An opossum will eat side by side with a cat out of a dish of cat food that is left outside, and it will consider the cat food a gourmet meal. Opossums are rarely seen together, and except for breeding season or a female with her babies, it is a solitary animal. It fights only if attacked, surprised, or cornered, but prefers to run away or 'play possum,' which is said to be an involuntary reaction to danger. An opossum will hiss or growl and show its sharp teeth when frightened. The opossum mating season is from January to July.
Females have litters up to twice a year.
Litter size can be as many as 22, but only 12 can survive. The average litter is 5-9. At one week, they weigh .05 of an ounce. At 36 days, whiskers start to appear, and body hair becomes visible at 45 days. By the time they are 60-70 days old, they can weigh an ounce and may start to leave the pouch.