Subject: assorted whale questions

Mike Williamson (m.dalebout@auckland.ac.nz)
Thu, 18 Sep 1997 2:14:46 GMT+1200

Dear Shirley and the class, 

I'm glad the answers I was able to give you to your last set of questions were
worthwhile.

On the next set of questions.....

Bobby and Justin asked what the most common whale off of New Zealand
is that was hunted?

The whale that was hunted most by the early New Zealand shore whalers (1940's and 50's)
was the right whale, so called because it was slow and easy to catch, and floated
when dead which made it a lot easier to tow back to shore. So it was the 
'right' whale to hunt. The right whale however was quickly hunted almost to extinction
around New Zealand, and is only now making a slow comeback. Two small breeding populations
were recently discovered overwintering at New Zealand's subantarctic islands, but right whales are still
a very rare sight around the mainland. 
Once the whalers had killed off most of the right whales, they moved to the faster humpback whales
which migrated along the west coast on their way to the Antarctic feeding grounds, and back again 
along the east to breeding grounds north of New Zealand. They were hunted at both their
feeding and breeding grounds too, and soon this species had been much reduced as well.
Like the right whale, humpback whales are now seen only very rarely around New Zealand coasts.
Sperm whales were also hunted around New Zealand by the early pelagic whaling ships in the 1960's.
Quite a number were caught, but luckily sperm whales are still found around New Zealand today. Many 
young bachelor bulls can be found in the Kaikoura canyon area off the east coast of the South Island in 
the summer where they are the focus of a quite intense whale-watching industry. 
So, in answer to your question I'd have to say that of the species of whales that were hunted around New
Zealand, the sperm whale is the only one to still be found in some number  in this area.

My last answer also answers Kaitlinn, Natalie and Maddy's question as to what the most common 
whale off of New Zealand is now (ie hunted or not). Still the sperm whale I'd say, although other species of whales
like the Bryde's whale are now being found in small numbers around the North Island in the 
summer, but we just don't know enough about them to determine how many there are.
Note that many species of dolphins are found around New Zealand too, and often in quite large numbers,
especially the dusky dolphin, the bottlenose dolphin and the common dolphin.

Adam, Rob and Eric ask ' How often do you find two whales that are related?'
Well, this depends on the species and their social structure. Some species appear to
live in tightly structured groups, such that  in a small area you may find several 
quite distinct populations which don't really mingle much with each other. Other species have a far looser
social structure or mix with other groups a lot more, which can mean that even over a large area you find that
most individuals are related to a degree. 
Remember though that at this stage of my research the level of 'relatedness' that I am looking
at is on the scale of millions of years or at the least a several thousand years. I'm still trying to figure out how
all those different species of beaked whales are related to each other, to try to discover how different morphological
features, feeding strategies and so on evolved in this group. Some day I hope to look at population-level 
relationships too, but I think this is still a few years off. 

Toby and Sam asked, 'How big is the tooth of a dolphin?'
This again depends on the species and there is quite a range. The killer whale for example, which belongs
to the family Delphinidae, is the largest of largest of all the dolphins and has teeth to match. In adults the
teeth may be as much as 12cm (almost 5 inches) long but only the last third emerges from the gum.
Adult killer whales have 10-13 (usually 11) of these teeth on each side of both jaws.
On the other end of the scale, the Hector's dolphin, which is one of the smallest of all cetaceans (individuals
are usually less than 4 3/4 feet long) have tiny teeth, less than a centimeter long, 52-64 on each side of both jaws.

And finally, Torie and Liz ask, 'How much does baleen weigh?'
Baleen is made of keratin, the same material as our hair and nails or the horns of a cow, and so is quite light.
The structure of the baleen plates also minimises their weight and maximises strength. Each plate consists of 
a dense cortical layer of keratin surrounding three or four layers of horny tubes. Bone is structured in much the 
same way. Right whales have the longest baleen, with plates about 10 feet long on average.  Rorqual whales 
have much shorter baleen. For example the baleen of humpback whales is about 2 1/2 feet long, 
and blue whale baleen is about 3 1/4 feet. Each baleen whale carries about  200-400 of these baleen plates in 
its mouth.


Hope that answers your questions. 

cheers

merel


***********************************
Ms. Merel Dalebout
Ecology & Evolution Research Group
Thomas Building, Level 1
School of Biological Sciences
University of Auckland
Private Bag 92-019
Wellesley Street
Auckland, N.Z.
Ph:09-373-7599 ext. 4588
Fax: 09-373-7417
e-mail: m.dalebout@auckland.ac.nz