Mass Migration Strategies May Make Certain Species Vulnerable to Population Collapses

Many animals undergo mass migrations to find food, avoid harsh environmental conditions, reproduce, or raise offspring. By migrating in large groups, the animals are more likely to successfully navigate to their destination. New research suggests that there may be a downside to this strategy. A study just published in the journal Movement Ecology shows that species using mass migration strategies may be more vulnerable to population collapses.

Migration has many advantages, including access to resources and avoidance of severe weather conditions. By traveling in a huge group, animals can minimize predation and improve the overall accuracy of their navigation. Previous research has already shown that groups are better at navigating than solo animals. Random and incorrect guesses by individuals are weeded out, allowing the group to act collectively and hone in on the correct direction.

Researchers were interested in investigating the possible ecological costs of mass migration. They used mathematical models to analyze what would happen to mass migration groups if the total population size dropped. The researchers found that if populations dipped below certain critical points, it could lead to population collapses. A small group may not be able to navigate accurately, potentially wiping out the entire group. The authors note that this wouldn’t be an issue for species that are capable of navigating individually. For animals that rely on collective navigation, however, even a small population drop could prevent the group from reaching their destination.

Mass migration strategies allow animals to navigate collectively, generally increasing the accuracy of the group. This tactic comes at a cost and may make certain migratory species more vulnerable to population collapses, including wild salmon and other economically important animals. A small population drop can be enough to decrease navigational accuracy. Since individuals may be poor navigators on their own, the group will likely fail to reach their destination. Successful migration is often critical for survival and reproduction; failing to migrate can lead the entire population to collapse. The researchers hope their findings will allow for better wildlife management of migratory animal species.

REFERENCE

Andrew Berdahl et al. Collective behavior as a driver of critical transitions in migratory populations. Movement Ecology (2016).

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