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The animals called "roos" in Australia are most famous for their bounding gaits and the pouches in which the females carry babies. But they have another unique adaptation: When their teeth get too dull to grind up food efficiently, kangaroos simply grow new ones. Kangaroos use their teeth for cutting off and chewing the vegetation they eat and, when necessary, for defending themselves. Yes, their teeth are sharp.
Kangaroos' Teeth, Past and Present
Kangaroos are marsupials -- their babies are born in an underdeveloped state and spend the first months of their lives developing inside their mother's pouch. All marsupials are diprotodonts, a scientific term meaning "two first teeth." Humans have two incisors, or front teeth, in their upper jaws, but kangaroos have three pairs of incisors in their upper jaws and one pair in their lower jaw. Even though modern kangaroos are herbivores -- strict vegetarians -- their prehistoric ancestors were carnivorous and like other carnivores, had pointed side teeth, called canines, designed to help tear meat from prey animals. Today's kangaroos have big spaces in their mouths where the canines of their forebears used to be.
Kangaroos Sprout New Molars
The gaps in a kangaroo's mouth, called diastemas, separate the incisors from the molars, or grinding teeth, that extend to the back of the mouth on the upper and lower jaws. These gaps allow the roo's tongue more room to move food around inside the mouth and push it back to be ground up by the molars. The molars need sharp surfaces to do that job properly, but they get worn down quickly. When this happens, those closest to the front fall out, and the diastemas permit the others to move forward to take their place, leaving room at the back for new molars to grow. Kangaroos must chew their food thoroughly, because their two-part stomachs don't produce digestive enzymes to break them down. The sack-shaped front part, called the sacciform, contains many tiny organisms that ferment the well-chewed food and extract nutrients from it.
Those Teeth Are Made for Biting
When roos feel threatened or angry, they can use their sharp teeth to bite whoever is causing them distress. In the 1980s, during live filming of a television show in Cleveland, Killer Willard, a 5-year-old red kangaroo, gave viewers a real-life demonstration of what can happen if you get on the wrong side of one of these marsupials. At the time, Willard, decked out in boxing gloves, was 6 feet tall but not fully grown. He was harnessed to a line held by Tony, the male half of a couple who had been profiting from displaying Willard's pugilistic skills for more than two years. After the roo's patience snapped, he punched Tony hard in the face. Then, supporting his entire body with his tail, Willard booted him in the abdomen, sending him flying. From there, the enraged roo turned his attention to Tony's wife, pinning her to the floor and trying to bite her head, face and neck. Neither human was hurt but, in 2008, the video of Killer Willard standing up for himself went viral as soon as it hit the Internet.
But Wait There's More
Australians call an adult male kangaroo a buck, boomer or jack, and a female a doe, flyer or jill. A group of kangaroos, which can number two specimens to 100, is a mob. The red kangaroo, the world's largest marsupial, is capable of reaching speeds of close to 40 mph, covering up to 25 feet per hop. When on land, roos' hind legs function together only, not independently -- so they can't walk or move backwards. But for some reason, when in the water, these excellent swimmers are able to kick each leg independently. Moreover, if a roo is being pursued by another animal such as a dingo or domestic dog, he will often head for the nearest body of water, try to entice his pursuer in, then grab and try to drown the animal.
- Encyclopedia.com: Diprotodontia (Koala, Wombats, Possums, Wallabies, and Kangaroos)
- Billabong Sanctuary: Aussie Animals
- Outback Australia Travel Guide: Kangaroo Facts
- Queensland Government: Department of Environment and Heritage Protection: Kangaroos
- Animal Planet: Untamed and Uncut: Kangaroo Goes Berserk
- Amazing Australia: Kangaroo Attacks
- Mail Online: The Killer Kangaroos That Roamed Prehistoric Australia
- Mammal Anatomy: An Illustrated Guide: Excerpt: Marshall Cavendish, 2010
- Tom Brakefield/Stockbyte/Getty Images