Presentation on theme: "RATS! Rachel Fewster Steven Miller James Russell Hamish MacInnes Department of Statistics University of Auckland."— Presentation transcript:
RATS! Rachel Fewster Steven Miller James Russell Hamish MacInnes Department of Statistics University 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 GOATS FERRETS MICE RATS DEER PIGS HUMANS Native birds can’t compete!
RATS are among the worst COMPETITION PREDATION HABITAT DESTRUCTION VANDALS! THIEVES! MURDERERS!
There are three rat species in New Zealand:
1. Ship rats: Rattus rattus The Climbers
2. Norway rats: Rattus norvegicus The Swimmers
3. Kiore (Pacific rat): Rattus exulans The first and smallest 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
How do they get there?
4. Conspiracy Our 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 different islands? Are rats swimming between different islands? RATS ? ? ? We might be able to tell from their genetics.
RATS ? ? ? If an island is truly isolated… RATS …the genetics of its rats may differ from other islands. Same with rats:
RATS ? ? ? 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...
Fitzroy Motu Kaikoura Fitzroy region, Great Barrier Island
Fitzroy Motu Kaikoura Fitzroy region, Great Barrier Island Genetic results Each point is one rat; Each colour is a different island Look for: Overlap: closely related populations Separation: isolated populations
Fit Kai Nel Haku
Clear left-right divide: something is stopping the rats from swimming this small gap?
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 rats Norway rats are good swimmers; BoI has short distances and easy beach landings
OKA WAE URU MAH Massive jumble! Motuarohia is furthest away and slightly different
OKA WAE URU MAH
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 Urupukapuka Rawhiti 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
Swimming Norway rats are a major threat Boat invasions are also a risk We all need to work together to keep the islands safe!