A coat of a certain color could be costly for wild boars, according to new research. The research found that boars with more reddish hair tend to have higher levels of oxidative stress — damage that occurs as toxins from cell respiration build up. The reason for this, the researchers suggest, is that the process of producing reddish pigment eats up a valuable antioxidant that would otherwise be fighting the free radicals that lead to oxidative stress.