We're going to be talking about some of the
more detailed analyses that we've done with
faunal samples from archaeological sites.
We're going to be looking at the breeding
distribution of Northern fur seals.
And we're also going to be looking at an example
of sea otters and trying to determine what
the genetic diversity of their population
was before genetic harvesting began.
Fur seals have been studied really really
intensively for about the past two hundred
years.
There was a very lucrative, very important
commercial harvest of their furs
and because of that there was a lot of very
detailed scientific studies determining where
they lived, what their breeding distribution
was.
Prior to the 1950's, they were only known
to be breeding in extremely remote islands
in the Central Bering Sea, in the Pribilof
Islands and then also in the Russian Far East
in a group of Islands called the Kuril Islands
and the Commander Islands which are an extension
of the Aleutian Island Chain.
In 1980 a new breeding colony was discovered,
it was newly formed and it was found in the
eastern Aleutians.
And in 1968, way down in Southern California
in the Channel Islands, a breeding colony
was discovered there, that had established
itself naturally.
After that archaeologists started to notice
that there were fur seal bones,
abundant fur seal bones in archaeological
sites along the west coast of the United States.
The next step to trying to figure out what
the historical breeding distribution was,
was to actually get fairly precise age estimates
for the bones of these seals.
The process is simply going through and measuring
as many complete bones as possible from archaeological
sites up and down the coast.
And what we found is that there is solid evidence
of rookeries or breeding colonies somewhere
near the Washington coast,
perhaps on the West coast of Vancouver Island.
But then there also is suggestion of extinct
rookeries on the Oregon Coast and on the Central
California coast
and potentially also in the Aleutian Islands
where there had never historically been reported
any breeding colonies before.
And today I'm at the Seattle aquarium.
And I'm meeting with Shawn Larson who is a
conservation biologist.
Shawn could you tell us a little about what
you do here at the aquarium.
Sure Mike, I'm the curator of conservation
research here at the Seattle Aquarium.
I study genetics and endocrinology of many
different species here at the aquarium, as
well as ecology.
But one of my primary research projects is
on sea otter genetics.
And we started this project by looking at
modern sea otter genetics and found that they
have relatively low genetic diversity compared
to other mammals.
And that led us to ask the question, Was that
always the case in sea otters or was this
something that was caused by past hunting,
extirpations that we know occurred during
the fur trade that began in 1741 and ended
in 1911.
So what was your approach to try to figure
that out?
How do you get samples from extinct animals?
What we did know is that in native American
midden remains there are a lot of marine mammal
bones.
You found out.
Right
And so we contacted you and asked you if there
was any sea otter bones out in the McCaw midden
remains.
And my answer was yes there are.
Yes
So Shawn we've got some bone samples here
and I was hoping you could talk a little bit
about how you took the samples from the ancient
midden samples that we analyzed.
So we are looking at long bones, and then
we would drill a little piece of the bone
and out of that bone dust we were able to
extract, the ancient DNA.
And what we found, based on the samples that
we got from the McCaw midden remains is that
sea otters that lived at least 400-600 years
prior to today, had twice the genetic diversity
of sea otters that exist today.
Wow, that's a lot.
Yeah
Sea otters and fur seals were hunted extensively
for the fur, during the fur trade that started
in 1741 and ended in 1911.
And the reason why it ended in 1911 was because
of the International Fur Seal Treaty.
The commercial harvest of fur seals led to
a complete population decline that was really
catastrophic.
They were down to a few hundred thousand individuals,
down from an original population level of
two and a half to three million animals.
Just in the Pribilof Islands.
And recently their population has been through
another steady decline and so there is concern
that the overall population levels are getting
dangerously low.
Right, very similar to sea otters.
They thought there was about 150,000 throughout
their whole range and after the fur trade
there was maybe 1000 animals
from Japan, the Aleutian chain and all along
the West coast of the United States they remained
absent except for that small little population
off of California.
When they discovered that population off of
California in the 30's it was like they discovered
dinosaurs because they thought sea otters
were extinct.
So then to link the two studies that we've
talked about in this session back to fur seals
and sea otters,
the archaeological record shows that not too
long ago both fur seals and sea otters had
pretty different characteristics, their overall
populations in terms of genetic diversity
and their geographic range.
Whereas today most people don't even know
what a Northern fur seal is, they used to
be one of the most abundant animals on the
pacific coast.
That's why we are really interested in using
these archaeological samples to understand
how the past was different from where we are
today.
And how that is mostly a consequence of the
commercial harvests that were going on in
the 19th and early 20th centuries.
As the climate is warming, and there are very
few people who deny that it is warming anymore.
The glaciers are going to be melting, the
ice caps are going to be melting, sea water
is going to be expanding just as a function
of becoming warmer, and that's going to lead
to sea level rise.
I've seen along the coast spectacular archaeological
sites, just incredible places that are such
unique repositories of data, you know they
just exist no where else.
Yes we have large samples already excavated
from some fairly important sites but there
are many many more that have not been examined.
I think that there is the potential for a
lot of information in those sites that exist
no where else.
This is what is called a sediment peel.
It is an epoxy impregnated section from a
real live midden site.
There are tools that are found in there, there's
the refuse from the meals.
There is raw material for making new tools.
There's all manner of stuff packed into these
deposits.
And the archaeologist's job is to figure out
what all that means.
.
