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Predator-Prey Interactions in an Individual Based Model
Ditte Katrine Hendrichsen
NERI / University of Copenhagen, Denmark
Population Cycles in Small Rodents
Ecological background
The aim of this project
Methods - ALMaSS
Preliminary results
Background
Population cycles are known in a number of species
The population cycles of small rodents in Fenno-Scandia show a characteristic north-south gradient
Several theories proposed to explain the cycles One these is the Specialist-Generalist Predation
Hypothesis or the Predation Theory
The Predation Theory
The composition of predator species Primarily specialists in north
Stoat (Mustela erminea) and Weasel (M. nivalis)
Greater diversity of predators towards south including more generalist species
Tawny Owl (Strix aluco)
The presence of snow cover
Landscape heterogeneity
The Predation Theory
The composition of predator species
What Do I Want to Know?
Can we generate cycles just by adding and changing predators?
What are the effects in the prey dynamics when different scenarios are run?
simulations with and without predators and different
ratios of generalists and specialist predators
simulations with different spatial characteristics
Methods
Model: ALMaSS Landscape model
Animal model
Model species: Field vole (Microtus agrestris)
The Predator Elements in ALMaSS
Death and reproduction rates
Home range size, the size of the search area within the home range
Efficiency
How long they stay in a particular area and how far they move
Preliminary Results I
Standard scenario - No predators
0
1
2
3
4
1 21 41 61 81
Years
log
(N+
1)
voles
Preliminary Results II
Standard scenario - No predators
0
1
2
3
4
5
1 21 41 61 81
Years
log
(N+
1)
voles
weasels
Preliminary Results III
Standard scenario - No predators
-2
-1
0
1
2
1 21 41 61
standardized voles
weasels
Preliminary Results IV
Predators present
0
2000
4000
6000
8000
10000
1 21 41 61 81
Years
N
voles
No Predators
0
2000
4000
6000
8000
10000
1 21 41 61 81
Years
N
voles
ALMaSS in Theoretical
Population Ecology
Modelling may allow us to test scenarios which does not occur in nature Effects of weather
Landscape structure and management
Fauna composition
ALMaSS in Theoretical
Population Ecology
Modelling may allow us to test scenarios which do not occur in nature
...and to run scenarios over several years, testing the long term influence of different parameters
Acknowledgements
Chris Topping
Department of Landscape Ecology, National Environmental Research Institute, Denmark
Mads Forchhammer
Department of Population Ecology, Institute of Zoology, University of Copenhagen, Denmark