A successful mouse eradication explained by site specific

A Successful Mouse Eradication Explained By Site Specific-Free PDF

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MacKay et al Successful house mouse eradication, Table 1 Summary of trapping visits to Saddle Island New whip aerial type Model BD 2NC Holohil Systems Ltd. Zealand CMR capture mark recapture Carp Ontario Canada fitted by looping the aerial wire. around the mouse s neck and crimping the wire to fasten. Month No trap nights Purpose it Animals were returned to closed traps to recover All. 1 January 2008 5 CMR animals including those not selected for radio tracking. 2 March 2008 4 CMR were returned to their capture locations and released. 3 May 2008 4 CMR Radio tracking began at 1800 h on 17 July 2008. 1 4 nights of Animals were tracked by two operators using TR4 receivers. 4 July 2008 Radio tracking Telonics Mesa Arizona USA with Yagi 3 stage folding. 5 August 2008 4 Removal trapping antennas Sirtrack Electronics Havelock North New. Zealand As most mouse activity was near the beach, tracking was most efficient when one operator walked. Taylor 1999 It is not known whether mice were present along the beach while the other confirmed locations from. concurrently with Norway rats or invaded following the cliff top above When the animal was between the. Norway rat eradication Further details of the island s trackers its location was noted by recording a bearing and. history fauna and flora are provided by Tennyson and estimating the distance from a marked point on the beach. Taylor 1999 When an animal ventured into the interior of the island. We established a grid of 62 stations Fig 1 at 25 m both people tracked the animal and a distance and bearing. intervals on the island in October 2007 This grid was used was recorded in a similar manner from the nearest trap. to place traps for live capture stations for poison bait other site Marked locations were then revisited in August and. devices for monitoring mouse activity and as an aid for mapped with a GPS Four or five fixes at approximately. navigation during night work A Longworth live capture 90 120 minute intervals throughout the night and one. mouse trap Chitty and Kempson 1949 was set at each daytime den site fix were obtained for each mouse over. station five times between January and August 2008 Table four nights of tracking Some night fixes were missed due. 1 Each trap contained Dacron fibre for bedding with to adverse weather conditions Daytime den fixes were. peanut butter on a carrot disk and oats as bait confirmed by using the telemetry receiver without an. antenna to maximise accuracy To minimise disturbance. Capture Mark Recapture protocol mice were not approached as closely at night as during the. Traps were checked daily during each four or five night day Despite this the mice were often seen while being. Capture Mark Recapture CMR session Captured mice tracked which confirmed the accuracy of night fixes. were weighed sexed and had a numbered tag National Removal trapping using Longworth live traps was. Band and Tag Co Newport Kentucky USA attached undertaken over four nights in August 2008 Table 1. to each ear After tagging the animals were released at Captured animals were euthanased by cervical dislocation. their capture site The tag numbers of previously marked Mice were then weighed sexed and any ear tags present. animals were recorded and the presence of torn ears was from previous trapping sessions or ripped ears were. noted Lost tags were replaced only when missing from recorded A small piece of tail tip was taken from each. both ears animal and preserved in 70 ethanol for future genetic. analysis Such samples obtained before eradication attempts. Radio tracking provide a means of distinguishing failed eradications from. Traps were set to catch mice for fitting with radio re invasion should mice reappear Abdelkrim et al 2007. collars on 16 July 2008 Table 1 and captured animals MacKay et al 2007 A WaxTag Thomas et al 1999. were processed according to the protocol above Only mice baited with peanut butter was placed at each trap station. 12 g were used for telemetry At this weight the 0 6 g on 7 August at the end of removal trapping and checked. transmitters were 5 of mouse body weight and therefore and removed on 19 August when poison was applied to the. unlikely to affect mouse behaviour Pouliquen et al 1990 island The locations of chewed tags showing where mice. Mikesic and Drickamer 1992 From the captured animals remained following removal trapping were recorded. four males and two females were selected for radio The anticoagulant toxin brodifacoum was applied to. tracking according to their capture location to achieve a the island on 19 August 2008 Toxin was applied in two. spread of animals across the whole island Six animals were formulations wax blocks Pestoff Rodent Blocks in bait. the maximum number that could be effectively tracked stations and approximately 15 kg of pellets Pestoff 20R. simultaneously Animals were transferred to a plastic bag Pellets spread around cliffs on the east coast the north and. and anaesthetised with a piece of cotton wool soaked in south points and areas with dense shrub cover or mixed. isoflurane As isoflurane is a rapid acting anaesthetic shrub and open grassland on the west coast Three wax. which wears off quickly animals required two or three blocks of toxin were wired to a tree under a plastic cover at. doses to fit the transmitter Transmitters were a single stage each trap station to make improvised bait stations designed. Table 2 Monitoring visits to Saddle Island following poison application. Date Event, 19 08 08 Poison bait distributed on the island in bait stations and hand spread on cliffs. 16 09 08 Poison bait stations checked and location of chewed blocks recorded WaxTags and ink tracking tunnels. baited with chocolate nut spread deployed on alternate lines across island. 18 09 08 Detection devices checked wax poison block placed in each tracking tunnel giving 31 more bait stations. Total bait density including pellets and blocks approximately 4 kg ha. 26 09 08 Poison bait stations removed from island WaxTags and tracking tunnels left in place poison in tracking. tunnels left in place, Eradication confirmation with trained rodent dog Occi poison removed from tracking tunnels traps set. 03 12 08 around small area of possible mouse scent since considered to be a response by the dog to skink scent M. Ritchie pers comm 19 01 10,15 12 08 Traps and devices checked.
Island invasives eradication and management, to shelter the poison blocks but to allow easy access to male or average female between fix movements The. mice Wax blocks in bait stations were not replaced and combined area of the circle of influence for each trap was. were removed from the island on 26 September 2009 compared with the total island area to obtain an estimate of. Table 2 Total bait density of wax blocks and pellets was the proportion of the island sampled by traps. approximately 4 kg ha Following poison application the. island was intensively checked Table 2 using 31 ink Results. based footprint tracking tunnels Gotcha Traps Warkworth. New Zealand and Connovation Ltd Auckland New Demographics. Zealand and 31 WaxTags set at trap stations on alternate Between January and August 154 mice were caught and. lines across the island Two unsecured poison blocks were tagged on the island Table 3 Many unmarked individuals. placed in each tracking tunnel on 18 September 2008 to entered the population in March resulting in a relatively. create 31 further bait stations These blocks were left in low recapture rate which then generally increased through. place until 3 December 2008 when the island was checked the year Table 3 Many mice were captured only in a. by a Department of Conservation rodent detection dog single session six were caught in four trapping sessions. Occi handler Miriam Ritchie Rodent detection dogs and none in all five There was a relatively high rate of. are commonly used in New Zealand and around the world tag loss between trapping sessions and 41 mice lost both. to aid in the confirmation of eradication success or failure ear tags between trapping sessions This meant that each. Gsell et al 2010 session had to be treated separately in CMR analysis Three. mice caught in January were captured and killed in August. Analysis indicating that they were at least 8 months old at time of. Four estimates of mouse population size on the island death Six mice died in traps during trapping sessions prior. were calculated using two methods Estimates for January to August and 51 mice were trapped and killed in August. March and May were calculated using closed capture leaving 97 animals of unknown fate Assuming tag loss. models in program MARK White and Burnham 1999 was random rudimentary survival analysis gave a monthly. Trapping data from August were analysed using a removal survival estimate of 0 6 a maximum lifetime of 26 months. trapping catch effort method augmented by independent and a mean life span of 5 months Tag loss between sessions. index data from WaxTags to reduce bias Russell et al will have biased the survival estimate downwards. 2009 For this augmented removal estimate we assumed Pregnant or lactating female mice indicated by. multiple mice could interfere with a single WaxTag prominent nipples were recorded only in January and. Analysis in MARK followed Wilson et al 2007a with March By July most animals caught were at least 12 g. three covariates used to model heterogeneity in the data in weight and were classified as adults which suggests. Two categorical variables sex and age and one continuous that breeding had ceased at least a month earlier The. variable weight were used as covariates in four models proportion of females caught tended to decrease through. incorporating both behavioural response to trapping and the year with females representing only 27 of the animals. variation in capture probability between trap nights Mice caught during removal trapping in August Table 4. are difficult to classify as adults or juveniles based on. external characteristics so we classified animals weighing Population size. less than 12 g as juveniles This weight was chosen Because models with age covariates consistently. based on the mean weight of non fecund mice recorded ranked higher than models with weight covariates based. during a study at nearby Tawharanui Open Sanctuary on Akaike s information criterion Burnham and Anderson. Goldwater 2007 Six covariate combinations none sex 2002 weight models were deleted before model averaging. weight age sex and weight sex and age were tested for The estimated population size varied between 53 and 115. each model The model averaging procedure in MARK individuals and was highest in March Fig 2 Confidence. was used to calculate population estimates based on all intervals were wide for population estimates in January. models except those where parameters were identified as and March because of the relatively high number of. singular or standard errors of estimates were very large or animals caught only once in these sessions 42 and 52. zero Confidence limits 95 of the averaged estimate respectively In May this group decreased to only 24. were adjusted to take into account the actual number of The removal trapping and WaxTag dataset produced a. mice caught in each trapping session White et al 1999 population estimate with very narrow confidence intervals. Population estimates were converted into density estimates This August population estimate was 53 animals whereas. mice ha by dividing the estimate by 6 ha the area of 51 mice were actually removed Mouse densities therefore. the island MARK was also used to obtain a rudimentary varied between 8 8 and 19 2 mice ha Table 5. survival estimate Capture data were pooled for all sessions. except the single night of trapping in July to estimate. monthly survival maximum lifetime and mean lifetime. Information on animal home ranges and ranging, behaviour was collected through trapping records and radio. tracking Home ranges were calculated for all individuals. that were trapped five or more times and trapping records. for the radio tracked individuals were combined with. radio tracking data to calculate home range sizes for these. animals Average movements were described from radio. tracking data alone Movement information was compared. to habitat observations from the island to investigate. whether different habitat affected movements Home, ranges were estimated using harmonic mean estimation in. Ranges7 South et al 2005 We estimated a 95 range, core to avoid outlying fixes biasing the range size estimate. upwards Moro and Morris 2000 Ranges7 was also used. to summarise animal movements and to estimate the area Fig 2 Number of mice caught open and estimated. of the island sampled by traps assuming each trap had a population size closed with 95 confidence interval CI. shown for each trapping session where population size. circle of influence with a radius equivalent to the average was estimated. MacKay et al Successful house mouse eradication, Table 5 Mouse density for each trapping session on Department of Conservation pers comm Ongoing.
Saddle Island Density was not calculated in July monitoring throughout 2009 did not detect any mice other. than those released deliberately during a study into mouse. Month Density range invasion behaviour J MacKay unpublished data. January 12 8 mice ha 8 5 36 2,March 19 2 mice ha 16 8 25 8 Rat incursions. May 11 3 mice ha 10 7 14 3 In March 2008 rat sign was detected on the island and. House mouse Mus musculus eradication attempts have been less successful than introduced rat Rattus spp eradication attempts and research is needed to identify the reasons for this disparity We studied and successfully eradicated a mouse population on a small

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