Post on 03-Oct-2021
Too many wild pigs? Effects of different approaches on population management
Giovanna Massei 1, Barbara Franzetti 2, Simon Croft 1
1 National Wildlife Management Centre, UK2 Italian National Institute for Environmental Protection and Research, Italy
Pathways 2019 Human Dimensions of Wildlife, 22-26 September 2019, Estes Park, USA
Wild boar and feral swine
Snow et al. 2017
Pittiglio et al. 2018
Bengsen et al. 2017
Number of wild boar culled in Europe
Massei et al. 2015 Massei et al. 2014
Trends in hunters in Europe
0
5,000
10,000
15,000
20,000
25,000
1982 1987 1992 1997 2002 2007 2012
Num
ber
of h
unte
rs
Montenegro Belgium
Luxembourg Slovenia
0
20,000
40,000
60,000
80,000
100,000
120,000
140,000
1982 1992 2002 2012
Num
ber
of h
unte
rs
Croatia SerbiaCzech Republic Hungary
0
50,000
100,000
150,000
200,000
250,000
300,000
350,000
400,000
1982 1987 1992 1997 2002 2007 2012
Num
ber
of h
unte
rs
Poland Austria Portugal
Sweden Germany
0
500,000
1,000,000
1,500,000
2,000,000
2,500,000
3,000,000
3,500,000
1982 1987 1992 1997 2002 2007 2012
Num
ber
of h
unte
rs
Italy Spain
Russia France
Massei et al. 2014
Traffic accidents
Threats to native species
Disease transmission
Predation on livestock
Damage to crops, amenities, infrastructures
Impact
Attacks on dogs
$$$
Impact
2006-07 hunting season in Spain: US$ 32M in revenues
Wild boar numbers are increasing in urban areas
Methods to decrease wild boar impact
Fertility control
Toxicants
Recreational ground hunting
Professional shooters/trappers
Culling from helicopters
Methods to decrease wild boar impact
Fertility control
Toxicants
Recreational ground hunting
Professional shooters/trappers
Culling from helicopters
Fertility control & culling to reduce n. of wild pigs
• Maintaining infertile > 40% of sows/year:
in isolated populations: 50% more pop. reduction than culling alone
in open populations: 30% more pop. reduction than culling alone
Pepin et al. 2017
Aims and Methods
MethodsDefined a stochastic stage-specific matrix model and applied an Approximate Bayesian Computation (ABC) approach to derive parametervalues
AimEstimate effects of various levels of culling (0-80%) and fertility control (0-80%) on wild boar number in two isolated populations
Castelporziano (Italy) and Forest of Dean (UK)
Data on n. boar present and removed/year
Data on hunting and traffic accidents
~ 2000 wild boar in 6000 ha
Target: reduce population to 400 animals
Wild boar in Castelporziano
• ~ 30% of estimated wild boar population culled in fall-winter (park rangers only) to reduce impact
• Distance sampling and CMR used to estimate n of wild boar since 2001
0
1000
2000
3000
4000
5000
2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017
Target : reduce population to ~ 400 boar
Results – integrating culling with fertility control
X % Contraception
X %
Cu
llin
g
Time (20 yrs)
Log n
. of
wild
boar
Red line: target (400)
Black line: 50% probability to reach target
Dotted line: confidence intervals
Results Castelporziano: culling and fertility control
0%
20%
40%
60%
80%
0% 20% 40% 60% 80%
Contraception
Culli
ng
Y axis: Log n boar
X axis: 20 years
Red line: target (400)
Black line: 50% probability (dotted line: confidence intervals)
Results Forest of Dean - culling and fertility control
0% 20% 40% 60%
40%
Contraception
Culli
ng
Red line: target (400) Black line: 50% probability
Time (20 yrs)
culling 40% maintains a stable populationculling 40% + 20% contraception 400 boar in ~18 yrs, 1000 boar in ~3 yrsculling 40% + 60% contraception 400 boar in ~3 yrs, 1000 boar in 1 yr
Log n
um
ber
wild
boar
Blue line: new target (1000)
Model summary and next steps
• Fertility control alone is incapable of reducing wild boar numbers
• Adding fertility control to feasible levels of culling can reduce the population faster than culling alone
Future work
• To estimate costs of current management (culling only) and compare with adding fertility control via oral & injectable contraceptives
Fertility control : when?
When lethal control is:
illegal
unacceptable
unfeasible
unsustainable
environmentally hazardous
ineffective when used as the sole method of management
Immunocontraception to manage wild boar in peri-
urban areas in Spain
Immunocontraception to manage wild boar in
Hong Kong
Hunters’ interest in fertility control!
Questions?
Giovanna.Massei@apha.gov.uk
Simon.Croft@apha.gov.uk
barbara.franzetti@isprambiente.it
Acknowledgements