HexSim Videos

The Metapopulation Dynamics video provides a simple illustration of colonization and extinction processes in a dynamic landscape.

The Predator-Prey video was made from a two-population HexSim model. Mean predator density is displayed in color, ranging from yellow (low) to blue (high).  The actual locations of predator individuals were smoothed to obtain this imagery. The prey population locations can be seen as the hexagons with a black outline. The video shows the predators (colored blobs) chasing down prey items (black patches).

In this video, a small number of simulated northern spotted owls are released into northern California, at the bottom of the image, and allowed to colonize an otherwise empty landscape. Owl locations are exaggerated in the video (they are smoothed), to make them easier to see. The simulation suggests that some connectivity exists up into the North Cascades area (top right), but the resources there are insufficient and the population can not persist in that portion of its range. In contrast, no owls ever make it up to Washington's Olympic Peninsula (top left), indicating that this area is disconnected from the rest of the owl's range.

The model used in this illustration is described in the paper cited below, which can be downloaded from this website (go to Background -> Publications).

Schumaker NH, Brookes A, Dunk JR, Woodbridge B, Heinrichs J, Lawler JJ, Carroll C, and LaPlante D. 2014. Mapping sources, sinks, and connectivity using a simulation model of northern spotted owls. Landscape Ecology 29:579-592.

Results from a simple HexSim model of disease spread. The landscape in this video includes an inaccessible matrix (gray), accessible non-habitat areas (gray-green), unoccupied habitat (yellow), occupied habitat areas (red), and locations that contain at least one infected individual (blue). Individual movement paths are displayed as the simulation runs. The disease is added to the population, at a single location, in time step 500.

Results from a simple HexSim model of disease spread. This video is made from changing maps of the cumulative probability of exposure, starting at the point at which the disease is introduced, and continuing on through the end of the simulation. Yellow representing the smallest nonzero exposure likelihood, and cyan representing the highest.

This simulation shows chytrid fungus invading a population of mountain yellow-legged frogs in Barrett Basin, California. The frog model itself has a daily time step, but it includes life history events that act on a monthly, seasonally, or yearly basis.

Unexposed frogs are shown in green, and frogs infected with the chytrid fungus are shown in yellow. Locations in which frogs have been extirpated by the fungus are shown in purple.

HexSim simulating a cellular automaton (CA) model on a hexagonal grid.