Cetaceans: Whales, Dolphins, and Porpoises
Marine mammals in the cetacean family include whales, dolphins, and porpoises. Although whales spend all their time in the oceans, they are mammals just like us. This means that they are warm blooded, give birth to live young, nurse their young, have traces of hair or fur, and must come to the surface to breathe air through their lungs.
Millions of years ago, the ancestors of whales lived on land. Scientists believe these land ancestors looked like small dogs, but were probably more closely related to hippos and went into the ocean about 60 million years ago. Over time, these ancestors adapted to survive solely in the ocean environment. Their front legs turned into paddle-shaped flippers, they lost their back legs, their tails grew larger and widened to form flukes, and they developed a thick layer of fat, called blubber, to keep warm in the ocean. Also, their skulls elongated and the nostrils shifted to the top of their heads (blowholes) to aid in breathing at the ocean's surface. They developed a series of adaptations related to diving, which include the ability to store more oxygen in their blood and muscles and having more blood volume relative to their body size than land mammals.
Cetaceans are separated into two groups: toothed and baleen whales. As their name suggests, toothed whales (or odontocetes) have teeth. They also have one opening at their blowhole. There are over 73 species of toothed whales, including sperm and beaked whales, belugas and narwhals, porpoises and dolphins, and even fresh water dolphins that live in rivers. They range in size from the 60-foot (21.1 m) sperm whale to the 5-foot (1.5 m) vaquita. Some toothed whales are quite unusual. For instance, the beaked whales spend most of their time in the deep water and, therefore, are rarely encountered by people, and new species are still being discovered! Some beaked whales are odd looking and often only the males will have teeth. The straptoothed whales have only two teeth, which wrap around the top of their jaws so they cannot fully open their mouths!
Toothed whales tend to be social and live in groups. Like bats, they use echolocation or sonar to detect objects in their environment. They produce sounds in the air passages in their heads, which are then projected out in front of them. The sound bounces off solid objects and returns to them (like an echo), so the animals are able to get a "picture" of what is around them. A lot of research is being done on whale sounds. Many species, such as the humpback and sperm whales, seem to have individually identifiable calls. Orcas (killer whales) live in groups or pods and each pod has a dialect or accent, just like we have accents depending upon which part of the world we are from.
The baleen whales (or mysticetes) are the other group of cetaceans. This group includes 11 species ranging in length from the pygmy right whale at 21 feet (6.4 m) to the largest whale, the blue whale at 100 feet (30.5 m). Baleen whales have two blowholes and instead of teeth, have hundreds of rows of baleen plates, which are made of keratin, a substance in our hair and fingernails. The baleen strains out small fish and plankton from the water for food. Most baleen whales feed by taking a large mouthful of food and water, and then push the water out gaps between their baleen plates with their tongues. The food gets trapped on the inside fringed edge of the baleen. Most baleen whales eat krill (shrimp-like animals) or small fish. Right and bowhead whales are baleen whales that feed in a slightly different way called skimming. Water and food flows through a gap in the front of their mouth where the baleen is missing and the food gets trapped in the baleen fringe while the water flows out between the baleen plates.
Even though baleen whales eat very small animals, which are low on the food chain, these whales are all very large and eat great quantities at once. For instance, the blue whale is the largest animal on earth, weighing up to 150 tons. Baby blue whales gain 10 pounds (4.5 kg) an hour!
Many whales are endangered, largely due to past hunting. Years ago, people used the oil from the blubber of whales for all sorts of items, including oil burned in lamps and ingredients for manufacturing lipstick. They also used whale meat to eat or make pet food, sinews for tennis racquet strings, and even used baleen as stays or supports in ladies underwear. A waxy substance called ambergris, which is from a sperm whale's digestive system, was used in making perfume. Ambergris was very valuable and a large lump found by a beachgoer was worth a fortune.
Since 1986, there has been a ban or moratorium on hunting the large whales for commercial uses. However, some countries still kill whales for scientific purposes, and others have illegally resumed commercial whaling. This is controversial because the products from these whales are still used commercially. Many scientists question whether the whales really need to be killed to learn the sorts of things being studied. Certain Native American tribes are still allowed to hunt whales for subsistence. These hunts are regulated with specific rules for the method of hunting and yearly quotas that limit the number of whales taken.
Many people are concerned about the fate of the small whales (the dolphins and porpoises). Thousands die every year from getting caught in fishing nets and plastic trash. Toxins and pollution in the ocean are affecting the health of these animals and likely their ability to fight off diseases. Around the world, there has been an increase in reported strandings of marine mammals. Other species are suffering due to loss of their habitat. Sometimes even whale watching can interfere with and harass whales, if the boats venture too close to the whales or separate mothers from calves. Small whales are sometimes captured for display in aquaria and even hotels, and many people question the quality of life and health for these animals. Other species of small whales are still sometimes hunted and eaten in some parts of the world.
In the recent past, popular movements helped to save the whales from hunting. Unfortunately, the whales are not completely safe. We need to understand and solve some of the problems currently threatening whales like climate change, boat strikes, entanglement in nets, and noise pollution. You can help by learning about the issues, letting others know what you have learned, and writing to lawmakers. Also, if you ever have the chance, try to see live whales in the wild. You will never forget it!