The Transmission of Migratory Behaviors

In nature, animals rely upon migratory behaviors in order to adapt to seasonal variations in their environment. However, the transmission of migratory behaviors within populations (either during lifetimes or throughout successive generations) is not well understood (Bauer et al., 2011). In Artificial Life research, Agent Based Modeling (ABM) is a bottom-up approach to study evolutionary conditions under which adaptive group behavior emerges. ABM is characterized by synthetic methods (understanding via building), and is becoming increasingly popular in animal behavior research (Sumida et al., 1990). Combining an Artificial Neural Network (ANN) and Evolutionary Algorithm (EA) for adapting agent behavior (Yao, 1993) has received significant research attention (Phelps and Ryan, 2001), (Lee, 2003). ABM is an analogical system that aids ethologists in constructing novel hypotheses, and allow the investigation of emergent phenomena in experiments that could not be conducted in nature (Webb, 2009). Numerous studies in ethology have formalized mathematical models of migratory patterns in various species (Bauer et al., 2011). However, there have been few studies that examine ontological and phylogenetic conditions requisite for emergent migratory behavior. ABM is advantageous (compared to formal mathematical models of migratory behavior), since various evolutionary processes can be simulated, and variations in resultant migratory behaviors examined. For example, ABM has been used to predict the consequences of forced human migrations (Edwards, 2009), and migratory behavior between groups of Macaque monkeys (Hemelrijk, 2004). In this research, ABM is used to investigate a hypothesis posited in ethological literature: that migratory behavior is adopted as an adaptive foraging behavior, where such behavior is either genetically or culturally determined (Huse and Giske, 1998). This study aims to investigate the evolutionary and cultural conditions that give rise to migratory behaviors and thus adaptive foraging. In cultural behavioral transmission, ontogenetic transfer occurs between agents during their lifetime. Alternatively, migratory behavior is phylogenetically transmitted through successive generations (Bauer et al., 2011). A minimalist simulation model (distribution of four food patches and 200 agents on a grid) demonstrates the impact of ontogenetic versus phylogenetic transmission of migratory behavior and thus agent group adaptivity. Agents use an ANN controller (figure 1, left). ANN connection weights are adapted with an EA. Agent fitness is the food amount consumed during a lifetime (200 iterations). The EA selects for effective foraging behaviors, which depends upon agents periodically migrating to where food is plentiful. Stimuli for migratory behavior take the form of cyclic seasons in the environment and agents signaling their movement direction to neighbors. When it is winter (food is scarce) in one half of the environment, it is summer (food is plentiful) in the other half, where each seasonal cycle (50 iterations) the winter and summer zones are switched. Each iteration, agents receive the sensory inputs: signal from the closest agent, their current fitness and recurrent connections (activation value of the hidden layer in the previous iteration). Agent behavior is: move to an adjacent grid square, mimic or mate with a neighboring agent. The output with the highest activation is selected (figure 1, left). Each iteration, agents also emits a signal (output not depicted in figure 1), conveying the sender’s current direction of movement and thus indicating migratory behavior. Via choosing to mimic or mate, agents either imitate their neighbor’s migratory behaviors or pass genetically encoded migratory behaviors onto their offspring. If an agent mimics, it copies the ANN connection weights of its closest neighbor, thus mimicking its neighbors behavior, which includes the direction signal sent each iteration. If an agent mates, fitness proportionate selection (Eiben and Smith, 2003) is used to select a mate from the agent population. Genotypes (floating-point value strings) encoding the ANNs are recombined using 2-point crossover (Eiben and Smith, 2003). Two child ANNs are produced and replace the parents to keep the population size constant. If an agent moves, then it moves one grid cell north, south, east, or west (figure 1, left). Figure 1 (center and right) illustrates agent adaptation occurring over evolutionary time. Agents become effective gatherers via learning a migration behavior allowing them Late Breaking Papers