The Townsend's Chart.
Photo: Genevieve Johnson
February 25, 2002
Sperm whales roam the world's oceans ranging from the equatorial waters to the polar
regions, yet we still do not know much more than the nineteenth century
whalers did about their migration patterns.
Scientists do know that the large mature bulls travel to the lower latitudes
(equatorial waters) in search of females during a breeding season that can
last for up to six months. For the remainder of the year, the large males
head for the cool waters of both the North and South poles for reasons we
are yet to understand. We still have no idea as to whether the same males
make the long journey in search of females every year, every other year or
every five years.
The remaining whales comprising of mother/calf pairs, sub adult males and
yearlings divide themselves into various groups, whose combinations and
dynamics are still unclear. These animals appear to remain in the tropical
and subtropical regions throughout the year.
Scienctists have alot to learn about sperm whale and their migration habits.
As a result of our lack of specific knowledge about the location of sperm
whales in the oceans of the world, we use a combination of information to finally locate them using our
underwater acoustic array.
In looking for populations of sperm whales we examine the bathymetric
features on navigation charts, assess local information and knowledge from scientists as well
as fisherman in any given area, research the latest available scientific data of that particular region online,
however, our search usually begins by studying the
The Townsend charts are the result of a compilation of
whaling records and logbooks kept by the Yankee whalers and compiled by
Charles Haskins Townsend. The location of sperm whale kills by the whalers
from the period of 1761 to 1920 where compiled and plotted onto a global
map. Townsend analysed the records of 744 whaling vessels with a combined
effort of 1,665 voyages that accounted for the deaths of 36,908 sperm
whales. The global charts are covered in an array of colored dots, each
represents the position of a whaling ship on a day when one or more whales
were taken. The various colored dots represent whale kills during particular
months of the year. For example, solid green dots represent whales killed in
May, hollow blue dots are whales killed in June, solid blue dots are whales killed
in July and so on. By correlating the areas in which kills were made with
the months of the year, we are able to arrive in a particular area during a
certain season with an increased chance of finding sperm whales.
These charts show the traditional grounds worked by the Yankee whalers,
however, they do not necessarily reveal all of the locations sperm whales
may congregate and therefore can only be used as a general guide. It was not
known that there were sperm whales to be found off the coast of Sri Lanka
until Jonathon Gordon and Hal Whitehead surveyed the area in the early 1980's.
In addition, the Townsend charts did not reveal large numbers of sperm whales in the
Bismarck Sea in Papua New Guinea that the Odyssey came across.
The Odyssey crew spent six months
in that region in 2001, finding over 400 animals, including large bulls,
sub-adults and mother/calf pairs, potentially indicating this area may be a breeding
ground for sperm whales.
Also, there are no records at all on these charts of
sperm whales along the pacific rim from northern Japan across the Pacific Ocean
and down to northern California, an area where sperm whales were heavily
harvested by the Japanese and Soviet whalers. The reason for the absence of
kills in these regions may be explained in two ways, either the Yankee
whalers did not go to these areas or they went to these areas in the wrong
season to find whales.
Captain Rodrigo Olson and Judith Scott examine the Townend's charts.
Photo: Genevieve Johnson
The Townsend charts have been divided into two maps; map Aâ and Map B.
Map A represents kills from the beginning of April through to the end of
September, while map Bâ tells us where the Yankee whalers hunted during the
months of October through March. While working off the coast of Western
Australia, we have been using Map Bâ as a guide. So far, we have yet
to find whales where they should be according to the charts. However, we
have found them in other areas not indicated by Townsend, such as in the Perth
Canyon, 55 nautical miles west of Perth.
When the Odyssey crew concludes scientific research in Australian waters, we
will once again be utilizing the information on these charts to assist in
planning our route across the Indian Ocean. A lot of the data displayed on
the Townsend charts is over 200 years old.
By gathering information on
whales throughout our five year global expedition, we intend to contribute
significantly to what is currently known about their
distribution patterns in order to aid in the protection and conservation of these great creatures.
This is Chris Johnson of the Research Vessel Odyssey.
Log by Genevieve Johnson