Download Losses of sheep on summer range in Norway

Losses of sheep on summer
range in Norway
Inger Hansen and Rolf Rødven
Bioforsk Nord
8th CAC, Girdwood, Sept 29-Oct 03 2013
Facts about losses of sheep in Norway
• 2 million sheep on summer range
• 125 000 sheep lost annually
• Increasing losses since 1990 due to increasing
carnivore populations (Mysterud & Mysterud 1995, Sagør et al.
1997, Kvam & Jonsson 1998, Nilsen et al. 2002, Andersen et al. 2003, Knarrum
et al. 2006, Hansen 2009, www.rovbase.no, www.rovdata.no)
• 12 million US $ payed for in compensations
• Large spatiotemporal variation in losses
• Causes of sheep mortality may be complex (Hansen 2006,
Grøva 2009)
8th CAC, Girdwood, Sept 29-Oct 03 2013
www.rovviltportalen.no
www.minskole.no
www.rovdata.no
www.njf.no
www.rovdata.no
www.avisa-st.no
Percentage of sheep killed by the
different carnivore species
8th CAC, Girdwood, Sept 29-Oct 03 2013
Primary objective
To identify characteristics of lambs killed by red fox,
wolverine and lynx and to find farm management
factors that may be significant for mortality on
summer range
8th CAC, Girdwood, Sept 29-Oct 03 2013
Animals and study areas
Year
No of
flocks
No of lambs
with
mortality
transmitters
No of
Area
lambs in
dataset
2002
4
300
288
Beiarn, Nordland county
2006
6
272
272
Tjongsfjord, Nordland county
2007
3
182
181
Krødsherad, Buskerud county
2011
2
241
423
Flå, Buskerud county
In total
15
995
1164
8th CAC, Girdwood, Sept 29-Oct 03 2013
Registrations
•
•
•
•
•
•
•
•
•
Birth weight
Spring weight
Autumn weight
Sex
Age of dam
Litter size
Location of carcass
Date of death
Cause of death
8th CAC, Girdwood,Sept 29-Oct 03 2013
Statistics
• Generalized linear models were used
• Binominal distribution was assumed
• Akaikes Selection Criterion adjusted for small
sample sizes (AICc) was used to select the most
parsimonious models
• Maternal age was excluded from the models to avoid
unbalance
8th CAC, Girdwood, Sept 29-Oct 03 2013
2
3
1
4
Survival of lambs
+/- 95% CI
in the four study
areas
8th CAC, Girdwood,Sept 29-Oct 03 2013
Beiarn (N=45)
Tjongsfjord
7%
8%
7%
(N=25)
2%
Woloverine
Red fox
Golden eagle
Disease
52%
40%
Disease
Accident
Accident
84%
Flå (N=15)
Krødshead (N=29)
3.5 % 3.5 %
13%
Lynx
Lynx
Disease
Accident
Accident
93%
8th CAC, Girdwood, Sept 29-Oct 03 2013
87%
0.9
0.8
0.6
0.7
Probability of survival
1.0
Survival versus body mass of lambs at release
0.5
Beiarn (Wolverine)
Tjongsfjord (Red fox)
Krodsherad (Lynx)
Flaa (Lynx)
0
10
20
30
Body mass at release (kg)
8th CAC, Girdwood, Sept 29-Oct 03 2013
40
Discussion
• Mortality is linked to lamb body mass at release in
three out of four areas
• The «weaker» the predator, the more important the
size of the prey
• Farmers following «best practice» loose few animals
due to disease, but may loose a lot to carnivores
8th CAC, Girdwood, Sept 29-Oct 03 2013
Preventive measures
• Red fox:
– Hunting
– Improved body mass at release
• Wolverine:
– Early gathering of the flock
• Lynx:
– Moving sheep herds from forest range to mountain
pasture
– Grazing within enclosed pastures
– Quota hunting
– (Improved body mass at release)
8th CAC, Girdwood, Sept 29-Oct 03 2013
Conclusion
• Mortality is linked to body mass of the lambs when
released
• The weaker the predator, the more important the
size of the prey
• Mortality caused by diseases and red foxes may be
prevented
• Effective, preventive measures against protected
carnivores are harder to find, as long as the
traditional free range summer grazing is practised
8th CAC, Girdwood, Sept 29-Oct 03 2013
Testing of a carnivore-proof vest
8th CAC, Girdwood, Sept 29-Oct 03 2013
70
70
50
40
60
Flaa
Daily growth rate
0
10
20
30
50
40
30
20
10
0
Body mass(kg)
60
Beiarn
100
150
0
50
100
150
100
150
70
50
70
0
10
20
30
40
50
60
Tjongsfjord
0
0
10
20
30
40
50
60
Krodsherad
0
50
100
150
0
50
Julian date (1 Jan = 1)
8th CAC, Girdwood, Sept 29-Oct 03 2013