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

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Fit

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Fit

Fit

Fit

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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

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Fit

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Fit

Fit

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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

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Kai

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Kai

Kai

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KaiKaiKai

Kai

Kai

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Fit

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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

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Fit

Fit

Fit

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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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OKA WAE

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Massive jumble!

Motuarohia is furthest away and slightly

different

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%var: PC1=0.63; PC2=0.27; Tot=0.9

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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: