RATS! Rachel Fewster Steven Miller James Russell Hamish MacInnes Department of Statistics University of Auckland.
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RATS!RATS!
Rachel FewsterSteven Miller
James RussellHamish MacInnes
Department of StatisticsUniversity of Auckland
Home, sweet home
Aotearoa New
Zealand is unique
Home, sweet home
... and under threat.
Aotearoa New
Zealand is unique
There are no native land mammals in
New Zealand.
POSSUMS
STOATS
CATS
GOATSFERRETS
MICE
RATS
DEER
PIGSHUMANS
Native birds can’t compete!
RATS are RATS are among the among the
worstworst
COMPETITION
PREDATION
HABITAT DESTRUCTIO
N
VANDALS!
THIEVES!
MURDERERS!
There are There are three rat three rat species in species in
New Zealand:New Zealand:
1. Ship rats: 1. Ship rats: Rattus rattusRattus rattus The Climbers The Climbers
2. Norway rats: 2. Norway rats: Rattus norvegicusRattus norvegicus The SwimmersThe Swimmers
3. Kiore (Pacific rat): 3. Kiore (Pacific rat): Rattus exulansRattus exulansThe first and The first and
smallestsmallest All three species
originate from Asia.
How to tell them apart?
First look at the foot:
Kiore have a brown diamond on the foot.
Then look at the tail:
• Ship rats have long tails for climbing!
• Norway rats have shorter tails, pale underneath.
• Ship rats are most common
• Norways are bigger but
less common
• Kiore are much
less common
All three species are present in the
Bay of Islands
Rats are everywhere in New Zealand
Even on islands
How do they get there?
1. Swimming
How do they get there?
They do it deliberately
2. Boat rides
How do they get there?
Moored boats are easy swimming targets
How do they get there?
3. Cling to driftwood
3. Cling to driftwood
How do they get there?
How do they get there?
4. ConspiracyOur aim is to understand rat movements,
for best protection of
sanctuary islands
Closely related rats mean lots of swimmers!Unrelated rats
mean isolation.
Our research at the University of Auckland:
Use genetics to see how much
movement there is between different
islands
If we eradicate rats on an island...and replace by threatened birds...will we get a reinvasion?
Basic idea: Populations that are isolated from each other have different genetics.
e.g. people in Germany...
...look different from people in Italy.
Same with rats:
• Are rats swimming between Are rats swimming between different islands?different islands?
RATSRATS
RATSRATS
RATSRATS
??
?
We might be able to tell from their genetics.
RATSRATS
RATSRATS
RATSRATS
?
??
If an island is truly
isolated…
RATSRATS
…the genetics of its rats may
differ from other islands.
Same with rats:
RATSRATS
RATSRATS
RATSRATS
??
?
If islands are linked by regular swimming…
…their genetics may be very similar.
Same with rats:
We use genetics to see how
much rats are swimming between islands.
First we had to catch
some rats....
The Fieldworker’s Problem
Fieldwork Rat: Rattus catchus
ifyoucanus
Catching rats….
…is not as easy as it sounds!
But even worse…
…there are some unwanted side effects…
So we asked DoC to catch some rats for us instead.
• 500 rats caught in total!• Norway rats hold the islands• Some ship rats and kiore on the islands• Ship rats hold the mainland
DNA from 300 Norway rats sent to the lab
DNA from 80 ship rats sent to the lab
These ship rats on Urupukapuka are new since the 1980s
Months of work for Hamish MacInnes, our lab scientist, to test the genetics of nearly 400 rats
We use the same lab techniques as the police use to solve murders with DNA evidence
What do genetic results look like?
We’ll use an example from Aotea, Great Barrier Island ...
FitzroyMotu
KaikouraFitzroy region, Great Barrier Island
-30 -20 -10 0 10 20 30 40
-30
-20
-10
010
2030
Kai
Kai
KaiKai
Kai
Kai
Kai
Kai
KaiKai
KaiKai
Kai
KaiKai
Kai
KaiKaiKai
KaiKai
Kai
Kai
KaiKai
KaiKai
Kai
Kai
KaiKai
KaiKaiKai
Kai
Kai
Kai
Kai Kai
Fit
FitFit
Fit
Fit
Fit
Fit
Fit
Fit
FitFitFit
HakuHaku
Haku
Haku
Haku
HakuHaku
Haku
Haku
Haku
Haku
Haku
Haku
HakuHakuHakuHakuHakuHakuHaku
Haku
Nel
Nel
NelNelNel
Nel
NelNelNel
NelNel
%var: PC1=0.68; PC2=0.15; Tot=0.83
FitzroyMotu
KaikouraFitzroy region, Great Barrier Island
-30 -20 -10 0 10 20 30 40
-30
-20
-10
010
2030
Kai
Kai
KaiKai
Kai
Kai
Kai
Kai
KaiKai
KaiKai
Kai
KaiKai
Kai
KaiKaiKai
KaiKai
Kai
Kai
KaiKai
KaiKai
Kai
Kai
KaiKai
KaiKaiKai
Kai
Kai
Kai
Kai Kai
Fit
FitFit
Fit
Fit
Fit
Fit
Fit
Fit
FitFitFit
HakuHaku
Haku
Haku
Haku
HakuHaku
Haku
Haku
Haku
Haku
Haku
Haku
HakuHakuHakuHakuHakuHakuHaku
Haku
Nel
Nel
NelNelNel
Nel
NelNelNel
NelNel
%var: PC1=0.68; PC2=0.15; Tot=0.83
Genetic results
Each point is one rat;
Each colour is a different
island
Look for:Overlap: closely related populationsSeparation: isolated populations
-30 -20 -10 0 10 20 30 40
-30
-20
-10
010
2030
Kai
Kai
KaiKai
Kai
Kai
Kai
Kai
KaiKai
KaiKai
Kai
KaiKai
Kai
KaiKaiKai
KaiKai
Kai
Kai
KaiKai
KaiKai
Kai
Kai
KaiKai
KaiKaiKai
Kai
Kai
Kai
Kai Kai
Fit
FitFit
Fit
Fit
Fit
Fit
Fit
Fit
FitFitFit
HakuHaku
Haku
Haku
Haku
HakuHaku
Haku
Haku
Haku
Haku
Haku
Haku
HakuHakuHakuHakuHakuHakuHaku
Haku
Nel
Nel
NelNelNel
Nel
NelNelNel
NelNel
%var: PC1=0.68; PC2=0.15; Tot=0.83
FitKai
Nel
Haku
-30 -20 -10 0 10 20 30 40
-30
-20
-10
010
2030
Kai
Kai
KaiKai
Kai
Kai
Kai
Kai
KaiKai
KaiKai
Kai
KaiKai
Kai
KaiKaiKai
KaiKai
Kai
Kai
KaiKai
KaiKai
Kai
Kai
KaiKai
KaiKaiKai
Kai
Kai
Kai
Kai Kai
Fit
FitFit
Fit
Fit
Fit
Fit
Fit
Fit
FitFitFit
HakuHaku
Haku
Haku
Haku
HakuHaku
Haku
Haku
Haku
Haku
Haku
Haku
HakuHakuHakuHakuHakuHakuHaku
Haku
Nel
Nel
NelNelNel
Nel
NelNelNel
NelNel
%var: PC1=0.68; PC2=0.15; Tot=0.83
Clear left-right divide: something
is stopping the rats from
swimming this small gap?
-30 -20 -10 0 10 20 30 40
-30
-20
-10
010
2030
Kai
Kai
KaiKai
Kai
Kai
Kai
Kai
KaiKai
KaiKai
Kai
KaiKai
Kai
KaiKaiKai
KaiKai
Kai
Kai
KaiKai
KaiKai
Kai
Kai
KaiKai
KaiKaiKai
Kai
Kai
Kai
Kai Kai
Fit
FitFit
Fit
Fit
Fit
Fit
Fit
Fit
FitFitFit
HakuHaku
Haku
Haku
Haku
HakuHaku
Haku
Haku
Haku
Haku
Haku
Haku
HakuHakuHakuHakuHakuHakuHaku
Haku
Nel
Nel
NelNelNel
Nel
NelNelNel
NelNel
%var: PC1=0.68; PC2=0.15; Tot=0.83
Cliffs at the
landing points!
The genetics tell us about rat movements in Aotea Great Barrier Island:
What do they say about the Bay of Islands...?
Results: Norway ratsNorway rats are good swimmers;
BoI has short distances and easy beach landings
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MAHMAH
MAHMAHMAH
MAHMAH
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MAHMAH
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MAHMAH MAHMAH
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MAHMAHMAHMAHMAHMAHMAH
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MAHMAHMAHMAHMAHMAHMAH
MAH
MAH
MAHKIEKIEKIE
KIE KIEKIEKIE
KIEKIEKIEKIEOKA
OKA
OKAOKA
OKAOKAOKA
OKA
OKAOKA OKA
OKAOKA
OKAOKA
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POR
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PORPORURU
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WAE
WAEWAE
WAEWAEWAE
WAE
WAE
WAE
WAE
WAE WAEWAEWAEWAE
WAEWAEWAE WAE WAEWAEWAE
WAEWAEWAEWAEWAE
WAEWAEWAEWAEWAEWAEWAEWAEWAE
WAE
WAE
WAE
WAEWAEWAE
WAE
WAEWAEWAEWAEWAEWAE
WAE
WAEWAE
WAEWAEWAE
WAEWAE
WAE
WAEWAE
BCP
RUA
CliffRockCliffRockRangiateaRangiatea
RBC
%var: PC1=0.63; PC2=0.27; Tot=0.9
OKA WAE
URU
MAH
Massive jumble!
Motuarohia is furthest away and slightly
different
-20 0 20 40
-30
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MAHMAH
MAHMAHMAH
MAHMAH
MAHMAHMAH
MAHMAH
MAH MAH
MAH
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MAH MAHMAH
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MAHMAH MAHMAH
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MAHMAHMAHMAHMAHMAHMAH
MAHMAH
MAHMAH
MAHMAH
MAHMAH
MAHMAHMAHMAHMAHMAHMAH
MAH
MAH
MAHKIEKIEKIE
KIE KIEKIEKIE
KIEKIEKIEKIEOKA
OKA
OKAOKA
OKAOKAOKA
OKA
OKAOKA OKA
OKAOKA
OKAOKA
OKAOKA
OKA
OKAOKAOKA
OKAOKA
OKA
OKA
OKA
OKAOKA
OKAOKAOKAOKA
OKAOKA OKA
OKAOKA
POR
POR
POR
POR
POR
PORPOR POR
POR
POR
POR
POR
PORPOR
PORPORPOR
PORPOR
POR
POR
PORPORPOR
PORPORPOR
POR
PORPORURU
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URU
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URU
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WAEWAEWAEWAEWAEWAE
WAE
WAEWAE
WAEWAEWAE
WAEWAE
WAE
WAEWAE
BCP
RUA
CliffRockCliffRockRangiateaRangiatea
RBC
%var: PC1=0.63; PC2=0.27; Tot=0.9
OKA WAE
URU
MAH
-20 0 20 40
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20
MAHMAH
MAHMAHMAH
MAHMAH
MAHMAHMAH
MAHMAH
MAH MAH
MAH
MAHMAH
MAH MAHMAH
MAHMAH
MAH
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MAHMAH MAHMAH
MAHMAHMAHMAHMAHMAHMAH
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MAHMAH
MAHMAH
MAHMAH
MAHMAH
MAHMAHMAHMAHMAHMAHMAH
MAH
MAH
MAHKIEKIEKIE
KIE KIEKIEKIE
KIEKIEKIEKIEOKA
OKA
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OKAOKAOKA
OKA
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URU URU
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WAE
WAE
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WAEWAEWAE WAE WAEWAEWAE
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WAE
WAEWAE
WAEWAEWAE
WAEWAE
WAE
WAEWAE
BCP
RUA
CliffRockCliffRockRangiateaRangiatea
RBC
%var: PC1=0.63; PC2=0.27; Tot=0.9
URU
MAH
Conclusion:No island is safe from
Norway rats!These results were
used to help justify the eradication scheme for
all 7 islands simultaneously
OKA WAE
What about ship rats?
Weaker swimmers;
Not present on islands in 1980s
Somehow a population of ship rats established on Urupukapuka in the last 20 years
Did they swim from Rawhiti?
Rawhiti
Urupukapuka
Kerikeri
Ship rat results
Urupukapuka rats are totally
different! Rawhiti
Kerikeri
Mainland rats from Kerikeri to
Rawhiti
Rawhiti
Urupukapuka
Kerikeri
Ship rat results
This invasion happened by
boat!Mainland rats are related over 80km
distance
Mainland rats from Kerikeri to
Rawhiti
Kerikeri Urupukapu
ka
RawhitiRawhiti
Urupukapuka
Kerikeri
Conclusion:We need to deal with the
risk of rats arriving by boat.
We don’t think ship rats swam the 800m gap from
Te Rawhiti to Urupukapuka.
The Bay of Islands has wonderful conservation potential
The Bay of Islands has wonderful conservation potential
The Bay of Islands has wonderful conservation potential
Swimming Norway rats are a major threatBoat invasions are also a riskWe all need to work together to keep the islands safe!
With thanks to our funding With thanks to our funding agencies:agencies:
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