Pygmy Blue Whale Facts – 8 of Your Questions, Answered
13 Aug 2018

Pygmy Blue Whale Facts – 8 of Your Questions, Answered

We have had lots of questions from our passengers about the pygmy blue whales that we have been seeing on our whale watching trips so, we thought we would share those questions and answers here too!

 

1) How many different types of blue whale are there?

There are at least 3 different subspecies of blue whale that can found around the world:

- the North Atlantic/Pacific blue whale (Balaenoptera musculus musculus)
           - IUCN Status: Not yet assessed
           - Range: found in the North Atlantic and North Pacific oceans

- the Antarctic/’true’ blue whale (Balaenoptera musculus intermedia)
           -  IUCN Status: Critically Endangered
           -  Range: Antarctic waters during summer, winter distribution not yet understood

 

- the pygmy blue whale (Balaenoptera musculus brevicauda)
          - IUCN Status: Data Deficient
          - Range: temperate and Sub-Antarctic waters

There is debate on whether there is a fourth subspecies, the Chilean blue whale (Balaenoptera musculus indica).

 

2) Where does the pygmy blue whale live?

Pygmy blue whales are seen in the Southern Hemisphere mainly in the Indian Ocean such as off the coast of Sri Lanka. Research has expanded the knowledge of that range in recent years to other areas including Indonesia, Philippines, Australia and of course, right here in New Zealand!

3) Pygmy blue whale vs true blue whale  – what’s the difference?

Physical comparison

The Antarctic or ‘true’ blue whale can grow up to 33m in length and weigh up to 200 tonnes (which is about 30-40 African elephants!). The pygmy blue whales, true to their name are slightly smaller, growing to a maximum length of 27m and weighing up to 90 tonnes (so about half that of the Antarctic blue whale).

 

Observation

In the field it is slightly harder to tell the two apart as a juvenile true blue whale could be mistaken for a fully grown pygmy blue whale! So, we rely on the knowledge and research of the two species here in New Zealand to determine which one we are looking at - more on this later on!

4) Pygmy blue whale vs Bryde’s whale – what’s the difference?

Physical comparison

Compared to the pygmy blue whale, the Bryde’s whale is smaller growing to a maximum length of 15m and weighing up 40 tonnes. Bryde’s whales have 3 longitudinal ridges running parallel down the head whereas other whales do not.

 

A Bryde's whale showing it's 3 ridges on the top of the head

Observation

In the field it is much easier to tell the two apart, not only because of the difference in maximum lengths but also through other clues including: their surfacing behaviour, size of the blow, dive time, swim speed, colouration and shape of their dorsal fin. In addition, Bryde’s whales are resident to the Hauraki Gulf and we have been observing them regularly for the past 18 years so we definitely know when we are watching a different whale species!

5)  What is the life cycle of the pygmy blue whale?

Sexual maturity is thought to be between 5-15 years and whilst the lifespan is unknown, it is estimated that it would be likely similar to Antarctic blue whales which is 70-90 years.

Mother and calf Bryde's whale

 

6) How many pygmy blue whales are in New Zealand?

Latest research suggests there are approximately 718 individuals living around New Zealand. We are proud to have played a small part in this research by contributing our data and photos to the researchers.

7) Do pygmy blue whales migrate?

Some populations of blue whales migrate but research on the pygmy blue whales here in New Zealand are not showing signs of migrating.  

 

Researchers at Oregon State University have determined this by 3 methods:

Hydrophones – pygmy blue whale calls were recorded on the underwater hydrophones throughout the year. If the population is migratory then researchers would expect to only hear them at certain times of the year.

 

Photo-ID – dorsal fin photos used to identify individuals showed that certain individuals were being seen throughout the year in different areas of the country. To further support the idea of a non-migratory population, the researchers compared their dorsal fin photos of individuals to dorsal fin photos of whales in Australia and Antarctica but did not find any matches.

 

DNA sampling/genetic testing – skin samples compared to those in Australia and Antarctica showed there wasn’t much genetic similarity to New Zealand whales suggesting that the whales found here may not mix with other populations.

 

The indication that these pygmy blue whales don't migrate means that we could see them on our trips at any time during the year!

7) What is the pygmy blue whale’s diet?

They feed almost exclusively on krill but can also eat plankton which is what they have been feeding on here in the Hauraki Gulf. A valuable feeding ground has been confirmed by researchers for the pygmy blue whales in the South Taranaki Bight.

 

8) Are there any threats to the pygmy blue whales?

Just like Bryde’s whales, these guys are not exempt from being struck by ships, In 1994, one was carried into the Hauraki Gulf on the bow of a container ship. The whale was towed to Motutapu Island and flensed. It’s bones are now at Te Papa and is one of their most famous display features.

 

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