Which mammal is the best known example of playing dead?

Apparent death, colloquially known as playing dead, feigning death, or playing possum, is a behavior in which animals take on the appearance of being dead. This form of animal deception is an adaptive behavior also known as tonic immobility or thanatosis. Apparent death can be used as a defense mechanism or as a form of aggressive mimicry, and occurs in a wide range of animals.

In mammals, the Virginia opossum is perhaps the best known example of defensive thanatosis. "Playing possum" is an idiomatic phrase which means "pretending to be dead". It comes from a characteristic of the Virginia opossum, which is famous for pretending to be dead when threatened. This instinct does not always pay off in the modern world; for example, opossums scavenging roadkill may use it in response to the threat posed by oncoming traffic, and subsequently end up as roadkill themselves.

The Virginia opossum (Didelphis virginiana), commonly known as the North American opossum, is the only marsupial found north of Mexico. In the United States, the animal is typically referred to simply as a possum. It is a solitary and nocturnal animal about the size of a domestic cat. It is a successful opportunist. It is familiar to many North Americans as it is often seen near towns, rummaging through garbage cans, and can become a nuisance.