Transcript Predator Prey Interactions in an Individual Based Model

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 FennoScandia 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 Predation
Theory

The composition of predator species

The presence of snow cover

Landscape heterogeneity
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
log(N+1)
Standard scenario - No predators
4
3
2
1
0
1
21
41
61
81
Years
voles
Preliminary
Results II
log(N+1)
Standard scenario - No predators
5
4
3
2
1
0
1
21
41
61
81
Years
voles
weasels
Preliminary
Results III
Standard scenario - No predators
2
1
0
1
21
41
61
-1
-2
standardized
voles
weasels
Preliminary
Results IV
Predators present
No Predators
N 10000
N 10000
8000
8000
6000
6000
4000
4000
2000
2000
0
0
1
21
41
61
81
Years
1
voles
21
41
61
81
Years
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