Migration

We are using digital evolution to investigate factors in the environment promoting the evolution of migration as a space-use strategy. In the sample videos shown below, we co-evolved prey along with predators in seasonal resource environments (predators were never introduced…they are actually prey lineage that evolved to eat other prey). In some cases, straight-forward herd-like migration from one resource to the next evolves. In others, complex and intricate migratory dances appear. In still other cases, prey evolve vertical-migration-like strategies in which they hide just out of sight of predators whenever ‘their’ resource patch is out of season, timing their return to that patch to perfectly correspond with the beginning of a new growing season.

[cvg-video videoId=’44’ width=’400′ height=’300′ mode=’playlist’ /]
Above: each population is begun with the introduction of just a single, blind prey that does nothing other than spin in place, and attempt to eat and reproduce. Prey are shown in blue. Predators (once they evolve into the system) in red. Black-to-white background shading indicates level of the seasonal food resources, with edible resources in black. Prey and predators can and do evolve vision, for detecting each other and food, though the original ancestor is blind. Consumption of food is a requirement for reproduction. After just a few cycles of the seasons (‘years’), reproduction, mutations, and selection has favored a population of organisms that move about randomly. After many more years, prey have evolved complex means of migrating from one resource to the next, while also avoiding the predators that emerged in the system.

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Above: in this population, prey have evolved to see, and very rapidly respond to, renewed resource growth at the start of each season.

[cvg-video videoId=’45’ width=’400′ height=’300′ mode=’playlist’ /]
Above: in this and the following populations, the colors of the prey reflect their chosen food resource (e.g., blue prey prefer the resource in the upper left), though they can change this preference at any time. Predators are still colored red. The prey in this population are using a strategy in which, rather than migrating with the seasons, they hide just out of sight of any predators, perfectly timing their return to their chosen resource patch as it comes into season. Though they rarely evolve to do so, there is nothing preventing predators from leaving the resource areas…there is simply a higher concentration of food (aka prey) in that region.

[cvg-video videoId=’47’ width=’400′ height=’300′ mode=’playlist’ /]
Above: in this population, prey have evolved a migratory dance which takes them away from their resource patch, and from predators, when the resource is out of season. The dance, again, perfectly times their return to coincide with renewed resource growth in their chosen patch.

[cvg-video videoId=’46’ width=’400′ height=’300′ mode=’playlist’ /]
Above: here, multiple stable predator avoidance strategies have evolved in the prey population. Note how the different ‘species’ (colors) of prey have evolved different travel distances and path types.