Mysticeti facts for kids

Kids Encyclopedia Facts
Baleen whales
Temporal range: latest Eocene - Recent
Humpback whale breaching
Scientific classification
Kingdom: Animalia
Class: Mammalia
Order: Cetacea
Suborder: Mysticeti
Cope, 1891
Families

Balaenidae
Balaenopteridae
Eschrichtiidae
Neobalaenidae
Janjucetidae†

Baleen
Baleen

The Mysticeti are one of the two suborders of the Cetacea. They are often called baleen whales, or 'whalebone whales' or 'great whales'.

Baleen whales have baleen plates made of keratin. The difference is connected with feeding. Baleen whales strain plankton out of the water, whereas the Odontoceti (toothed whales) eat larger prey.

The suborder contains four families and fourteen species.

Baleen

Baleen whales do not have teeth, except as embryos. Fossil adult baleen whales did have teeth, but modern adults have only baleen. The embryo teeth are replaced by baleen, which look like a curtain of long plates hanging down from the top of the whale's mouth. Those plates might be 12 feet long, and a foot or more wide. Looking at them from the outside, they look like straight knives hanging down, but from the inside, they are like a big toothbrush or comb. Baleen is made of keratin, a tissue also found in mammalian hair and nails.

Feeding

A baleen whale uses its baleen to eat. In order to feed, a baleen whale opens its mouth widely and scoops in dense shoals of plankton and other small prey (such as krill, copepods, small fish and sometimes birds that happen to be near the shoals), together with a large volume of water.

The whale then partly shuts its mouth and presses its tongue against its upper jaw, forcing the water to pass out sideways through the baleen, thus sieving out the prey which it then swallows.

Differences between families

Baleen whale sizes
Baleen whales vary considerably in size and shape, depending on their feeding behavior.

Rorquals use throat pleats to expand their mouths, which allow them to feed more effectively. However, rorquals need to build up water pressure in order to expand their mouths, leading to a lunge-feeding behavior. Lunge-feeding is where a whale rams a bait ball (a swarm of small fish) at high speed. Rorquals generally have streamlined physiques to reduce drag in the water while doing this.

Balaenids rely on their huge heads, as opposed to the rorquals' throat pleats, to feed effectively. This feeding behavior allows them to grow very big and bulky, without the necessity for a streamlined body. They have callosities, unlike other whales, with the exception of the bowhead whale.

Rorquals have a higher proportion of muscle tissue and tend to be negatively buoyant, whereas right whales have a higher proportion of blubber and are positively buoyant.

Gray whales are easily distinguished from other extant cetaceans by their sleet-gray color, dorsal ridges (knuckles on the back), and their gray-white scars left from parasites. As with the rorquals, their throat pleats increase the capacity of their throats, allowing them to filter larger volumes of water at once. Gray whales are bottom-feeders, meaning they sift through sand to get their food. They usually turn on their sides, scoop up sediment into their mouths and filter out benthic creatures like amphipods, which leave noticeable marks on their heads.

The pygmy right whale is easily confused with minke whales because of their similar characteristics, such as their small size, dark gray tops, light gray bottoms, and light eye-patches.

Breaching

Although they are very heavy, baleen whales are able to jump completely out of the water. Humpback whales are known for their jumping skills, but other baleen whales also jump out from the water with their body or beat it loudly with their fins. Nobody knows for sure why the whales do this. It may be a type of communication.

Evolution

The oldest true fossils of baleen are only 15 million years old, but baleen rarely fossilizes, and scientists believe it originated considerably earlier than that. Genetic evidence from DNA sequence analysis supports this idea.

Baleen-related skull modifications being found in fossils from considerably earlier. Baleen is believed to have evolved around thirty million years ago, possibly from a hard, gummy upper jaw, like the one a Dall's porpoise has. In fact, it resembles baleen closely at the microscopic level. Many early baleen whales also had teeth, but these were probably used only peripherally, or perhaps not at all (again like Dall's porpoise, which catches squid and fish by gripping them against its hard upper jaw).

Importance to humans

From the 11th to the late 20th centuries, baleen whales were hunted for their oil and baleen. Their oil can be made into margarine and cooking oils. Baleen was used to stiffen corsets, as parasol ribs, and to crease paper.

Images for kids


Mysticeti Facts for Kids. Kiddle Encyclopedia.