Baiting Method

Has the baiting approach been decided?

The overall baiting approach has been decided and will be put forward in the approvals and permit applications for the various regulators to approve. This includes aerial broadcasting over uninhabited parts of the island and a combination of hand broadcasting and bait stations in the settlement area.  The actual treatment methodology over individual properties will be discussed and negotiated with individual leaseholders and residents through Property Management Plans but will be in accordance with any regulatory approvals or conditions received.

Why do aerial baiting, why not do the whole island with bait stations?

It is simply not possible to effectively and safely distribute the bait on areas such as the Southern Mountains and Northern Hills by any other means. Aerial application of bait has been a key factor in previous successful eradications, because it means that every rat on the island has the opportunity to find and eat enough bait, within a short period of time. Due to the small size of some mouse territories it would require putting bait stations at close intervals over the whole island, including the sides of Mt Gower and Mt Lidgbird which is not feasible.

Why can we not use the SenesTech fertility control method?

Fertility control has been used with limited success as a method of pest management in a few species, primarily larger mammals where individuals can be targeted for treatment Experimental sterilization methods have included chemicals and proteins delivered by vaccine, and genetically-modified viral pathogens. However, the effectiveness of these experimental techniques in the wild, and their impacts to non-target animals are unknown.

The possibility of using a new rodent sterilisation technology called “Contrapest”, developed by SenesTech Ltd was considered with the following issues identified:

  • The product, Contrapest, aims to reduce rat populations through sterilisation, by reducing fecundity but leaving some animals to defend territories i.e. ongoing control not eradication.
  • It requires every female to be dosed with the product i.e. it needs to be regularly dispensed as there is no inherited or contagious transmission of the reduced fertility.
  • The fertility control compounds (VCD and Triptolide) are not species-specific and could affect other mammals including humans.
  • Currently the product is designed for rats although the developers state that it has the potential to be modified to target mice, along with other species, although dispensing the appropriate dosage is problematic at this stage.

The product is not suitable for the rodent eradication program on LHI as:

  • The product is aimed at reducing rat numbers not eradicating them.
  • The product needs to be ingested over a prolonged period (approx. 75 days) and all female rats would need to be exposed to the product. This would effectively mean that the product would need to be put out continually for the foreseeable future.
  • While reducing rat numbers would have some benefits, only total eradication of rats and mice will give the anticipated ecological, social, economic and human health benefits.
  • The product is currently dispensed by adding it to water. This is problematic for LHI as dispensers would need to be put over the whole island at approximately the same spacing as bait stations. The product needs to be consumed over many feeds as it affects the reproductive system slowly meaning that the bait would need to be made available in every territory for a prolonged period to affect even one generation of rats.
  • Even if the product was used on the accessible areas and was able to reduce numbers, this would only be short term while the product was being dispensed. Also, rodents from the untreated areas would soon move in as resources, food and territory were freed up
  • The current product Contrapest is only for rats which would leave mice untreated.

Contrapest has been investigated for both the LHI program and by other rodent eradication organisations internationally and its use would be experimental hence it is not currently considered a feasible option for rodent eradication in the foreseeable future.

Repeated baiting of uncertain oral contraceptives on an inhabited and rugged island across seasons or capturing, vaccinating, and releasing every member of a single gender of the LHI rodent population is unfeasible. This lack of data and tools disqualifies the use of fertility control from detailed consideration.


How much poison will be used?

Less than 1.2kg of the active ingredient (toxin) Brodifacoum will be used in total, over 2 baiting applications.

Each pellet has a Brodificoum concentration of 20 parts per million, 2 ½ times lower than the bait that can be bought in shops.

Can the Board do more than two aerial bait applications?

No, we only have approval for two.
The project, including aerial baiting, cannot deviate from what was presented in our original application documents as this is what our permits and approvals are based on. More than two aerial baiting applications would be in breach of our approval conditions and exceed our project budget.

Will I have advance notice of a bait application?

Before any bait is distributed on the island, the community and tourists will be informed about the nature and timing of the operation and the need to avoid ingesting or handling baits.

Will the aerial baiting be done over people’s houses?

Absolutely not. Aerial baiting will not be undertaken in the settlement area. Residents on the edges of the settlement have a say in how far they would like aerial baiting from their properties and this is something we will continue to discuss with them. We cannot legally aerially bait within 150m of a house without owners consent. Where we have people’s consent we still would not aerially bait within 30m of houses. There are three different setups for the bait buckets, see below. The directional swathe is used for the edges of the aerial baiting areas to only spread bait on one side of the helicopter, i.e. away from houses.

If the program is considered safe, why do you need to do monitoring afterwards?

Scientific monitoring is considered standard practice and prudent for a project such as this. Monitoring before, during and after provides evidence of whether anything has changed or not. It can indicate progress toward achieving project goals, it can provide reassurance, it can be used in decision making for many other projects.

How will the baiting be undertaken and over what time period?

Baiting will be undertaken using a combination of aerial, hand broadcasting and bait stations. No aerial baiting will be undertaken over the settlement area. The aerial and hand broadcasting will be undertaken twice over a 21 day period to minimise any gaps in the bait broadcast and expose any surviving young that have recently emerged from the nest after the first baiting. Bait stations around the settlement area will be monitored by work crews and loaded with bait as required.

After a non-toxic baiting trial on Lord Howe Island in 2007, results showed that both 5.5 mm and 10mm baits in all three habitats were in advanced stages of decomposition after 55 days and 164.2 mm of rainfall.  Further monitoring showed that all baits had completely disappeared by 100 days.

Bait stations will be physically removed from properties after intensive monitoring has found no sign of rodent activity and Project Managers are confident that all rodents have been eradicated.

How will you get the rodents off the sides of the mountains especially where there are cliffs and caves?

Spreading bait from a bucket slung under a helicopter has been very successful in removing all rodents in similar situations such as Campbell Island (11,300 hectares) which has 300m cliffs and sea caves. Raoul Island (2900 hectares) in the Kermadec group – about 2000 km east of Lord Howe is similar topographically to lord Howe although its mountains at 516m are not a high as those on LHI. A project is also underway on 352,800 hectare South Georgia Island in the South Atlantic which includes mountains up to 2900m in height.

What will happen to all the dead rodents after the baiting has occurred?

It is estimated that 50-70 employees, many from the island community, will be required for the eradication operational phase to assist with its implementation. With the bait station monitoring continuing throughout the settlement area, crews will also be engaged in collecting as many dead rodents as possible and disposing of them appropriately to minimise the impacts to residents and the environment.

Why eradicate rats and mice now?

Lord Howe Island is not unique in having rats and mice, but it does have a rare opportunity to solve the problem. Most inhabited islands around the world have rats, as does every major city, and some manage them better than others. Lord Howe does a good job of managing them around the settlement but they are still impacting on most of the island and they won’t go away unless we do something to get rid of them.

A window of opportunity

The complete eradication of invasive rodents has now been carried out on over 300 islands around the world. It has been done elsewhere, it can be done here. There are solid precedents for what needs to be done and how to do it. Careful feasibility planning indicates it can be done here, and this has led to the availability of funds and expertise to protect Lord Howe Island now. The window will not stay open for long and if the eradication did not go ahead the funds will go back to the mainland, they are not available for other projects on the island.


Everywhere in the world we are seeing a frightening trend: resistance to once effective treatments including antibiotics and pesticides. This is currently happening with TB where strains are appearing which are resistant to all normal antibiotics. Similarly, many other bacteria are becoming resistant to penicillins (which were far more effective when introduced 70 years ago). The mice on Lord Howe Island are already resistant to Warfarin, one of the earlier rodenticides

Imagine an island without rats and mice

Lord Howe is special in many ways, and its unique wildlife, history and its people are reflected in its World Heritage status. Removing rodents completely and for good will make it even more special and enhance a worldwide reputation as an ecotourist destination. Rodents are currently only being controlled on a small percentage of the island. Elsewhere they are having a major impact on the wildlife and vegetation. Without the rodents, plants and wildlife will flourish. People will no longer have to bait around their homes and businesses. There will be no more risk of the ongoing poisoning of native species that is currently happening or the risk to children or dogs.


How do we keep rodents off the island after the eradication?

The LHI Biosecurity Strategy has recently been revised to significantly increase the level of protection from introduction (or reintroduction) of invasive species. It is important to note that biosecurity on the island will be improved regardless of whether or not the rodent eradication proceeds, in order to keep a wide range of invasive plants and animals off the island.  If the eradication does proceed, special consideration will be given to keeping rodents off the island. The Biosecurity Strategy will continue to be revised and updated during and after the REP process.


Wildlife Impact
What is the impact on birds and plants?

Expect increasing numbers and types of birds and other wildlife

Eradicating rats and mice from LHI is expected to result in marked increases in the abundance of land birds and seabirds. Eradicating these pests from LHI will reduce the risk of extinction of many threatened species and help protect the island’s biodiversity and World Heritage status.

There will be substantial increases in the distribution and abundance of the LHI skink and gecko, all species of land snails, as well as many other creatures. There will be an increase in the abundance of seeds and seedlings, increasing recruitment of many threatened plants and enhancing the process of forest regeneration.

With the rats and mice gone, bird populations will flourish, increasing in abundance to levels not seen for many decades. Nesting colonies of storm-petrel and Kermadec petrel are likely to re-establish on the main island. Also, the opportunity would then exist to return some of the species that have been lost from LHI, such as the, fantail, warbler, pigeon and boobook.

Fact Sheet Birdlife – what will Brodifacoum do? PDF 603 KB

What will happen if bait goes into the sea?

To minimise the amount of bait that goes into the sea, as much as possible of the area around the lagoon and other sites such as Ned’s beach will be hand-baited. While it is not possible to guarantee that no bait will go into the sea where aerial broadcasting takes place, as it is important to get bait as close to the high tide line as possible, this will be minimised by the use of a deflector in the bucket which directs the bait just out one side.

What about fish, is it true there will be a ban on catching and eating fish after the eradication?

No, there is no fishing ban proposed. No impacts to fish and marine life are expected due to the very small amount of bait likely to enter the ocean, the huge dilution factor and because Brodifacoum is practically insoluble in water. The Human Health Risk Assessment overseen by the NSW Chief Scientist looked at the potential for human exposure from fish and concluded that transfer of Brodifacoum to seafood would not be expected to present a risk to residents and visitors. It did not recommend the need for a fish ban here. To be extra safe, samples of sea water and local fish will be laboratory tested for any Brodifacoum residue before and after baiting occurs.

What about the whale stranding’s on Kaua‘i?

There have also been unsubstantiated claims that the stranding and death of five pilot whales in Kauai could be linked to the Lehua eradication. Personnel from multiple agencies worked together to conduct a necropsy (post-mortem examination) on all five whales to investigate the cause of stranding. The preliminary results showed no obvious cause of death. Samples were taken and sent out to labs for further analysis which may provide more insight into the general health of these animals as it may relate to possible infectious pathogens, toxins, trauma, and individual organ function. The liver tissue of the whales will also be tested for the presence of the rodenticide (diphacinone) which was applied at Lehua Island. Mass stranding’s for this particular species are fairly common globally. Since pilot whales are social, when one individual strands, others tend to follow (not necessarily for the same cause of stranding).

What’s happening in Lehua?

The Lehua Island Restoration Project has recently been completed. The Department of Land and Natural Resources, Island Conservation, and other Project partners became aware of social media posts, photos and video that show dead fish or birds that posters claim were killed by a rodenticide (diphacinone) used to eradicate invasive rats from the island. However unlikely the connection, the project partners take any potential risks to non-target species and marine life, extremely seriously. The monitoring team has confirmed and collected 45 dead fish which appear to be mullets and two dead birds which appear to be juvenile Brown boobies. The samples do not show any immediate evidence of impact from diphacinone. Mortalities of fish and seabirds occur regularly, and there a many other plausible causes for these deaths. The samples are under USDA chain-of-custody and will be processed to determine likely cause of death or presence of diphacinone.
Have a read for yourself

World Heritage
How will the eradication affect Lord Howe Island’s World Heritage Status?

Successful eradication would protect and enhance the Island’s World Heritage Status. Tim Badman, the Director of the IUCN World Heritage Programme has written to confirm support for the program.

Why are Islands so important for biodiversity?
  • Islands make up less than 5% of the earth’s land area, but are home to an estimated 20% of all bird, reptile, and plant species.
  • Islands also contain 40% of all critically endangered species, and extinction rates are disproportionately greater on islands.
  • 80% of all known extinctions have occurred on islands.
  • Nearly a quarter of the world’s plant species exist only on islands.
  • Some individual islands are home to hundreds—or even thousands—of plant and animal species found nowhere else in the world (endemic species). Other islands have a few or even a single unique endemic species.
  • Many islands are home to species yet to be described by science. We don’t even know what we might be losing—such as sources of food or medicine.
  • On islands, species under threat of extinction have nowhere else to go, so they must be protected on-site.
  • Many migratory species breed and raise their young only on a few islands, or sometimes only on one single island.

Source: Island Conservation


Is it safe for humans?

Yes, it is. Provided basic precautions are taken, the risk of brodifacoum poisoning during the proposed eradication is remote.

The current practice of using rodenticides (such as Ratsak Plus® and Talon®) containing brodifacoum on an ongoing basis for rodent control on Lord Howe Island poses an ever present risk for residents, their pets and local wildlife. The eradication of rodents will remove the need for the ongoing use of rodenticides and the risks that go with it.

How do I approach the baits?

For the most part, the risks to human health associated with the proposed eradication operation are similar to those that currently exist through the domestic use of products likeTalon®. In brief, the baits should be treated like any other poison. They should not be eaten or handled. Residents with children already exercise care when using baits domestically. Baits used domestically have a much higher concentration of brodifacoum, 2.5 times greater than the baits that will be used in the eradication. However, there will be more baits on the ground during the eradication and care must be taken with children and those unable to read the signage that is posted.
The only way residents could be exposed to brodifacoum absorption from the skin is by handling baits directly. However, for there to be any adverse effects a person would need to handle large quantities of bait for long periods of time. The risk of such exposure is negligible.

What do I do if I come into contact with bait?

Swallowing one or two baits seldom requires medical treatment. In the extremely unlikely event that medical treatment is required (involving vitamin K injections), it will be available. Nevertheless, anyone suspecting brodifacoum poisoning should seek medical advice.

Visitors and Residents REP Information Sheet PDF 499 KB

Is there a danger from dust?

Only those working directly with the baits around the helicopter will be exposed to significant dust and they will be wearing protective equipment.  Bait will not be spread in high winds to minimise the risk of any dust being widely dispersed.

What about water tanks?

Aerial baiting will not be conducted over the settlement and will not be conducted in high wind. Combined with the fact that brodifacoum has very low solubility in water i.e. would sink to the bottom of a tank and bind with any material there, it means that there is effectively no risk to human health from dust in water tanks.

What about my vegie garden?

Brodifacoum has very low solubility in water, and therefore will not be taken up by plants. No exposure risk is anticipated from plant-based food grown on the island.

As an added precaution there will be no bait put in vegie gardens as these areas will be done by hand broadcast or bait stations as per the Property Management Plan for each site.

What about the water and soil?

To date, brodifacoum residues have not been detected in water bodies following any aerial baiting operations—not surprising, given that brodifacoum has very low solubility in water.

The baiting operation will be conducted to avoid bait going into the lagoon and minimise the entry of baits into the ocean.

What we already know, fresh water

From other aerial baiting operations, we know that there is a very low chance of any streams and other water bodies on Lord Howe Island containing detectable levels of brodifacoum, much less biologically harmful concentrations, as a result of the eradication.

Because brodifacoum has very low solubility in water and binds strongly to soils it is unlikely to get washed into the marine environment. Any baits entering streams or other water bodies sink, and disintegrate, usually within a few hours, depending on turbulence and rate of flow. The minute amount of brodifacoum in the bait (20 parts per million) settles in the sediment where it binds to organic material and breaks down.

Brodifacoum binds strongly to soil particles, where it is broken down by soil micro-organisms to its base components, carbon dioxide and water. While the cereal bait pellets disintegrate and disappear within 100 days or so, the toxin itself takes longer to break down but by this stage the concentration is so low that it poses no risk to humans or wildlife.  Laboratory studies have shown that brodifacoum is effectively immobile (i.e. not leached) in the soil.

Nonetheless, water samples will be collected at various intervals after the baiting and analysed by an independent laboratory to reassure residents and tourists that the water (along with locally produced milk and locally caught fish) is not contaminated.

In the marine environment, outside the lagoon

Outside the lagoon, any baits that might enter the ocean will be exposed to wave action and strong currents resulting in rapid breakdown and dispersal. This, together with the high dilution factor, and the fact that brodifacoum has very low solubility in salt water, means that the potential risk to marine organisms is very low.

In the marine environment, within the lagoon

Within the lagoon, the physical breakdown of baits would not be as rapid, so entry of baits into the lagoon will be prevented by hand distribution of bait, rather than aerial distribution, along the accessible shoreline of the lagoon. As there is very low risk of brodifacoum being at detectable levels in the streams, any water entering the ocean or lagoon is unlikely to carry detectable levels of brodifacoum.

Fact Sheet Brodifacoum – is it the best choice? PDF 774 KB

My Property

What will happen on my property?

The Property Management Plans (PMPs) include the agreed baiting methods for each lease on the Island, including the settlement area. They are discussed and negotiated with the leaseholders / residents individually and consider mitigation of specific risks and areas of concern on individual properties. The PMPs will not impact on the tenure of the leases. As discussed during the Property Management Planning process, livestock owners will only begin reducing their cattle numbers in preparation for the operational phase when it proceeds.

Will the project progress if not everyone agrees?

The Board will act to keep the Island’s people safe and to protect the Island’s environment, World Heritage status and unique tourism assets. The actual treatment methodology over individual properties will be discussed and negotiated with individual leaseholders and residents through Property Management Plans. Every plan will be completely bespoke and take into consideration individual situations to abate concerns. The project will progress if not everyone agrees.