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
anddispersal_duration
. All groups containing more females than the cells’ breeding capacity and a minimum number of sub-adults to movemin_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 distancedispersal_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 lengthdispersal_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