The Kangaroo is a common marsupial from the islands of Australia and New Guinea. 
There are 47 species of "roos." Kangaroos can hop up to 40 miles per hour (74 kph) 
and go over 30 feet (9 m) in one hop. 
Roos and wallabies range in size from 2 pounds (the Rock Wallaby) up to 6 ft and 300 pounds (the Red Kangaroo). 
The soft, woolly fur can be blue, grey, red, black, yellow or brown, depending on the species. 
Most roos are nocturnal (active at night). 
Many roos are in danger of extinction, but are also considered pests due to crop damage. 

An adult male is called a buck, boomer or jack. 
An adult female is called a doe, flyer, roo, or jill. 
A baby is called a joey. A group of roos is called a mob. 
In a fully mature kangaroo population, females outnumber males 5 to 1. 

A newborn kangaroo is even more helpless than a human infant. 
Blind and the size of a honeybee, the newborn joey is essentially a fetus, 
still enclosed in a baglike amnion. The tiny creature bursts out of the amnion 
and immediately "swims" through its mother's fur to reach the pouch. 
In just three minutes, it disappears over the lip of the pouch. 
To find its way, the joey uses its sense of smell and built-in gravity receptors 
(located in the middle ear) the only two senses that are functional at this point.
When it finds a nipple, the joey latches on and stays physically fused for 4 to 5 weeks. 
Usually the newborn is alone, twins are extremely rare in most macropods. 
But while a newborn is attached, an older sibling that has left the pouch and is not 
yet weaned may poke its head in to feed. 
Each of the offspring feeds only from its own individual teat, and the two teats each 
supply different mixes of nutrients depending on the age of the young.
At about 150 days the joey starts poking it's head out of the pouch 
and starts to nibble at the grass.
40 to 50 days later the joey starts making short journeys away from 
it's mother.
Although not fully weaned until a year old, the joey permanently leaves 
the pouch at about 240 days old.

These herbivores (plant-eaters) eat grass, leaves, and roots. 
Roos need little water, going for months without drinking, sometimes digging their own water wells.