Many examples of melanism are known among felines. Melanism is due to changes in the agouti gene which controls banding of black and light areas on the hair shaft. Leopards and jaguars with this condition are often called panthers or black panthers (although pumas are also known as panthers, there are no verified cases of melanism in that species). However, leopards, jaguars, lions and tigers are all members of the Panthera genus. One good example of melanism expressed within a certain animal community is that of the leopard population in Malaysia, South East Asia, in which case up to 50% of the population has melanism. That is one reason why black panthers are so commonly sighted in those rainforests. . Better resistance to viruses may also explain the greater prevalence of black leopards in those areas.