Thomas, B.; R. Taylor, P. Dunlevy, K. Mouritsen, and J. Kemp. The Ka Mate reverse-bait snap trap – a promising new development
The Ka Mate reverse-bait snap trap – a promising new development
B. Thomas¹, R. Taylor², P. Dunlevy³, K. Mouritsen4, and J. Kemp5 ¹Ka Mate Traps Ltd, 190 Collingwood St., Nelson 7010, New Zealand.
INTRODUCTION Advances worldwide in rodent control or eradication comm.). Poor trap performance has exacerbated negative on islands during the past three decades have centred on public attitudes, resulting in stricter rules for trapping and the use of rodenticides (Howald et al. 2007). However, the animal welfare now embedded in policy and law (Mason propensity for rodents to develop a tolerance for toxicants and Litten 2003; Powell and Proulx 2003; Litten et al. (Bailey and Eason 2000) and increasing public opposition 2004). to use of poisons may limit their continued use, particularly Traps have traditionally varied from toggle trigger traps in mainland situations (Williams 1994; Towns and Broome with a small (baited) trigger to large treadle plate designs 2003; Mason and Littin 2003; Towns et al. 2006). Traps that use a lure to entice target species to step onto a plate to have similarly evolved in design and strategic use but they spring the device. Treadle snap traps are generally easier to also attract a public opposition, ostensibly over animal use than trigger traps. Many trap designs are operationally welfare issues. unstable and not robust enough to withstand the rigours of The New Zealand Department of Conservation long term field use. Baseboards on wooden models warp (DOC) requires a better performing snap trap that gives or split, staples pull and weak points on plastic variations more consistent catch/kill rates; improved animal welfare soon break. The larger trigger area of treadle traps makes outcomes; less non-target catch and environmental them more prone to misfire due to environmental events interference; enable higher quality trapping data; have and the presence of non target species. greater durability; less maintenance; quicker servicing during routine checks; and are easier for operators to use THE KA MATE REVERSE-BAITING SNAP TRAP than current preferred rodent traps. In short, better returns from traps in relation to money expended (Keith Broome Trap development pers. comm., April 2004). During the mid-1980s, two of us (RT and BT) In this paper, we describe the development and field experimented with ways to improve snap trap efficiency. trials of Ka Mate (KMT) reverse-bait snap traps, which Modifications were made to wooden based trigger “Ezeset” have been designed to meet modern efficacy and animal traps being used to catch Norway rats (Rattus norvegicus) welfare requirements. which led to “reverse-baiting” snap traps with dense, supportive bait beneath rather than on top of the trap trigger. Traditional, wooden based “break-back” traps (snap This utilised the bait as a removable structural component traps), have been used in New Zealand since at least 1920, of the trap, introducing significantly more stability into the particularly for bio-security at ports, rodent control around trigger function. factories, and as a health measure in urban environments (Wodzicki 1950). They have also been used internationally Six steel reverse-bait snap traps were then engineered for scientific data collection and in conservation management in 2003 and of the five ship rats Rattus( rattus) these first programmes (Bull 1946; Watson 1956; Wodzicki 1969; killed, three were cranial and two were humane neck strikes. Daniel 1973; Innes et al. 1995; Dunlevy et al. 2000; Efford Fifty of these traps were subsequently incorporated into a 6 et. al. 2006; Malcolm et al. 2008; Theuerkauf et al. 2010). month paired trial with “Victor Professional” traps at Weka More recently, snap traps have been employed in many Bush, Nelson Lakes National Park. In 2005, 100 handmade large-scale New Zealand mainland island rodent control aluminium prototypes (Fig. 1), which we called Ka Mate programmes (Saunders 2000, 2003; Speedy et al. 2007; (KMT) traps, were integrated with the steel traps into an Ogden and Gilbert 2008) and as adjuncts to toxicants in alternating trap trial with “Victor Professional” rat traps island eradication campaigns (Morrell et al. 1991; Taylor and tested over 13 months in Nelson Lakes Big Bush rodent et al. 2000; Merton et al. 2002; Thomas and Taylor 2002; control area. Another 100 KMT prototypes were included MacKay and Russell 2005; Nugent et al. 2007; Witmer and in an alternating trap trial with Victor Professional rat traps Burke 2007; Varnham 2010). in DOC’s 2005 trap research programme in Te Urewera National Park. Rats have been eradicated from at least two islands of up to 21 ha with snap traps (Moors 1985; MacKay and The KMT traps caught and killed mice (Mus musculus), Russell 2005; Howald et al. 2007), but trapping is usually rats (Rattus rattus), weasels (Mustela nivalis), stoats considered to be too labour intensive and expensive as a (M. erminea) and hedgehogs (Erinaceus europaeus). In sole eradication technique for rats (Keith Broome pers. the Te Urewera trial, the KMT traps also had far fewer
Pages 233-238 In: Veitch, C. R.; Clout, M. N. and Towns, D. R. (eds.). 2011. Island invasives: eradication and management. IUCN, Gland, Switzerland. 233 Island invasives: eradication and management
Fig. 1 Relative condition of Ka Mate prototype (left) and Victor Professional (right) after equal environmental exposure at adjacent sites in the Big Bush trap trial. Fig. 2 Ka Mate “safeTcatch” trap - with trigger cowling and wax bait. unsprung/bait missing events than Victor traps (2 versus 71, respectively), indicating that the reverse-bait trigger it was mechanical malfunction (rectified in seconds with a reduced problems with non-target and environmental file) that caused the problem in the small number of KMT triggering. When compared with wooden-based wire striker traps afflicted whereas learned avoidance behaviour by rats traps, operators also found the aluminium KMT to be the was the cause with the CM traps. safest to set and handle, easiest to clean and maintain (Fig. From 2007-2010, KMT prototype traps were used in 1), required the least service time during routine checks, ecological surveys on New Caledonia, Wallis and Futuna and had the greatest durability in the field (Paton et al. Islands (Theuerkauf et.al 2010) and in trials to test the 2007; Morriss et al. 2007; Moorcroft et al. 2010). efficacy of unprotected KMT traps against “Ezeset” In August 2005 on the Seychelles Islands, Gideon wooden based trigger traps on Pacific, ship, and Norway Climo (pers. comm.) undertook three 2 hour evening rats (Theuerkauf et.al 2011). These studies concluded trapping sessions using six KMT prototype traps, which from C. 2900 trap nights that KMT traps were the more were systematically set, checked, cleared and rebaited effective against rats > 100 g (i.e. predominantly ship and with coconut on a rotational basis. He caught over 60 ship Norway rats), whereas “Ezeset” traps were more effective rats, achieving 100% humane head and neck strikes on the against rats < 100 g (predominantly Pacific rats). A high adults and predominantly shoulder and mid torso strikes percentage of “Ezeset” traps were sprung by heavy rain on small rats. but rain had no effect on the KMT traps, which maintained The first Norway rat (R. norvegicus) caught in a KMT a significantly higher percentage of operational traps prototype was on Adak Island, Alaska in May 2006. The throughout the trials. The durability of the KMT traps was technician reported “a perfect kill just behind the eyes” and considered an advantage for long term field use. that the unprotected traps remained set and continued to catch after exposure to “gales whipping vegetation, deluges The “safeTcatch” rat trap of rain and burial in snow” (Lisa Spitler pers. comm.). The first commercial KMT trap to be produced was the On Wake Atoll in October 2007, BT and PD established “safeTcatch” (“sTc”) rat trap (Fig. 2), which incorporates a 200 x 200 m trapping grid for rats consisting of 100 traps a safe set mechanism and is currently available from KMT spaced at 20 m. Fifty KMT prototypes formed a central core Ltd, Nelson, NZ. The traps are constructed from extruded within the grid and were surrounded by 50 Catchmaster aluminium with stainless steel shafts and fasteners and (CM) wooden based trigger traps modified to operate as double sprung with galvanised springs. Bar catches that “treadle” traps. Midway through the trial an extra 32 CM engage when arming the trap work in conjunction with traps were added to the periphery, creating double trap sets the wide retainer arm that automatically releases the safety on three sides of the grid. All traps were tacked to plywood base boards, placed unprotected on the ground and baited with cubes of fresh coconut. The grid was checked and serviced morning and late afternoon, totalling 13 check periods over 7 days. Wake had a high density rat population and a total of 549 rats (520 R. exulans and 29 R. tanezumi) were caught ─ 297 from 650 individual KMT trap checks and 252 from 810 individual CM trap checks. KMT traps scored 157 head/neck strikes to 125 body strikes, whereas CM traps scored 94 head/neck strikes to 152 body strikes and both trap types recorded low numbers of limb and tail strikes. Non-catch interference also varied between trap types, with KMT recording 85 traps sprung/empty and 13 traps set/bait missing, compared to CM with100 traps sprung/empty and 172 traps set/bait missing. Hermit crabs were the only non-targets caught, 6 in KMT and 22 in CM (BT & PD unpublished data). Clearly the KMT traps out- performed the CM traps on Wake, scoring higher catch rates to trap check ratios and a greater percentage of head and neck strikes. The considerable disparity in trap set/ Fig. 3 Typical humane head strike - ship rat in unprotected bait missing totals is hugely significant, especially since Ka Mate “sTc” trap.
234 Thomas et al.: Ka Mate snap trap catch during setting, which makes the process easier for Bait development those with weaker hand strength. The traps are supported The bait is crucial to the function of Ka Mate traps and with replacement parts, which means that KMT traps can requires removal by a positive twist or tug to extract it from be easily repaired, upgraded or converted as design of beneath the trigger to spring the trap. Rodents invariably component parts develops to improve trigger configuration take baits by mouth, which ensures the animals’ head is or to suit a different target species. Replacement of any part in an optimum position to achieve an efficient fatal head can be easily undertaken using a simple custom-designed strike. Bait can be household food items, such as hazel trap tool, so there is no reason to discard a whole trap. nuts, brazil nuts, walnuts, dog and cat pellets, chocolate, A detachable plastic trigger cowl forces rats to take dried cheese and cubes of fresh coconut, or any other food the bait from the front of the trap, ensuring a humane firm enough to support the downwards pressure of the head strike (Fig. 3) while reducing potential for learned trigger. KMT has also developed and tested purpose-built trap avoidance. Baits held firmly beneath the curve in the baits using “Pestoff” non-toxic pre feed (Animal Products, trigger ensure the trap will not trigger prematurely when Wanganui) as a base ingredient. When mixed into palm knocked or when non-target species such as lizards, birds, nut wax with different flavoured additives, the baits can or small mammals walk, crawl, or bounce on the trigger. be moulded into plugs of optimum shape and size to fit Since it requires a concerted effort by the rat to remove the KMT trigger (Fig. 2). These baits can be effective for the bait from beneath the trigger (which can cause the up to a month in dry conditions, but earlier replacement is trap to move), it is essential that the trap be restrained for recommended. maximum efficiency. Holes are therefore provided in the base for spikes, screws or ties, which enable it to be secured Utilisation and user perception to a backing board or either horizontally or vertically to a When the Ka Mate “sTc” trap became available in natural substrate. The operational stability inherent in the June 2008, prospective users such as community trapping design of the trap (especially the trigger function) reduces groups began undertaking trials to test the new traps. They spontaneous misfire and by-catch and the simple trap setting invariably set up proximately paired and/or alternating procedure minimises operator bias between trappers. trap trials with Victor Professional traps and early anecdotal feedback indicated some disappointment over Ka Mate “flat-pack” protective station KMT trap performance. The issues apparently arose from Protective covers are used with traps to restrict entry by long established practices associated with the operation non-target fauna and to protect the baits, but many covers of traditional snap traps, which were problematic when in use are bulky, heavy, flimsy or difficult to access. Ka universally applied to Ka Mate traps. For example, trappers Mate has produced a trap station fabricated in one-piece assumed that baits placed under the extreme end of the from “Corflute” cellular plastic sheeting. KMT flat“ pack” KMT trigger would be easier to remove (i.e. the equivalent stations fold compactly for storage and transport and have of hair triggering old style traps) and consequently improve a lid that provides easy access (Figs. 4 and 5). “sTc” trap performance. The practice instead exacerbated The stations have entrances on each side at one end for the incidence of rats beating the striker, being injured by rats and centrally placed for mice, which provide alternative a glancing blow or caught by a limb. It also increased avenues for entry or escape and create a 90 degree entry the chance of catching non-target species. Furthermore, angle that reduces the reach of non-target birds. When trappers often did not appreciate that the curved “sTc” stations are fixed with stakes or weighted with rocks on trigger that accommodates the bait is specifically designed the side flaps, target species can enter and walk up to the to slow rats down by forcing them to twist the bait sideways trap on natural substrate. Decomposing carcases suppurate to remove it, ensuring the head is in optimum position to directly into the ground. Alternatively, KMT stations and receive an efficient cranial strike. traps can be screwed vertically onto trees/posts/walls at a height that allows target species easy access. When set vertically, the rats are confined to a smaller floor space, preventing pull back as the trap triggers and enhancing catch effectiveness (Fig. 5).
Fig. 4 Corflute “flatpack” trap-station (assembled for use and folded for storage). Fig. 5 Vertically set “flatpack” station with the door open.
235 Island invasives: eradication and management
Similarly, when several users complained that their KMT traps several times, often from different angles, KMT traps were not achieving high catch rates, it transpired before even putting a foot on them and they sometimes that during service checks any traps found still set were departed altogether for several hours or overnight before bypassed, with many baits unchanged for two or three returning to check out a trap again. As their confidence months. Contrary to common belief, rodents do not like grew, they would on occasion mouth the bait several times stale mouldy food and it is imperative that the bait on KMT or nibble it a little before making the fatal decision to take traps be replaced regularly. a firm hold and twist or pull it from beneath the trigger Also, people placed new sterile KMT traps alongside (BT, RT, PD and Gideon Climo pers. obs., Baki Bakhshi pre-used odour saturated treadle traps, creating an obvious video recording). Many trappers fail to understand that the disadvantage for the KMT traps because of rats’ inherent most important function to test for in a new trap is not how nervousness around new equipment. Neophobic behaviour quickly it catches rats, but how effectively it kills them. combined with differences in trap function (e.g., the Since results from several of the field trials raised issues arbitrary depression of the treadle foot-plate vs conscious, with regard to the validity of proximal paired testing, we controlled reverse-trigger bait removal) tended to skew considered a well planned, large scale trial was needed the trials into a “race” to see which trap would catch the to test the efficacy of the commercially produced KMT same rat first. Trap catch data and observations made on “safeTcatch” rodent traps in isolation of other brands. several occasions indicates that in most instances (unless An opportunity for a major collaborative “trap trial by there is intense competitive pressure) it takes much longer management” arose in late 2008 using “sTc” traps for rat for rats to trigger a KMT trap than a large-plate treadle control in a private eco-restoration project in Northern trap. Rats have been seen to cautiously approach baited Coromandel.
Fig. 6 Waiaro grid layout and Year 1 tracking-tunnel results.
236 Thomas et al.: Ka Mate snap trap
WAIARO SANCTUARY TRAPPING PROGRAMME month, but probably lost their attractiveness as bait for rats much sooner. Operators found the KMT stations convenient Waiaro Sanctuary is private land in the Moehau Kiwi to install and access, and the traps easy to operate and Recovery zone, Moehau Forest, ten kilometres north of service. Colville. The first phase goal of this new rodent trapping programme was to achieve a toxin-free eradication of ship DISCUSSION rats, or to reduce and hold their densities at low levels (5- 10% tracking tunnel indices) over a 75 ha block, using only Varied outcomes from the early field trials made it KMT traps. difficult to determine what advantages the KMT prototypes A 75 ha grid was created with 427 single “sTc” rat provided over the traditional trigger and treadle traps. As traps at 25 m intervals along 10 trap lines spaced 75 m the data base grew we began to speculate that rat behaviour apart, with a perimeter line set along three sides of the coupled with trap function was elemental to the different grid (Fig 6). Fifty of the perimeter traps were in protective catch rates being recorded between the trap types, the KMT “flatpack” stations. The rest of the traps were fitted main contributing factor being that it took rats longer to with plastic trigger cowls and secured, uncovered, by spring a KMT trap than a traditional trigger or treadle being pinned to the ground or tied to tree roots. Five trap. The dense population of Pacific rats on Wake Atoll index lines (10 tracking tunnels per line) were installed to coupled with the use of night vision equipment (plus the independently monitor trapping success, three within the mass of data this project generated) and Gideon Climo’s grid and two outside (Fig 6). trapping of ship rats in the Seychelles provided the first Traps were given time to weather and three applications opportunities to evaluate rat behaviour in conjunction with of Pestoff RS5 nontoxic pre-feed was hand broadcast KMT trap function from direct observation. Although we sequentially across the block, along trap lines and then in have drawn our conclusions from all the studies, it is the close proximity to the traps only. The traps were then set significant level of rat control achieved with Ka Mate traps using KMT RS5 wax plug baits. in Waiaro Sanctuary that verifies its potential when used alone, unencumbered by the proximity of other trap types Fifteen full checks with all traps serviced in a 24-48 hr (Fig. 7). period were completed in the 12 months from 22 January 2009 to 21 January 2010, the majority in the first 6 months. The functional stability of the reverse-bait trigger Alternatively, progressive servicing was carried out line generates a very consistent catch performance. The by line over periods of a week to a month and in winter percentage of quality-kill head and neck strikes can service checks were restricted to perimeter lines only. be increased and environmentally generated misfire, Head and neck strikes on adult rats were so consistent that rodent induced trap disturbance, and non-target by-catch the field teams stopped recording the category, insisting significantly reduced when using KMT traps. Such results that the KMT traps were achieving “99%” humane kills, minimise the opportunities for rats to learn trap avoidance including body blows to smaller rats (KM pers. obs.). Four and reduces animal welfare issues. The simple standard index tracking sessions were undertaken both inside and setting procedure of KMT traps eliminates operator bias outside the trapped area - two prior to trapping and two and improves population indexing. during trapping. The functional stability of KMT traps coupled with The traps caught 656 rats, with index tracking trap durability enables traps to be screwed vertically onto frequencies reduced from up to 100% before trapping bulkheads in ships and permanently fixed inside containers to 10% during the trapping period (Fig 6). An initial or onto wharves. KMT traps can easily be cleaned and knockdown of 299 rats was achieved in less than three sterilised for bio-security purposes by boiling and are robust weeks with tallies rising to 558 at three months. A further enough to operate with minimum maintenance in estuarine 98 rats were caught during the next nine months with 15 of and marshland environments. They could be hoisted into these in the six weeks before the final January 2010 check trees to sample for rodents in forest canopies or provide (Fig. 7) - a marked contrast to the 117 caught on night one protection to hole nesting birds, and are safe enough to be 12 months earlier. The reduction of rats was substantial and set in many situations where use of other traps would pose only one bird (not identified) and 81 mice were the by- a risk to vulnerable non-target species. catch from one year’s trapping (approx 90,000 trap nights) In New Zealand, increasing numbers of community in Waiaro Sanctuary with unprotected traps. groups vie for the same resources to set up predator control The RS5 wax plugs remained intact for more than a programmes and many established projects are continually expanding the areas already being trapped. Development of effective long-life bait will be the key for using traps instead of toxicants to control rats in mainland situations, or for long term surveillance on islands. As trapping technology and deployment improves, wider spacing and less frequent servicing may make it possible to manage larger areas for the same capital outlay, but care must be taken to get the strategy right.
ACKNOWLEDGMENTS We are indebted to Bernard Goetz for engineering advice and for fabricating the steel prototypes, to Jean Fleming and Mary McEwen for the grant received from the C.A. Fleming Trust and Alan Hall who made the “Weka Bush” trial traps, but wouldn’t send a bill. Matt Maitland and Dan Baigent organised the pilot trials with Department of Conservation support and Manaaki Whenua Landcare Research provided financial assistance for the independent report. To Gideon Climo and Jörn Theuerkauf for sharing valuable results from their trap trials in the tropics and Fig. 7 Waiaro trapping - comparative totals of rats caught by period. Katie Swift (USFWS), US Air Force and our Wake Atoll
237 Island invasives: eradication and management survey colleagues for the opportunity to run the airfield Morrell, T.E.; Ponwith, B.; Craig, P.C.; Ohashi, T.J.; Murphy, J.G. and Flint, E. 1991. Eradication of Polynesian rats (Rattus exulans) from trapping grid. To Dion and Caren Paul (cofounders of Rose Atoll National Wildlife Refuge, American Samoa. Appendix 3. Ka Mate Traps Ltd) for the company name, logo and DMWR Biological Report Series, No 20. Department of Marine and generosity when moving on to bigger things and Fuka (Liu Wildlife Resources, Pago Pago, American Samoa. Xuezheng “Allen” and Shi Cheng “Johnson”) for their Nugent, G.; Morgan, D.R.; Sweetapple, P. and Warburton, B. 2007. patience and producing a quality product. The Biodiversity Developing strategy and tools for local elimination of multiple pest Condition Fund team provided advice and funding to species. In: Witmer, G.W.; Pitt, W.C. and Fagerstone, K.A. (eds.). Waiaro Sanctuary, and to neighbours for their cooperation Managing vertebrate invasive species, pp. 410-417. Proceedings of an International Symposium, USDA/APHIS/WS, National Wildlife and input into the project. To supportive friends such as Research Centre, Fort Collins, U.S.A. Ken Lipsmeyer, Ruth and Lance Shaw, Ron and Robynne Peacock, Richard van den Berg and Richard Daem, Anna Ogden, J. and Gilbert J. 2008. Prospects for the eradication of rats from a large inhabited island: community based ecosystem studies on Great Clark and numerous colleagues in science and conservation Barrier Island, New Zealand. Biology Invasions 11(7): 1705-1717. circles who have provided help and encouragement over many years, and more recently the Ka Mate trap users Paton, B.R.; Maitland, M.J.; Bruce, T.A.; Wotherspoon, J.A.; Brow, A.K.; Leggett, S.A. and Chisnall, D.T. 2007. Rotoiti Nature Recovery Project who have provided feedback and useful suggestions. To Annual Report: July 2005 – June 2006. Occasional Publication No. 71. Keith Broome, John Innes and another reviewer who made Department of Conservation, Nelson, New Zealand. suggestions that improved the manuscript and Dave Towns Powell, R.A. and Proulx, G. 2003 Trapping and marking terrestrial and Dick Veitch for editorial improvements. But not least mammals for research: integrating ethics, performance criteria, we acknowledge Pam and the long suffering Thomas techniques, and common sense. ILAR Journal 44(4): 259-276. whanau for their vital role in the development of Ka Mate Saunders, A.J. 2000. A review of Department of Conservation mainland Traps and this paper – arohanui ki a koutou katoa. restoration projects and recommendations for further action. Department of Conservation, Wellington, New Zealand, 219 pp. REFERENCES Saunders, A. 2003. New Zealand “mainland islands”: ecological Bailey C.I. and Eason C.T. 2000. Anticoagulant resistance in rodents. restoration through intensive multi-pest control. Aliens 17. 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