Unfortunately, although being part of a pride may help, lion cubs still face many challenges if they are to survive to adulthood. It is estimated that only one in five cubs reaches two years old. Initially, teething is painful and this weakens the cubs, causing many early deaths. Disease is an important factor in cub mortality, as is predation by other carnivores. A new male lion taking over a pride may kill cubs under a year. Cubs are at the bottom of the food chain, and a hungry mother will let her cubs starve if she cannot feed herself properly . Older cubs who cannot keep up with the pride get left behind and struggle to survive.