Steven Grant, age 11, of Topton, North Carolina, for his questian:
Why are bate opossums so small?
Some people insist that the opossum is a dope with hardly enough sense to take care of himself. Actually his family has survived successfully through millions of years, while many other species became extinct. There are two reasons for this success story. One is the opossum's cautious, peace loving character. The other is something to do with those very tiny opossum babies.
People who think the opossum is stupid may never have met him on friendly terms. Or perhaps they judge him by their own ideas of what is smart. A handsome opossum named Gerald happens to live in a little den, way back in Andy's garden. Every evening at 8 he comes to the patio where he finds a paper plate of meat scraps, fruit and vegetables. He dines slowly, using his 50 sharp teeth to chew every bite, and washing his dainty hands after each course. He saves the fruit until last.
Gerald does all this slowly, while cautiously glancing around. When a sound or shadow seems suspicious, he disappears into the shrubbery. However, he is polite and friendly to polite and friendly visitors. Like all opossums he is a devout pacifist. Some things scare him, though he never gets angry and he tries not to stir up anger in other animals.
His gentle, non aggressive character keeps the oppossum out of trouble and helped his family to survive through more than 60 million years. During this time, saber toothed tigers and dozens of other more aggressive species became extinct. He may also survive the age of pollution better than most living species. This is because he produces large families of very tiny babies.
His long success story dates back to ancient times when many of the mammals were marsupials, like the pouched kangaroos of Australia. These animals bear tiny, immature babies and incubate them in the mother's pouch. Mrs. Opossum may bear a litter of 20 bee sized babies, weighing about two grams apiece. The infants are blind and naked. But they know enough to scramble through her fur and creep into her pouch.
She has only 12 or 13 milk pouches, so the late comers of the litter get nothing. In a week, the successful ones gain about 20 grams apiece. In two months, they are as big as mice and eager to poke out their furry little white faces for a look at the world. Soon they enjoy rides on mother's back, clinging to her thick fur for dear life. Later they toddle along behind her. At the age of three or four months, they go off to live their separate lives.
A mother opossum bears one litter a year and in the Southern states she may bear two. As a rule, seven, eight or nine in each brood survive and become adults. This multiplication is one reason why the opossum's survival record is so successful.
A very successful animal has little reason to change to keep pace with the times. This may be why the opossum remained a marsupial, long after other marsupials became extinct through most of the world. And all marsupials bear immature little babies which are incubated in the mother's pouch. In this matter, our opossum is a relic from the remote past.