10 Facts You Didn't Know About Pygmy Blue Whales
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 the answers here too!
1. How many different types of blue whale are there?
The jury is still out as to how many different subspecies of blue whale there are. Currently there are thought to be up to five:
- the North Atlantic/Pacific blue whale (Balaenoptera musculus musculus)
- the Northern Indian blue whale (Balaenoptera musculus indica)
- the Antarctic blue whale (Balaenoptera musculus intermedia)
- the pygmy blue whale (Balaenoptera musculus brevicauda)
- the Chilean blue whale (Balaenoptera musculus unnamed)
2. When was the pygmy blue whale discovered?
In 1966, records and observations of differences with other blue whales led to the confirmation of the pygmy blue whale as a separate subspecies.
3. 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!
4. 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). True to their name, pygmy blue whales are slightly smaller, growing to around 24m 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!
5. 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.
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!
6. 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.
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. Researchers have confirmed a valuable feeding ground for the pygmy blue whales in the South Taranaki Bight.
8. What are the threats to the pygmy blue whales?
Just like Bryde’s whales, these guys are not exempt from human impacts including 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. Its skeleton is now at Te Papa in Wellington and is one of the museum’s most famous display features.
The Hauraki Gulf Transit Protocol was established in 2013 by The University of Auckland in collaboration with Ports of Auckland, the shipping industry and the Department of Conservation. It is designed to reduce the ship strike rate of the resident Bryde’s whales in the Gulf, as well as other large whale visitors.
9. How many pygmy blue whales are in New Zealand and do they migrate?
The 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. They are also showing signs of presence in our waters year-round.
Researchers at Oregon State University have determined this by three 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.
10) When do we see blue whales in the Hauraki Gulf?
Pygmy blue whales are visitors to the Hauraki Gulf. Before 2017, we had only had a handful of sightings of these whales. Since 2018, we have sighted them every winter. Sightings can occur anywhere between May and November.
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