Aquatic alien mammals introduced into Italy: their impact and possibility of control

Transcription

1 Aquatic alien mammals introduced into Italy: their impact and possibility of control Sandro Bertolino University of Turin, DIVAPRA Entomoloy & Zoology Genovesi Piero National Wildlife Institute Biological Invasion in Inland Waters International Workshop Florence, May 5-7, 2005

2 Outline Aquatic Mammals introduced into Italy who are they? where are they? what are they doing? what are we doing? Control vs eradication: an example from the management of coypu in Italy and England An example of strategic approch to coypu control General conclusions

3 Outline Aquatic Mammals introduced into Italy who are they? where are they? what are they doing? what are we doing? Control vs eradication: an example from the management of coypu in Italy and England An example of strategic approch to coypu control General conclusions

4 Aquatic mammals introduced in Europe Species Origin American beaver Castor canadensis North America Muskrat Ondatra zibethicus North America Coypu Myocastor coypus South America American mink Mustela vison North America

5 American mink Mustela vison World spread and introduction Source: J. L. Long, 2003 Introduced mammals of the world

6 American mink Mustela vison Introduction causes Italian distribution Escape from fur farms Deliberate releases

7 American mink Mustela vison Presently no damage is reported in Italy, but in other European countries the American mink threatens other species through: predation (ground nesting birds, water vole) competition (European mink)

8 American mink Mustela vison Propagule pressure Recent releases from fur farms in Italy 5000 animals Parma 3000 animals Forlì (2001) 5000 Treviso (2002) Ferrara (2003) 200 Padova (2005)

9 American mink Mustela vison Prevention To prevent new establishment it is important to build-up a rapid response system. Thus the National Wildlife Institute is preparing an action plan, with the constitution of task-forces at the Regional or Provincial level in order to capture the animals in few days after their releases.

10 Muskrat Ondatra zibethicus World spread and introduction Source: J. L. Long, 2003 Introduced mammals of the world

11 Muskrat Ondatra zibethicus Introduction causes Italian distribution Escape from fur farms Deliberate introductions

12 Muskrat spread The beginning of an invasion: the spread of the muskrat from the point of introduction of five individuals near Prague in 1905 (modified from Ulbrich 1930).

13 Muskrat Ondatra zibethicus Presently no damage is reported in Italy, but in other European countries the muskrat damage aquatic vegetation, undermines river banks and dikes for its burrowing activity, there is some evidence of negative impacts on invertebrates through the change in habitat structure

14 Coypu Myocastor coypus World spread and introduction Source: J. L. Long, 2003 Introduced mammals of the world

15 Coypu Myocastor coypus Introduction causes Italian distribution Escape from fur farms Deliberate introductions Source: Mitchell-Jones et al, 1999 The Atlas of European mammals

16 Alien species management The coypu is considered a pest because of the damage produced to crops, the damage produced by feeding on aquatic vegetation, for its burrowing activity that undermines river banks and dikes, a negative impact on birds nesting in the aquatic vegetation and near the rivers has been suggested.

17 Outline Aquatic Mammals introduced into Italy who are they? where are they? what are they doing? what are we doing? Control vs eradication: an example from the management of coypu in Italy and England An example of strategic approch to coypu control General conclusions

18 Cost/benefit analysis of two opposite approaches to pest species management: permanent control of Myocastor coypus in Italy versus eradication in East Anglia (UK) Panzacchi et al. submitted

19 Coypu s eradication in East Anglia (Gosling et al., 1981; Gosling & Baker, 1999) Official eradication started in 1981 (intensive trapping before). 24 trappers involved, ensured salary for the entire period; reward for earlier completion of the eradication 31,822 coypus killed After 1989 no occurrence recorded

20 Coypu s eradication in East Anglia (Gosling et al., 1981; Gosling & Baker, 1999) 24 trappers, traps per person rafts 4-5 boats Costs, actualised to yr 2000, about 5 million IS IT TOO MUCH?

21 Coypu s range in Italy Introduced in the 1960s Range = Kmq Continuous range in North and Central Italy Still scattered in the South Progressive expansion Recently introduced in Sicily and Sardinia

22 survey on the economic losses 297 public institutions contacted sending 2 questionnaires: Q1 (focusing on damage to agriculture and coypus control) was sent to Regional and Provincial Wildlife Departments and to Park Departments; Q2 (focusing on damage to river banks and drainage channels) was sent to he Drainage Authorities.

23 survey on the economic losses Cost of control including : MATERIAL All costs were corrected to year 2000 value, using an economical revaluation coefficient table PERSONNEL traps (8 yr amortisation) kits for euthanasia anaesthetics bullets plastic gloves freezers (12 yr amortisation) use of cars or boats rafts, baits plastic bags disposal of carcasses (incinerated or buried), staff salary volunteers reimbursement training courses for the volunteers

24 Impact on crops and n killed coypus Compensated damage to crops Killed coypus R 2 = 0.93, P = Damage to crop R 2 = 0.93, P = N. killed coypus Pearson R = 0.92, P = 0.008

25 Damage to riverbanks R 2 = 0.96, p < Costs of floods not considered: e.g.: 7 th August 1998 Brenta river bank collapsed devastated the community of Loreggia, destroying buildings and fields. Est. losses ca. 16 Mln.

26 Cost of control R 2 = 0.85, p =

27 Total costs 3.77 MILLIONS TOTAL R 2 = 0.87, P = Damage to riverbanks Costs of control Damage to crops

28 Future costs of Coypu management in Italy Present range = 68,599 Kmq Potential expansion habitat) 330% (suitable Total costs (yr 2000) = 3,773,786 Potential future costs > 12 mln /yr Million Ottaviani, UK eradication Mngmt cost/yr Predicted Italy mngmt cost/yr

29 Conclusions: control vs eradication 1. Widespread perception that costs of eradications generally outweigh benefits, and that eradications in most cases fail 2. But! costs of permanent control largely exceed costs of eradication 3. Thus, eradication, when feasible, is the best option in the long term

30 Recommendation for the management of aquatic species 1. Competent authorities should eradicate small populations of the American mink and adopt a rapid response system to face new releases 2. and eradicate Muskrat in northeastern Italy, adopting a subsequent control campaign to prevent new arrivals from East

31 Recommendation for the management of the coypu 1. Eradicate coypus in isolated and newly colonised areas where it is still technically possible and cost effective (eg. Sicily and Sardinia in Italy, but also Spain). 2. Carefully plan control activities of large populations 3. Always evaluate the efficacy of control operations and adjust future plans accordingly. 4. Concentrate control operation in the most vulnerable areas in terms of biodiversity (protected areas), economically valuable crops (vegetables) and important hydraulic systems. 5. Support research on more effective control methods and prevention strategies

32 Outline Aquatic Mammals introduced into Italy who are they? where are they? what are they doing? what are we doing? Control vs eradication: an example from the management of coypu in Italy and England An example of strategic approch to coypu control General conclusions

33 A strategic approch to coypu control in small wetland areas Bertolino et al Wildl. Soc. Bull.

34 Damage to natural vegetation in the Piedmont Region (Northwestern Italy) In these protected areas: Garzaia di Valenza Natural Reserve Restoration area in the Garzaia di Valenza Biotope (Natura 2000) Fontana Gigante Biotope (Natura 2000) Palude di San Genuario Lago di Candia Park A drastic reduction on aquatic vegetation has been observed Phragmites australis, Thypa spp., Nymphaea alba, Nuphar lutea, Trapa natans

35 A strategic approach to coypu control Problem definition Adapted from Braysher 1993 Feasibility Definition of objectives Preparing a plan Implementation of the plan Monitoring and evaluation

36 Problem definition In the 90s the coypu colonized an area, the lakes of La Spes, where the Po River Park was re-creating some wetlands in previous agricultural areas The animals with their foraging activities were stopping the colonization of the aquatic vegetation, limiting the naturalization of the area

37 The coypu was stopping the evolution of the area toward a functional ecosystem

38 Yesterday

39 Today

40 Feasibility of control from literature Trasimeno Lakes Coypu control: YES Campotto Coypu control: NO Source: Cocchi e Riga 2001

41 Population growth curve of an introduced species Carrying capacity Number of animals 1 Time 2 Control not possible Possibility to control the population

42 From the literature: if the effort is appropriate and the density not too high, it is possible to control coypu populations with cage-traps Gosling 1990; Cocchi & Riga 2001

43 Definition of objectives Allow the natural vegetation to grow Recover the functional ecology of the area Prepare an action plan for the control of the coypu in other wetlands managed by the park

44 Feasibility: an experimental approach Trapping in 2 areas Aclosedarea surrounded by crop fields and poplar plantations, with a probable low degree of colonization by coypu dispersing from other areas An open area a canal flowing into the River Po. Here coypus were part of a larger population distributed along the River Po

45 Control results 1998 Coypus removed R 2 = 0.89; P = Closed area Weeks of capture Open area Coypus removed Weeks of capture

46 Control results 1999 Coypus removed Closed area Open area Winter Spring Summer Autumn Difference between seasons Closed P<0.01 Open N.S.

47 Implementation of the plan: Methods Control in 2 periods: winter and autumn Use of 5-10 cage-traps per area 1 person working Traps activated for 2-3 days a week For a period of 5-7 weeks

48 Implementation of the plan: Areas Continuing the control started in 1998 in the restoration area (closed area) In 2000 starting the control in the EU Biotope (Natura 2000) Fontana Gigante In 2001 starting the control in the EU Biotope (Natura 2000) Palude di S. Genuario

49 Fontana Gigante

50 Palude di S. Genuario

51 Monitoring and evaluation: results Animals removed Valenza Fontana Gigante S. Genuario Win. Aut. Win. Aut. Win. Aut Period Coypus removed in the 3 areas during the period:

52 Monitoring and evaluation: results Density (coypus/ha) Carrying capacity 1 2 Wetlands in the park Other areas 0 Removal densities of coypu in the 3 areas and different periods ( , light blue dots) and density of coypu populations from other areas (red dots) Red dots data from: Norris 1967, Brown 1975, Willner et al. 1979, Doncaster and Micol 1990, Velatta and Ragni 1991, Reggiani et al. 1993).

53 Monitoring and evaluation: coypu populations Coypu populations were limited by the control effort in the 3 areas but this is not enough! Thus did we meet all the objectives of the control plan?

54 We were interested in the recovery of natural vegetation!

55 Monitoring and evaluation: natural vegetation Surface (sq m) Before colonization Pond 1 Pond 2 Pond 3 Coypu feeding After control Surface covered by yellow waterlilies in 3 ponds, before coypus colonization, during coypu feeding, and after coypu removal

56 Conclusion In small areas it is possible to control coypu in order to let the natural vegetation to recover When control campaign are planned it is important to evaluate the efficacy of the control operations and adjust future plans accordingly

57 Outline Aquatic Mammals introduced into Italy who are they? where are they? what are they doing? what are we doing? Control vs eradication: an example from the management of coypu in Italy and England An example of strategic approch to coypu control General conclusions

58 General conclusion I Prevention is a better strategy than eradication or control!! Every alien species needs to be managed as potentially invasive, until convincing evidence indicates that it is not threatening, avoiding its release in the wild and maybe limiting the importation in the country

59 General conclusion II Accordingly to the European strategy, Italy is called to build-up a rapid response system in order to avoid further releases of alien mammals in the wild. Considering the risks posed to biodiversity and human activities, Italy must adopt a precautonary principle, removing small nuclei of introduced species before they spread in large area.

60 Thank you for your attention!!