Although typically found feeding near to or on the sea-bed, the dusky shark will also readily hunt within the water column and at the surface, often following ships that dump food scraps into the water (1) (3). This species takes a variety of prey, including fish, sharks and rays, crustaceans, octopi, cuttlefish, squid, starfish, barnacles, whale meat, and occasional garbage (1). As a large and formidable predator, the mature dusky shark is rarely preyed upon by other animals, although smaller, younger specimens may fall victim to attacks by larger sharks, such as the bull shark (3).
Mating is believed to occur during the spring in the western Atlantic, while populations off the coast of Africa appear to be born throughout the year with a peak between April and June (3). Dusky shark embryos develop within the adult female’s uterus, receiving nourishment from a yolk sac and, later in development, from the mother via a structure similar to an umbilical cord and placenta (4). After an extensive gestation period, which may last as long as 16 months, a small litter of six to ten young are born, each measuring between 85 and 100 centimetres in length (2) (3). This dusky shark is among the slowest and latest-maturing of known sharks, with males becoming sexually mature when 2.79 metres in length, at around 19 years old, and females at 2.84 metres in length, at around 21 years old (1) (2). As a result of the long gestation period, dusky shark individuals usually reproduce only once every three years (2). After birth, the young congregate in very shallow coastal waters, where they are afforded some protection from larger sharks, while the adult females return to deeper waters (3).
In temperate and subtropical areas of the western Atlantic and eastern Pacific the dusky shark is highly migratory, travelling northwards during the warmer summer months and heading south again in the winter (1) (3).