Long-Lived Omnivores. Shriekbats live for nearly 50 years. They are social and promiscuous creatures that live in small groups in large caverns. They are omnivorous but prefer fresh meat to other food with lizards taking up the majority of their diet. Shriekbats can survive on rotten flesh, which allows them to eat ghouls and other undead populating the Underworld, but they find it less palatable.