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RATS!

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:. Our aim is to understand rat movement & invasion, to protect sanctuary islands.

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RATS!

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  1. RATS! Rachel Fewster Steven Miller James Russell Hamish MacInnes Department of Statistics University of Auckland

  2. Hauraki Gulf islands in the last year

  3. Our research at the University of Auckland: Our aim is to understand rat movement & invasion, to protect sanctuary islands 1. Put a rat invader on an uninhabited island and study its behaviour 2. Use genetics to study current and historic movement between islands

  4. 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

  5. 1. Put a rat on an island and see what happens... Noises Islands Rangitoto Motutapu

  6. 1. Put a rat on an island and see what happens... Rat ‘Razza’ released on Motuhoropapa Noises Islands After a month, tried to catch him again...

  7. 1. Put a rat on an island and see what happens... Razza dropped his tag and swam 400m to Otata... Noises Islands James caught up with him two months later, but by boat...

  8. Bad news for us, but 100 newspapers worldwide loved the story... New York Times Oct 2005

  9. … and Razza still lives on!

  10. Our research at the University of Auckland: Closely related rats mean lots of swimmers. Unrelated rats mean isolation. 2. Use genetics to see how much movement there is between different islands

  11. What do genetics look like?

  12. Fitzroy Fitzroy region, Aotea / Great Barrier Island Motu Kaikoura

  13. Fitzroy Each point is one rat; Each colour is a different island Look for: Overlap: closely related populations Separation: isolated populations Fitzroy region, Aotea / Great Barrier Island Motu Kaikoura Genetic results

  14. Haku Fit Kai Nel

  15. Haku Fit Kai Nel Look for: Overlap: closely related populations Separation: isolated populations

  16. Clear left-right divide: is something stopping the rats from swimming this small gap?

  17. Cliffs at the landing points? Or rat sociology?

  18. Kaikoura region Mainland Broken Islands

  19. Broken Islands Results Lots of overlap between Rangiahua and Mahuki Motutaiko separate

  20. 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

  21. We see this pattern all over New Zealand: No gap in genetics over 10s of km of mainland

  22. We see this pattern all over New Zealand: Then a short water crossing…

  23. We see this pattern all over New Zealand: … and a clear gap.

  24. We see this pattern all over New Zealand: Ship Rats!

  25. Reinvasion or failed eradication? All three species of rats were eradicated from Pearl Island in July 2005: By May 2006, there were 4 Norway rats and 1 ship rat back on the island… HOW DID THEY GET THERE? Pearl Island, off Stewart Island

  26. Reinvasion or failed eradication? Survive the eradication? Reinvade from Stewart Island? HOW DID THEY GET THERE? Worst possible news! Better security needed

  27. Reinvasion or failed eradication? 250m

  28. Norway Rats Eradication planning Norways are strong swimmers, but this 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

  29. Post-eradication Norways all grouped with Stewart Island rats: phew!

  30. 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

  31. Ship rats

  32. Ship rats

  33. Once again, the ship rat is grouped with the Stewart Island rats: NOT a survivor! The genetic work showed DoC that their eradication procedures had not failed: all rats found on Pearl Island were reinvaders. Ship rats HOW DID THEY GET THERE? THEY SWAM!

  34. 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

  35. Thanks to our funders!

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