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