The best adapted rabbits may be able to run faster from predators, digest their food more efficiently, have larger litters or grow coats that camouflage them better or more effectively reduce heat losses. These rabbits will survive longer and leave more offspring. If the offspring inherit the advantageous characteristics of their parents, they may give rise to a new race of faster, different coloured, thicker furred and more fertile rabbits, which gradually replace the original, less well-adapted varieties. The new variations are said to have survival value.