 In Darwin Harbor, mating occurs from January to March and birthing occurs in October and November following a gestation period of eight to nine months.In Shark Bay, mating occurs from late October to early November and birthing occurs around the same time the following year, following a gestation period of 11 months; this slower development likely reflects the cooler temperatures of Shark Bay.Females produce litters on an annual cycle in Darwin Harbor and on a biennial cycle in Shark Bay.