Rat eradication on Italian islands: benefits, costs and future challenges

Dario Capizzi

Regional Parks Agency - Latium Region

Nicola Baccetti, ISPRA - Paolo Sposimo, Nemo srl

N. BACCETTI, C. GOTTI, E. R. PELLICCIONI (ISPRA)

F. CORBI (GPRO)

S. FRANCESCATO, S. ZERUNIAN (CFS, UTB Sabaudia)

F. GIANNINI, F. ZANICHELLI (PN Arcipelago Toscano)

B. MASSA (Univ. of Palermo)

A. NAVONE, G. SPANO, M. PUTZU (AMP Tavolara)

M. PANELLA (CFS)

A. PERFETTI (PN Migliarino)

P. SPOSIMO (Nemo s.r.l.)

S. VAGNILUCA, G. QUILGHINI, G. MARSIAJ (CFS, UTB Follonica)

and many others

Data and experience shared with:

LIFE PROJECTS:

Capraia e Isole Minori (LIFE97 NAT/IT/004153)

Isole di Toscana (LIFE04 NAT/000172)

Montecristo 2010 (LIFE08 NAT/IT/000353)

Pelagic birds (LIFE11 NAT/IT/00009)

Puffinus Tavolara (LIFE12 NAT/IT/000416)

PROTECTED AREAS:

Marine Protected Area of Tavolara - Punta Coda Cavallo

Circeo National Park

Rat eradication actions have been founded either by Life Projects or protected areas

What do rats on islands?

Rats may have a detrimental impact on island ecosystems

The good news is that the problem can be solved

A natural experiment: rat-free vs rat-inhabited islands

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1999 2000 1999 2000 1999 2000 2003

nu

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surveyed successful

Cerboli

La Scola

Zannone

Argentarola

X

χ2 test: each comparison between rat-free and rat inhabited: at least P<0.03,

except for Arg. 1999 vs La Scola 1999, P<0.10; other tests n.s.

Foradada (Sardinia), one of the few surviving colonies of Storm petrel’s

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Tavolara Montecristo Tavolara Montecristo

Linosa Molara Molara

Tavolara Montecristo

Molara

Tavolara

Molara

Montecristo Tavolara

Molara

Rat abundance

Linosa

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% of juveniles Montecristo Tavolara

Linosa Molara

reproduction (2010): late spring

reproduction (2009-2010): mainly winter

Reproduction (2011): autumn

Linosa

reproduction (2013-14): late summer and late winter

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ture

s/tr

apn

igh

ts

Home range

Home-range size of black rats at Ponza (9 females and 6 males) (method: MCP)

femmine maschi

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4000.0

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females males

1999-2001: the first rat eradication projects

Black rat eradication on 7 small islands in the Tuscan Arcipelago National Park (area between 1 and 6.5 ha)

Rodenticide bait placed inside bait station (6-10 bait station/ha)

Islands closer 350 m from mainland were reinvaded

2005-2007: two large islands

Rat eradication on Giannutri (239 ha, Tuscan Archipelago NP) and Zannone (104 ha, Circeo NP)

The largest Mediterranean islands free of rats up to the success of Dragonera (290 ha)

Bait inside bait stations, at an average density of 4 per ha

No rat reinvasion

2008: Molara (430 ha)

First aerial broadcast in the Mediterranean basin

Bait density: 10 kg/ha of grain pellets

Island reinvaded in 2010 (after 21 months)

Too distant from mainland or rat-inhabited islands (swimming distance >1500 m)

The invaders were genetically different from “native” population, thus supporting the hypothesis of a man-driven reinvasion

Cory’s shearwater

Shearwater nesting success before and after rat eradication

Yelkouan shearwater

La Scola

eradication

eradication

sampled successful

Molara

Benefits for target species

Cory’s shearwater

rat control

Zannone

Data from: Baccetti et al. (2010) RIO; Corbi et al. (2005)

Where the few money available should be invested?

In 2010 we developed a model to prioritize rat eradication on Italian islands based upon: biological value of the islands (number of shearwater nesting pairs) monetary costs of the action (in €) risk of reinvasion (distance from mainland/islands and boat service)

La Scola – Pianosa: 242 m!

English name:

Black rat, Roof rat

and…

SHIP RAT!

Accounting for the risk of rat reinvasion

• Rats can reinvade islands by swimming or by passive transport on boats

• Between 2001 and 2010, we observed black rat recolonization of 4 islands distant between 200 and 382 m from rat-inhabited islands or mainland

2 recolonizations between 2001 and 2014

Photo: G. Muscetta

Rank Island Region Area (ha) P.

yelkouan C.

diomedea

Island Region Area (ha) Berta

minore Berta

maggiore

1 SAN NICOLA Puglia 46,2 70-100 -

2 TAVOLARA Sardegna 602,0 1200-7800 10-50

3 LA SCOLA Toscana 1,6 - 60-100

4 PAN DI ZUCCHERO Sardegna 4,1 - 300-400

5 LINOSA Sicilia 545,1 2-20 10000

6 PALMAROLA Lazio 125,1 10-30 100-150

7 CARPA Sardegna 0,4 - 80-120

8 SAN DOMINO Puglia 208,6 30-50 200-240

9 VENTOTENE Lazio 143,6 10-30 25-40

10 MOLARA Sardegna 347,9 300-600 -

11 FORADADA Sardegna 5,1 - 50-200

12 FIGAROLO Sardegna 22,1 10-100 30-100

13 CAPRARA Puglia 49,5 - 100-160

14 PIANA DI ALGHERO Sardegna 13,3 - 100-200

15 MONTECRISTO Toscana 1071,7 400-750 -

16 SANTO STEFANO Lazio 31,0 1-10 5-10

17 CAMERE W Sardegna 3,6 - 40-60

18 CAMERE E Sardegna 4,8 - 40-60

19 BARRETTINI Sardegna 10,3 - 50-100

20 LAMPEDUSA Sicilia 2059,6 500-1000 20-50

Ranking with islands at high risk of recolonization

Rank Island Region Area (ha) P.

Yelkouan C.

diomedea

1 TAVOLARA Sardinia 602,0 1200-7800 10-50

2 PALMAROLA Latium 125,1 10-30 100-150

3 BARRETTINI Sardinia 10,3 - 50-100

4 MONTECRISTO Tuscany 1071,7 400-750 -

5 GIANNUTRI Tuscany 239,5 - 50-200

6 ZANNONE Latium 104,7 1-10 24-30

7 Soffi group Sardina 4 islands - 80-120

8 SANTO STEFANO Latium 31,0 1-10 5-10

9 MOLARA Sardinia 347,9 300-600 -

10 MORTORIO Sardinia 55,7 - 40-60

11 LA VACCA Sardinia 9,1 1-20 5-50

12 S. Maria group Sardinia 14 islands 1-20 200-600

13 PIANOSA-LA SCOLA Tuscany 2 islands - 90-150

14 ROSSA DI TEULADA Sardinia 10,5 - 1-50

15 SPARGI Sardinia 421,9 10-20 90-150

16 SERPENTARA Sardinia 31,3 10-50 -

17 CAVOLI Sardinia 42,1 1-20 5-30

18 Corcelli group Sardinia 3 islands - 2-20

From: Capizzi, Baccetti, Sposimo (2010) Biol. Cons.

Eradication planned (2015)

Eradication to be confirmed

Eradicated 2007

Eradicated 2006

Eradicated on La Scola (2001), eradication on Pianosa proposed

Action plan available

Eradicated, reinvaded, new eradication?

Linosa: eradication planned for 2014, accounting for risk of reinvasion by setting appropriate prophylaxis measures

Ranking of Italian islands for rat eradication

SPECIES ISLANDS IMPACT

Larus michaellis All islands No impact, except at Montecristo where colony size decreased

Ovis musimon Zannone No impact (population stable at 45 individuals)

Podarcis muralis/sicula 10 islands No impact (populations stable or increasing, no extinction)

Hemidactylus turcicus Giannutri, Molara No impact

Hierophis viridiflavus Giannutri, Molara No impact

Tyto alba Giannutri, Molara Extinct? (1-2 pairs per island)

Falco peregrinus Giannutri, La Scola, Zannone

No change in the number of nesting pairs

Corvus corax Molara, Palmaiola

No change in the number of nesting pairs

Impact on non-target species on Italian islands

2012: Montecristo

Hosting an important Yelkouan shearwater colony (second in Italy after Tavolara)

Rats have been eradicated by using bait aerial spread

It is now the largest Mediterranean island free of rats

2015: Tavolara, Linosa…

Main Italian shearwater colonies

A positive outcome may reverse the conservation status of two shearwater species

Aerial distribution is crucial for Tavolara (planned for 2015)

but…

A legal perspective: aerial distribution is no longer allowed? Ordinance of Ministry of Health, February 10, 2012

“Rules on the prohibition of the use and possession of poisoned bait”

Italian text

Nelle aree protette (…) e'

possibile effettuare (…) operazioni

di derattizzazione mediante

rodenticidi senza l'utilizzo degli

appositi contenitori di esche a

condizione che:

a) il principio attivo utilizzato

come rodenticida sia a bassa

persistenza ambientale, al fine di

evitare la contaminazione della

catena alimentare e dell'ambiente;

Temptative translation

In protected areas (...) it is

possible (...) to eradicate rats

using rodenticides without the use

of bait dispenser, provided that:

a) the active ingredient used as

a rodenticide has low

environmental persistence, in

order to avoid contamination of

the food chain and the

environment;

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brodifacoum

(n=322)

diphacinone

(n=39)

failed successful

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brodifacoum

(n=149)

diphacinone

(n=6)

total aerial broacast

Why use brodifacoum?

Brodifacoum: highly persistent, alta tossicità

Diphacinone: media persistenza, media tossicità

From: Parkes et al., 2011, Conservation Evidence

A challenge for the future: eradicating rats from man-inhabited islands

Many important colonies are on man-inhabited islands, at high risk of reinvasion by boats

Implementing the appropriate biosecurity measures may also allow eradication of rats from islands with small human settlements

This will also return benefits in terms of the welfare of the resident population

…the conservation of shearwaters in the Mediterranean largely depends on the outcome of these projects!

In conclusion…

Thanks for your attention!