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Deriving space use patterns from animal interaction mechanisms

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Deriving space use patterns from animal interaction mechanisms

Jonathan Potts, Postdoctoral Fellow, University of Alberta, May 2013

Movement

Directinteractions

Mediated interactions

Environmental interactions

- Modelling animal movement: the “correlated random walk” framework

- Modelling animal movement: the “correlated random walk” framework
- Adding in environmental interactions: step selection functions

- Modelling animal movement: the “correlated random walk” framework
- Adding in environmental interactions: step selection functions
- Including animal-animal interactions: coupled step selection functions

- Modelling animal movement: the “correlated random walk” framework
- Adding in environmental interactions: step selection functions
- Including animal-animal interactions: coupled step selection functions
- Throughout: how do these models help us understand space use phenomena?

Example step length distribution:

Example step length distribution:

Example turning angle distribution:

Probability of moving to position x given that the animal was previously at position y and arrived there on a trajectory is:

where is the step length distribution and the turning angle distribution.

A, B, C different habitats. B = worse, A = better, C = best.

Probability of moving to position x given that the animal was previously at position y and arrived there on a trajectory is:

- is the step length distribution,
- is the turning angle distribution
- is a weighting function
- E is information about the environment

Fortin D, Beyer HL, Boyce MS, Smith DW, Duchesne T, Mao JS (2005) Wolves influence elk movements: Behavior shapes a trophic cascade in Yellowstone National Park. Ecology 86:1320-1330.

- is a function denoting the value of each point in the study area

Potts JR, Mokross K, Stouffer PC, Lewis MA (in review) Step selection techniques uncover the environmental predictors of space use patterns in flocks of Amazonian birds. Ecology

- is a function denoting the value of each point in the study area
- Notice that is independent of (please ask).

Potts JR, Mokross K, Stouffer PC, Lewis MA (in review) Step selection techniques uncover the environmental predictors of space use patterns in flocks of Amazonian birds. Ecology

- is a function denoting the value of each point in the study area
- Notice that is independent of (please ask).
- Use this to test various
hypotheses about the

nature of .

Potts JR, Mokross K, Stouffer PC, Lewis MA (in review) Step selection techniques uncover the environmental predictors of space use patterns in flocks of Amazonian birds. Ecology

1. Birds are more likely to move to higher canopies:

1. Birds are more likely to move to higher canopies:

2. In addition, birds are more likely to move to lower ground:

(

1. Find the that maximises:

where and are, respectively, the sequence of positions and trajectories from the data, and

2. Find the that maximises:

where is the value of that maximises the likelihood function on the previous page, and

- From the step selection function to a master equation:
where is the intersection of with the half-line starting at and continuing on a bearing of .

Potts JR, Bastille-Rousseau G, Murray DL, Schaefer JA, Lewis MA (in prep) Predicting local and non-local effects of resources on animal space use using a mechanistic step-selection model

- From the step selection function to a master equation:
where is the intersection of with the half-line starting at and continuing on a bearing of .

- PDE in the simple case where the turning angle distribution is uniform and :

Potts JR, Bastille-Rousseau G, Murray DL, Schaefer JA, Lewis MA (in prep) Predicting local and non-local effects of resources on animal space use using a mechanistic step-selection model

Moorcroft and Barnett (2008) Mechanistic home range models and resource selection analysis: a reconciliation and unification.Ecology 89(4), 1112–1119

Movement data

Statistical tests, e.g. MLE

Step selection functions

Simulations

Master equations, PDEs

Mathematical analysis

One step selection function for each agent and include an interaction term :

where represents both the

population positions and any

traces of their past positions

left either in the environment

or in the memoryof agent .

Potts JR, Mokross K, Stouffer PC, Lewis MA (in prep) A unifying framework for quantifying the nature of animal interactions

Territorial marking (vocalisations):

if any flock is at position at time t

otherwise.

Territorial marking (vocalisations):

if any flock is at position at time t

otherwise.

Hypothesis 1 (tendency not to go into another’s territory):

Territorial marking (vocalisations):

if any flock is at position at time t

otherwise.

Hypothesis 1 (tendency not to go into another’s territory):

Hypothesis 2 (tendency to retreat after visiting another’s territory):

where is a von Mises distribution, is the bearing from to and is the bearing from to a central point within the territory and if X is true and 0 otherwise.

between competing models

Mark Lewis (UofA)

Karl Mokross (Louisiana State)

Guillaume Bastille-Rousseau (Trent)

Philip Stouffer (Louisiana State)

Dennis Murray (Trent)

James Schaefer (Trent)

Members of the Lewis Lab (UofA)

Conclusion

Movement and interaction data

Statistical tests

Coupled step selection functions

Simulations

“The challenge is to develop a statistical

mechanics for ecological systems” Simon Levin

The final frontier!

Spatial patterns

Mathematical analysis