Name: Sei whale (Balaenoptera borealis)
Length: 16 – 20 m
Weight: 4 – 10 tonnes
The sei whale is a medium-sized species, with dark steely-grey body with irregular white markings along its ventral (under) side. Within their northern range, sei whales mate between November and February, giving birth after an 11 - 12 month gestation period to a single calf. However, research has shown that whereas females tended to give birth every other year, the reproductive rate in sei whales is steadily increasing – which may be due to the pressure caused by human hunting; changing rates in reproduction. These whales have been estimated to live to an age 70 years and are known for their incredible speed (up to 50 km/hr) and their shallow diving.