A happily expectant mother always is a cause for celebration. When the mother is one of the rarest mammals on the planet, it is a cause for resounding joy.

Emi, a Sumatran rhinoceros (Dicerorhinus sumatrensis) living at the Cincinnati Zoo and Botanical Garden, is pregnant. Rhinos are nearing extinction and the Sumatran rhino is one of the scarcest varieties of all. There are fewer than 300 of these marvelous creatures left on Earth.

They are only about half the size of their better known and more numerous cousins in Africa and India, and are covered with coarse, reddish hair. They live in the tropical forests of Malaysia and Indonesia, and in sanctuaries such as the zoo. It is estimated that 70 percent of the Sumatran rhino population has been lost since 1985 as its lush habitat is logged and as poachers kill them off for their horns.

Without places such as the Cincinnati Zoo, Emi's species doesn't have a chance of survival. Emi and her mate, Ipuh, are the only breeding pair of Sumatran rhinos in the United States. Her first calf, born two years ago, is now at the Los Angeles Zoo.

If all goes well, she should give birth again in about 400 days. When she does, the whole world should celebrate.