swifco_rs.dispersal module

swifco_rs.dispersal.default_female_dispersal(min_group_size=2, dispersal_radius=4.0, distance_bias=1.0, dispersal_start=20, dispersal_duration=10)

Group splitting is performed in the weeks of the year indicated by dispersal_start and dispersal_duration. All groups containing more females than the cells’ breeding capacity and a minimum number of sub-adults to move min_group_size, are processed. From such groups, the model collects sub-adult female yearlings without offspring. Then, an empty habitat cell is selected randomly among all accessible cells. Groups are iterated randomly for the splitting sub-model. All dispersing individuals of the group disperse as a cohort and establish the new group on the target habitat cell. If no empty habitat is available, disperser females do not move. Accessible habitat cells are cells within Euclidean distance dispersal_radius that can be reached accounting for landscape map structure (i.e., water bodies or other barriers). Accessible cells are determined using breadth-first search on the passable cells (nodes of a graph) and connecting edges along paths up to length dispersal_radius.

Parameters:

min_group_size - minimum number of females to disperse together

dispersal_radius - maximum dispersal radius in grid cells (default value based on [Sodeikat_2003])

distance_bias - factor to exponetially bias dispersal against more distance cells

dispersal_start - start of the dispersal season, as week of year

dispersal_duration - duration of the dispersal season, in weeks

swifco_rs.dispersal.default_male_dispersal(dispersal_probability=0.5, dispersal_ticks=2, dispersal_radius=8.0, distance_bias=0.5, dispersal_start=20, dispersal_duration=10)

Default male dispersal

Male dispersal is performed in weeks 20 to 30 of the year only (i.e., mid-June to the end of July). Uniformly distributed over the weeks of the dispersal period sub-adult males start to disperse. During dispersal, a male does move from cell to cell along connecting edges which are not blocked or lead to impassible cells.

Each week, cells within the radius given by dispersal_radius are considered. The boar moves to the cell with the highest habitat value among the accessible cells ([Pe_er_2013], [Graf_2007], [Jeltsch_1997]). Additionally, cells further away are less likely than cells close by with an exponental weighting determined by the distance_bias exponent. [Prevot_2013]

Parameters:

dispersal_probability - individual dispersal probability

dispersal_ticks - ticks for which an animal is on the move

dispersal_radius - maximum dispersal radius in grid cells (default value based on [Truv__2003]_)

distance_bias - factor to exponetially bias dispersal against more distance cells

dispersal_start - start of the dispersal season, as week of year

dispersal_duration - duration of the dispersal season, in weeks