Movements of minke whales in the eastern North Pacific

There are some species of cetacean that are more difficult to study than others. The minke whale, for example, is a small, uncommon and normally solitary rorqual that lives in the eastern North Pacific. As a result of their size, abundance and behaviour, minkes are difficult to find and once observed, they often make a long dive and are not seen again. Not surprisingly, little is known of their natural history.

A rare view of a minke whale breaching off of northeastern Vancouver Island. Photo: JTowers

A rare view of a minke whale breaching off of northeastern Vancouver Island. Photo: JTowers

To learn more about this cryptic species, we at MERS undertook a photo-identification study of minke whales beginning in 2005. With some help from many colleagues up and down the coast we accumulated 405 encounters with minkes in Washington and British Columbia by 2012. The data we gathered included 6,990 identification photos. Over the first few years of the study a few things quickly became apparent when analyzing the images.

Red dots indicate the locations where minke whales were encountered between 2005 and 2012.

Red dots indicate the locations where minke whales were encountered between 2005 and 2012. CBC: Central British Columbia, NVI: Northern Vancouver Island, WVI: Western Vancouver Island, SVI: Southern Vancouver Island. Map: CMcMillan

First, encounters with minke whales occurred predominantly between spring and autumn. Despite our best efforts searching for minke whales in all the places that we found them during summer, we did not see any of these whales during the winter.

Seasonal distribution of all encounters with minke whales from 2005 to 2012 shown for each area.

Monthly distribution of all encounters with minke whales from 2005 to 2012 shown for each area. Graph: JTowers

Secondly, known individual minke whales could often be found in the same areas within and among years. These animals would spend long periods of time during summer in very localized regions of the coast. After an absence during winter they would return to the same regions the following year. Some animals were so predictable that we could often correctly guess where we would find them on certain days.

The number of encounters with minke whales, the number of individuals photo-identified and the number of new animals each year from 2005 to 2012 in the northern Vancouver Island area.

The number of encounters with minke whales, the number of individuals photo-identified and the number of new animals documented each year from 2005 to 2012 in the Northern Vancouver Island area. Graph: JTowers

Third, some of these very predictable animals showed up in other parts of the coast hundreds of kilometres to the south during spring or autumn. These relatively long-range intra-annual movements (up to 424 kilometres between encounter locations) are the furthest documented for this species in the Pacific Ocean! The patterns of these movements indicate not only that the minke whales we photo-identified have different seasonally preferred foraging ranges but also that they undertake seasonally-based long distance travels.

Green lines indicate northerly  travels of minke whales M002, M006 and M008 during spring. Orange lines indicate southerly travels of minke whales M003, M008 and M021 during autumn.

Green lines and arrows indicate northerly travels of minke whales M002, M006 and M008 during spring. Orange lines and arrows indicate southerly travels of minke whales M003, M008 and M021 during autumn. Map: CMcMillan

It is generally assumed that minke whales in the North Pacific migrate to higher latitudes in the spring to feed in cold waters during the summer and to lower latitudes in the autumn to breed in warm waters during the winter. However, several authorities refer to minke whales in coastal waters of the eastern North Pacific as resident or behaviourally distinct from migratory populations. Instead, based on the temporal distribution and movement data we collected from minke whales in these waters it can be inferred that they do indeed migrate.

M003 also known as Galaxy  in Queen Charlotte Strait off northeastern Vancouver Island during summer. Galaxy has also been observed in Washington state on several occasions during spring and autumn.

M003 also known as Galaxy in Queen Charlotte Strait off northeastern Vancouver Island during summer. Galaxy has also been observed in Washington state on several occasions during spring and autumn. Photo: JTowers

To find out more about the movements of minke whales in our coastal waters and other evidence that reveals where these animals may migrate to during winter check out our latest peer-reviewed article recently published online in the Journal of Cetacean Research and Management. It can also be found on the MERS site.

About MERS

We are a non-profit organization dedication to promoting conservation and understanding of marine ecosystems through scientific research and environmental education.
This entry was posted in Uncategorized. Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s