The Mediterranean monk seal male averages 2.4m in length and weighs approximately 315kg. Females are slightly smaller, weighing approximately 300kg. Adults are generally brown or grey on the back, and lighter on the belly. A white patch is common on the underside of the belly, and other irregular light patches are not uncommon. Older males tend to be black. Pups are born from 88-103cm in length and weigh 16-18kg.
Males and females are thought to reach sexual maturity between 5 and 6 years, although some females may mature as early as 4 years. Pups are born over much of the year although peak pupping occurs in September and October. Monk seal pups can swim and dive at about two weeks of age and are weaned at about 16-17 weeks. Monk seals are thought to forage in nearshore waters for fish and octopus. Individuals may live for 20-30 years in the wild.