Opossum
Diet

Opossums eat insects, rodents, birds, eggs, frogs, plants, fruits and grain. Some species may eat the skeletal remains of rodents and roadkill animals to fulfill their calcium requirements. In captivity, opossums will eat practically anything including dog and cat food, livestock fodder and discarded human food scraps and waste.

Many large opossums (Didelphini) are immune to the venom of rattlesnakes and pit vipers (Crotalinae) and regularly prey upon these snakes. This adaptation seems to be unique to the Didelphini, as their closest relative, the brown four-eyed opossum, is not immune to snake venom. Similar adaptations are seen in other small predatory mammals such as mongooses and hedgehogs. Didelphin opossums and crotaline vipers have been suggested to be in an evolutionary arms race. Some authors have suggested that this adaptation originally arose as a defense mechanism, allowing a rare reversal of an evolutionary arms race where the former prey has become the predator, whereas others have suggested it arose as a predatory adaptation given that it also occurs in other predatory mammals and does not occur in opossums that do not regularly eat other vertebrates. The fer-de-lance, one of the most venomous snakes in the New World, may have developed its highly potent venom as a means to prey on or a defense mechanism against large opossums.
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