Hawaiian monk seals are the only true seals to be found year-round in tropical waters. After the annual moult, this monk seal is a silvery grey colour on the back, with cream colouring on the throat, chest and underside. Over time the coat looks brown above and yellow below; males, and some females, turn almost black with age. Certain individuals may have a red or green tinge or spots due to algal growth. Pups measure about one metre at birth and have a silky black coat, which moults after around a month into the silvery adult-like fur.