Name: Sei whale (Balaenoptera borealis)

Measurements
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.