A potential new tool to help with the eradication of cats on islands

Control and eradication of feral cats: field trials of a new toxin
Murphy, E.C.,1,2 Shapiro, L.,3 Hix, S.,3 MacMorran, D.3 & Eason, C.T.3,4 Research & Development Group, Department of Conservation, PO Box 13 049, Christchurch 8141, New Zealand. E-mail: [email protected] Invasive Animals Cooperative Research Centre, University of Canberra, Canberra, ACT Connovation Ltd., 36B Sir William Ave, East Tamaki, Manukau 2013, New Zealand Faculty of Agriculture and Life Sciences, Lincoln University, PO Box 94, Lincoln, Abstract
Feral cats (Felis catus) have caused the decline and extinction of threatened species on islands worldwide. Their eradication or control is an essential part of restoring biodiversity on these islands. In most situations, a combination of lethal techniques are required to remove feral cats, including trapping, hunting and poisoning. Para- aminopropiophenone (PAPP) is being developed as a new, humane poison for feral cats. Mammalian carnivore species appear more susceptible to PAPP than birds, so it potentially has higher target selectivity than other available toxins. A proprietary formulation of PAPP (PredaSTOP®) developed by Connovation N.Z. Ltd. has been shown to kill cats humanely when delivered in a meat bait in pen trials. Two field trials of the formulation were undertaken with radio-collared cats. Toxic baiting was carried out by placing meat baits containing 80 mg PAPP in bait stations. 5/8 radio-collared cats in the South Island study and 13/16 radio-collared cats in the North Island study were poisoned. In the latter study, an additional three cats without collars that were monitored using infra-red cameras were also poisoned. Our results indicate that PAPP is an effective toxin for cats in the field, with potential application for their eradication or control on islands. Keywords
Control; eradication; feral cat; Felis catus; field trial; humane; para- aminopropiophenone; PAPP; poison; radio-tracking; toxin Running Head: Field trials of a new cat toxin
INTRODUCTION
Domestic cats (Felis catus) were brought to New Zealand from 1769 onwards and transported to many offshore and outlying islands. As well as causing some initial extinctions, they are responsible for the ongoing decline of a number of threatened species (Dowding and Murphy 2001; Gillies and Fitzgerald 2005). Cats have caused the extinction and decline of threatened species on islands worldwide and their eradication or control on these islands is an essential part of preserving and restoring biodiversity (Courchamp et al. 2003; Nogales et al. 2004). In most situations several lethal techniques are required to achieve their eradication, including trapping, hunting and poisoning (Veitch 1985, 2001; Nogales et al. 2004). In a recent review of cat eradications on islands, the application of toxic baits targeting cats was used in 32% of operations where the eradication methods were documented (Campbell et al. Para-aminopropiophenone (PAPP) is being investigated as a new humane toxin for introduced predators, including feral cats, in both New Zealand and Australia (Marks et al. 2004; Fisher et al. 2005; Murphy et al. 2007; Johnston et al. this issue). Previous research on PAPP has explored its potential as a cyanide antidote (Baskin and Fricke 1992), as a radio- protective agent (DeFeo et al. 1972), and as a selective toxin for controlling coyotes, Canis latrans (Savarie et al. 1983). The toxic effects of PAPP appear to be related to the rapid formation of methaemoglobin in some species. A high concentration of methaemoglobin leads to a rapid and lethal deficit of oxygen in cardiac muscle and the brain, resulting in animals becoming lethargic and unconscious prior to death (Vandenbelt et al. 1944; Marrs et al. 1991). PAPP has generally lower oral toxicity to birds than to mammalian carnivores, so presents some degree of target selectivity (Savarie et al. 1983; Fisher et al. 2008; Eason et al. 2010). PAPP is rapidly metabolised and excreted and is unlikely to cause secondary poisoning (Wood et al. 1991; Eason et al. 2010). Dogs (Canis familiaris), laboratory rats (Rattus norvegicus) and macaques monkeys (Macaca fascicularis) given sub-lethal doses of PAPP excreted 75-85% of it within 24 hours (Wood et al. 1991). Methylene blue is a widely- available and effective antidote for methaemoglobinemia caused by PAPP poisoning A proprietary formulation of PAPP (PredaSTOP®) has been developed by Connovation N.Z. Ltd. Feral cats fed 80 mg of PAPP in this formulation in meat baits became lethargic after 22- 55 minutes, lost consciousness without spasms or convulsions and died after 54 to 125 minutes (Murphy et al. 2007). The aim of the study reported here was to determine the field efficacy of PredaSTOP® in reducing feral cat numbers, to provide data for registration MATERIALS AND METHODS
Study areas
The first trial was undertaken in May 2008 in the South Island, at two sites in North Canterbury; the Patoa pig farm near Culverden (c. 480 ha) and the Kate Valley landfill near Waipara (c. 100 ha). The second trial was undertaken in June 2009 at Ngamatea Station, between Taihape and Napier on the central plateau in the North Island. This site was c. 1500 ha, and consisted mainly of pasture, pine windbreak hedging, and seral vegetation. Radio tracking
Cats were trapped using Havahart® live capture traps and were injected intramuscularly with Domitor® (50-100 µg/kg) in the first trial, and Domitor® (50-100 µg/kg) and Ketamine (100 mg/kg) in the second trial. Radio transmitters with an external whip aerial were attached to the cats using collars. After securing the collars in the first trial, the cats were injected intramuscularly with Antisedan® (125-375 µg/kg) to reverse the anaesthesia until they were fully revived (c.10-30 min) and then released. In the second trial, cats were returned to covered cages to recover and released when fully revived (c.30-40 min). The radio transmitters (Sirtrack Ltd) emitted 40 pulses per minute with a ‘mortality’ function that switched to 80 pulses per minute after 12 hours without movement. Tracking was carried out using a TR4 (Telonics, Inc) receiver and a Yagi three-element aerial. Three infra-red motion- detection cameras (DigitalEye™ 12.1 in IR Stealth Flash, Pixcontroller) were used in the second trial to monitor cats visiting bait stations. Cameras were moved around the study area and put at each station for at least two nights in the pre-feeding stage and were then used to check that cats came back to the stations after being radio-collared. Once this was confirmed, the cameras were used to monitor three cats without collars that were consistently identified Poison baiting
PredaSTOP® paste (200 mg) was applied to c.15 g meat baits to deliver 80 mg of PAPP in each bait. Meat baits consisted of minced beef (trial 1) and minced rabbit (trial 2) in a ball with the PAPP paste placed inside. ‘Submarine’ bait stations (see Fig 2 in Warburton and Poutu 2002) were used in both trials to minimise non-target interference. Before toxic baiting, pre-feeding was carried out by removing the wire mesh from the ends of the bait stations and placing tracking cards inside. Once prints of cats were found in the majority of feed stations the wire mesh was then attached to either end of the bait station, limiting access to the top Twenty-two bait stations were spread around the pig farm and 10 bait stations were distributed at the landfill. There were three nights of PAPP baiting at the pig farm and eight nights at the landfill. 1-3 baits were placed in each bait station and checked each day to assess condition. Cats were radio-tracked daily to determine whether they were still alive and in the Toxic baiting was carried out for five nights by placing five baits in each of 22 bait stations spread around the farm. Weather conditions were recorded and baits were checked, counted, removed each morning and replaced each evening. A snow storm on the fourth night meant that this night of baiting was delayed until the following night. As before, cats were radio- Eleven cats were captured and radio collared - six at the Patoa pig farm and five at the Kate Valley landfill. Of the six collared cats at the pig farm, one left the study area before toxic baiting, four were found dead after the first night of baiting and the remaining cat survived. Four cats without collars were also found dead, three after the first night of baiting, and one Of the five cats collared at the Kate Valley landfill, two were found dead before toxic baiting and appeared to have been crushed by heavy machinery. Of the remaining three collared cats, one was found dead after the first night of baiting and the other two survived. One cat without a collar was found dead after the first night of baiting and a second cat without a collar was found dead after the second night. The additional nights of baiting at the landfill site did not increase mortality amongst the radio-collared cats. All 11 cats found dead after PAPP baiting (5 radio-collared and 6 without collars) showed cyanosis around the mouth, consistent with poisoning by PAPP. Cats poisoned by PAPP in this trial ranged in weight from 1.31-3.35 kg. Twenty-one cats were caught and radio-collared - one of these died and four left the study area before toxic baiting. Thirteen of the 16 that were alive and in the study area at the time of toxic baiting died (Table 1). The three cats without collars monitored by cameras were also found dead after toxic baiting. All 16 cats showed cyanosis around the mouth, consistent with poisoning by PAPP. The 16/19 cats poisoned results in a mortality rate of 0.84 (95% binomial confidence interval 0.60-0.97 for underlying mortality rate based on assuming each cat had an equal probability of mortality). Cats poisoned by PAPP in this trial ranged in Over the five nights of toxic baiting there was confirmed bait take by feral cats on 23 occasions, with sixteen of these attributed to the radio-collared and camera-monitored cats. Unidentified cats were therefore also probably poisoned, as bait take and cat prints were recorded from seven bait stations where no carcasses were found. On four occasions multiple baits in stations were not entirely eaten but a monitored cat was found dead in the vicinity DISCUSSION
The results reported here are from the first field trials of PAPP baits targeting feral cats in New Zealand. They support the results of earlier cage trials (Murphy et al. 2007), and suggest that PAPP is an effective new tool for feral cat control in the field. Mortality was also achieved when cats partly ate baits, indicating that using multiple baits in stations could be an effective strategy to overcome the reluctance some cats may have about eating whole baits. Although feral cats are naturally cautious and can be difficult to trap (Twyford et al. 2000; Veitch 1985, 2001), cameras showed that all 21 cats in the North Island trial fed regularly on non-toxic bait from the submarine stations before being captured and collared. Four of the collared cats left the trial area immediately after release, suggesting that these procedures may have changed their normal ranges and behaviour. Although the other cats remained in the area, their foraging behaviour may also have been affected by capture and an association with human presence, possibly explaining why three of them did not enter the bait stations after being collared. In operational poisoning using bait stations, without prior live-capture, a higher bait take and resulting mortality seems likely. Nogales et al (2004) recommended that feral cats should be routinely eradicated from islands where possible and that new techniques should be developed to do this. PAPP promises to be a useful addition to available tools for cat eradications, especially on larger islands and in the early stages of eradication. After trapping and hunting, the most frequently used technique for eradicating cats from islands is direct poisoning (Nogales et al. 2004). Poisoning can be the most successful and effective technique for reducing the population quickly (Veitch 1985; Twyford et al. 2000) and the most commonly used toxin for primary poisoning is sodium monofluoroacetate (1080, Campbell et al. this issue). Although its use for island eradications of cats has been successful, the use of 1080 can be controversial; it has broad-spectrum toxicity to mammals and birds, and primary and secondary mortality of non-target species can therefore be a concern (Eason 2002; Weaver 2003). Although PAPP has some selectivity, in that mammalian carnivores are more susceptible weight-for-weight than most bird species tested, there is considerable inter-specific variation in response to PAPP in terms of susceptibility and toxico-dynamics (Savarie et al. 1983; Fisher et al. 2008; Eason et al. 2010). Also, as most birds weigh considerably less than cats, some bird species could still be at risk of poisoning if they ingest PAPP baits intended for feral cats (Murphy 1995). Reptiles may also be vulnerable to the toxic effects of PAPP. Acetaminophen (paracetamol) is used for control of brown tree snakes (Boiga irregularis) on Guam (Savarie et al. 2001) and this compound, like PAPP, elevates methaemoglobin to lethal levels in some species. No evidence was found of any non-target species eating PAPP baits in our trials, and we believe the submarine bait stations we used help ensure targeted delivery in Other methods of delivering PAPP to feral cats (and other pests) are also being trialled. A tunnel system has been designed which uses compressed gas to propel a measured amount of PAPP paste onto the abdomen of pests as they pass over a trigger. Oral exposure occurs when the animal grooms the paste from its coat. Cage trials have achieved proof of concept for this method as a means of killing stoats (Mustela erminea), indicating that a device capable of safely delivering multiple lethal doses of toxin without regular resetting can be produced In conclusion, the promising mortality established in these trials suggests that PAPP could be a useful additional tool for the control and eradication of feral cat populations. Despite some selective toxicity of PAPP for mammalian carnivores, there are potential non-target issues for birds that access bait, but it may be possible to lessen these by development of targeted delivery systems, such as bait stations, the tunnel system mentioned above, or by specific bait presentations that exploit cat feeding behaviour and physiology (Marks et al. 2004; Marks et al. 2006; Johnston et al. this issue). Few toxins are currently available for the control or eradication of cats. We believe the development of PAPP represents a significant advance. It is humane in comparison to available toxins, more toxic to cats than birds, and presents a low ACKNOWLEDGEMENTS
Thanks to John Dowding for help and advice with the North Canterbury trial and comments on this manuscript. Thanks also to the two referees for their helpful comments and Ian Westbrooke for statistical advice. Thanks to staff at the Kate Valley landfill and the Patoa pig farm for letting us work at their sites and helping with fieldwork. Thanks to Renata Apatu of Ngamatea Station for agreeing to the North Island study and to Martin Benstrum at Central Districts Pest Control for identifying an ideal site. Graham Dixon helped set up the North Island trial and provided ongoing support. Alan Beer and Rod Dixon at Hawkes Bay Regional Council supplied live capture traps and field support. Thanks also to Dr Lynn Booth for QA analyses and Paul Aylett for formulation. The use of PAPP in these field studies was authorised by the Environmental Risk Management Authority approval numbers HSC000319 and HSC10000. Provisional registration was also obtained from the NZ Food Safety Authority (V9513). All animal manipulations were approved by the Lincoln University Animal Ethics Committee (Approval# 189). The authors acknowledge the funding support of the NZ Department of Conservation under DOC Science Investigation No. 3932. REFERENCES
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their fates. Toxic baiting was carried out for five nights, using five baits in each of the 22 bait

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