A liger is a cross between a male lion and a female tiger. The liger, like the tigon, is a zoo-bred hybrid created by mating a male tiger with a female lion. The liger and tigon have characteristics of both parents in varying quantities, but they are often larger than either. Male ligers and tigons are assumed to be sterile in the majority, if not all, cases. Females, on the other hand, may be able to bear children on rare occasions.  The words liger and tigon are a combination of the words lion and tiger. 

Ligers tend to be larger and heavier than members of their parent species. Biologists suggest that the liger’s large size, or “growth dysplasia,” results from the absence of certain growth-limiting genes. Female lions mate with several male lions throughout their lives, so the genes of a male lion are adapted to maximize the growth of his offspring, since his offspring may be required to compete with those of other males produced by the same lioness. The genes of female lions, however, are adapted to cancel or dampen the effects of the growth-maximizing genes of male lions, so lions remain within a given size range. Tigers, on the other hand, have no such competitive mating strategy, and many biologists argue that tigresses do not possess the growth-limiting adaptations of their lioness counterparts. As a result, the influence of the growth-maximizing adaptations provided by male lions is greater, which allows ligers to become larger than their parents. However, for tigons, growth-limiting genes are found in both male tigers and female lions, so their offspring possess an abundance of these genes, which accounts for their smaller size. As a result, the influence of male lions’ growth-maximizing adaptations is higher, allowing ligers to grow larger than their parents. Growth-limiting genes are found in both male and female tigers in tigons, therefore their offspring have an abundance of these genes, which explains their reduced size.

The largest ligers can reach lengths of more than 3.3 meters (10.8 feet) and weights of more than 400 kilograms (900 pounds); nevertheless, some individuals have been reported to weigh over 1,000 kilograms (1 metric ton [about 2,200 pounds]). Because both parents carry the growth-limiting genes, tigons likely to be the same size or smaller than their parents.

Although lions and tigers can mate in the wild, they are geographically and behaviorally isolated, and hence all known ligers are the result of unintentional mating between lions and tigers, as well as deliberate breeding efforts in captivity. The first known captive breeding of a lion and a tigress took place in the late 1700s. There are approximately 100 ligers and fewer than 100 tigons thought to exist. Many national governments and animal-rights organizations consider lion and tiger mating to be unethical because ligers are prone to birth defects that cause death soon after birth, as well as obesity and irregular growth that puts stress on their internal organs. Furthermore, ligers and tigons have difficulty communicating with members of their parents species because their behavioral features are generally a blend of both species’ habits rather than one or the other (see also animal social behaviour). Other opponents of liger breeding argue that ligers take up valuable zoo space that may be better used for endangered species habitat.