Read the following text and answer the questions.

    Living in the grasslands, scrub, and open woodlands of sub-Saharan Mrica, the lion is the second largest cat in the world. It is dwarfed slightly by the tiger, which is closely related and has a very similar body type.

    Unlike other cats, lions are very social animals. They live in groups, called prides, of around 30 lions. A pride consists of up to three males, a dozen related females, and their young. The size of the pride is determined by the availability of food and water. If resources are scarce, the pride becomes smaller.

    Pride members keep track of one another by roaring. Both males and females have a very powerful roar that can be heard up to 8 km (5 mi.) away.

    Lions usually hunt at night. Their prey includes antelopes, buffaloes, zebras, young elephants, rhinos, hippos, wild hogs, crocodiles and giraffes. But they also sometimes eat smaller prey like mice, birds, hares, lizards, and tortoises. They are not above stealing kills from other carnivores, like hyenas, wild dogs, cheetahs, and leopards, or scavenging spoiled meat.

How do lion keep track of one another?