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Blog: Whale tales

Paul Chai journeyed up the NSW coastline during the 2012 whale migrating season. Recount his trip.


Whale Life Cycle

Whales are remarkably diverse creatures with Baleen Whales and Toothed Whales experiencing very different life histories.  Life cycles can vary quite dramatically species to species, but roughly divided, most life cycles can be split into the three stages of Baby, Adolescent  and Adult.  The duration of each stage varies substantially according to the species– and there are even species we know very little about!

Baby whales

Baby whales are called calves. The gestation period in most whale species is 11 to 16 months. Generally a single young is born, tail first likely in order to prevent drowning, and twins are very rare. The newborn calf is usually one-quarter to a third the length of the mother.

The ‘baby’ stage runs from birth until the calf is weaned, during which time the calf frequently nurses on the mother’s nutrient rich milk. Baleen whales will wean their calves by their first summer when they are less than a year old, while toothed whales take up to 3 years to be completely weaned. Calves grow very rapidly, thanks to the extremely high proportion of fat and proteins contained in whale milk.

Adolescent whales

The adolescent, or juvenile, stage runs from the moment the calf is weaned to when it reaches sexual maturity. Again, this varies according to the species.

Once weaned, juveniles start to mix with whales of the same age and gender. Male juvenile whales will form bachelor pods and leave their original pod. They will start searching for sexually mature cows, female whales, with whom to mate.

Female juveniles also start exploring outside their pod, but they are more likely to return to their matriarchal pod or to their mother.

Adult whales

The adult whale stage starts when the whale reaches sexual maturity. This can occur between the ages of 6 and 13 years, varying dramatically depending on the species.

Breeding often takes place seasonally in migrating species but in others it seems to occur through most of the year. In the adult stage, whales of both genders start searching for mates with whom to breed.

Sexually mature whales migrate to warmer waters during winter to mate. This ensures that when they return the next year, their calves will be born in more temperate conditions. Mating takes place every two to three years for the cow as her gestation period lasts for between 10 and 14 months. 

Some whales, like Humpbacks can theoretically produce one calf each year, with a gestation period of 11-12 months, but this rarely ever happens as it would strain the mother too much to calve every year.

  • NSW National Parks & Wildlife Service
  • NSW