food from the water) instead of teeth. The exact means by which baleen is used differs among species (gulp-feeding, skim-feeding, and bottom-feeding). All have a double blowholes.
The main characteristics of whales & dolphins are:
Cetaceans breathe air. They surface periodically to exhale carbon dioxide and inhale a fresh supply of oxygen. During diving, a muscular action closes the blowholes (nostrils), which remain closed until the cetacean next breaks the surface; when it surfaces, the muscles open the blowholes and warm air is exhaled.
Cetaceans’ blowholes have evolved to a position at the top of the head, simplifying breathing in sometimes rough seas. When the stale air, warmed from the lungs, is exhaled, it condenses as it meets colder external air. As with a terrestrial mammal breathing out on a cold day, a small cloud of ‘steam’ appears. This is called the ‘blow’ or ‘spout’ and varies by species in terms of shape, angle and height. Species can be identified at a distance using this characteristic. A blue whales ‘blow’ can be nearly 9m high!
Cetaceans can remain under water for much longer periods than most other mammals, (approximately 7–30 minutes, varying by species) due to large physiological differences. Grey whales can hold their breath for 1 ½ hours, possibly the longest of all the whales.
Why do some whales have one blowhole and some have two?
Most mammals have two nostrils (blowhole equivalents). One of the nostrils (air-passages) of toothed whales evolved into their echolocation system (the sensing system in which they make and recieve high-pitched sounds in order to orient themselves, catch prey, and communicate), leaving them with only one blowhole.
Cetacean eyes are set on the side rather than the front of the head. This means that only cetaceans with pointed ‘beaks’ (such as dolphins) have good binocular vision forward and downward. Tear glands secrete greasy tears, which protect the eyes from the salt in the water. The lens is almost spherical, which is most efficient at focusing the minimal light that reaches deep water. Cetaceans make up for their generally poor vision (with the exception of the dolphin) with excellent hearing.
As with the eyes, cetacean ears are also small. Life in the sea accounts for the cetacean’s loss of its external ears, whose function is to collect and focus airborne sound waves. However, water conducts sound better than air, so the external ear is unneeded: it is a tiny hole in the skin, just behind the eye. The highly developed inner ear can detect sounds from dozens of miles away and discern from which direction the sound comes.
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Toothed whales have excellent hearing and use echolocation (also known as SONAR) to sense objects. They make short, intense, broad-band pulses of ultra-sonic sound which bounce off objects near it. The animal “hears” the objects in its environment, creating an acoustical picture. In echolocation, a high-pitched sound (usually clicks) is sent out by the whale. The sound bounces off the object and some returns to the whale. The whale interprets this returning echo to determine the object’s shape, direction, distance, and texture. Bats and some other marine mammals also use echolocation. A toothed whale’s echolocation starts with a series of low-frequency clicks (called a train) produced by the animal. This train passes through the melon of the whale (a fat-filled organ in the head of the toothed whale that focuses the sound wave). The train of clicks is focused into a beam that bounces off objects and reflects (echoss) back to the whale.
Cetaceans also use sound to communicate, whether it be groans, moans, whistles, clicks or the complex ‘singing’ of the humpback whale.
Cetaceans have a very limited or non-existent sense of smell. The olfactory bulb in the brain is primary in the sense of smell, but these olfactory bulbs are reduced in baleen whales and are absent in toothed whales (toothed whales have no sense of smell at all).
Research on the existence whales’ taste buds is mixed and contradictory. Experiments have shown that dolphins do have a sense of taste.
Cetacean skin is very sensitive to touch. Also, most Cetaceans have stubble-like whiskers on their snouts called vibrissae. These vibrissae are thought to be an additional tactile indicator (like a cat’s whiskers).
Whales may use the magnetic field of the Earth for navigation purposes on their long migrations across the oceans. It is not known how they sense magnetism. Many mass whale beaching occur at places where there in an anomaly (abnormality) in the Earth’s magnetic field, perhaps confusing the whales.
Do Cetaceans sleep?
Whales sleep possibly about 8 hours each day. Whales don’t go into a deep sleep like we do, because they have to be partially conscious to breathe. Whales are able to partly sleep by letting one half of their brain sleep at a time. This is called unihemispherical sleeping.
Scientists have performed EEG sleep studies on dolphins. They found that during their light sleep, dolphins are rarely (if ever) in REM (Rapid Eye Movement) sleep. This level of sleep has been associated with dreaming in humans.
A whale’s tail is called its flukes. The flukes are used in swimming. A whale’s tail is composed of two lobes, each of which is called a fluke. There is a notch, a v-shaped indentation where the flukes (or lobes) of a whale’s tail meet. Flukes move up and down to propel the whale through the water. (This is unlike fish tails which move left and right.) Flukes have no bones in them. They are made of muscles and dense fibrous tissue. The arteries that supply the flukes with blood are surrounded by veins to maintain the whale’s temperature.
FACT: The blue whale’s flukes are the largest and are 25 feet (7.6 m) wide.
Whales are mammals and are nourished in the womb through an umbilical cord (as we are). They even have a belly button after birth (this is the place where the umbilical cord used to attach). Cetaceans are viviparous, they give birth to live young (unlike fish, most of which lay eggs, except some sharks). Like all mammals, whale calves are nourished with milk from their mothers. Cetaceans breed seasonally, usually in warm tropical waters, and females usually have one calf every 1-3 years. The gestation times range from 9-18 months. Whale calves can swim at or soon after birth. Mother whales care for their young for an extended period of time, usually at least a year, feeding them milk and protecting them. The calves are often born tail first so they don’t drown. Young cetaceans are frequently mottled in color; this camouflages them from predators. Newborns have a sparse covering of hair which they lose as adults.
FACT: During the first 7 months of its life a blue whale calf drinks approximately 400 litres (100 US gallons) of milk every day.
FACT: Southern Right Whale’s testicles have a combined weight of 1 tonne which is 20x heavier than the blue whale’s. Southern Right whales have a 9ft long penis – the longest in the animal kingdom
Toothed whales mostly eat fish and squid , along with shrimp, and some marine mammals. Orcas will sometimes eat other whales.
Baleen whales sieve small organisms through their baleen for nourishment. They filter feed tiny crustaceans (krill – mainly Euphausia superba, copepods, etc.), plankton, and small fish (including herring, mackerel, capelin, and sandeel) from the water (or the sediment on the ocean floor). Baleen whales can be gulpers or skimmers:
- Gulpers are filter feeders that occasionally take large gulps of concentrated food (usually tiny crustaceans and small fish). Food is then pushed into the gullet with the tongue. Blue whales, Humpback whales, Bryde’s whales, and fin whales are gulpers.
- Skimmers (also known as skim feeders) are filter feeders which swim slowly through the water with their mouth open, letting water flow through their baleen plates, collecting food all the while. Right whales are skimmers; bowheads and sei whales are skimmers some of the time.
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