Why do tropical rat eradications fail?

Posted by James Russell @IsldJames

The answer is self-evident: because we didn’t kill all the rats. However, the answer to the question “why didn’t we kill all the rats” is more complex. Tropical rat eradications currently fail more often than those in temperate or polar regions (16.1% vs 6.3%). If we discount operational reasons (i.e. the eradication wasn’t undertaken properly), the two prevailing biological hypotheses are that either with rats constantly breeding some pups may be able to survive and re-populate the island, or food is so abundant that not all adult rats diet switch to the poison bait.


A radio-collared rat on Reiono Island (Photo: James Russell)

Experimental rat eradications have proven very profitable in the past for advancing the science of rat eradications, but not everyone wants to allow their rat eradication for conservation to be an experiment, particularly when this increases the risk of failure. This week a team of scientists from University of Auckland (Araceli Samaniego, Markus Gronwald, James Russell) have been undertaking an experiment in association with a tropical rat eradication on Reiono Island in French Polynesia. The 22 hectare island will be treated with poison to eradicate the rats which are widespread across the otherwise relatively pristine island dominated by Pisonia forest and native seabirds and reptiles.


An alive 5 day old rat pup (Photo: James Russell)

The team have radio-collared over 60 female rats and will track them throughout the course of the eradication. They will monitor their nests to determine the likelihood of any baby rats surviving over the two weeks of the eradication. This intensive monitoring effort will reveal the most detailed data yet on the behaviour of rats during a tropical eradication campaign, and hopefully inform future rat eradications on tropical islands so that they may be as successful as those undertaken in temperate and polar regions around the world.

For more information see the special issue of Biological Conservation on tropical rat eradication.

Conservation in Aotearoa in 2030

Posted by Cate Macinnis-Ng @LoraxCate

The theme for this year’s University of Auckland Winter Lecture Series is Aotearoa in 2030. James Russell and I were invited to speak about conservation in Aotearoa in 2030. James covered the vision for Predator Free 2050 and I talked about some things we need to think about to make the most of the One Billion Trees policy. In short, we need to think carefully about which trees we plant where.

You can view this recording of the talk for more details.


Maintaining biodiversity in urban areas

Post by Anna Frances Probert @AFProbert

Urbanisation has come at a cost to greenspaces and biodiversity. Worldwide, pressures for development to sustain our growing human population has led to the loss of vast areas of natural habitats and agricultural land. The associated loss of habitats that sustain populations of native species is considered a driving force in global biodiversity declines.

Central park.jpg

Greenspace in a very urban setting; Central Park, New York. Photo: Walkerssk Pixabay

Greenspace is a general term used to characterise vegetated areas of land, whether that be a natural ecosystem such as forest, or a park and recreation area. The benefits of greenspace are broad-reaching; greenspaces can function to increase the quality of living and well-being of residents and visitors to the area. Growing evidence supports the notion that greenspace is an important component of healthy urban living, and greenspace is now a priority area for urban planners. Furthermore, greenspaces provide habitat for biodiversity, providing pockets of refuge within the urban matrix, and allowing the movement of species across the landscape. The protection of greenspace is therefore an important priority to maintain and promote biodiversity in urban areas.

At a smaller scale, urban gardens can act as a type of greenspace, particularly when interconnected with other gardens. Urban residents can therefore play an important role in the maintenance of native biodiversity, by using their gardens and other outdoor spaces in ways that support populations of native birds and invertebrates. Promoting biodiversity in smaller pockets can build up to become part of larger habitat and movement networks that support populations throughout the landscape.

bug hotel

A bug hotel provides habitat for invertebrates such as wēta. Photo: anpe Pixabay

So what can you do to help in your backyard? Well, many councils are now beginning to provide excellent online resources for community members learn about how to support local wildlife. Whether it is building a wētā hotel in your backyard or porch, planting kaihua (a native jasmine, which I have climbing inside my central Auckland apartment) and other native plants, or keeping your cat indoors and installing predator traps, there are many ways we can participate in enhancing our local environment, for both the benefit of people and biodiversity.




MeblogAnna Probert is a PhD student in the Centre for Biodiversity & Biosecurity, School of Biological Sciences, University of Auckland. She is using ants as a model to assess the risk posed by exotic invertebrates to native ecosystemsShe is supervised by Margaret StanleyJacqueline Beggs, and Darren Ward.