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INTRODUCTION

The eradication of invasive pests is increasingly being attempted by conservation managers while the size and complexity of successful eradications has surpassed what was previously considered feasible (Donlan et al. 2003). Feral pigs and goats have been eradicated from several large islands in the Galapagos (Cruz et al. 2005; Campbell and Donlan 2005) and the size of New Zealand Islands from which Norway rats have been successfully eradicated has increased logarithmically (Clout and Veitch 2002).

The Delmarva Peninsula, which is bordered by the Chesapeake and Delaware Bays and the Atlantic Ocean, comprises the state of Delaware and parts of Maryland and Virginia (Fig. 1). The peninsula supports tidal wetland habitats recognised as among the most important in the United States and as “Wetlands of International Importance” under the Ramsar Convention Treaty (Tiner and Burke 1995). The wetlands are home to numerous fish and wildlife species, and support commercial and recreational fishing, hunting, trapping, bird watching, wildlife viewing, and photography.

Nutria (Myocastor coypus), a tropical, aquatic South American rodent, was introduced to the United States in California in 1899 and to southern states in the early 20th Century for fur farming and weed control (Evans 1970; Willner et al 1979; LeBlanc 1994; Hess et al. 1997). After their introduction to Delmarva Peninsula in 1943, numbers of nutria increased to at least 50,000 in the early 1990s (Carowan pers. comm.). In the Delmarva marshes, nutria mostly feed on the roots of Olney three-square bulrush (Scirpus olneyi), a native emergent grass that grows 1-1.5 meters above water and supports a submersed root mat in highly erodible sediment. When nutria excavate roots, they expose the sediment to tidal erosion and brackish wetlands to salt water intrusion (Haramis and Colona, unpublished). Wetlands are converted to open water, removing all habitat benefits of the marsh for native species. On the Blackwater National Wildlife Refuge (CMNWRC), for example, nutria destroyed more than half of its original marsh (2833 ha).

Efforts to control nutria on Delmarva through commercial and recreational trapping did not prevent damage to three-square bulrush marsh. Maryland officials then consulted Dr. L.M. Gosling who, after several decades of research, failed attempts and effective trials, led a team of 24 trappers to successfully eradicate nutria from Britain over six years in the 1980s (Gosling 1989). Based

on Gosling’s recommendations, the task force focused on eradication as the primary strategy for restoring and protecting nutria-damaged marshlands in the Chesapeake Bay. Systematic trapping was identified as the primary method for reducing nutria populations.

In 1997, a partnership of federal and state agencies and private interests was formed to develop and implement a pilot project with the ultimate goal of eradicating nutria on Maryland’s Eastern Shore. The Nutria Control/Marsh Restoration Pilot Project aimed to gather data on the population of nutria in CMNWRC, Fishing Bay Wildlife Management Area (FBWMA), and Tudor Farms and adjacent properties in Dorchester County. Information on nutria population size, physiology, reproduction, behaviour, and movement were used to develop and test trapping strategies to maximise removal. Two years were dedicated to the collection of baseline data (Phase I) and four years (2002-2006) to test and implement eradication strategies on the 24,300 ha encompassed by these areas (Phase II). In 2007, trapping of nutria began in neighbouring counties and the eradication zone was redefined to include all of Delmarva Peninsula. Although not an island per se, the peninsula is sufficiently isolated from mainland nutria populations that the risk of recolonisation through immigration is thought to be near zero.

This paper describes the methods used to reduce nutria populations to near zero densities from 2002- 2009 as part of a campaign to eradicate the species from the Delmarva Peninsula.

MATERIALS AND METHODS

Project management and staffingAn eight member management team of senior-level

representatives from U.S. Fish and Wildlife Service, U.S. Department of Agriculture (USDA), Maryland Department of Natural Resources (MDNR), U.S. Geological Survey (USGS), and Tudor Farms oversaw the project and was primarily responsible for securing funding, obtaining political support, and providing technical support to field operations. A full-time wildlife biologist managed operations and supervised staff members, which included 17 full-time wildlife trapping specialists, one full-time maintenance worker who maintained vehicles, boats and trapping equipment, and a part-time administrative assistant.

Restoration through eradication: protecting Chesapeake Bay marshlands from invasive nutria (Myocastor coypus)

S. R. KendrotUSDA APHIS Wildlife Services. 2145 Key Wallace Drive, Cambridge, MD 21613, USA. <skendrot@aphis.usda.gov>.

Abstract Coastal marshes on Delmarva Peninsula, Chesapeake Bay, Maryland, USA, provide valuable ecosystem services including flood prevention, erosion control, filtration, and carbon sequestration, and support commercial and recreational fishing, trapping, hunting, and ecotourism that generate billions of dollars for the region. Nutria (Myocastor coypus) were introduced to Dorchester County on the eastern side of Delmarva peninsula in 1943. They spread rapidly and reached peak densities in the late 1990s when vegetation studies linked nutria herbivory to massive wetland loss throughout Maryland’s lower eastern shore. A coalition of state, federal and non-governmental organisations obtained congressional funding to eradicate nutria from the Delmarva Peninsula and, beginning in 2002, implemented a systematic eradication plan. The eradication team used integrated methods to complete the initial reduction of nutria populations on 60,000 ha of marsh in five counties across Maryland’s lower eastern shore. Population reductions to near-zero were accomplished using trapping and shooting applied systematically using GPS and GIS to apply removal efforts at the landscape level. Residual animals were removed using dogs and targeted trapping. New techniques for detecting nutria at low densities are currently being evaluated including dogs, lures and attractants, call surveys, judas nutria, and decoy cages. Recovery of nutria-damaged marsh has been significant and has halted further conversion of marsh to open water. The programme now aims to create a nutria-free coastal marsh ecosystem across the Delmarva Peninsula by 2014.

Keywords: Coypu, impacts, eradication, Chesapeake Bay, Delmarva Peninsula, trapping

Pages 313-319 In: Veitch, C. R.; Clout, M. N. and Towns, D. R. (eds.). 2011. Island invasives: eradication and management. IUCN, Gland, Switzerland.

Kendrot, S.R. Restoration through eradication: protecting Chesapeake Bay marshlands from invasive nutria (Myocastor coypus)

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Phases of EradicationOur nutria eradication campaign can be broken into six

phases:Survey: Define the distribution of nutria on the 1) Delmarva Peninsula.Knock-down: Rapid depopulation of 2) metapopulations identified in the survey phase. Mop-up: Targeted removal of residual nutria 3) remaining after the knock-down phase is completed.Verification: Population monitoring to confirm 4) that eradication at the management unit level was successful.Surveillance: Continued monitoring at the 5) landscape level.Biosecurity: Implementation of strategies to 6) prevent the reinvasion of nutria.

While the process outlined above was generally followed sequentially, we were frequently engaged in multiple phases simultaneously in different management units. In addition, the progression between phases was not always linear and the transition between phases was not always discrete.

Removal methodsNutria were primarily removed through trapping,

hunting and shooting. Trap devices used included rotating-jawed body-gripping traps (Conibear type) (Fig. 2), foothold traps (Fig. 3), cage/box traps, and cable restraining devices (snares). Traps were set on nutria trails, in ditches, along waterways and at approaches to natural and artificial (false) nutria beds and haul-outs, on floating support frames, and floating platforms. Methods used included: 1) “blind” sets in natural travel ways; and 2) lured sets using urine collected from captive animals, scats, anal gland lure, disturbed earth, and cut vegetation. Traps were typically set on sign of nutria presence. In low density areas, where nutria are more difficult to detect, trapping specialists used their understanding of nutria behaviour and movement to place sets where they were most likely to capture nutria

Fig. 1 Distribution of wetland habitats on Delmarva Peninsula and population status by subwatershed in May, 2011.

Fig. 2 A 17.8 cm body-gripping (Conibear) trap set on a floating platform. The trap triggers are spread to allow smaller non-target species to pass through the trap.

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moving through the area. Kill traps were checked within 96 hrs and live traps within 24 hrs. Non-target captures of native mammals, birds and reptiles were minimised by manipulating trap trigger and pan configurations, placing jump sticks or obstructions to block non-target access to traps, and selectively avoiding areas used by non-target species.

Hunting and shooting using small calibre rifles, shotguns, and handguns, was conducted year round, but was most effective in winter when marshes and waterways froze and reduced escape routes for nutria and snow cover provided a tracking substrate. Trained dogs were used throughout the year to detect and remove nutria, particularly in previously trapped areas.

Use of toxicants (e.g., zinc phosphide) was considered during the planning phase of the programme, but rejected because of concern over potential non-target impacts. The high success of nutria removal through trapping and hunting, followed by spot removal using detection dogs, has so far precluded any need to use toxicants.

Initial Population Reduction StrategiesThere are almost 200,000 ha of wetland habitats on the

Delmarva Peninsula, which required a systematic trapping programme in manageable trapping units. A Geographic Information System (GIS) was used to overlay a 402 m x 402 m rectangular grid of trapping units on a wetland map of the Delmarva Peninsula. Two removal strategies were implemented based on the spatial distribution of marsh habitat.

First, progressive sweeps were used in large contiguous blocks of marsh habitat. A continuous band of trapping units was established across the marsh, bridging non-nutria habitat (uplands or open water) on either side. Trapping specialists used handheld GPS receivers to ensure that they were trapping assigned units. As nutria in each band of trapping units were reduced to very low density, trappers moved forward to the next un-trapped unit. When capture rates in a trapping unit slowed, traps were established in the next adjacent trapping unit, leaving some traps behind to capture animals attempting to penetrate the trapping front. A swath of continuous trapping activity was thus spread across the marsh, three to four trapping units wide, with trapping intensity highest at the leading edge.

Second, a simultaneous blitz removal strategy was used in smaller, isolated marshes that could be trapped as a single unit. Such marshes typically bordered rivers throughout their tidal reach. Trappers were assigned to each section of river frontage and all marsh units were trapped simultaneously.

Trapping units were considered as depopulated after two weeks without a nutria capture. Data collected included the number of trap nights, the location, age, and sex of each nutria removed, and the identity and location of all non-target captures.

Hunting and shooting were used extensively during winter, when freezing conditions impeded trapping efforts and often caused nutria to aggregate. Areas that were heavily hunted were subsequently trapped once weather conditions permitted.

MonitoringFollowing initial knock-down, trapping units were

monitored every 3-12 months, depending on access and risk of reinvasion, for signs of nutria activity using: 1) intensive ground or shoreline searches documented with GPS tracks; 2) searches with dogs trained to find nutria; and 3) surveys of nutria sign at false beds. In order to reduce non-target impacts, traps were not used as monitoring devices unless sign was detected. Nutria population status was assigned to one of three categories for each trapping unit surveyed:

Resident: Evidence of occupancy including well-used nutria trails, bedding and feeding activity and/or the presence of multiple sizes of fresh scats indicating the presence of different age groups of nutria. Set traps would have a high probability of capture.

Transient: Evidence that a nutria passed through, but was not inhabiting the area. Usually a lone set of tracks or small amounts of scat of indeterminate age would be classified as transient. Set traps would have a low probability of capture.

Absent: No evidence of nutria detected.With increasing size of the eradication zone, monitoring

effort in previously trapped areas increased proportionately and competed directly with efforts to expand knock down efforts into new areas. In order to manage these competing needs, monitoring areas were prioritised for survey based on their risk of re-infestation as determined by prior occupancy, proximity to un-trapped areas, or presence of preferred habitat. High priority trapping units were monitored with increased frequency until failure to detect nutria after repeated visits warranted a reduction in priority. Mop-up trapping efforts were initiated upon the discovery of resident sign and discontinued after two weeks without a capture and failure to detect fresh sign.

Kendrot: Chesapeake Bay nutria eradication

Fig. 3 A foothold trap set on an imitation nutria bed. The trap is wired to a one-way slide lock attached to a cable anchored in deep water. This submersion set is designed to quickly drown captured nutria. Bamboo poles are placed to reduce non target bird captures.

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AnalysisWe tallied the amount of effort required to reduce the

nutria population to near-zero by counting the number of weeks of trapping required and back-calculating the percentage of the pre-existing population captured during each week of trapping, accepting that this slightly overestimates percentage removed as an unknown number of nutria remained un-trapped. By determining the total number of nutria removed from a trapping unit during initial removal and dividing that number into the weekly capture total, we were able to determine the percentage of the presumed population that was taken during each successive week of trapping.

Initial knock-down areas (IKDAs) were defined by the year in which knock down activities were initiated and the area covered in that year. We determined the number of nutria removed from each IKDA during the year of initiation and compared the number of nutria removed during mop-up efforts in the same areas in subsequent years. Traps were only set when sign was detected during monitoring, thus trapping effort was not applied equally across years and catch per unit effort data was not compared. However, the reduction in number of nutria removed was evaluated to gauge the magnitude of the population reduction.

Table 1 Total wetland area (ha) in Maryland counties and areas subject to nutria control in 2003-2008. No nutria control was conducted in Queen Anne, Kent, Cecil, and Worchester Counties (29,520 ha of marsh) and no new area received treatment in 2009.

County Avail. wetland 2003 2004 2005 2006 2007 2008 Area

trappedPercent

availableDorchester 54,628 11,738 11,798 6607 10,254 2248 253 42,897 79%Somerset 42,715 0 0 0 0 6833 2901 9734 23%Wicomico 13,272 0 0 0 0 5473 0 5473 41%Talbot 5122 0 0 0 0 0 1482 1482 29%Total 118,448 11,738 11,798 6607 10,254 14,554 5407 60,358 41%

Table 2 Number of nutria removed and percent of first year removal from Initial Knock-down Areas (IKDAs) during eradication efforts on Delmarva Peninsula.

IKDA 2003 2004 2005 2006 2007 2008 2009 Total2003

%4795100%

3707.7%

1272.6%

701.4%

160.3%

190.4%

50.1%

5402

2004%

3071100%

2909.4%

632.1%

200.7%

411.3%

40.1%

3489

2005%

677100%

10815.9%

172.5%

12718.8%

6910.2%

998

2006%

318100%

3210.1%

226.9%

92.8%

381

2007%

812100%

799.7%

8810.8%

979

2008%

1183100%

38732.7%

1570

Total 4795 3441 1094 559 897 1471 562 12819

Table 3 Time required to achieve an approximate 100% reduction in nutria numbers in trapping units during initial trap out, and number of nutria removed. Data based on IKDAs trapped in 2003-2008.

Trapping units reduced to near-zero density Nutria RemovedWeek Number % Cumulative % Number % Cumulative %

1 0 0.0 0.0 4584 51.1 51.12 145 11.4 11.4 1779 19.9 71.03 208 16.3 27.7 837 9.3 80.34 176 13.8 41.5 447 5.0 85.35 177 13.9 55.4 303 3.4 88.76 153 12.0 67.4 247 2.8 91.57 99 7.8 75.1 148 1.7 93.18 63 4.9 80.1 148 1.7 94.89 44 3.5 83.5 70 0.8 95.510 38 3.0 86.5 64 0.7 96.311 23 1.8 88.3 45 0.5 96.812 18 1.4 89.7 28 0.3 97.1

13-30 131 10.3 100.0 262 2.9 100.0Total 1275 8962

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RESULTS

Between 2003 and 2008, the campaign against nutria was conducted over nearly 61,000 ha of the 148,000 ha wetland habitat on Maryland’s eastern shore, as determined from National Wetland Inventory maps (Table 1). Knock-down activities were initiated on new areas each year until 2009, when verification and mop-up activities left little time for expansion into new areas. Nutria catches on IKDAs were used to track progress in population reduction (Table 2). In the third year following initial knock-down, mop-up efforts yielded <3% of the population removed in the initial year of treatment for IDKAs 2003-2006. The exception was IKDA 2005, where an area was not trapped until 2008 due to access restrictions imposed by a private landowner (Table 2). More than 100 nutria were removed from this property. In fact, many of the nutria captured in 2003 and 2004 IKDAs during monitoring were trapped within 13 km of this property, well within dispersal distances observed by GPS/radio-tagged nutria released as part of an ongoing Judas experiment (not reported here).

Nutria were encountered in approximately one third of the trapping units inspected and were reduced to very low numbers in 75 % of those within seven weeks of trapping (Table 3). A few units required up to 30 weeks to capture the last one or two nutria. Typically, more than half of the original population was captured in the first week of trapping, 80% by the end of the third week, and more than 90 % by the end of the sixth week of trapping. In many trapping units, catching the last 5-10% of the population took as long as or longer than capturing the first 90-95 %.

The most productive methods of nutria removal during the initial depopulation phase were body-gripping traps, shooting, footholds set on submersion cables, dogs, and staked foothold traps (Table 4). Staff accumulated 652,334 and 76,233 trap nights during knockdown and mop-up trapping efforts, respectively. Body gripping traps accounted for 92 % of trap nights and 84% of captures during knock-down trapping and 59% of trap nights and 75% of captures during mop-up trapping. Submersion footholds accounted for 6% of trap nights and 10% of captures during knock-down, but 23% of trap nights and 35% percent of captures during mop-up trapping. Staked footholds accounted for 2% of trap nights and 6% of captures during both knock-down and mop-up trapping phases. During initial knockdown, catch rates were lowest for body-gripping traps and highest for staked foothold traps. These latter were marginally more effective during mop-up trapping (Table 5).

Populations that remained or developed after initial population reduction typically comprised small groups ranging in size from two to six animals, although one group of 41 animals eluded detection for three years. Analysis of the sex and age distribution of the captured nutria led us to conclude that this abnormal population arose from a small group of three to six females that immigrated sometime during the third year following initial knock-down.

Kendrot: Chesapeake Bay nutria eradication

Table 4 Number and percent of nutria removed by method during initial population reduction and clean-up phases of eradication.

Knock-down Mop-up TotalMethod Number % Number % Number %Conibear 7457 67.9% 762 42.4% 8219 64.3%Shooting 1316 12.0% 101 5.6% 1417 11.1%

Submersion foothold 927 8.4% 449 25.0% 1376 10.8%

Dog 470 4.3% 344 19.2% 814 6.4%Foothold 460 4.2% 78 4.3% 538 4.2%Snare 105 1.0% 13 0.7% 118 0.9%Floating Conibear 97 0.9% 10 0.6% 107 0.8%Hand caught 66 0.6% 15 0.8% 81 0.6%Platform Trap (foothold) 62 0.6% 18 1.0% 80 0.6%

Platform (conibear) 15 0.1% 2 0.1% 17 0.1%Cage 8 0.1% 4 0.2% 12 0.1%Spotlight/shoot 6 0.1% 0.0% 6 0.1%Grand Total 10,989 100 % 1796 100 % 12,785 100 %

Table 5 Trap nights and catch per unit effort (nutria/1000 trap nights) for top three trapping methods and total captures using non-trapping methods during initial knock-down and mop-up during eradication efforts on Delmarva, 2002-2008.

Initial Knock-down Mop-upMethod Trap nights Captures CUE Trap nights Captures CUEBody-grip 602,636 7462 12.38 56,917 746 13.11Submersion 36,538 928 25.39 17,356 434 25.01Foothold 13,160 460 34.9 1960 78 39.79Shooting n/a 1316 n/a n/a 1417 n/aDog n/a 470 n/a n/a 814 n/a

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DISCUSSION

We implemented a systematic hunting and trapping programme that effectively reduced feral nutria populations within 16 ha trapping units to near zero within four to eight weeks per unit. Progressive and sequential treatment of trapping units across larger management units (watersheds) enabled us to effectively eliminate nutria over >60,000 ha of sensitive coastal wetlands in the Chesapeake Bay Watershed. Several mop-up sessions have been applied throughout this area, much of which is now in the verification phase. Nutria have not been detected in some watersheds for several years and these sites are now in the surveillance phase.

Although the same removal methods were used during knock-down and mop-up trapping phases, the relative importance of different trapping techniques was influenced by the needs of knock-down versus mop-up trapping strategies. For example, body-gripping traps accounted for the largest number of animals in both phases, but submersion footholds and detector dogs played a greater role in removal during mop-up efforts. One possible explanation for the increased importance of submersion footholds is that nutria at low densities move greater distances along waterways in search of other nutria and are therefore more vulnerable to footholds set at false beds along waterways. In addition, specialists aided by dogs are more efficient at finding nutria in areas of low density than specialists without dogs. We thus relied heavily on detection dogs during mop-up phases.

In England, catch per unit effort was used to indicate declines in population (Gosling and Baker 1987), but we did not detect significant changes in catch per unit effort between knock-down and mop-up trapping phases. Furthermore, box traps were used in England to allow the release of non-target species and a consistent trapping effort during consecutive trapping sessions. However, we set kill traps only where evidence of nutria was documented during intensive sign searches. This targeted approach to removing residual populations enabled us to reduce impacts to non-target species by restricting trapping to areas occupied by nutria. Compared with experiences in England, our approach required a greater investment in alternative detection methods.

Differences were recorded in the catch per unit effort of body-gripping versus foothold traps is likely due to the way in which traps are set. Body-gripping traps are often set as blind trail sets in higher trap densities to cover the myriad of trails available. Footholds, in contrast, are most often set selectively along waterways in conjunction with a false bed and/or urine or other visual or olfactory attractant. The difference between submersion and staked foothold efficiency is probably due to small sample sizes and the fact that staked footholds were only used during the first few months of knock-down trapping. The use of staked footholds was largely discontinued after submersion sets were approved as a lethal trapping technique, allowing us to increase trap check intervals from 24 to 96 hours.

Monitoring the previously trapped populations remained one of the programmes biggest challenges. With 61,000 ha of depopulated habitat spread across five counties, returning to these areas on a regular basis required an exhaustive effort that precluded expansion into new areas. Yet, expansion into new areas was necessary to reduce the risk of reinvasion of the nutria-free zone. Thus, these priorities competed for limited staff resources and time. Additionally, many private landowners continued to

restrict our access during the non-growing season, from September to the end of January, primarily because of recreational hunting.

Damaged marshes often recovered rapidly after nutria were removed. As nutria populations approached zero, staff reported that nutria swim channels were reclaimed by rhizome growth from three square bulrush. The resulting network of new roots trapped sediments that filled in swim channels, thereby eliminating the primary route of erosion for organic soils dislodged by nutria foraging habits. These anecdotal observations were corroborated by quantitative vegetation studies conducted at Patuxent Wildlife Research Center, which showed a dramatic recovery in areas extensively damaged by nutria (e.g., Figs 4a, b; Haramis et al. 2006).

This project was the first large scale attempt to eradicate nutria in North America. The type and distribution of habitat on Delmarva differs significantly from nutria habitat in England. While the UK example provided valuable insights, the political, social, and ecological conditions dictated a different approach in Delmarva and yielded new lessons including:

Eradication is achievable at the trapping unit level 1) when integrated methods are applied systematically by skilled technicians. By replicating the process progressively across management units nutria densities were reduced to near zero at the landscape level.

Fig. 4 (A) A wildlife specialist examines a nutria eat out in Monie Bay watershed, Somerset County, Maryland in May 2007. (B) the same marsh in May 2009, during the second growing season following eradication of nutria.

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Cooperation of private landowners is important to 2) putting every nutria at risk, although it is likely that nutria residing in relatively small private in holdings can be trapped from the periphery.Techniques used effectively during the knock-3) down phase may not be sufficient to achieve final eradication once the population has been reduced to extremely low densities.Staff must be prepared to develop and adapt tactics and 4) strategies when new challenges reveal themselves.Efficiency varies seasonally. Nutria are more 5) difficult to detect during the summer months when lush vegetation conceals evidence of occupancy and nutria movements appear to be minimal. Conversely, late fall through early spring is an optimal period for detecting nutria as vegetation dies back and nutria are more active.Nutria may restrict activity or abandon sites 6) subjected to intense daily human activity. Reducing the frequency of trap checks to 96 hours appeared to reduce incidence of site abandonment.

CONCLUSIONS

The Chesapeake Bay Nutria Eradication Program now aims to create a nutria-free coastal marsh ecosystem across Delmarva Peninsula by 2014. Given the worldwide distribution of nutria and its status as an invasive pest (Carter and Leonard 2002), the lessons learned from our programme will help instruct those interested in controlling or eradicating nutria elsewhere. Ongoing control programmes in Italy and Louisiana, USA, show promise for reducing damage to acceptable levels if eradication is deemed impossible (Bertolino and Viterbi 2009, Wiebe and Mouton 2009). The Delmarva programme has important implications for enhancing the effectiveness of control efforts, identifying additional eradication opportunities, and preventing invasion through the early detection and removal of invaders.

ACKNOWLEDGEMENTS

The Nutria Project is funded by the US Fish and Wildlife Service Partners for Fish and Wildlife programme and Blackwater National Wildlife Refuge. Other partner agencies and organisations include: USDA APHIS Wildlife Services, USGS Patuxent Wildlife Research Center, Maryland Department of Natural Resources, University of Maryland Eastern Shore, Tudor Farms, Inc. Additional funding for development of Judas nutria technique is provided by the National Fish and Wildlife Foundation and Tudor Farms, Inc. I am greatly appreciative to Mike Haramis for assistance in drafting this manuscript and Dan Murphy, Jonathan McKnight, Kevin Sullivan, Glenn Carowan and Leo Castro Miranda for reviewing this manuscript. Special thanks go to the field staff whose tireless efforts and sacrifices have made this possible.

REFERENCESBertolino, S. and Viterbi, R. 2009. Long-term cost-effectiveness of coypu

(Myocastor coypus) control in Piedmont (Italy). Biological invasions 12: 2549-2558.

Campbell, K. and Donlan, C.J. 2005. Feral goat eradications on islands. Conservation Biology 9: 1362-1374.

Carter, J. and Leonard, B.P. 2002. A review of the literature on the worldwide distribution, spread of, and efforts to eradicate the coypu (Myocastor coypus). Wildlife Society Bulletin 30: 162-175.

Clout, M.N. and Veitch, C.R. 2002. Turning the tide of biological invasion: the potential for eradicating invasive species. In: Veitch, C.R. and Clout, M.N. (eds.). Turning the tide: the eradication of invasive species, pp. 79-84. IUCN SSC Invasive Species Specialist Group, IUCN, Gland, Switzerland and Cambridge, U.K.

Cruz, F.; Donlan, C.J.; Campbell, K. and Carrion, V. 2005. Conservation action in the Galapagos: feral pig (Sus scrofa) eradication from Santiago Island. Biological Conservation 121: 473-478.

Donlan, C.J.; Tershy, B.R.; Campbell, K. and Cruz, F. 2003. Research for requiems: the need for more collaborative action in eradication of invasive species. Conservation Biology 17: 1850-1851.

Evans, J. 1970. About nutria and their control. U.S. Department of the Interior Bureau of Sport Fisheries and Wildlife, Denver. 65 pp.

Gosling, L. M. and Baker, S.J. 1987. Planning and monitoring an attempt to eradicate coypus from Britain. Zoological Society of London. Symposia, No. 58: 99-113.

Gosling, L.M. 1989. Extinction to order. New Scientist 1654: 44-51.

Haramis, G.M.; O’Connell, A. and Kendrot, S. 2006. USGS Research to assist nutria eradication in Maryland: Detection and monitoring a major need. [On-line] Available at: http://www.pwrc.usgs.gov/research/scimtgs/2006/posters/Haramis_marsh_loss_new.pdf [Accessed 17 Jan 2010]

Hess, I.D.; Conner, W. and Visser, J. 1997. Nutria - another threat to Louisiana’s vanishing coastal wetlands. Aquatic Nuisance Species Digest 2: 2.

LeBlanc, D. 1994. Nutria. Animal and Plant Health Inspection Service. B71-B80. Animal Damage Control, Port Allen, LA., U.S.A.

Tiner, R.W. and D.G. Burke. 1995. Wetlands of Maryland. U.S. Fish and Wildlife Service, Hadley, MA., U.S.A. 193 pp.

Weibe, J. and Mouton, E. 2009. Coastwide nutria control program 2008-2009: nutria harvest and distribution 2008-2009 and a survey of nutria herbivory damage in coastal Louisiana in 2009. [On-line]. Available at: http://www.nutria.com/uploads/0809CNCPfinalreportforwebsite.pdf [Accessed 17 Jan 2010]

Willner, G.R.; Chapman, J.A. and Pursley, D. 1979. Reproduction, physiological responses, food habits, and abundance of nutria on Maryland marshes. Wildlife Monographs 65: 43 pp.

Kendrot: Chesapeake Bay nutria eradication