Handedness in whales

From: Phil Clapham (phillip.clapham@noaa.gov)
Date: Thu Oct 11 2001 - 13:45:53 EDT


Hi:

> What makes a whale right-handed or left-handed? How did you find out? What
> behaviors does a right-handed whale display? What does the whale use its
> flipper for besides a paddle?
Well, strictly of course whales aren't "handed", but they do show what
we call "lateralized behaviors" - lateralized just means biased towards
one side. This is going to be more of an explanation than you asked for
but here goes...

For a very long time many scientists believed that truly lateralized
behaviors such as handedness were only found in humans (this relates to
theories about the development of the human brain, and the idea that the
two halves of the brain have different specializations - they control
different behaviors, like language, which is controlled by the brain's
left-side).

The question is whether other animals show lateralized behaviors at THE
POPULATION LEVEL. In humans, handedness is about 80% biased to the
right, and this has been true in all cultures and across history (and
even prehistory, if you look at certain things in prehistoric art).
years ago some scientists took a bunch of mice and had them press a
lever to get food, and found that half the mice used their left paw,
half their right. So they took all the lef-pawed mice and bred them
together, then took all the left-pawed mice from their kids and bred
them together again... and kept doing this for several generations. In
the last batch/generation, they ended up with a bunch of mice (who at
that point were probably pretty stupid from so much inbreeding!) who
were still half left- and half right-pawed. The interpretation? The
paw a mouse uses is determined by chance, and then just reinforced by
use. In other words, this isn't a population-level asymmetry in
behavior the way handedness is in humans.

With humpback whales, we first noticed this in scarring on their jaws.
Many humpbacks go down to the sea floor and scare up sand lance (a small
fish that hides in the sand). When they do this, they seem to turn on
one side and brush their jaw along the bottom, and in doing so they get
scratches and scrapes. We noticed that in most of the whales the scars
were on the right jaw. Since we know the individuals and see the same
whales come back year after year, we were able to look through photos
from previous years. And we found two things: 1) 80% of whales had the
scarring on the right jaw; and 2) that the same individuals ALWAYS had
the scarring on the same side - it never changed sides.

this got me looking at other behaviors where there might be a bias
towards one side. Sure enough, humpbacks use their right flippers much
more in displays (when they slap them down on the surface) than their
left. There is also a bias in what we call tail breaches - where the
animal throws its back end out of the water to one side.

So humpback whales seem to have a population-level asymmetry in certain
behaviors, which corresponds very well with the percentage for right
handedness in humans.

Now you can have fun translating this into age-appropriate language for
your kids!

> >From Jehane and Tim: Does baleen grow back if it breaks? If the baleen did
> not grow back, would the whale starve?
Baleen grows constantly, so yes, it would grow back if it broke. But
the growth is slow - like your fingernails.
 
> >From Samantha and George: What was the most exciting discovery, in your
> opinion, ever made about whales?
O lord, that's quite a question! The fact that humpback whales sing is
a very big deal; this was a discovery made in 1971. Also the fact that
blue whale voices can be heard over hundreds of miles or more is pretty
amazing.

-- 
The Society for Marine Mammalogy will be holding its 14th Biennial
Conference from 28 November to 3 December 2001, in Vancouver, BC.  Visit
the conference Web site at www.smmconference.org for full details of
this important meeting.

Phillip J. Clapham, Ph.D. Large Whale Biology Program Protected Species Branch Northeast Fisheries Science Center 166 Water Street Woods Hole, MA 02543, U.S.A.

tel. 508 495-2316 fax 508 495-2066 email: phillip.clapham@noaa.gov



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