The breeding cycle in the minke whale is believed to be an  annual event. Pregnancy has  been estimated to last 10 months and lactation is thought to last 4-6 months. Conception occurs when the whale is lactating in the warmer waters at low latitudes before migration occurs. Birth occurs after the whale has returned from its feeding grounds to the warmer waters once again. Sexual maturity usually occurs at the ages of 6-8 years in females and 5-8 years for males. 

The timing of conception and birth varies between region. 

In the North Atlantic conception takes place from December to May with a peak month of February  with birth taking place from October to March with a peak in December. 

In the North Pacific off Japan there appears  to be two phases of conception, the majority of which occurs from February to March but also from August to September, with births occurring from December to January and June to July. In the Yellow Sea stock these two phases have not been noted with conception occurring from July to September and birth peaking from May to June. 

In the Southern Hemisphere conception takes place from June to December with a peak in August and September. Peak birth time occurs from July to August.

The short lactation period  in minke whales usually means that the calves are weaned before they arrive on summer feedings grounds and as a result calves accompanying adult females are rarely documented. In 1994 Sea Life Surveys encountered a large minke whale which was accompanied by a smaller animal, believed to be its calf. This is shown in the photograph to the left. This encounter lasted for over an hour during which time the younger animal stayed close to the other whale. 

We often encounter many small minke whales throughout the summer season and we believe these animals to be less than a year old. These appear to be on their own but in many cases there is a much larger minke whale not far off. Maybe these large whales are the mothers. During one encounter, it was noted that a minke whale that hovered by the vessel was only about 12 feet in length. Surprisingly this was during the month of September. Just a few moments after we left this tiny whale we encountered a very large minke  whale and interestingly this whale did exactly the same behaviour around the vessel as the tiny whale.


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