Archives For Ulva Island

The DOC website has the latest updates on the Ulva Island rat eradication.

It has now been two weeks since the public meetings and I’m sure that many of you are wondering what is happening. Unfortunately, we have very little news from the island itself. As mentioned previously, the rat traps have gone past the point of preventing population growth, so we have scaled our trapping checks back to once per fortnight so that staff can focus on the planning to eradicate rats. The last check, just prior to the meeting, brought the total number of rats caught to 70. These have been caught all over the island. The next trap check is scheduled for Friday – I’ll update you as soon as I get the results.

This upcoming rat trap check will be our last. We will close the traps after this so that the 3 days of effort per check can be redirected onto more urgent tasks – such as planning for the eradication. It is important to understand that the rat population has reached a point where its growth will no longer be influenced by any efforts that we put into trapping – even if we were checking traps daily.

Project Manager

Effort has continued toward planning for an eradication operation. The Department will finalise its planned approach by the end of this week and we will then focus our effort onto the required preparation and planning. Regardless of the method chosen, we have appointed a project manager, Paul Jacques, who will be able to work full time on making Ulva Island rat free again. Paul has been the project manager for the possum control work on Stewart Island and we are reallocating his essential possum control tasks to other people and deferring or cancelling non-essential work.

Has this been tried before?

As part of the planning, we have also been reviewing other island eradication operations and discovered that we aren’t the first group to be in this situation after all. Back in 1995, Fregate Island in the Seychelles group (located in the Indian Ocean) was invaded by rats and they attempted to eradicate them while numbers were still low using bait stations. This is a similar situation to Ulva in that rat numbers were building rapidly and had unlimited food supplies. The bait station operation failed and they had to wait until rats reached peak population density and exhausted the food supply before they were able to eradicate them using an aerial bait drop.


Recently we received a real boost to fundraising for the eradication from Birdlife International Community Conservation Fund. This fund donated $5000 to kick-start fund raising. If you wish to help Ulva Island become rat free again, then the Ulva Island Trust will be co-ordinating any donations. Keep an eye on their website ( for details about how to donate.

Do you have a Question?

In the last few weeks there have been lots of good questions asked about what is going on and why. We will try to capture these questions and answers in a Frequently Asked Questions section loaded on the Ulva page of the DOC website. We should have this in place within the next two weeks.

If you have a question, feel free to give me a call or send me an e-mail.


Hi Everyone,

I wanted to keep you informed of the events unfolding on Ulva Island at the moment.

Twelve rats have been caught on Ulva Island in the last two weeks.

After four rats were caught on Ulva Island in June/July 2010, DOC staff were hopeful that the incursion to this rat free island had been contained. However, in October a keen eyed member of the public passed on a photo of animal prints he took in a muddy creek on the island. DOC experts confirmed that these were made by a rat.

Ulva Island has a network of traps and poison bait stations that are run year round to kill any rats that may get to the island and extra traps were added to this and the frequency of checks increased. Tracking tunnels were also used to try and detect any rats on other parts of the island.

Between August and December, no further rats were caught or detected. This all changed after Christmas day – a total of 12 rats have since been trapped. Of greatest concern is that one of the rats was a juvenile which indicates there is now a breeding population on the island.

DOC staff have been diverted from other work to check the traps and tunnels on a weekly basis. A DOC team of experts will meet shortly to plan a course of action to remove rats from Ulva Island as rapidly as possible.

Since rats were first removed from Ulva Island, on average one rat a year manages to get to Ulva Island either by swimming or hitch-hiking with boats. To date, we have managed to catch these rats as they arrive, preventing them from breeding. This is the first time a rat has evaded all of our traps, established and bred.

Removing and then keeping rats off the island is a difficult task and there is always a chance that we may not succeed. DOC has an excellent record in this field but as always we will need the help and support of the public to achieve this.

I’ll aim to send regular updates out over the next few weeks.


26 January update

Unfortunately, the picture isn’t getting any better on Ulva Island. Further trap checks have now brought the total number of rats caught to twenty. On top of this, we have been running ten lines of tracking tunnels (baited with peanut butter and have an ink card in them that records footprints). Five of these lines have recorded rat footprints (34% of tunnels). This confirms that the rats are widespread over Ulva Island.

We are meeting tomorrow to plan the best way to eradicate these rats. Luckily, within New Zealand, we are able to draw on some of the best rat eradication expertise in the world. I will let you know what the recommendation is as soon as I practically can.

The rats that we have caught aren’t going to waste. Tissue samples are being sent away for DNA analysis to confirm that they are all related (and hence only one invasion event) and to work out where they came from. This will be achieved by comparing the DNA of rats on Ulva with sample rats from different locations around Paterson Inlet and Bluff. The rest of the rat will be sent to the vet school at Massey University who will be able to provide information on sex, age and if they have bred or not.

We will continue trapping and running the monitoring tunnels to keep track of the dispersal and population growth of these rats. Hopefully, this will also keep numbers suppressed. The set-up that we have on Ulva will not achieve eradication of the rat population that has established. Something further will be required.

We have had many offers of help and support. These are really appreciated and are being built into the planning of how we might achieve eradication.


8 February update

The last few weeks that we have been doing intensive trapping have revealed quite a depressing picture. Over 40 rats have now been caught and most of the tracking lines across the island are tracking rats. In short, the population of rats is widespread and rapidly growing.  The trap set up that is presently on Ulva Island was designed to catch and dispatch individual rats as they invaded the island. The trap set up is no longer going to prevent this rat population from growing rapidly on Ulva Island. They are expected to reach maximum population density (regardless of trapping effort) within the next 12 months, possibly as soon as five months. The impacts on the island at this point will be severe. We plan on continuing to check the traps and tracking tunnels to keep track of rat population growth, but apart from this, the traps are past the point of achieving anything useful.

The best focus of activity now is on actions around eradication options. Last weeks expert meeting (involving members of the Islands Eradication Advisory Group) came out with only two options that had any hope of achieving eradication. Both of these involve getting widespread rat bait onto Ulva Island either by an intensive bait station network or by helicopter spreading. We are currently working through the financial costs and the pros, cons and risks of both options and this is what we will be discussing at the series of meetings on Stewart Island during the week of the 14th Feb. Once we, as a community, agree to the best path forward then we can get stuck into achieving it as rapidly as possible.

So, thanks heaps for your support and I am very sorry to have to send this message. It is really hard to believe that it was only one month ago that the first of these rats started turning up in traps.