Pest animals. Chapter Pest animals

Transcription

1 Chapter 3 Pest animals 3.1 Pest animals For each pest animal we present a brief description of its relevant biology, summarise its impacts of assorted values in the Bay of Plenty, and present the results of a cost-benefit analysis of available data for the species assigned to two or more of the Exclusion, Control, and Advisory categories. The pest fish are dealt with separately in more detail in the next chapter. See the Appendices for information on the methods, assumptions, and data limitations. 206

2 Table 3.1: Summary of pest animal CBA results showing which of the three RPMS control scenarios are regarded as economically beneficial regional investments over 50 years. The Exclusion scenario is not included for proposed Advisory pests. Note that the pest fish are considered in more detail in the next chapter and are not included here. Pest 2010 RPMS category Advisory Control Exclusion Argentine ant Advisory TRUE TRUE Darwin ant Advisory TRUE TRUE Eastern rosella Advisory TRUE TRUE Feral cat Advisory TRUE TRUE Feral goat Control (defined areas) TRUE TRUE TRUE Ferret Advisory TRUE TRUE Gambusia Advisory TRUE Hedgehog Advisory TRUE TRUE Magpie Advisory TRUE FALSE Mouse Advisory TRUE TRUE Possum Advisory TRUE TRUE Rabbit Advisory TRUE TRUE Rat (ship and Norway) Advisory TRUE TRUE Rook Exclusion TRUE TRUE TRUE Stoat Advisory TRUE TRUE Wasp Advisory TRUE TRUE Weasel Advisory TRUE TRUE 207

3 3.1.1 Argentine ant (Linepithema humile) Argentine ant biology and impacts Proposed RPMS Category: Advisory Overall impact: Major Table 3.2: Relevant biology Attribute Form Habitat Regional distribution Competitive ability Reproductive ability Resistance to control Description Wingless, light to dark honey-brown 2-3 mm long. Inhabits a wide range of urban and rural habitats. Presence confirmed in Mount Maunganui/Tauranga, Whakatane and Rotorua, unknown for rest of the region. Very aggressive and competitive to other invertebrate species. Colonies cooperate resulting in even higher competition with other species. Breeds prolifically and new infestations bud-o and walk to new locations. Natural spread is slow, but can be transported around the region in contaminated material. Control can be successful with chemicals, however eradication is very di cult. Table 3.3: Impact evaluation Category Current Potential Comment Source impact impact Species diversity L H Displaces most other ant species. Has 1, 2, 3 broad diet and impacts many invertebrate species through predation, competition, interference, and egg predation. Threatened species L H 1, 2, 3 Soil resources Water quality Production - H Feeds extensively on honeydew produced by homopterans (aphids), actively disperses and protects them from predation. May lead to death of trees in domestic and commercial orchards, due to an increase in scale insects. Helps transmit diseases between plants. 1, 2, 5 International trade L H Could invade food processing plants. 1, 2, 4 Could impact kiwifruit industry (esp. organic production), due to increase in scale insects. Could lead to trade restrictions with countries without this species. Human health L M Can bite people and be a major nuisance 1, 2, 4 in homes and gardens. Recreation L M See Human Health. 1, 2 Māori culture L M Could form large colonies and be a nuisance at cultural sites, esp. thermal areas (hotpools). 2, 6 Source: 1: Harris (2002), 2: Don & Harris (2010b), 3: Clements (2005), 4: Severinsen (2003), 5: Lester et al. (2003), 6: Watchman (2009) 208

4 Argentine ant CBA results The following are results for cost-benefit analyses for three scenarios, no regional RPMS control, RPMS control as a Control Pest, and RPMS control as an Advisory Pest. For the purposes of the CBA calculations, the pest is assumed to continue expanding with no regional RPMS control, its spread is assumed to be near-arrested under Advisory Control but not reduced, and it is assumed to be successfully reduced to the expected smaller extent when listed as a Control Pest, more so as an Exclusion pest. Table 3.4: Argentine ant CBA results for three RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values. Scenario Pest impacts Control benefit Expenditure Net benefit No RPMS 14,205, ,205,577 (6,258,634 49,984,946) (-6,258,634-49,984,946) Control Pest 1,483 14,204, ,055 13,934,039 (280 2,821) (6,258,354 49,982,125) (5,988,299 49,712,070) Advisory Pest ,204,854 39,636 14,165,218 (126 1,473) (6,258,508 49,983,473) (6,218,872 49,943,837) Table 3.5: Argentine ant CBA base assumptions. Base assumptions Values Current area infested (ha) 200 Total area potentially infested (ha) 102,728 (34, ,775) Years from naturalisation to total area 50 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) (0.1 8) Any benefits provided by the weed 0 Discount rate 8 Table 3.6: Argentine ant RPMS Exclusion Pest assumptions. Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 25 (0 50) Table 3.7: Argentine ant RPMS Control Pest assumptions. Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 200 ( ) Table 3.8: Argentine ant RPMS Advisory Pest assumptions. Advisory Pest assumptions Values Years to achieve objectives 5 Final area infested (ha) 325 ( ) 209

5 Table 3.9: Argentine ant estimated total annual cost of di erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed. Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 0 1,021,992 20,440 3,000 Argentine ant conclusions In the absence of regional control, the projected total regional damage in net present value is -$14,205,577 over the next 50 years (the minimum projected impact is -$6,258,634). Managing Argentine ant as a Control pest has a projected net benefit to the region of $13,934,039. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Argentine ant as an Advisory pest has a projected net benefit to the region of $14,165,218. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Argentine ant, Advisory, therefore meets the requirements of Section 72(1a) of the Act. 210

6 Calibrated logistic growth curve, no RPMS control Proportion of maximum extent Current extent (ha): 200 Potential extent (ha): 102,728 (34, ,775) Time to potential (yr): 50 Current prop. of potential: 03 Figure 3.1: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report. 211

7 Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory control Proportion of initial area Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 800 Discount rate: 8 Total multiplier: ( ) Discounted annual cost Years of control Years of control Years of control (a) (b) (c) (d) Proportion of initial area Discounted annual cost Proportion of initial area Discounted annual cost Proportion of initial area Discounted annual cost Figure 3.2: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 212

8 3.1.2 Darwin ant (Doleromyrma darwiniana) Darwin ant biology and impacts Proposed RPMS Category: Advisory Overall impact: Major Table 3.10: Relevant biology Attribute Form Habitat Regional distribution Competitive ability Reproductive ability Resistance to control Description Length about 2 mm, colour of head dark brown, rest of the body and legs light brown. Similar in appearance to Argentine ants but workers give o a strong odour when crushed (c.f. little or no odour for Argentine ants). Workers have 12-segmented antennae. Mandibles have 4-5 teeth and 4-5 denticles. Inhabits a wide range of urban and rural habitats. Presence confirmed in Mount Maunganui and Whakatane, unknown for rest of region. Strongly competitive with other invertebrates. Breeds prolifically building up large colonies. Control can be successful with chemicals, however eradication is very di cult. Table 3.11: Impact evaluation Category Current Potential Comment Source impact impact Species diversity L H Strongly competitive and displaces other 1, 2 ant species. Predator of many invertebrates. Threatened species L H 1, 2 Soil resources - - Water quality - - Production L H Tend aphids and mealy bugs and may also spread disease in the same manner as Argentine ants. 1, 2 International trade L H Could invade food processing plants. 1, 2 Could lead to trade restrictions with countries without this species. Human health L M Can bite people and be a major nuisance 1, 2 in homes and gardens. Recreation L M See Human Health. 1, 2 Māori culture L M Could form large colonies and be a nuisance at cultural sites, esp. thermal areas (hotpools). 1, 2, 3 Source: 1: Anon. (2010a), 2: Don & Harris (2010a), 3: Watchman (2009) 213

9 Darwin ant CBA results The following are results for cost-benefit analyses for three scenarios, no regional RPMS control, RPMS control as a Control Pest, and RPMS control as an Advisory Pest. For the purposes of the CBA calculations, the pest is assumed to continue expanding with no regional RPMS control, its spread is assumed to be near-arrested under Advisory Control but not reduced, and it is assumed to be successfully reduced to the expected smaller extent when listed as a Control Pest, more so as an Exclusion pest. Table 3.12: Darwin ant CBA results for three RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values. Scenario Pest impacts Control benefit Expenditure Net benefit No RPMS 12,217, ,217,410 (5,227,398 46,636,583) (-5,227,398-46,636,583) Control Pest 74 12,217, ,730 11,424,606 (14 141) (5,227,384 46,636,442) (4,434,654 45,843,712) Advisory Pest 36 12,217,374 15,855 12,201,519 (6 74) (5,227,392 46,636,509) (5,211,537 46,620,654) Table 3.13: Darwin ant CBA base assumptions. Base assumptions Values Current area infested (ha) 10 Total area potentially infested (ha) 102,728 (34, ,775) Years from naturalisation to total area 50 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) (0.1 8) Any benefits provided by the weed 0 Discount rate 8 Table 3.14: Darwin ant RPMS Exclusion Pest assumptions. Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 1.2 (0 2.5) Table 3.15: Darwin ant RPMS Control Pest assumptions. Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 10 (12 8) Table 3.16: Darwin ant RPMS Advisory Pest assumptions. Advisory Pest assumptions Values Years to achieve objectives 5 Final area infested (ha) 16 (20 12) 214

10 Table 3.17: Darwin ant estimated total annual cost of di erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed. Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 0 3,000,000 60,000 1,200 Darwin ant conclusions In the absence of regional control, the projected total regional damage in net present value is -$12,217,410 over the next 50 years (the minimum projected impact is -$5,227,398). Managing Darwin ant as a Control pest has a projected net benefit to the region of $11,424,606. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Darwin ant as an Advisory pest has a projected net benefit to the region of $12,201,519. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Darwin ant, Advisory, therefore meets the requirements of Section 72(1a) of the Act. 215

11 Calibrated logistic growth curve, no RPMS control Proportion of maximum extent Current extent (ha): 10 Potential extent (ha): 102,728 (34, ,775) Time to potential (yr): 50 Current prop. of potential: <1 Figure 3.3: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report. 216

12 Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory control Proportion of initial area Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control Discount rate: 8 Total multiplier: ( ) Discounted annual cost Years of control Years of control Years of control (a) (b) (c) (d) Proportion of initial area Discounted annual cost Proportion of initial area Discounted annual cost Proportion of initial area Discounted annual cost Figure 3.4: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 217

13 3.1.3 Eastern rosella (Platycerus eximius) Eastern rosella biology and impacts Proposed RPMS Category: Advisory Overall impact: Moderate Table 3.18: Relevant biology Attribute Form Habitat Regional distribution Competitive ability Reproductive ability Resistance to control Benefits Description Vivdly coloured, with a scalloped yellow-green back, pale green rump, yellow and green belly, and white cheek patches. Much larger than native parakeets (avg size is 330 mm). Has a loud carrying call and swift undulating flight. Inhabits a wide range of urban, rural and forest habitats. Unknown. Breeds between October and January.Usually nests in cavities in trees or dead tree fern trunks, laying 4-6 white eggs which the female incubates for days.chicks fledge around 30 days and remain with parents for several months. Unknown. Kept as pets. Table 3.19: Impact evaluation Category Current Potential Comment Source impact impact Species diversity L L Eats a wide range of seeds, fruits, flowers, 1, 2, 3 buds and shoots and occasional insects - could alter food webs. Threatened species L M Could compete with native parrots (kaka, 2, 3 kakariki) for food and habitat and transmit disease. Soil resources - - Water quality - - Production L M Eats seeds of grasses, shrubs and trees; also fruits, buds, flowers, nectar, insects 1, 2 and larvae. Causes minor damage to citrus and kiwifruit in Northland. Eats tomatoes, apples and other orchard fruit occasionally. International trade - - Human health - - Recreation - - Māori culture - - Source: 1: Heather & Robertson (1996), 2: Wright & Clout (2001), 3: Department of Conservation (2004) 218

14 Eastern rosella CBA results The following are results for cost-benefit analyses for three scenarios, no regional RPMS control, RPMS control as a Control Pest, and RPMS control as an Advisory Pest. For the purposes of the CBA calculations, the pest is assumed to continue expanding with no regional RPMS control, its spread is assumed to be near-arrested under Advisory Control but not reduced, and it is assumed to be successfully reduced to the expected smaller extent when listed as a Control Pest, more so as an Exclusion pest. Table 3.20: Eastern rosella CBA results for three RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values. Scenario Pest impacts Control benefit Expenditure Net benefit No RPMS 50,100, ,100,764 (5,723, ,570,406) (-5,723, ,570,406) Control Pest 24,702,749 25,398,015 3,963,649 21,434,366 (4,843,417 43,314,666) (879, ,255,740) (-3,083, ,292,091) Advisory Pest 12,022,069 38,078,695 79,273 37,999,422 (2,176,262 22,801,644) (3,547, ,768,762) (3,467, ,689,489) Table 3.21: Eastern rosella CBA base assumptions. Base assumptions Values Current area infested (ha) 50,000 Total area potentially infested (ha) 142,645 (48, ,264) Years from naturalisation to total area 50 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) ( ) Any benefits provided by the weed 1 Discount rate 8 Table 3.22: Eastern rosella RPMS Exclusion Pest assumptions. Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 6,250 (0 12,500) Table 3.23: Eastern rosella RPMS Control Pest assumptions. Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 31,250 (25,000 37,500) Table 3.24: Eastern rosella RPMS Advisory Pest assumptions. Advisory Pest assumptions Values Years to achieve objectives 5 Final area infested (ha) 68,750 (75,000 62,500) 219

15 Table 3.25: Eastern rosella estimated total annual cost of di erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed. Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 0 15,000, ,000 6,000 Eastern rosella conclusions In the absence of regional control, the projected total regional damage in net present value is -$50,100,764 over the next 50 years (the minimum projected impact is -$5,723,365). Managing Eastern rosella as a Control pest has a projected net benefit to the region of $21,434,366. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Eastern rosella as an Advisory pest has a projected net benefit to the region of $37,999,422. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Eastern rosella, Advisory, therefore meets the requirements of Section 72(1a) of the Act. 220

16 Calibrated logistic growth curve, no RPMS control Proportion of maximum extent Current extent (ha): 50,000 Potential extent (ha): 142,645 (48, ,264) Time to potential (yr): 50 Current prop. of potential: Figure 3.5: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report. 221

17 Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory control Proportion of initial area Proportion of initial area Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control Discount rate: 8 4 Total multiplier: (14 36) Discounted annual cost Years of control Years of control Years of control (a) (b) (c) (d) Discounted annual cost Proportion of initial area Discounted annual cost Proportion of initial area Discounted annual cost Figure 3.6: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 222

18 3.1.4 Feral cat (Felis catus) Feral cat biology and impacts Proposed RPMS Category: Advisory Overall impact: Major Table 3.26: Relevant biology Attribute Form Habitat Regional distribution Competitive ability Reproductive ability Resistance to control Benefits Description Resemble domestic cats in both size and colouration. Females average about 75% of the weight of males. Inhabits a wide range of urban, rural and forest habitats. Ffound from sea level to alpine habitats. Widespread throughout region. Diet is wide ranging and includes small mammals, fish, birds and invertebrates. 2-3 litters per year with an average of 4 young in each. Controlled by poisons, trapping and shooting. No natural predators. Control rodents and to some degree mustelids (young stoats and weasels). Table 3.27: Impact evaluation Category Current Potential Comment Source impact impact Species diversity M H Eats native birds, lizards and invertebrates. 1, 2 Threatened species M H 1, 2 Soil resources Water quality Production L M 1, 2 International trade - L 1 Human health L L Can bite and scratch. 3 Recreation L M See Human Health. 1 Māori culture L M 1 Source: 1: Severinsen (2003), 2: Auckland Regional Council (2004), 3: Hutchison (2009) 223

19 Feral cat CBA results The following are results for cost-benefit analyses for three scenarios, no regional RPMS control, RPMS control as a Control Pest, and RPMS control as an Advisory Pest. For the purposes of the CBA calculations, the pest is assumed to continue expanding with no regional RPMS control, its spread is assumed to be near-arrested under Advisory Control but not reduced, and it is assumed to be successfully reduced to the expected smaller extent when listed as a Control Pest, more so as an Exclusion pest. Table 3.28: Feral cat CBA results for three RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values. Scenario Pest impacts Control benefit Expenditure Net benefit No RPMS 135,905, ,905,727 (46,391, ,457,095) (-46,391, ,457,095) Control Pest 64,466,570 71,439,157 7,927,298 63,511,859 (12,645, ,110,226) (33,746, ,346,869) (25,819, ,419,571) Advisory Pest 28,690, ,215, , ,056,678 (5,681,866 53,878,376) (40,710, ,578,719) (40,551, ,420,173) Table 3.29: Feral cat CBA base assumptions. Base assumptions Values Current area infested (ha) 2e+05 Total area potentially infested (ha) 176,243 (58, ,736) Years from naturalisation to total area 50 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) ( ) Any benefits provided by the weed 1 Discount rate 8 Table 3.30: Feral cat RPMS Exclusion Pest assumptions. Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 25,000 (0 50,000) Table 3.31: Feral cat RPMS Control Pest assumptions. Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 2e+05 (250, ,000) Table 3.32: Feral cat RPMS Advisory Pest assumptions. Advisory Pest assumptions Values Years to achieve objectives 5 Final area infested (ha) 275,000 (3e ,000) 224

20 Table 3.33: Feral cat estimated total annual cost of di erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed. Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 0 30,000, ,000 12,000 Feral cat conclusions In the absence of regional control, the projected total regional damage in net present value is -$135,905,727 over the next 50 years (the minimum projected impact is -$46,391,866). Managing Feral cat as a Control pest has a projected net benefit to the region of $63,511,859. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Feral cat as an Advisory pest has a projected net benefit to the region of $107,056,678. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Feral cat, Advisory, therefore meets the requirements of Section 72(1a) of the Act. 225

21 Calibrated logistic growth curve Proportion of maximum extent Current extent (ha): 2e+05 Potential extent (ha): 176,243 (58, ,736) Time to potential (yr): 50 Current prop. of potential: Figure 3.7: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report. 226

22 Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory control Proportion of initial area Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 1.5 Discount rate: Total multiplier: (43 17) Discounted annual cost Years of control Years of control Years of control (a) (b) (c) (d) Proportion of initial area Discounted annual cost Proportion of initial area Discounted annual cost Proportion of initial area Discounted annual cost Figure 3.8: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 227

23 3.1.5 Feral goat (Capra hircus) Feral goat biology and impacts Proposed RPMS Category: Control (defined areas) Overall impact: Major Table 3.34: Relevant biology Attribute Description Form Feral goats vary in size and colour. Can be white, black, brown or a combination of colours. Both sexes have horns. Adult males stand approximately 70 cm high and weigh kg. Females are smaller. Habitat Inhabits a wide range of rural and forest habitats. Favours steep, dry, sunny faces. Regional distribution Relatively common throughout eastern Bay of Plenty with isolated pockets occurring elsewhere. Competitive ability Diet is wide ranging. Able to exploit a wide variety of habitats. Reproductive ability Females begin breeding at 6 months and can breed twice a year. Twins are common. Males can mate from 6 months but are usually excluded by other males until 3-4 years of age. Resistance to control No natural predators in New Zealand. Controlled by shooting and highquality fencing. Benefits Some value as feral meat. Some farmers muster out goats infrequently and sell them o. Table 3.35: Impact evaluation Category Current impact Potential impact Comment Source Species diversity H H Eats a wide variety of plant species 1, 2, 3, and can eliminate preferred (palatable) 4 species, leading to changes in plant species composition, and preventing forest regeneration and succession. Threatened species M H 1, 2 Soil resources M H Removal of vegetation through browsing 4 and trampling can cause erosion. Water quality M H Erosion of soil can lead to increased sedimentation 5 in waterways. Production M M Causes damage to young trees. 3, 4, 5, 6 International trade L M 5 Human health - - Recreation L M 4, 5 Māori culture M H Destroys native forests and eats culturally important plants (e.g. koromiko). 4, 5 Source: 1: Husheer (2006), 2: Clements (2004), 3: Auckland Regional Council (2004), 4: Anon. (2010b), 5: Severinsen (2003), 6: King (2005) 228

24 Feral goat CBA results The following are results for cost-benefit analyses for four scenarios, no regional RPMS control, RPMS control as an Exclusion Pest, RPMS control as a Control Pest, and RPMS control as an Advisory Pest. For the purposes of the CBA calculations, the pest is assumed to continue expanding with no regional RPMS control, its spread is assumed to be near-arrested under Advisory Control but not reduced, and it is assumed to be successfully reduced to the expected smaller extent when listed as a Control Pest, more so as an Exclusion pest. Table 3.36: Feral goat CBA results for four RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values. Scenario Pest impacts Control benefit Expenditure Net benefit No RPMS 40,123, ,123,258 (17,410,563 62,835,953) (-17,410,563-62,835,953) Exclusion Pest 17,287,532 22,835,726 1,868,819 20,966,907 (7,976,197 25,360,419) (9,434,366 37,475,534) (7,565,547 35,606,715) Control Pest 36,310,176 3,813, ,032 3,211,050 (16,218,347 55,195,615) (1,192,216 7,640,338) (590,184 7,038,306) Advisory Pest 15,836,229 24,287,029 59,455 24,227,574 (6,179,522 27,299,050) (11,231,041 35,536,903) (11,171,586 35,477,448) Table 3.37: Feral goat CBA base assumptions. Base assumptions Values Current area infested (ha) 68,490 Total area potentially infested (ha) 68,490 (68,490 68,490) Years from naturalisation to total area 50 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) ( ) Any benefits provided by the weed 1 Discount rate 8 Table 3.38: Feral goat RPMS Exclusion Pest assumptions. Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 42,806.2 (34,245 51,367.5) Table 3.39: Feral goat RPMS Control Pest assumptions. Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 59,929 (51,368 68,490) Table 3.40: Feral goat RPMS Advisory Pest assumptions. Advisory Pest assumptions Values Years to achieve objectives 5 Final area infested (ha) 85,612 (102,735 68,490) 229

25 Table 3.41: Feral goat estimated total annual cost of di erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed. Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 0 277,000 45,566 4,500 Feral goat conclusions In the absence of regional control, the projected total regional damage in net present value is -$40,123,258 over the next 50 years (the minimum projected impact is -$17,410,563). Managing Feral goat as an Exclusion pest has a projected net benefit to the region of $20,966,907. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Feral goat as a Control pest has a projected net benefit to the region of $3,211,050. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Feral goat as an Advisory pest has a projected net benefit to the region of $24,227,574. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Feral goat, Control (defined areas), therefore meets the requirements of Section 72(1a) of the Act. 230

26 Calibrated logistic growth curve Proportion of maximum extent Current extent (ha): 68,490 Potential extent (ha): 68,490 Time to potential (yr): 50 Current prop. of potential: 1 Figure 3.9: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report. 231

27 Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory control Proportion of initial area Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control Discount rate: 8 Total multiplier: (13 13) Discounted annual cost Years of control Years of control Years of control (a) (b) (c) (d) Proportion of initial area Discounted annual cost Proportion of initial area Discounted annual cost Proportion of initial area Discounted annual cost Figure 3.10: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 232

28 3.1.6 Ferret (Mustela furo) Ferret biology and impacts Proposed RPMS Category: Advisory Overall impact: Major Attribute Form Habitat Regional distribution Competitive ability Reproductive ability Table 3.42: Relevant biology Description Up to half a metre long and has a creamy-yellow undercoat, with long guard hairs that are black at the tip, giving a generally dark appearance. The lighter facial region has a dark, mask around the eyes and across the nose. Inhabits a wide range of urban, rural and forest habitats. Found from sea level to alpine habitats. Widespread throughout region. Diet is wide ranging and includes small mammals, fish, birds and invertebrates. Females produce 1 or 2 litters per year with average 6 young, but high juvenile mortality. Resistance to control Highly mobile with large home ranges. Di cult to trap or poison. Benefits Some benefit in rabbit control. Table 3.43: Impact evaluation Category Current Potential Comment Source impact impact Species diversity M H Mainly preys on rabbits, but also eats 1, 2, 3 hares, possums, birds, eggs, lizards, hedgehogs, frogs, eels and various invertebrates. Diet varies with season and food availability. When rabbit numbers are low, ferrets can change their diet to other species. Threatened species M H Predator of adult birds and eggs of North 1, 3 Is kokako and kiwi. Soil resources Water quality Production L M Vector for Tb spread. 1, 2, 3 International trade - L Presence of Bovine Tb in cattle has major 1 impact on exports. Human health L L Can bite and scratch. 2 Recreation L M 1 Māori culture L M 1 Source: 1: Severinsen (2003), 2: Anon. (2010g), 3: Auckland Regional Council (2007) 233

29 Ferret CBA results The following are results for cost-benefit analyses for three scenarios, no regional RPMS control, RPMS control as a Control Pest, and RPMS control as an Advisory Pest. For the purposes of the CBA calculations, the pest is assumed to continue expanding with no regional RPMS control, its spread is assumed to be near-arrested under Advisory Control but not reduced, and it is assumed to be successfully reduced to the expected smaller extent when listed as a Control Pest, more so as an Exclusion pest. Table 3.44: Ferret CBA results for three RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values. Scenario Pest impacts Control benefit Expenditure Net benefit No RPMS 145,228, ,228,518 (50,983, ,058,419) (-50,983, ,058,419) Control Pest 54,856,265 90,372,253 1,585,460 88,786,793 (11,056, ,574,704) (39,926,996 61,483,715) (38,341,536 59,898,255) Advisory Pest 24,413, ,815,030 31, ,783,321 (4,967,940 45,699,996) (46,015, ,358,423) (45,983, ,326,714) Table 3.45: Ferret CBA base assumptions. Base assumptions Values Current area infested (ha) 2e+05 Total area potentially infested (ha) 137,918 (46, ,322) Years from naturalisation to total area 50 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) ( ) Any benefits provided by the weed 1 Discount rate 8 Table 3.46: Ferret RPMS Exclusion Pest assumptions. Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 25,000 (0 50,000) Table 3.47: Ferret RPMS Control Pest assumptions. Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 2e+05 (250, ,000) Table 3.48: Ferret RPMS Advisory Pest assumptions. Advisory Pest assumptions Values Years to achieve objectives 5 Final area infested (ha) 275,000 (3e ,000) 234

30 Table 3.49: Ferret estimated total annual cost of di erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed. Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 0 6,000, ,000 2,400 Ferret conclusions In the absence of regional control, the projected total regional damage in net present value is -$145,228,518 over the next 50 years (the minimum projected impact is -$50,983,483). Managing Ferret as a Control pest has a projected net benefit to the region of $88,786,793. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Ferret as an Advisory pest has a projected net benefit to the region of $120,783,321. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Ferret, Advisory, therefore meets the requirements of Section 72(1a) of the Act. 235

31 Calibrated logistic growth curve Proportion of maximum extent Current extent (ha): 2e+05 Potential extent (ha): 137,918 (46, ,322) Time to potential (yr): 50 Current prop. of potential: Figure 3.11: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report. 236

32 Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory control Proportion of initial area Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control Discount rate: 8 Total multiplier: (54 14) Discounted annual cost Years of control Years of control Years of control (a) (b) (c) (d) Proportion of initial area Discounted annual cost Proportion of initial area Discounted annual cost Proportion of initial area Discounted annual cost Figure 3.12: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 237

33 3.1.7 Hedgehog (Erinaceus europaeus) Hedgehog biology and impacts Proposed RPMS Category: Advisory Overall impact: Moderate Table 3.50: Relevant biology Attribute Form Habitat Regional distribution Competitive ability Reproductive ability Resistance to control Benefits Description Grey-brown, noctural insectivore, with a pointed face and powerful forefeet. Back and sides are completely covered with spines. Inhabits a wide range of urban, rural and forest habitats, including coastal dunes and beaches. Widespread throughout region. Diet is wide ranging. Able to exploit a wide variety of habitats. Can be controlled by trapping and poisoning. Eat slugs and snails in home gardens Table 3.51: Impact evaluation Category Current Potential Comment Source impact impact Species diversity M M Mainly insectivorous, but eats a wide variety 1 of species including plants, mice, birds, lizards, frogs, and chicks and eggs of ground nesting birds. Threatened species M H Predator of eggs of NZ dotterel along 1 coast. Soil resources - - Water quality - - Production International trade - - Human health - - Recreation - - Māori culture - - Source: 1: Auckland Regional Council (2004) 238

34 Hedgehog CBA results The following are results for cost-benefit analyses for three scenarios, no regional RPMS control, RPMS control as a Control Pest, and RPMS control as an Advisory Pest. For the purposes of the CBA calculations, the pest is assumed to continue expanding with no regional RPMS control, its spread is assumed to be near-arrested under Advisory Control but not reduced, and it is assumed to be successfully reduced to the expected smaller extent when listed as a Control Pest, more so as an Exclusion pest. Table 3.52: Hedgehog CBA results for three RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values. Scenario Pest impacts Control benefit Expenditure Net benefit No RPMS 7,665, ,665,169 (4,263,141 8,319,091) (-4,263,141-8,319,091) Control Pest 3,679,959 3,985, ,365 3,588,845 (1,176,315 6,461,006) (3,086,826 1,858,085) (2,690,461 1,461,720) Advisory Pest 1,637,746 6,027,423 7,927 6,019,496 (528,546 2,850,773) (3,734,595 5,468,318) (3,726,668 5,460,391) Table 3.53: Hedgehog CBA base assumptions. Base assumptions Values Current area infested (ha) 2e+05 Total area potentially infested (ha) 178,467 (59, ,445) Years from naturalisation to total area 50 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 1.49 ( ) Any benefits provided by the weed 0 Discount rate 8 Table 3.54: Hedgehog RPMS Exclusion Pest assumptions. Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 25,000 (0 50,000) Table 3.55: Hedgehog RPMS Control Pest assumptions. Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 2e+05 (250, ,000) Table 3.56: Hedgehog RPMS Advisory Pest assumptions. Advisory Pest assumptions Values Years to achieve objectives 5 Final area infested (ha) 275,000 (3e ,000) 239

35 Table 3.57: Hedgehog estimated total annual cost of di erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed. Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 0 1,500,000 30, Hedgehog conclusions In the absence of regional control, the projected total regional damage in net present value is -$7,665,169 over the next 50 years (the minimum projected impact is -$4,263,141). Managing Hedgehog as a Control pest has a projected net benefit to the region of $3,588,845. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. Managing Hedgehog as an Advisory pest has a projected net benefit to the region of $6,019,496. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Hedgehog, Advisory, therefore meets the requirements of Section 72(1a) of the Act. 240

36 Calibrated logistic growth curve Proportion of maximum extent Current extent (ha): 2e+05 Potential extent (ha): 178,467 (59, ,445) Time to potential (yr): 50 Current prop. of potential: Figure 3.13: The modelled pest spread until it reaches its anticipated maximum extent. Shown are the results of the average (solid line), minimum (dotted line), and maximum (dashed line) scenarios. (A horizontal line means that the pest has already reached its maximum extent.) The vertical dotted-dashed lines indicate the CBA assessment period used in this report. 241

37 Population growth, no RPMS control Population growth, exclusion control Population growth, control control Population growth, advisory control Proportion of initial area Discounted growth Discounted growth, exclusion control Discounted growth, control control Discounted growth, advisory control 1.5 Discount rate: 8 Total multiplier: (42 17) Discounted annual cost Years of control Years of control Years of control (a) (b) (c) (d) Proportion of initial area Discounted annual cost Proportion of initial area Discounted annual cost Proportion of initial area Discounted annual cost Figure 3.14: The modelled population changes over the CBA assessment period for (a) no regional control, (b) Exclusion Pest control, (c) Control Pest control, and (d) Advisory Pest control. The upper graphs show the population changes, and the lower graphs show the discounting of associated impacts each year (impacts in the future are of less value economically than impacts of the same size now). 242

38 3.1.8 Magpie (Gymnorhina hypoleuca) Magpie biology and impacts Proposed RPMS Category: Advisory Overall impact: Minor Table 3.58: Relevant biology Attribute Description Form cm in length, weighing g. There are 2 species, whitebacked and black backed, which may inter-breed. Habitat Open land, edges of native and exotic forest, garden, orchards and urban areas. Regional distribution Widespread throughout region. Competitive ability Extremely territorial and attempt to exclude other birds from their breeding territories. Are omnivorous, could pose a threat to other small birds (eggs and chicks) and animals. Reproductive ability Produces 2-5 eggs per year. Resistance to control Controlled by trapping and poisoning. Can become extremely wary making shooting di cult. Table 3.59: Impact evaluation Category Current Potential Comment Source impact impact Species diversity L L Very territorial, restricts movement of native 1 birds between forest patches. May compete with native bird species. Threatened species L L 2 Soil resources Water quality Production - - 1, 3 International trade Human health L L Extremely territorial, shows aggressive behaviour 1, 3 towards humans, especially chil- dren, during the nesting season. Recreation L L See Human Health. 1 Māori culture L L See Human Health. 3 Source: 1: Auckland Regional Council (2004), 2: Corbett (2009), 3: Severinsen (2003) 243

39 Magpie CBA results The following are results for cost-benefit analyses for three scenarios, no regional RPMS control, RPMS control as a Control Pest, and RPMS control as an Advisory Pest. For the purposes of the CBA calculations, the pest is assumed to continue expanding with no regional RPMS control, its spread is assumed to be near-arrested under Advisory Control but not reduced, and it is assumed to be successfully reduced to the expected smaller extent when listed as a Control Pest, more so as an Exclusion pest. Table 3.60: Magpie CBA results for three RPMS scenarios, presented as net present value (NPV, $) over 50 years. The expenditure refers to regional expenditure under the RPMS. Minimum and maximum values are in brackets beneath average values. Scenario Pest impacts Control benefit Expenditure Net benefit No RPMS 3,339, ,339,668 (1,112,243 2,192,385) (-1,112,243-2,192,385) Control Pest 653,456 2,686,212 7,134,568-4,448,356 (125,551 1,240,697) (986, ,688) (-6,147,876-6,182,880) Advisory Pest 276,872 3,062, ,691 2,920,105 (50, ,430) (1,061,513 1,644,955) (918,822 1,502,264) Table 3.61: Magpie CBA base assumptions. Base assumptions Values Current area infested (ha) 2e+05 Total area potentially infested (ha) 67,539 (23, ,087) Years from naturalisation to total area 50 Assessment duration (yr) 50 Weighted average impact per hectare of infested land ($/ha) 0.1 ( ) Any benefits provided by the weed 0 Discount rate 8 Table 3.62: Magpie RPMS Exclusion Pest assumptions. Exclusion Pest assumptions Values Years to achieve objectives 9 Final area infested (ha) 25,000 (0 50,000) Table 3.63: Magpie RPMS Control Pest assumptions. Control Pest assumptions Values Years to achieve objectives 50 Final area infested (ha) 2e+05 (250, ,000) Table 3.64: Magpie RPMS Advisory Pest assumptions. Advisory Pest assumptions Values Years to achieve objectives 5 Final area infested (ha) 250,000 (3e+05 2e+05) 244

40 Table 3.65: Magpie estimated total annual cost of di erent RPMS scenarios (includes inspection, control, monitoring, enforcement, administration etc.). Subsequent years are assumed to have the same value as the last year listed. Exclusion Pest Control Pest Advisory Pest Year Total Costs Total Costs Total Costs 0 27,000, ,000 10,800 Magpie conclusions In the absence of regional control, the projected total regional damage in net present value is -$3,339,668 over the next 50 years (the minimum projected impact is -$1,112,243). Managing Magpie as a Control pest has a projected net benefit to the region of -$4,448,356. Since this is negative, this means that this management scenario does not meet the requirements of Section 72(1a) of the Act. Managing Magpie as an Advisory pest has a projected net benefit to the region of $2,920,105. Since this is positive, this means that this management scenario meets the requirements of Section 72(1a) of the Act. The proposed management scenario for Magpie, Advisory, therefore meets the requirements of Section 72(1a) of the Act. 245