There are four species of hyenas: spotted hyenas, brown hyenas, striped hyenas, and aardwolves. They primarily live in Africa, with different species inhabiting parts of the Sahara desert, grasslands, and Southern Africa. Hyenas compete with lions for food resources, though hyenas outnumber lions in Africa. Hyenas have adaptations like strong jaws, long tongues, and warning calls that help them survive threats from other predators and find food. Their ancestors were smaller but evolved over time to become larger like modern hyenas.