Lions have also been known to breed with their close counterparts, tigers (most often Siberian), while in captivity to create interesting mixes. These two new breeds are called ligers and tigons. The liger originates from mating a male lion and a tigress. Because the lion passes on a growth-prompting gene, but the corresponding growth inhibiting gene from the female lion is not present, ligers are larger than either parent. It is said that ligers do not stop growing and will grow constantly through their lifespan, until their bodies cannot sustain their huge size any longer, reaching up to half a tonne. Ligers share some qualities of both their parents (spots and stripes) however they enjoy swimming, a purely tiger activity, and they are always a sandy colour like the lion. Male ligers are sterile, but female ligers are often fertile.