Stochastic modelling of rat invasions among islands in the New Zealand archipelago
This project was formulated with the purpose of advancing knowledge of the invasion dynamics of rats within archipelagos in New Zealand. The concentration
on islands reflected the conservation focus of this project - islands are the last
refuges for many native New Zealand species that cannot survive in the wild on
This project can be divided into four areas:
1. Data collection: There was no intent for innovation here, but a deeper understanding of the environments in which rats are born, breed, migrate, and
die was developed.
2. Development of tools for data exploration:
• A user-friendly point-and-click graphical interface for the R program
was designed to allow any user to easily explore simple genetic characteristics of the data.
• A novel method for exploring the genetic similarity between individuals
was developed and showcased with real data, proving successful in cases
of both high and low genetic differentiation, and in detecting likely
3. Improvement of a method for estimating migration: • An attempt was made to improve the Markov chain Monte Carlo procedure underlying this method.
• The migration model used by the method was significantly improved,
so that it could cope with any level of migration. Previously, results
from situations where migration rates were high were invalid.
4. Investigated topics of ecological interest:
• Field measurements of rats were used to show that Norway rats tend
to have larger masses than ship rats, southern rats are generally larger
than northern rats, but the effect on mass of living on an island as
opposed to the mainland depends on the latitude. It was also shown
that relative tail length is a good species discriminator.
• Multiple paternity was confirmed for both Norway and ship rats. This
breeding characteristic might form part of the explanation for why rats
are such successful invaders.
During the project, case studies involving rats on Big South Cape Island, Great
Barrier Island and in the Bay of Islands were used to highlight the methods developed, and provided some unexpected and fascinating results.
School:The University of Auckland / Te Whare Wananga o Tamaki Makaurau
School Location:New Zealand
Source Type:Master's Thesis
Keywords:rattus spp island ecology population genetics fields of research 230000 mathematical sciences 230200 statistics 270000 biological 270700 and evolution
Date of Publication:01/01/2008