Beavers and porcupines enter the world as precocial young -- fully furred, with teeth erupted and eyes open. Beavers, one of the few mammals that mate for life, breed in February and 12 weeks later give birth to four or five young.
Porcupines have a much slower reproductive rate. After mating some time in October or November and a 210-day pregnancy, females give birth to a single porcupette.
Bobcats can breed throughout the year but most mating takes place in late winter. After a gestation period of 60 days, two to four kittens are born in the spring. Raccoons mate in January or February, and after a pregnancy of 63 days give birth to three to six pups.
White-tailed deer roam widely in search of mates from October through December during the rut. Gestation lasts 200 days and twins are typical when fawns are born in May or June.
And then there's the opossum, North America's only marsupial. They often mate two times a year, once in February and again in early summer. Just 13 days after mating as many as 13 honey bee-sized young are born. Litter size is limited by the 13 teats females have in their pouch. The tiny newborns are naked and blind, but they have well developed forelimbs with sharp claws. They scramble up the female's belly and into her pouch, where they attach themselves to one of her nipples. The tip of the nipple then swells and essentially locks each baby to the teat, where it remains for about 60 days. So though a 'possum pregnancy lasts just 13 days, it essentially continues in the external pouch for two more months.
Though hardly a comprehensive review of mammalian reproductive biology, this brief summary illustrates the diversity of strategies that larger mammals use to get a head start on the mating season.
Send questions and comments to Dr. Scott Shalaway, 2222 Fish Ridge Road, Cameron, WV 26033 or email sshala...@aol.com.