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Eradication of norway rats (rattus norvegicus) from hawea island, fiordland, using brodifacoum

R.H. TAYLOR and B.W. THOMAS Ecology Division, Department of Scientific and Industrial Research, Nelson.
ERADICATION OF NORWAY RATS (RATTUS NORVEGICUS)FROM HAWEA ISLAND, FIORDLAND, USING BRODIFACOUM Summary: Norway rats were eradicated on bush-covered Hawea Island (9 ha) in Breaksea Sound, using the
anticoagulant rodenticide "Talon 50 WB" (brodifacoum). The work was done as a conservation measure and to
evaluate the feasibility and costs of eradicating rodents quickly from islands. The 50-100 rats present were
eradicated in about two weeks by applying a simple strategy that took full account of the characteristics of the
poison, the environment, and the behaviour of the target species. The technique used was designed to monitor
its own progress, kill every rat as quickly as possible, continually detect the presence of surviving rats, limit the
risk to non-target species, and overcome the many problems often associated with "getting the last rat".
Keywords: Norway rat; Rattus norvegicus; Rodentia; Fiordland; Hawea Island; Breaksea Sound; New Zealand;
eradication; poisoning; brodifacoum.
IntroductionIn eradication campaigns when few of the target rattus), and kiore (R. exulans) from several New species are left, the operations usually become Zealand islands up to 22 ha in extent (Moors, 1985a; protracted, costs become increasingly high for each Taylor, 1984a; Towns, 1988). Following long-drawn- animal killed, and field staff tend to lose motivation.
out campaigns against Norway rats on the Noises Unfortunately, there is also a tendency for managers, Islands, Moors (1985a) concluded that "the last few or those providing finance, to stop the campaign rats are certainly the most expensive and exacting to before eradication is achieved, on the grounds of destroy, but they are also obviously the most vital if excessive costs without any certainty of success the campaign is to succeed". He also found that the (Merton, 1978).
greatest practical difficulty encountered was detecting In 1976, Yaldwyn (1978) concluded a conference the continued presence of rats at very low density on the ecology and control of rodents in New Zealand (Moors, 1986).
by stating that the possibility of complete Most recent commentators on methods of rat extermination of rodent populations from New extermination have stressed the difficulty of getting Zealand offshore islands was "remote, or at least a the last rat, and the importance of using as many very, very difficult thing indeed". By the early 1980s methods of killing rats as possible and never relying it was still widely held that no real breakthrough in on one weapon alone (Moors, 1985a; Wace, 1986).
this field was in sight (Atkinson, 1986).
Moors' (1985a) plan of campaign was to use sodium Today the scene is very different. New, potent monofluoroacetate (1080) to try and obtain a rapid and highly palatable "second-generation" initial reduction in rat numbers, and then follow up anticoagulant poisons have been developed to improve with the anticoagulant brodifacoum "against those control of rats and mice, and to combat the genetic rats which had become shy of 1080, or had not been resistance to warfarin that has developed in many attracted to bait containing 1080".
populations of rodents throughout the world Repeated control with poison or traps represents (Greaves, 1985). Unlike warfarin and other earlier a major selective pressure on Norway rat populations anticoagulants, second-generation anticoagulants kill (Barnett, 1975). One result is the very rapid after a single feeding and so dispense with the need development of genetical resistance to frequently used for ingestion over several days. Rats will consume a poisons (Howard, Marsh and Palmateer, 1973; lethal dose well before they begin to experience toxic Greaves, 1985). Another is an increase in the level of effects (Redfern, Gill and Halder, 1976), and unlike neophobia (sometimes called "new object reaction") many other acute or chronic poisons, sub-lethal doses among members of controlled populations (Shorten, are not known to cause bait aversion in Norway rats 1954; Cowan, 1977). Neophobia is an inherited tendency - which can be reinforced by learning - Since the early 19805, these new poisons have for animals to avoid any new object or changed been used to eradicate Norway rats, ship rats (R. situation in the environment. Of course all new things New Zealand Journal of Ecology l2:New Zealand Ecological Society NEW ZEALAND JOURNAL OF ECOLOGY, VOL. 12, 1989 will eventually become familiar - so the effect isalways temporary (Barnett, 1975). Usually theavoidance of new bait stations lasts from one to tendays, but novel baits in familiar surroundings areoften accepted in one or two days (Elton and Ranson,1954). Another behavioural response is a learnedaversion to a poison, type of bait, or bait station.
Such "bait shyness" occurs in individuals that havepreviously suffered from sub-lethal poisoning, and itseffects can be long lasting (Rzoska, 1953; Chitty,1954).
With these problems in mind, our approach to practical rat eradication from islands has been todevelop a strategy that will be closely adhered tothroughout the campaign and require little, if any,additional input to get the last rat. We aim for aplanned programme for each island that takes account Figure 1: Islands at the entrance of Breaksea Sound. of the behaviour and ecology of the target species andall aspects of the local environment. This programmeshould progressively kill rats in the shortest possible to eradicate rats from the large (170 ha) and rugged time, continually monitor its own progress, detect the Breaksea Island (Thomas and Taylor, 1988), where presence of surviving rats, limit the risk to non-target Norway rats have affected the population densities of species, and - most importantly - maintain the many invertebrate groups (Bremner, Butcher and confidence of administrators and the morale of the Patterson, 1984).
campaign personnel. We consider that for each A concurrent study of the effects on Hawea campaign the operators should select the single best Island's other biota from rat eradication (Taylor, method available and employ it with the aim of Thomas and Taylor, 1986; Taylor and Thomas, 1986) achieving a 100% kill in the shortest possible time. If is still underway and will be reported separately.
this initial plan fails, then contingency techniques canbe resorted to, but it will be easier to understand any problems if the effectiveness of each killing method is Hawea Island (45o 35 'S, 166 o 38 'E) is a 9 ha bush- clad island in the entrance of Breaksea Sound, The work reported here involved the eradication Fiordland National Park. A small vegetated islet, of a population of Norway rats from Hawea Island, "The Hump", lies less than 5 m off its southern shore Fiordland, using the anticoagulant rodenticide "Talon (Fig. 2). Apart from a narrow zone of bare rock 50 WB" (ICI New Zealand Ltd), a wax briquette around the coast, both islands are covered with peaty formulation containing brodifacoum. The need for soils which are deepest on the ridges and spurs, and this action became clear during biological surveys of less than 1 m deep in most other areas.
islands in Doubtful, Breaksea and Dusky Sounds A vegetation survey in October 1986 showed that undertaken by Ecology Division and Fiordland the forest was tallest (6-18 m) towards the centre of National Park staff in the period 1974-84. These Hawea Island and was dominated by southern rata surveys disclosed that Norway rats were plentiful on (Metrosideros umbellata) and kamahi (Weinmannia Breaksea Island and also present on neighbouring racemosa), with pigeonwood (Hedycarya arborea), Hawea Island, that rats had not yet reached adjacent stinkwood (Coprosma foetidissima), kotukutuku Wairaki Island - only 300 m away, and that these (Fuchsia excorticata), five-finger (Pseudopanax three islands (Fig. 1) had high conservation potential colensoi), miro (Prumnopitys ferruginea) and (Thomas, 1985), being among the very few in broadleaf (Griselinia littoralis). In less sheltered parts, Fiordland that remained free of stoats Mustela where the canopy was lower, the main species were erminea (Taylor and Tilley, 1984). Other major Dracophyllym longifolium, five-finger, southern rata, objectives of the rat extermination campaign were to pigeonwood, mapou (Myrsine australis), kotukutuku, test our strategy and techniques for rat eradication on broadleaf, kamahi and stinkwood. The exposed islands, and to evaluate the feasibility of using these coastal scrub fringe was mainly of Dracophyllum, TAYLOR and THOMAS: RAT ERADICATION ON HAWEA ISLAND Hebe elliptica, Olearia oporina, O. reinoldii and flax mainland is about 900 m which is well in excess of a rat's swimming range in southern New Zealand waters In most parts of the forest there was a thick (Taylor, 1984b).
understory of kiekie (Freycinetia baueriana), tree ferns(Dicksonia squarrosa and Cyathea smithii), haumakaroa (Pseudopanax simplex), mahoe The broad plan of campaign was to observe the rats (Melicytus ramiflorus), the above-mentioned canopy and their environment on Hawea Island; to avoid any species, and other shrubs. The forest floor was unnecessary actions that would induce food aversion covered by hen and chicken fern (Asplenium or neophobia in the population; to eradicate the rats bulbiferum), other ferns, Astelia fragrans, flax, moss, as quickly as possible using Talon poison; to continue liverworts and seedlings. In open areas the main plants monitoring with Talon and non-toxic baits to confirm were shore tussock (Poa astonii), Anisotome lyallii, eradication; and to investigate the potential for using Carex appressa, moss and lichens.
the same methods to eradicate rats from Breaksea In 1985 and 1986 the common native forest birds on Hawea Island were the New Zealand pigeon(Hemiphaga novaeseelandiae), grey warbler (Gerygone Presence, distribution and behaviour of rats igata), South Island fantail (Rhipidura fuliginosa fuliginosa), yellow-breasted tit (Petroica macrocephala Observations on the presence, abundance and macrocephala), bellbird (Anthornis melanura) and distribution of rats on Hawea Island before and silvereye (Zosterops lateralis). New Zealand falcons during the poisoning included: recording rat sightings (Falco novaeseelandiae) were regular visitors.
by day and night; detecting rat tracks on prepared Common introduced species were the hedgesparrow surfaces of damp sand; counting rat burrows on three (Prunella modularis), blackbird (Turdus merula), song marked plots (Fig. 3) of 400 m2 at the centre of the thrush (Turdus philomelos) and chaffinch (Fringilla island, 175 m2 near the south coast, and 675 m2 on coelebs). Breeding sea birds were southern blue The Hump; searching for rat burrows, droppings and penguin (Eudyptula minor), Fiordland crested penguin feeding sign; and kill-trapping. Twenty rat snap-traps (Eudyptes pachyrhynchus), broad-billed prion were set under sheet metal covers and operated over (Pachyptila vittata), sooty shearwater (Puffinus three nights in both April 1984 and October 1985, and griseus), and southern great skua (Stercorarius 73 similar sets were operated over five nights from 17 to 21 April 1986 during the latter part of the Although the creviced rocky foreshore is a poisoning campaign. All traps were baited with fish- suitable habitat for Fiordland skinks (Leiolopisma flavoured pet food. The results of the trapping are acrinasum), none have been found on Hawea Island expressed as captures per 100 trap nights (C/l00 TN) (Thomas, 1985). Similarly, large flax weevils after correcting for unavailable traps by the method of (Anagotus fairburni) and stag beetles (Dorcus helmsi) Nelson and Clark (1973).
appear to be absent, although the dried mandibles of The behaviour of Norway rats towards bait a stag beetle were found on The Hump. Fiordland stations, Talon bait, apples, and to other rats in the skinks and these large flightless insects are abundant vicinity of these stations, were observed incidentally only 300 m away, on adjacent Wairaki Island during the poisoning operations on Hawea Island.
(Thomas and Taylor, 1988). Presumably, they were These aspects were also studied in more detail and exterminated from Hawea Island by rats.
with a variety of non-toxic baits (bacon, cheese, It is not known exactly when or how Norway rats bread, shellfish) on Breaksea Island.
reached Hawea Island, but they could well have beenthere for over 150 years. They first arrived at Dusky The poisoning campaign Sound, Fiordland, in May 1773 on Captain James Bird-proof bait stations (illustrated in Thomas and Cook's Resolution, and most likely reached Breaksea Taylor, 1988) were constructed from 100 mm and Hawea Islands during the intense period of diameter, yellow, non-perforated, plastic "Nova-coil" sealing that followed Cook's reports (Thomas and pipe. Their colour made them easy to find, even Taylor, 1988). In modern times the risk of re-invasion among thick ground vegetation. Stations were 400 mm seems slight. There are no regular anchorages or long, had a tracking surface of damp sand at each end landing beaches at Hawea Island, visitors are few and and a watertight, transparent lid in the centre for no stores are landed there. The distance to the nearest inserting and checking the baits. They were heldfirmly to the ground by two hoops of fencing wire.
NEW ZEALAND JOURNAL OF ECOLOGY, VOL. 12, 1989 In March 1986, 73 bait stations were distributed The eradication of rats from Hawea Island was over Hawea Island at about 40 m intervals, using a network of tracks (Fig. 2) which had been cut and 1) Checking all 73 bait stations for interference in marked during this and a previous visit. To minimise June, July, August and October 1986, and in neophobic avoidance by rats, the bait stations were March and October 1987; old baits in each station left in position for three weeks before poison was laid were replaced with two fresh talon baits in July on 10 April. During the poison operation each station and October 1986, and March and October 1987.
was baited with two 15 g Talon poison baits, each 2) Snap-trapping at each bait/trap station for a total containing 0.005% brodifacoum, placed loosely in the of 2,139 trap nights, from 27 July to 27 August tunnels and not anchored in any way. The number of baits taken from each station was recorded, and the 3) Placing ripe eating apples on the ground near baits replenished daily from 11 to 22 April 1986. At each of the 73 bait/trap stations for a total of the end of this period each station was left baited with 3,286 apple nights; from 27 July to 27 August four Talon baits.
1986, from 24 to 29 October 1986, from 11 to 16March 1987, and from 15 to 21 October 1987.
Between 12 and 24 apples were similarly placedon Breaksea Island during each of these fourvisits to test their acceptability to Norway rats atthose times. Apple is a favoured food of bothNorway and ship rats (pers. obs.) and distinctivegrooves left by the rodents' incisors show upclearly on its skin and flesh. Some birds andinvertebrates will also feed on apples (particularlyover-ripe ones), but their feeding signs are easilydistinguished from that of rats.
4) Searching for fresh sign of rats in locations on Hawea Island previously favoured by them.
Full details of time and expenditure were recorded during all operations.
Presence, distribution and behaviour of ratsEleven Norway rats (20/100TN) were trapped near thesouth coast of Hawea Island in April 1984, and eight(14/100TN) in October 1985. On later visits, evidenceof rats was found over the entire island, including TheHump. In March and April 1986, rats were commonlyencountered on Hawea by day and by night, mostoften in the taller forest at the southern end. Ingeneral, rats on Hawea Island were most common inareas with miro trees, areas where ferns and other lowplants covered more than 25% of the ground, andareas close to an extensive intertidal zone. Rat burrowdensity was measured as four per 100 m2 on TheHump, seven per 100 m2 at the centre of the island,and 34 per 100 m2 near the south coast. Thedistribution of rats on the island was also indicated by Figure 2: Hawea Island, showing cut tracks and routes, and the amount of bait removed from each station; most the distribution of poison-bait and rat-trapping stations bait was taken from the south end of Hawea Island and the least from The Hump (Fig. 3).
TAYLOR and THOMAS: RAT ERADICATION ON HAWEA ISLAND invariably carried away whole, and rats commonlyreturned to the bait stations for the second bait within30 seconds of removing and cacheing the first. Onelarge male rat continued to return as long as thetunnel was re-baited, and took a total of five Talonbaits within approximately 3 minutes. On several lateroccasions, when the observer visited and touched thebait station but did not re-bait it, the rat almostimmediately returned and entered the tunnel.
Large rats carried off whole apples in their mouths. Smaller rats occasionally rolled apples away,sometimes to burrow entrances, but usually they tookvery large bites and carried off that portion beforequickly returning for further bites. Large pieces ofbread, cheese and bacon were similarly carried off.
Only small crumbs of food were eaten in situ, whetherin a bait station or in the open.
Large male rats aggressively defended the baited tunnels from the rest of the population. Althoughsmaller rats were obviously attracted to the smell ofthe baits, they appeared reluctant to approach closerthan about 2-3 m while a large rat was nearby. Somelarge males were seen to chase smaller rats away forperiods of up to two hours, biting any they managedto catch. Finally, when the dominant animals hadapparently had their fill and left, smaller rats(sometimes several at one time) cautiously approachedto feed, and similarly carried off the larger items. Onegroup of three small rats moved around a particular Figure 3: Hawea Island, showing the number of nights over circuit several times, returning to the tunnel every which poison was taken by rats on different parts of the 15-20 minutes apparently to check for competitors, island, and the position of plots (stars) on which rat burrows before they finally carried off the baits.
were counted. The poisoning campaignThe nightly take of poison bait over the period of theApril 1986 visit is shown in Fig. 4. Eighty-threepercent of the amount available was taken by rats on Rat tracks were found on the sand surfaces of 13 the first night, and 100% on the second and third (18%) of the 73 unbaited tunnels left on Hawea Island nights. Bait take remained above 75% for a total of for three weeks between March and April 1986.
five nights before dropping to 25% on the sixth night, During the poisoning campaign on Hawea the rats and then quickly tailing off. After the seventh night of almost always removed entire Talon baits from the poisoning, no more rats were seen on Hawea Island stations, and it seems from direct observations and by day or night. Seventy-three snap-traps set adjacent from lack of residue that fewer than 4% of baits were to the bait stations during the last five nights of the eaten in situ. Despite this behaviour, only six baits or l2-night operation failed to catch any rats, and part baits, of a total of 734 poison baits removed by showed no sign of rat interference. No Talon bait was rats on Hawea Island, were found on the surface - taken on the twelfth night of poisoning. However, a and it is certain that all others were taken into rat check of all bait stations on 3 June showed that two burrows before being eaten or stored. During later more baits had disappeared. These were both from tests on Breaksea Island, Norway rats were observed one bait station in an area with many rats, which had readily entering the Nova-coil tunnels soon after the previously had more poison taken from it than had tunnels were positioned and baited. Talon baits were any other station.
NEW ZEALAND JOURNAL OF ECOLOGY, VOL. 12, 1989 poison, 50 m of Nova-coil pipe, 80 rat snap-traps andassociated materials, and apples for detecting thepresence of rats.
In addition there were travel and servicing costs associated with moving personnel and gear to andfrom Fiordland (c. $7,300), and the support providedby Fiordland National Park's MV Renown and hercrew (c. $27,000).
It seems certain that all rats living on Hawea Islandwere killed within a period of about two weeks duringthe April 1986 poisoning, and that the two talon baitsfound missing on 3 June were taken soon after thetwelfth night of poisoning by an already dying rat.
Figure 4: The percentage of "Talon 50 WB" baits taken When poisoning started, rats were abundant.
each 24 hours on Hawea Island during the first 13 days ofthe poisoning campaign. Note: A total of 146 baits was They were commonly seen during day and night, there available each day. were many fresh burrows, and the Talon baits weretaken promptly from most tunnels. A comparison of Eradication of the rats from Hawea Island was the numbers kill-trapped on Hawea Island (20 and confirmed as follows: 14/100 TN in April 1984 and October 1985 1) Although Talon baits were continually available respectively), with kill-trapping results and population in the 73 bait stations, none were touched by rats densities based on live trapping on three other islands in a total of 36,866 bait-station nights between Ö Motuhoropapa Island (9.1/100 TN and 2.6-4.2 June 1986 and October 1987.
rats/ha; Moors, 1985b), Whale Island (6.9 and 2) No rats were caught, or traps interferred with by 23.6/100 TN and 5-10 rats/ha; Bettesworth, 1972), rats, during 2,139 snap-trap nights between April and Campbell Island (14.6/100 TN and 10 rats/ha; and July 1986.
Taylor, 1986) - indicates that the Hawea population 3) No apples were touched by rats during a total of may have been in the order of 6-11 rats/ha, i.e., a 3,286 apple nights in July, August and October total population of around 50-100 rats.
1986, and in March and October 1987. Eighty- Our observations of Norway rats at bait stations eight percent of apples placed on Breaksea Island on Hawea and Breaksea Islands showed that Talon during these same visits were eaten by rats either was extremely attractive and palatable to them. Their within a few hours, or during the first four nights behaviour of removing and cacheing baits (Calhoun, after being put out - giving an overall take of 70 1962), and chasing away subordinate rats, means that per 100 apple nights.
not all rats will have ready access to the bait during 4) No fresh sign of rats has been found on any of the first few days of a poisoning operation.
ten visits to Hawea Island between April 1986 and Each 15 g Talon bait contains 0.005% brodifacoum, and it has been estimated that at thisconcentration the LD ,. for Norway rats weighing 250 g is 1.3 g of bait (Dubock and Kaukeinen, 1978). One The campaign involved a total of 154 person-days bait, therefore, is sufficient to kill several rats.
(PD) by paid and volunteer workers. This included However, since rats die several days after they have time spent in planning and organising (23 PD), consumed a lethal dose of brodifacoum, each rat travelling (51 PD), surveying and tracking (29 PD), poisoned on Hawea would almost certainly have eaten constructing bait stations (8 PD), poisoning (27 PD), several baits. Norway rats can die within 4 days of checking results on two follow-up visits (3 PD), and consuming large doses of brodifacoum, whereas those analysing data and writing two preliminary reports (13 that have ingested little more than a lethal dose may PD). The total cost in salaries and wages was about live for up to 12 days (Dubock and Kaukeinen, 1978).
As a consequence, it would be expected that dominant Major material costs were less than $700 at 1986 individuals would eat a surfeit of bait and die in the values, and comprised the cost of 32.5 kg of Talon first 3-4 days. Less dominant rats should then TAYLOR and THOMAS: RAT ERADICATION ON HAWEA ISLAND successively gain access to bait, whether in bait were habituated to the poison baits but were avoiding stations or in caches down burrows, and be poisoned fish-flavoured baits on newly-positioned snap-traps set over the following two or three weeks, until all are near each bait station. It seems likely that dying rats could become dependent on Talon, from bait stations The 100 mm diameter bait stations were an ideal or from caches in burrows, for food. If so, they size for Norway rats. As expected, their yellow colour would spend little time in the open, and thus reduce seemed not to concern the rats, which are colour the risk of secondary poisoning to other species. The blind. In fact, rats are thought to prefer yellows and main avian predators at risk on Hawea Island were greens - which would appear to them as light grey - southern great skuas and New Zealand falcons, both to many other colours (Brooks and Rowe, 1987).
of which may have preyed on live but poisoned rats.
The approximate 40 m spacing between bait However, comparable numbers of both species were stations used on Hawea Island followed Moors seen in the vicinity of Hawea Island before and after (1985a), and was based on the average distance the poisoning, and there was no evidence of adverse between successive captures found for marked Norway rats on Motuhoropapa Island - 113 m for males and The major advances of the Hawea Island 49 m for females. However, the mean range-length operation' over most previous rat control or was about 200 m for five male and 108 m for three eradication exercises in New Zealand were: female rats trapped at least twice on forested 1) Eradication was achieved in one continuous short Motuhoropapa Island (Moors, 1985b), and about 232 operation - not in irregular bursts.
m for three male and 141 m for five female Norway 2) The poison used had no history of inducing food rats similarly studied in forest on Stewart Island aversion in rats eating a sub-lethal dose.
(Hickson, Moller and Garrick, 1986). For several 3) Only one poisoning technique was used, and its species of rodents, including house mice (Mus effectiveness could therefore be fully evaluated.
musculus), ship rats, and Norway rats (Fitzgerald, 4) All poison bait was presented in standard Karl and Moller, 1981; Innes and Skipworth, 1983; amounts at fixed points, and checked and Taylor, 1986), it has been shown that surviving replaced daily - this not only allowed accurate animals quickly expand their home ranges once their data to be gathered on the amount of poison neighbours are removed. These studies, of home range taken by rats, and for the progress of the and swift invasion response, suggest that the spacing campaign to be continuously monitored, but also of bait stations on Hawea Island was unnecessarily for the rats to learn where food was regularly The possibility of accidental exposure of non- 5) The bait stations used were bird proof and with target species to primary or secondary poisoning was an entrance of sufficient diameter to be readily closely monitored during the poisoning campaign, but accepted by Norway rats.
no such deaths were identified. Insects are not known 6) The Talon baits, each containing well in excess of to be directly affected from feeding on Talon. Bird a lethal dose, could be readily removed by rats to species vary widely in their susceptibility to eat in a secure place of their own choice. This will brodifacoum, and a secondary hazard can also exist to have increased the chance of a lethal dose being insectivorous birds and raptors feeding on prey that consumed quickly. With oats, wheat or similar has consumed poison bait (Godfrey, 1985). There was baits, rodents are forced to frequently visit, or no evidence that birds were interfering with the poison stay in, the bait stations while they feed on inside the bait stations, and the rats scattered very little about outside. On Hawea Island, some baits that 7) An excellent method was devised for detecting the were left in the tunnels for long periods showed presence of rats, by laying out whole apples. This evidence of being chewed by insects, probably wetas, simple technique is an important advance in cockroaches and ants.
helping to decide if rats have reached an island, Despite careful searches, no poisoned rats were or if eradication has been achieved.
found on the surface of Hawea Island, and it appears 8) The possibility of neophobia causing some rats to that most died in their burrows or under thick cover.
avoid Talon baits was countered by setting out Our snap-trap results near the end of the Hawea the bait stations three weeks prior to poisoning, poisoning operation suggest that the last surviving and keeping Talon constantly available to rats at rats, all of which would already have eaten Talon, the same sites for over two years.
NEW ZEALAND JOURNAL OF ECOLOGY, VOL. 12, 1989 9) No special effort, or perseverance, was needed to choice of diet, rats that have smelled a particular food get the last rat.
on another rat's breath prefer it, even to other more 10) Only 154 person-days were required to complete familiar foods. Similarly, rats that have acquired an the eradication campaign and to confirm its aversion to a food will eat it again after exposure to success, at a total cost of about $65,000.
conspecifics that have recently fed on it (Galef, 1987; There is no simple way to predict the costs of Galef, Mischinger and Malenfant, 1987). It seems eradication campaigns on other offshore islands, sensible, therefore, to take advantage of this especially those outside of Fiordland, by extrapolation knowledge and keep poison baits continually available from the Hawea Island operation. Some work was at regular sites during eradication campaigns against developmental and will not need repetition. Cost/area Norway rat populations using second-generation relationships will be roughtly linear for materials, but anticoagulants. Thus at any moment during the course the cost of transport, accommodation, and wages will of a campaign, a large proportion of the living rapidly decrease per unit area with increasing island population will have consumed some poison and will size. These items will also vary immensely according to be influencing the remaining population to eat it, even circumstances, such as the location, topography, and though temporarily they may be chasing some less vegetative cover of the island, and facilities already dominant individuals away. It is likely that other species of rats and house mice are also susceptible to We consider that the "pulse baiting" technique, similar "peer pressure" (Galef and Clark, 1971; Galef of replacing poison baits every five to seven days and Heiber, 1976; Bean, Galef and Mason, 1988).
(Dubock, 1979) or the "minimal baiting" system We therefore recommend that whenever possible (Richards and Huson, 1985) usually recommended for all poison baits be checked and replaced daily, during economy and safety when controlling rodent rodent eradication campaigns using anticoagulant populations with second-generation anticoagulants, are poison. For each island being poisoned, a knowledge not appropriate when attempting eradication of rats of the fauna likely to be at risk, appropriately from an island. In these circumstances the main designed bait stations, and the shortest possible priorities are to kill every rat, and to guard against poisoning campaign are important safeguards against any possibility of encouraging the development of bait primary or secondary poisoning of non-target species.
shyness, poison resistance, or neophobia in the Any extra financial costs, through more bait being taken by the rats, will be more than offset by the We detected little evidence of neophobia in this lower cost of a much shorter and more predictable population of Norway rats which has possibly been isolated from the selective pressures of human control The rodent extermination strategy and techniques, for over 150 years. Moors (1985a, 1986) claimed that as developed on Hawea Island and described in this Norway rats are more wary of man-made objects, paper, were applied with only slight modifications on such as traps and bait stations, than are ship rats or Breaksea Island in May/June 1988. We are currently kiore. However, we know of no evidence supporting part way through the planned campaign, but five visits this generalisation from uninhabited islands or remote to the island since July 1988 have failed to detect any parts of New Zealand. A lack of severe neophobia sign of surviving rats.
could well be a common characteristic of long-isolated populations of commensal rats (Mitchell, Kirschbaum Thanks are due to: the former Department of Lands and Perry, 1975; Cowan, 1977). Therefore, we suggest and Survey, the Fiordland National Park Board, and that the best chance of eradicating any species of rat the Department of Conservation for financial and from New Zealand's island reserves is when the job, logistic assistance; Lance Shaw, Peter Brotherston, once started, is completed quickly before the Ruth Dalley, Bob Walker, and other members of the population is affected by the human-induced phobias crew of MV Renown for their active support and that have frustrated many control operations companionship; Ron and Robynne Peacock for their generous hospitality at Te Anau; and Kim Morrison, Behavioural research has shown that Norway rats Paul Green, Richard Sadleir, Graeme Taylor, Ian rely on their peers in deciding where and what to eat.
Flux, Jane Maxwell, Sandra Higgins, Phil Denny, Ron When given a choice of feeding locations they prefer Peacock, Robynne Peacock, Colin McColl, Shaunagh sites that conspecifics are exploiting (Shorten, 1954; O'Halloran, Mick Clout, and others who assisted at Barnett, 1975; Galef and Heiber, 1976). When given a TAYLOR and THOMAS: RAT ERADICATION ON HAWEA ISLAND various times in the field. Jocelyn Tilley drew the Elton, c.; Ranson, R.M. 1954. Containers for baiting.
maps and graph, and Jacqueline Beggs and Mike In: Chitty, D. (Editor), Control of rats and mice, Fitzgerald commented on the manuscript.
Vol. 1, pp. 147-159. Clarendon Press, Oxford.
305 p.
Fitzgerald, B.M.; Karl, B.J.; Moller, H. 1981. Spatial organization and ecology of a sparse population Atkinson, I.A.E. 1986. Rodents on New Zealand's of house mice (Mus musculus) in a New Zealand northern offshore islands: distribution, effects forest. Journal of Animal Ecology 50: 489-518.
and precautions against further spread. In: Galef, B.G. 1987. Social influences on the Wright, A.E.; Beever, R.E. (Editors), The identification of toxic foods by Norway rats.
offshore islands of northern New Zealand, pp.
Animal Learning and Behaviour 15: 327-332.
13-40. New Zealand Department of Lands and Galef, B.G.; Clark, M.M. 1971. Social factors in the Survey Information Series 16. 255 p.
poison avoidance and feeding behaviour of wild Barnett, S.A. 1975. The rat: a study in behaviour. and domesticated rats. Journal of Comparative Chicago University Press, Chicago. 318 p.
and Physiological Psychology 75: 341-357.
Bean, N.J.; Galef, B.G.; Mason, J.R. 1988. The Galef, B.G.; Heiber, L. 1976. The role of residual effects of carbon disulfide on food consumption olfactory cues in the determination of feeding site by house mice. Journal of Wildlife Management selection and exploration patterns of domestic 52: 502-507.
rats. Journal of Comparative and Physiological Bettesworth, D.J. 1972 (unpublished). Aspects of the Psychology 90: 727-739.
ecology of Rattus norvegicus on Whale Island, Galef, B.G.; Mischinger, A.; Malenfant, S.A. 1987.
Bay of Plenty, New Zealand. M.Sc. Thesis, Hungry rats' following of conspecifics to food University of Auckland. 67 p.
depends on the diets eaten by potential leaders.
Bremner, A.G.; Butcher, C.F.; Patterson, G.B. 1984.
Animal Behaviour 35: 1234-1239.
The density of indigenous invertebrates on three Godfrey, M.E.R. 1985. Non-target and secondary islands in Breaksea Sound, Fiordland, in relation poisoning hazards of "second generation" to the distribution of introduced mammals.
anticoagulants. Acta Zoologica Pennica 173: Journal of the Royal Society of New Zealand 14: Greaves, J .H. 1985. The present status of resistance to Brooks, J.E.; Rowe, F.P. 1987. Commensal rodent anticoagulants. Acta Zoologica Pennica 173: control. Vector control series. World Health Organisation, Geneva, VBC/87.949. 102 p.
Hickson, R.E.; Moller, H.; Garrick, A.S. 1986.
Calhoun, J.D. 1962. The ecology and sociology of the Poisoning rats on Stewart Island. New Zealand Norway rat. United States Department of Health, Journal of Ecology 9: 111-121.
Education and Welfare. Public Health Service Howard, W.E.; Marsh, R.E.; Palmateer, S.D. 1973.
Publication 1088, Washington DC. 288 p.
Selective breeding of rats for resistance to sodium Chitty, D. 1954. The study of the brown rat and its monofluoroacetate. Journal of Applied Ecology control by poison. In: Chitty, D. (Editor), 10: 731-736.
Control of rats and mice, Vol. 1, pp. 160-305.
Innes, J.G.; Skipworth, J.P. 1983. Home ranges of Clarendon Press, Oxford. 305 p.
ship rats in a small New Zealand forest as Cowan, P.E. 1977. Neophobia and neophilia: new- revealed by trapping and tracking. New Zealand object and new-place reactions of three Rattus Journal of Zoology 10: 99-110.
species. Journal of Comparative and Merton, D. V. 1978. Controlling introduced predators Physiological Psychology 91: 63-71.
and competitors on islands. In: Temple, S.A.
Dubock, A.C. 1979. Alternative strategies for safety (Editor), Endangered birds: management and efficacy of rodenticides. Proceedings of the techniques for preserving threatened species, pp.
5th British Pest Control Conference, Stratford 121-128. University of Wisconsin Press, Madison.
Upon-A von: Session 5, paper 14. 15 p.
Dubock, A.C.; Kaukeinen, D.E. 1978. Brodifacoum Mitchell, D.; Kirschbaum, E.H.; Perry, R.L. 1975.
(Talon rodenticide), a novel concept. Proceedings Effects of neophobia and habituation on the of the 8th Vertebrate Pest Conference, poison-induced avoidance of exteroceptive stimuli Sacremento, California: 127-137.
NEW ZEALAND JOURNAL OF ECOLOGY, VOL. 12, 1989 in the rat. Journal of Experimental Psychology: Taylor, R.H., 1984b. Distribution and interactions of Animal Behaviour Processes 104: 47-55.
introduced rodents and carnivores in New Moors, P.J. 1985a. Eradication campaigns against Zealand. Acta Zoologica Fennica 172: 103-105.
Rattus norvegicus on the Noises Islands, New Taylor, G.A. 1986 (unpublished). The ecology of Zealand, using brodifacoum and 1080. In: Moors, Norway rats on Campbell Island. Ecology P.J. (Editor), Conservation of island birds, pp.
Division report, D.S.I.R. 169 p.
143-155. ICBP Technical Publication 3. 271 p.
Taylor, R.H.; Thomas, B.W. 1986 (unpublished).
Moors, P.J. 1985b. Norway rats (Rattus norvegicus) Second progress report on a rat eradication on the Noises and Motukawao Islands, Hauraki project at Breaksea Sound, Fiordland National Gulf, New Zealand. New Zealand Journal of Park. Ecology Division report, D.S.I.R. 14 p.
Ecology 8: 37-54.
Taylor, R.H.; Thomas, B.W.; Taylor, G.A. 1986 Moors, P.J. 1986. Eradication campaigns against (unpublished). Preliminary report on a rat Norway rats on the Noises Islands, Hauraki Gulf.
eradication project at Breaksea Sound, Fiordland In: Wright, A.E.; Beever, R.E. (Editors), The National Park. Ecology Division report, D.S.I.R.
offshore islands of northern New Zealand, p.
246. New Zealand Department of Lands and Taylor, R.H.; Tilley, J.A.V. 1984. Stoats (Mustela Survey Information Series 16. 255 p.
erminea) on Adele and Fisherman Islands, Abel Nelson, L.; Clark, F.W. 1973. Correction for sprung Tasman National Park, and other offshore traps in catch-effort calculations of trapping islands in New Zealand. New Zealand Journal of results. Journal of Mammalogy 54: 295-298.
Ecology 7: 139-145.
Redfern, R.; Gill, J.E.; Hadler, M.R. 1976.
Thomas, B.W. 1985. Observations on the Fiordland Laboratory evaluation of WBA 8119 as a skink (Leiolopisma acrinasum Hardy). In: Grigg, rodenticide for use against warfarin-resistant and G.; Shine, R.; Ehmann, H. (Editors), The non-resistant rats and mice. Journal of Hygiene, biology of Australasian frogs and reptiles, pp.
Cambridge 77: 419-426.
17-22. Royal Zoological Society of New South Richards, C.G.J.; Huson, L.W. 1985. Towards the Wales. 527 p.
optimal use of anticoagulant rodenticides. Acta Thomas, B.W.; Taylor, R.H. 1988. Rat eradication in Zoologica Fennica 173: 155-157.
Breaksea Sound. Forest and Bird 19: 30-34.
Rzoska, J. 1953. Bait shyness, a study in rat Towns, D. 1988. Rodent eradication from islands - behaviour. British Journal of Animal Behaviour the conservation potential. Forest and Bird 19: 1: 128-135.
Shorten, M. 1954. The reaction of the brown rat Wace, N.M. 1986. The rat problem on oceanic islands towards changes in its environment. In: Chitty, - research is needed. Oryx 20: 79-86.
D. (Editor), Control of rats and mice, Vol. 2, pp.
Yaldwyn, J.C. 1978. Chairman's summing up during 307-334. Clarendon Press, Oxford. 532 p.
"General Discussion on Part 3". In: Dingwall, Taylor, D.P. 1984a (unpublished). The identification P.R.; Atkinson, I.A.E.; Hay, C. (Editors), The and detection of the rats of New Zealand and the ecology and control of rodents in New Zealand eradication of ship rats on Tawhitinui Island. nature reserves, p. 237. New Zealand Department Dissertation for diploma in Parks and Recreation, of Lands and Survey Information Series 4. 237 p.
Lincoln College, Canterbury. 73 p.

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