The transmission dynamics of migratory knowledge as a socially learned behavior: Understanding the risk of migratory culture loss

Background/Question/Methods

Migration events that occur in small groups or subsets of a population present a unique challenge compared to larger, mass migrations.  In order to successfully migrate, each of these small groups must each be able to navigate the migratory pathway by innate sensing of the landscape or, in some species, by information learned by individuals.  In the case of a learned migratory route, the risk of a population losing the migratory culture becomes a concern, particularly when group and population sizes are small.

In this study we model the dynamics of migratory systems where migration information is passed from one individual to another.  We developed a discrete-time probabilistic model to understand which grouping conditions and population characteristics lead to the loss of migratory culture and which provide stable migratory persistence.  Through understanding how these factors influence the transmission of information, we will gain a better understanding of group migration dynamics.

Results/Conclusions

Our results show that the risk of migratory culture loss becomes greatest in populations with small group sizes, fixed group associations, and even group size distributions.  Migratory groups behave as subpopulations, with the connectivity determined by mixing between migration events.  Therefore as the group associations become more random and are allowed to mix freely between migrations, migratory knowledge is more rapidly transmitted and easily preserved in the population.  Average group size and size distribution affect migratory culture preservation because the presence of large groups containing many individuals allows for transmission of migratory routes from one knowledgeable individual to many unlearned individuals.

When learned migratory pathways are important to the survival of a population, understanding the spread of learned behavior is crucial.  This is particularly true in endangered species, such as whooping cranes, where the combination of sophisticated learned migratory behavior and dangerously small population sizes complicates conservation efforts.  By identifying population measures and group behaviors that serve as indicators of migratory health, our study provides valuable information that can help practitioners recognize when a migratory species might be at risk of migration loss.  Steps can then be taken to prevent migratory loss before it further imperils survival of the species.