NZ546316A - Management of vertebrate pests - Google Patents

Abstract

Disclosed is a bait for the control or eradication of animal pests, comprising an ingestible base material and as a percentage by mass of the base material, the active ingredients: (a) 0.01% -0.5% Vitamin D sterol, such as cholecalciferol. (b) 0.1%-5% Calcium compound selected form a calcium phosphate and a calcium sodium lactate, or mixtures thereof, wherein the calcium sodium lactate may be replaced with calcium potassium lactate, (c) 0.0005%-0.005% Anticoagulant compound selected from chlorphacinone, flocoumafen, brodifacoum, bromadiolone, or mixtures thereof. (61) Addition to 329006

Description

New Zealand Paient Spedficaiion for Paient Number 546316 Patents Form No 5 NEW ZEALAND 546316 PAT 5 PATENTS ACT 1953 COMPLETE SPECIFICATION MANAGEMENT OF VERTEBRATE PESTS I ERIC RAYMOND WEAVER of 24 Umere Crescent, Ellerslie, Auckland, New Zealand, a New Zealand Citizen, Hereby declare the invention, for which I pray that a patent may be granted to me and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to animal pest control and has been devised particularly but not solely to provide enhanced toxic baits for the control and eradication of vertebrate animal pests.

A common problem worldwide is that exotic animals have been introduced both intentionally and accidentally to ecosystems where they do not belong and where they become animal pests. The introduced animals may become predators of indigenous animals or destroy pre-existing habitats and stable ecosystems. Typically the indigenous flora and fauna cannot adapt to the changing conditions and often plant and animal species are lost altogether.

IPONZ 0 4 APR 2006 1 The animal pests may also have a significant economic impact in the new region by destroying crops or pastures, or become a feral vector responsible for spreading disease.

Of necessity, toxic baits and methods of use have been developed to control or eradicate animal pests as humanely as possible. An obvious example widely known to the general public is the use of rodent baits of various kinds.

On a larger scale, a range of toxic baits and considerable expertise has been developed over time (which includes the experience of some failures), to successfully control or eradicate animal pests often in quite sophisticated operations. Islands in particular have been rehabilitated ecologically by eradication of animal pests, and in some cases extensive and expensive predator proof fences have been established on the mainland to enable pest eradication and to minimise further incursions, supported by ongoing and costly monitoring programs to maintain the new condition indefinitely. Without these measures some indigenous species that were once common and widespread in their range would join the growing list of extinct animals and plants.

As a general rule the toxins used can be sorted into two groups depending upon whether their effect is acute or chronic, and this has to be taken into account when selecting the most appropriate toxin system for a particular operation. Acute toxins have characteristics more suited to control than eradication. This is because it is not possible to always ensure that all target animal pests receive a lethal amount of toxin prior to the onset of symptoms. Should the onset of symptoms occur first the animals are likely to associate the effect with the bait ingested and quickly learn to avoid it. Because the developed aversion may last for a long time, such as many months or even a year or more, a serious problem can be created. If the original objective was eradication the options for progress then become limited and require such costly measures as the extensive and prolonged use of traps, firearms, and trained dogs, to deal with animals which will no longer take bait. Such mop-up operations have been known to take many years, simply because the wrong choice of toxin was made in the first place. Examples of acute toxins carrying a significant risk of bait aversion developing are 1080 (sodium monofluoroacetate) and cyanide (sodium and potassium cyanide). These toxins are therefore not usually preferred for animal pest eradication purposes, and are better suited to control purposes, where they can be very effective if used property.

Toxins falling into the chronic group typically have characteristics of delayed onset of symptoms such that by the time the symptoms occur the animal pests have already received a lethal dose of toxin. Because the onset of symptoms is delayed the animal pests seldom associate the symptoms with the bait and therefore do not learn to avoid it. For this reason the aversion problem seen with acute toxins and described above does not develop and the toxins are therefore more preferred where the objective is eradication. In fact the target animal pests may continue to feed on bait if available long after a lethal amount of toxin has been ingested. Two examples of chronic toxins are the anticoagulant compounds commonly known by the names pindone and brodifacoum.

Most of my experience with animal pests has been on the island of Kawau in the Hauraki Gulf, New Zealand, where an assemblage of mammalian animal pests has accumulated since human occupation began many centuries ago. A unique feature of Kawau Island history is that a governor of New Zealand Sir George Grey, purchased it in 1862 as a private retreat and imported many exotic plants and animals for the purpose of creating a botanical and zoological park for himself and his visitors. Some of the animal species did not survive but others have multiplied and done considerable harm to the indigenous flora and fauna of the Island as well as causing siltation of the surrounding marine environment as skeletal soils are stripped from the bare ground during heavy rain and carried into the sea. The looming New Zealand possum problem was first identified there as long ago as 1955. Government agencies were of no help at all when I alerted them to the problem. In 1985 advice was that we were witnessing well adapted introduced animals occupying their ecological niche in a new country and it was hopeless to consider doing anything about it. In 1990 Kawau Island was described as "not stacking up - it is important historically rather than botanically". Kawau Island was said to have no particular significance for botany or native wildlife values. Based on assessments at the time local government and agencies accepted the expert advice that "the ecological changes on Kawau Island cannot now be reversed".

Meanwhile, the landowners established control of possums by applying technology and know-how they had developed. The main method initially was trapping although there was also some poisoning. The landowners saved a New Zealand icon, the coastal pohutukawa tree on the island at a time when it was predicted to disappear by 1990. The project was so successful that it encouraged a core group of landowners to formally establish a Charitable Trust, the Pohutukawa Trust New Zealand (the Trust), with an objective "to rehabilitate the native flora and fauna of Kawau Island" and to return the island to a state of sustainable land use for the future of the community.

Since the Trust was established in 1992 a process of surveys and newsletters has lead to the identification of a number of remnant forest fragments, a growing inventory of remnant plant species, and an assemblage of animal pests which included four species of wallaby, possums, ship rats, stoats and ferrets, and feral cats, all requiring control or eradication in order to enable the Trust's restoration objectives to be achieved. The approach has been to consider the pests "misplaced animals that have been brought to a place where they do not belong" and to deal with them as humanely and cost effectively as possible.

The environment has also been carefully considered, and the remnant native bird populations still on the island, since Kawau is the home of two thirds of the entire population of North Island weka, as well as a small population of Kiwi. Kaka, bellbirds, tui, pateke and others.

Control of possums by trapping has been sustained at a maintenance level as part of the strategy and toxic baits to be used for eradication were carefully researched and chosen so as not to introduce substances that would cause long term harm to the environment or threaten the population of North Island weka on the island. While being aware that second generation anticoagulants were more effective toxins, the first generation toxin pindone was chosen initially because it was claimed to have a significantly shorter half life in the environment. We found from experience that with care it could be used quite effectively in the presence of weka without causing a serious non-target bi-catch problem, although its relatively low toxicity was obvious. A practical limit of 1% bi-catch of our estimated 3,500 weka population was easily achieved in extended trials. We were advised that a bi-catch of up to 10% is considered acceptable by most authorities, the key point being that the loss of non-target animals does not threaten the population of any species to be conserved. We were also advised that the loss of non-target animals which were declared animal pests was of no consequence unless the operation increased the eco-toxicity or risk to humans. Concerning the weka population the Trust has been able to do very much better than a 10% bi-catch, simply by careful location and management of bait stations.

When baits containing cholecalciferol became available it was found that the efficacy of the pindone bait could be noticeably enhanced by including cholecalciferol bait with it. The inclusion of cholecalciferol copied the rodenticide composition used in a watering trough/feeder (Polish registrations Tox-392/92 and 444/93) wherein cholecalciferol was used with the first generation anticoagulant chlorphacinon. Much progress was achieved and a transition to the more effective brodifacoum was made only after reducing animal pest numbers with pindone and the mixture of pindone with cholecalciferol.

Along with others, we then discovered that the commercial cholecalciferol bait had an inherent sensitivity to ambient exposure conditions on the island and quickly became soft and unpalatable to target animal pests after only a few days exposure in bait stations. The problem rendered the bait of little practical use in the field. This was partially overcome by heat-sealing the bait in polyethylene bags with a wall thickness of between 25 and 35 microns. We found that the aroma of bait permeated the bag wall sufficiently to attract animal pests and they readily opened the bags to access the contents.

Because the new cholecalciferol bait was believed to be less toxic to avian species than the anticoagulants, interest was retained in it and the cause of deterioration was investigated and efforts made to overcome the problem. We had a particular interest in the comparatively low toxicity of cholecalciferol to avian species, because of the weka population on Kawau Island. Eventually this led to baits as disclosed in New Zealand patents No 329006 and No 537368.

New Zealand patent No 329006 discloses bait for control or eradication of animal pests which overcomes or at least minimises the stability disadvantages of the prior art cholecalciferol based bait, and has been found very effective.

The management of vertebrate pests is an art requiring an adaptive strategy and continuous improvement based on experience, and an important aspect of this is the availability of a choice of effective baits to suit purposes of both control and eradication. Surprisingly for example the acute toxin 1080 is persistently being advocated by some authorities for eradication of animal pests from Kawau Island when experience clearly indicates that 1080 is not the most suitable for the purpose.

New Zealand patent No 537368 is a patent of addition after No 329006 wherein the quantity of active compound used in an effective bait for control or eradication of animal pests is reduced. The present invention is also a patent of addition to New Zealand Patent No 329006 wherein the quantity of active compound is further reduced by adding a minor quantity of a selected anticoagulant compound.

An object of this invention is to provide bait for control or eradication of animal pests which represents an improvement on the bait disclosed in New Zealand patents No 329006 and No 537368 by further reducing the total quantity of the active compounds already disclosed in New Zealand patent No 329006 while retaining or even enhancing the efficacy of the bait..

It is also an object of this invention to provide bait for control or eradication of animal pests which overcomes or minimises some of the disadvantages of prior art bait, or at least provides the public with a useful choice.

In an example according to one aspect of this invention there is provided bait for control or eradication of animal pests said bait including an ingestibie base material (as defined herein) and including the following active materials expressed as percent of the mass of the ingestibie base material: (1) Vitamin D sterol 0.01% to 0.5% (2) Calcium compound selected from a calcium phosphate and a calcium sodium lactate, or mixtures of a calcium phosphate and a calcium sodium lactate: 0.1% to 5%. (3) Anticoagulant compound selected from the anticoagulant compounds Chlorphacinone, flocoumafen, brodifacoum, bromadiolone, or mixtures thereof: 0.0005% to 0.005%.

In a further example according to an aspect of this invention there is provided bait for control or eradication of animal pests, said bait including an ingestibie base material (as defined herein) and including the following active materials expressed as percent of the mass of the ingestibie base material. (1) Vitamin D sterol: 0.05% to 0.25% (2) Calcium compound selected from a calcium phosphate and a calcium sodium lactate, or mixtures of a calcium phosphate and a calcium sodium lactate: 0.1% to 2.5%.. (3) Anticoagulant compound selected from the anticoagulant compounds chlorphacinone, flocoumafen, brodifacoum, bromadiolone or mixtures thereof: 0.0005% to 0.005%.

Claims (4)

The proportion of the various active ingredients in the examples given above is not narrowly critical in achieving the objects of this invention.. As is known in the prior art potassium may be substituted for sodium in the calcium sodium lactate and this direct substitution may be done without compromising the present invention. A preferred vitamin D sterol is vitamin D3, which has the chemical formula C27H44O, and is known in the art as cholecalciferol. A preferred anticoagulant compound has the chemical formula C3iH23Br03> and is known in the art as brodifacoum. In vertebrates vitamin D3 is made naturally by irradiation of cholesterol by sunlight reaching the skin. Vitamin D3 is well known to be essential to health in appropriate amounts. The sunlight irradiation converts cholesterol (C27H46O) to cholecalciferol (C27H44O) by removing H2 from the cholesterol molecule. The process can be duplicated using an artificial source of ultraviolet light. With a wide range of potential animal fat feedstocks available in New Zealand it seems surprising that facilities have not been established to extract cholesterol from these fat sources for straightforward irradiation with ultraviolet light to convert it to cholecalciferol. The present cost of cholecalciferol is significant and limiting its use in bait for management of vertebrate pests. For the purpose of this invention, ingestibie base material is defined as any feed material acceptable to the target animal pest. An example of a utility ingestibie base material suitable for most purposes contains milled or ground cereal or cereal residues. Other materials such as dried fruit, meat or fish meal for example may also be used or included in a mixture to suit a particular target pest. Another example is milled or ground nut or nut residues, which may be in the form of a paste including vegetable oils. Both the preferred vitamin D sterol compound and the preferred anticoagulant compound are hydrophobic substances (unlike 1080 and cyanide for example) so there is no significant risk of contamination of waterways or groundwater by active substances in the bait described in the invention. The invention has been described by way of example only, and equivalent materials and substances will be apparent to those skilled in the art, and these are included as if all were individually recorded in the description of the invention. 54 63 16 What I claim is:

1. Bait for the control or eradication of animal pests including an ingestibie base material (as defined herein) and including the following active materials expressed as percent by mass of the ingestibie base material: (a) Vitamin D sterol: 0.01% to 0.5% (b) Calcium compound selected from a calcium phosphate and a calcium sodium lactate, or mixtures of a calcium phosphate and a calcium sodium lactate: 0.1% to 5%, and wherein said calcium sodium lactate may be replaced directly with calcium potassium lactate. (c) Anticoagulant compound selected from chlorphacinone, flocoumafen, brodifacoum, bromadiolone, or mixtures thereof: 0.0005% to 0.005%.

2. Bait for the control or eradication of animal pests including an ingestibie base material (as defined herein) and including the following active materials expressed as percent by mass of the ingestibie base material. (a) Vitamin D sterol: 0.05% to 0.25%. (b) Calcium compound selected from a calcium phosphate and a calcium sodium lactate, or mixtures of a calcium phosphate and a calcium sodium lactate: 0.1% to 2.5%, and wherein said calcium sodium lactate may be replaced directly with calcium potassium lactate. (c) Anticoagulant compound selected from chlorphacinone, flocoumafen, Brodifacoum, bromadiolone, or mixtures thereof: 0.0005% to 0.005%.

3. Bait as claimed in Claim 1 or Claim 2, wherein the vitamin D sterol is Vitamin D3, known in the art as cholecalciferol.

4. Bait as claimed in any one of the preceding claims wherein the selected anticoagulant compound is brodifacoum. ERIC RAYMOND WEAVER