A leopard's first concern isn't always food, most spend their time checking their territory for clues of other leopards. They cover many miles each day, checking trees, renewing scent and claw marks. The marked trees are like noticeboards and any leopard can add a message which can last for weeks. A female may also spray a more pungent and detailed signal, revealing if she's ready for a mate. Where leopards are rare, and in huge territories, this system of scent marking is a crucial way to pass on messages and communicate with other animals. A female with cubs under a year old is unlikely to be receptive to a male who wants to mate, but she must be careful, males have been known to kill cubs in order to get a female to come into season.