Transcript Document

RATS!
Rachel Fewster
Steven Miller
James Russell
Hamish MacInnes
Department of Statistics
University of Auckland
Hauraki Gulf islands in the last year
Our research at the
University of Auckland:
1.
Put
a
rat
invader
on
Our aim is to
an uninhabited island
understand rat and study its
movement &
behaviour
invasion,
to protect
sanctuary
islands
2. Use genetics to
study current and
historic movement
between islands
1. Put a rat on an island and
see what happens...
• Study led by Mick Clout (UoA)
and Dave Towns (DoC)
• …with unsuspecting PhD
student James Russell…
• Controlled releases of lone
rats on small islands
1. Put a rat on an island and
see what happens...
Noises
Islands
Rangitoto
Motutapu
1. Put a rat on an island and
Rat ‘Razza’
see what
happens...
Noises
released on
Motuhoropapa
Islands
After a month, tried to catch him again...
1. Put
a
rat
on
an
island
and
Razza dropped
see what
happens...
his tag
and
Noises
swam 400m to
Otata...
James caught up
with him two
months later, but
by boat...
Islands
Bad news for
us, but 100
newspapers
worldwide
loved the
story...
New York Times Oct 2005
… and Razza
still lives on!
Our research at the
Closely related
University of Auckland: rats mean lots
2. Use genetics to see
how much movement
there is between
different islands
of swimmers.
Unrelated rats
mean isolation.
What do genetics look like?
Fitzroy region,
Aotea / Great
Barrier Island
20
30
%var: PC1=0.68; PC2=0.15; Tot=0.83
-10
0
10
Nel
NelNel
Nel
Nel
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Nel
Kai KaiKai
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Kai Kai
KaiKai
KaiKai Kai
KaiKai Kai
Kai
Kai
Nel
Haku
Kai Kai
Kai Kai
Kai
Fit
Kai
Haku
Kai
Haku
Fit
FitFit Kai
Kai
Kai
Haku
Kai
Kai
Haku
KaiKai
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Fit
Kai
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Haku
HakuHaku
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Fit Kai Kai
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Haku
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Haku
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FitKai Fit
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Haku
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Haku
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Motu Kaikoura
Fitzroy
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40
Fitzroy
Each
point
is
one
Fitzroy
region,
Motu
Kaikoura
Look for:
Aotea / Great
rat;
Overlap: closely related Barrier Island
Each colour is a
populations
different island
20
30
Separation: isolated
populations
%var: PC1=0.68; PC2=0.15; Tot=0.83
-10
0
10
Nel
NelNel
Nel
Nel
NelNelNel
Nel
Kai KaiKai
Kai
Nel
Kai Kai
KaiKai
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KaiKai Kai
Kai
Kai
Nel
Haku
Kai Kai
Kai Kai
Kai
Fit
Kai
Haku
Kai
Haku
Fit
FitFit Kai
Kai
Kai
Haku
Kai
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Haku
KaiKai
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Kai
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Haku
HakuHaku
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Fit Kai Kai
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FitKai Fit
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Haku
Haku
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Haku
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Genetic results
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0
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40
Haku
Kai
Fit
Nel
20
30
%var: PC1=0.68; PC2=0.15; Tot=0.83
-10
0
10
Nel
NelNel
Nel
Nel
NelNelNel
Nel
Kai KaiKai
Kai
Nel
Kai Kai
KaiKai
KaiKai Kai
KaiKai Kai
Kai
Kai
Nel
Haku
Kai Kai
Kai Kai
Kai
Fit
Kai
Haku
Kai
Haku
Fit
FitFit Kai
Kai
Kai
Haku
Kai
Kai
Haku
KaiKai
Kai
Fit
Kai
Kai Fit
Haku
HakuHaku
Haku
Haku
Kai
Fit
Haku
Fit Kai Kai
Haku
Fit
Haku
Haku
Haku
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FitKai Fit
Haku
Fit
Haku
Haku
-30
-20
Haku
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0
10
20
30
40
Haku
Kai
Nel
Look for:
Overlap: closely related
populations
Separation: isolated
populations
Fit
Clear left-right divide:
is something
stopping the rats
from swimming this
small gap?
Cliffs at the
landing
points?
Or rat
sociology?
Kaikoura region
Mainland
Broken Islands
Broken Islands Results
Lots of overlap between
Rangiahua and Mahuki
Motutaiko separate
Broken Islands Results
One rat caught on the
mainland appears to have
come from the islands
Lots of overlap between
Rangiahua and Mahuki
Motutaiko separate
Real separation between islands and mainland
We see this pattern all over New Zealand:
No gap in genetics over
10s of km of mainland
We see this pattern all over New Zealand:
Then a short water
crossing…
We see this pattern all over New Zealand:
… and a clear gap.
We see this pattern all over New Zealand:
Ship Rats!
Reinvasion or failed eradication?
All three species
of rats were
By May 2006, there
eradicated from were 4 Norway rats
Pearl Island
in DID
HOW
and THEY
1 ship rat back
July 2005: GET THERE?
on the island…
Pearl Island, off Stewart Island
Reinvasion or failed eradication?
Survive the
eradication?
Reinvade from
Stewart Island?
HOW DID THEY
GET THERE?
Worst possible
news!
Better security
needed
Reinvasion or failed eradication?
250m
Norway Rats
Norways
are strong swimmers, but
Eradication
this planning
far south…?
10 rats caught on Pearl Island
after eradication, May-July 2006
12 rats caught on Pearl Island
before the eradication (July 2005)
9 rats caught on adjacent Stewart
Island
Reinvasion
response
Post-eradication
Norways all
grouped with
Stewart Island
rats: phew!
Ship rats
Ship rats are weaker swimmers, so
did some survive the eradication?
1 rat caught on Pearl Island after
eradication (May 2006)
11 rats caught on Pearl Island
before the eradication (July 2005)
8 rats caught on adjacent Stewart
Island
Ship rats
Ship rats
Theagain,
geneticthe
work
showed
Once
ship
rat DoC that their
eradication
procedures
Ship
is grouped
with
the ratshad not failed:
all rats
foundrats:
on Pearl Island were
Stewart
Island
reinvaders.
NOT a survivor!
HOW DID THEY
GET THERE?
THEY SWAM!
Conclusions
• Ship rats are weaker swimmers than
Norways
• We see genetic separation even over
small water crossings
• But we don’t know whether this is
because they don’t swim, or don’t breed
• Norway rats are strong swimmers, luckily
absent from Aotea
Thanks to our funders!